Infrared-Driven Charge-Transfer in Transition Metal-Containing

Subscriber access provided by UNIV OF NEW ENGLAND ARMIDALE

A: Spectroscopy, Molecular Structure, and Quantum Chemistry

Infrared-Driven Charge-Transfer in Transition Metal-Containing B X (X = H, F) Clusters 12

122#

Isaac J. S. De Vlugt, Michael J Lecours, Patrick J. J. Carr, Ahdia Anwar, Rick A Marta, Eric Fillion, Vincent Steinmetz, and W. Scott Hopkins J. Phys. Chem. A, Just Accepted Manuscript • DOI: 10.1021/acs.jpca.8b05750 • Publication Date (Web): 15 Aug 2018 Downloaded from http://pubs.acs.org on August 21, 2018

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

The Journal of Physical Chemistry

1

Infrared-Driven Charge-Transfer in Transition Metal-Containing B12X122‾ (X = H, F) Clusters Isaac J. S. De Vlugt,1 Michael J. Lecours,1 Patrick J. J. Carr,1 Ahdia Anwar,1 Rick A. Marta,1 Eric Fillion,1 Vincent Steinmetz,2 W. Scott Hopkins1* 1. Department of Chemistry, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1 2. CLIO/LCP Bat. 201, Porte 2, Université Paris-Sud 11, Orsay 91405 Cedex, France

AUTHOR INFORMATION Corresponding Author *Scott Hopkins: [email protected]

ACS Paragon Plus Environment

The Journal of Physical Chemistry 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 34

2

Abstract Density functional theory (DFT) calculations and infrared multiple photon dissociation (IRMPD) spectroscopy are employed to probe [TM•(B12H12)]– and [TM•(B12H12)2]2– clusters [TM = Ag(I), Cu(I), Co(II), Ni(II), Zn(II), Cd(II)]. A comparison is made between the charge-transfer properties of the clusters containing the hydrogenated dodecaborate dianions, B12H122−, and the fluorinated analogues, B12F122−, for clusters containing Cd(II), Co(II), Ni(II), and Zn(II). IRMPD of the [TM•(B12H12)]– and [TM•(B12H12)2]2– species yields B12H11− via hydride abstraction and B12H12− in all cases. To further explore the IR-induced charge-transfer properties of the B12X122− (X = H, F) cages, mixed-cage [TM(B12H12)(B12F12)]2– [TM = Co(II), Ni(II), Zn(II), Cd(II)] clusters were investigated. IRMPD of the mixed-cage species yielded appreciable amounts of B12F12− and B12H12− in most cases, indicating that charge-transfer to the central TM cation is a favorable process; formation of B12F12− is the dominant process for the Co(II) and Ni(II) mixedcage complexes. In contrast, the Zn(II) and Cd(II) mixed-cage complexes preferentially produced fragments of the form BxHyFz‾/2‾, suggesting that H/F scrambling and/or fusion of the boron cages occurs along the IRMPD pathway.


Page 3 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


3

I. Introduction The remarkable advancements in carbon chemistry since the 1990s have recently reinvigorated efforts to develop new boron-based compounds and nanomaterials.1-32 For example, the structures of anionic elemental boron clusters, Bn−, which are thought to be quasiplanar up to n ≤ 38,33 suggest that it might be possible to prepare borophene (atomically thin boron sheets) via cluster deposition.10-13, 21-22, 34-38 In 2014, Zhai et al. reported that the transition to three-dimensional (3D) structures at B40− yields borospherene, an all-boron analogue to buckminsterfullerene, C60.24, 31, 39 The Wang group at Brown has since reported observation and characterization of the smallest borospherene structure, B28−.40 Interestingly, the larger, neutral B80 species is predicted to be very stable and have an almost identical structure to C60, but with an additional boron atom in the centre of each hexagonal face.26 However, this species has yet to be isolated and characterized, and recent computational work has shown that the fullerene cage isomer should lie at an energy well above the global minimum structure.41-45 The incorporation of hydrogen or halogen atoms strongly affects the 2D-to-3D structural transition of boron clusters.46-52 In fact, the most stable polyhedral borane species is the icosahedral B12H122− cluster.23,

48, 50, 53-54

Owing to the size, stability, and high-symmetry of

B12H122− and its halogenated derivatives, these species have found use in several applications, including energy storage and neutron capture cancer therapy.5, 30, 55-62 Despite the importance of these applications, there have been relatively few experimental studies exploring the structures and properties of the isolated species.60, 63-67 Our 2015 study of complexes containing B12F122− and transition metal (TM) cations is of particular pertinence to the present work.63 In the condensed phase, the strong B–F bonds are expected to be very weakly basic towards Lewis acidic metal ions.57 Consequently, the F atoms act to separate the HOMO of the B12F122−



Page 4 of 34

4

(delocalized inside the boron cage) and the metal center. As a result of this weak coordination, the reactivity of metal ions in Mn+(B12F122−)m salts might approach that of the corresponding gas phase Mn+ species, thereby providing a new mechanism for delivering highly reactive catalysts in solution.5, 55-58 In contrast, gas phase studies of 3d and 4d transition metal-containing clusters of the form [TM•(B12F12)n]n− revealed strong interactions between B12F122− and the metal cations, which facilitated IR-induced charge-transfer and, in some cases, subsequent reaction of the dodecaborate cages.63 Natural Bond Order (NBO) analyses of the complexes showed substantial stabilizing interactions between the F lone pairs and the metal centers. This begs the question as to whether the hydrogenated analogues of these clusters, i.e., [TM•(B12H12)n]n−, would exhibit similar physicochemical behaviour given the lack of possible H lone pair interactions. In their 2011 study, Warneke et al. showed that the [B12F12 + CnH2n+1]− fragments produced by collision induced excitation of [B12F12 + N(CnH2n+1)4]− go on to react via loss of a radical alkyl group to form B12F12• −.65 In our analogous study of [Cu•(B12F12)]− and [Ag•(B12F12)]−, production of B12F12• − was also observed.63, 68 The observation of such oxidation reactions are found to be in good qualitative agreement with the oxidation potential of the anion and the reduction potential of the cation.3, 65 Since B12H122– is more easily oxidized than B12F122–, the expectation is that clusters such as of [Cu•(B12H12)]− and [Ag•(B12H12)]− should produce B12H12• −

upon fragmentation. However, it is worth noting that fragmentation of the ion pair [B12F12 +

N(CnH2n+1)4]− did exhibit a weak signal for [B12F11−].65 Should a similar process occur for, e.g., [Ag•(B12H12)]−, the loss of AgH as a neutral fragment would result in the formation of a vacant boron site in the nascent [B12H11−]. It has recently been shown that the free boron site in [B12X11−] (X = F – I) clusters is strongly electrophilic and binds unusually strongly to residual gases in the ion trap, including noble gases.60,

65

In particular, reactions with residual water


Page 5 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


5

molecules which result in halogen-hydroxyl substitutions may be observed.65 Thus, there may be a competition between charge-transfer and hydride abstraction in TM-containing B12H122– clusters. Here, we have conducted a combined computational and experimental study to probe the structures and properties of [TM•(B12H12)n]n– clusters [TM = Ag(I), Cu(I), Cd(II), Co(II), Ni(II), Zn(II)]. To further explore the IR-induced charge-transfer properties of the B12X122− (X = H, F) cages, mixed-cage [TM(B12H12)(B12F12)]2– clusters were also investigated. II. Methods i. Experiment The synthesis of the TM(solvent)nB12H12 salts employed to produce the clusters of interest follows the procedure described in reference

57

. In short, commercially available K2B12X12 was

dissolved in acetonitrile and was added to anhydrous AgNO3 to produce Ag2(CH3CN)4B12X12 and KNO3, which was removed by filtration. The Ag2(CH3CN)4B12X12 was then used in substitution reactions with TM chloride salts of Ag(I), Cd(II), Co(II), Cu(I), Ni(II) and Zn(II) in acetonitrile and / or water. The TM(solvent)nB12X12 salts were obtained by removal of the AgCl precipitate followed by evaporation of the filtrate. Electrospray ionization of acetonitrile solutions containing the TM(solvent)nB12H12 salts yielded gas phase clusters of TMs and B12H122−. For clusters that contained both B12H122− and B12F122−, two acetonitrile solutions, one containing TM(solvent)nB12H12 and the other containing TM(solvent)nB12F12, were simply mixed together and then electrosprayed. Infrared multiple photon dissociation (IRMPD) experiments were performed at the Centre Laser Infrarouge d’Orsay (CLIO) free electron laser (FEL) facility of the University of Paris 11.



Page 6 of 34

6

The experimental set up there has been described in detail previously.69-70 The specific 3d and 4d TMs were chosen for experimentation due to their ability to form stable [TM•(B12X12)n]n− (X=H,F) clusters in the gas-phase upon electrospray ionization (ESI) of acetonitrile solutions (100 µg mL‾1) containing TM(solvent)nB12X12. All [TM•(B12X12)n]n− (X=H,F) cluster species were easily identified based on their m/z and associated isotopic distributions (see Supporting Information). Since this work wishes to compare the charge-transfer properties of [TM•(B12H12)n]n− clusters to those of analogous [TM•(B12F12)n]n− clusters, ESI of acetonitrile solutions containing TM(solvent)nB12H12 for TMs that successfully made [TM•(B12F12)n]n− clusters upon ESI of acetonitrile solutions containing TM(solvent)nB12F12 were employed (see reference

63

). IRMPD spectra were recorded in the region of the B12H122‒ and B12F122‒ cage

vibrations (i.e., 850 – 1550 cm‒1). The [Cu•(B12H12)]− and [Ag•(B12H12)]− clusters required the maximum power (ca. 1 W) of the IR-FEL to induce fragmentation, whereas the spectra of the metal-bound homodimers and heterodimers were acquired with 3 dB attenuation to prevent signal saturation. The IR beam is softly focused into the trap to yield a beam waist of ca. 1 mm. ii. Computational Details Density functional theory (DFT) calculations were conducted using the Gaussian 09 suite for computational chemistry.71 Owing to the icosahedral symmetry of the B12X122− (X = H, F) cages, cluster structures could be generated manually with relative ease. For example, the [Ag(I)•B12H12]− cluster can have the silver cation located at an apex site (180o B–H•••Ag bond angle), an edge site (adjacent to two H atoms), or a facial site (adjacent to three H atoms). All [TM•(B12X12)n]n− optimized cluster geometries are available in the Supporting Information that accompanies this manuscript. Calculations for the 3d TMs clusters were conducted at the B3LYP/6-311++G(d,p) level of theory, whereas clusters containing 4d TMs employed the Def2-


Page 7 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


7

TZVPPD/ECP basis set and effective core potential.72-75 It is known that DFT can perform badly when calculating charge-transfer properties, especially for excited electronic states,76 and that ascribing too much meaning to individual molecular orbitals calculated by DFT can be controversial.77 However, DFT has been applied successfully to model charge-transfer in isolated organometallic complexes and at graphene surfaces,77-78 and the computational method employed here has previously been demonstrated to capture accurately the structures and properties of similar chemical species.50-51, 63 Geometry optimizations were followed by normalmode analyses to ensure that the cluster geometries corresponded to a local minimum on the potential energy surface. These calculations also provided the harmonic vibrational frequencies of each cluster. To ensure convergence of the calculations and to enhance numerical integration, an integration grid with 225 radial shells and 974 angular points per shell was used. Finally, natural bonding orbital (NBO) analysis was conducted for the geometrically optimized clusters to obtain natural partial charges of the metal ions in each cluster and to obtain interaction energies between the metal cation and B12X122‾ (X = H, F).79 Based on previous work,63, 80-81 we expect that this approach is valid for the complexes studied here. III. Results and Discussion i. Single Cage Clusters, [Cu(I)•B12H12]− and [Ag(I)•B12H12]− Figures 1A and 1B show the mass spectra recorded following isolation of [Ag(I)•B12H12]− when interrogating with IR light of 1375 cm‒1 and 1050 cm‒1, respectively. By monitoring the fragmentation efficiency as a function of IR wavenumber, one can generate IRMPD spectra like those shown in Figures 2A–C, which plot the results obtained for for B12H122−, [Cu(I)•B12H12]−, and [Ag(I)•B12H12]−, respectively. The dominant fragmentation pathway observed for all three species was production of fragments at ca. m/z 140. Based on comparison with the analogous



Page 8 of 34

8

[Cu(I)•B12F12]−, and [Ag(I)•B12F12]− clusters,63, 68 one might expect these products to be B12H12• − fragments. However, the observed relative abundances for the fragment isotopologues do not match perfectly with expected natural isotopic distributions (see Supporting Information). This discrepancy could potentially be attributed to three factors: (1) the mass isolation window of the parent, which can slightly skew relative intensities near the mass cut-off, (2) the fact that spectra were recorded for only ca. 50 s at each IR wavenumber (thus limiting statistical sampling of the relative peak intensities), and (3) that excitation at a specific IR wavenumber induces fragmentation of the species which absorb within the bandwidth of the IR-FEL; owing to the vibrational isotope effect,82 a subset of isotopologues can be in-resonance at a particular wavenumber, while others are not. This introduces ambiguity for fragment peaks assignments for the [Cu(I)•B12H12]− and [Ag(I)•B12H12]− complexes. As mentioned in the introduction section, hydride abstraction, in a process similar to that observed for alkylated B12X122‒ (X = H, halogen) clusters,65 would yield B12H11‒ isotopologues that could be confused with B12H12‒ isotopologues (e.g.,

11

B12H11‒ and

B B11H12‒ have the same m/z). Unfortunately, since we are employing

10 11

mass spectrometric detection for the products, we are blind to any neutral CuH or AgH cofragments. Fluoride abstraction was not observed in the analogous species,63,

65, 68

nor was

production of [TM‒F]+ or [TM‒H]+ from B12X122‒ (X = H, F) clusters containing TM = Co(II), Ni(II), Zn(II), or Cd(II). This suggests that the m/z ~140 species is B12H12• −. However, the series of fragment peaks observed upon IRMPD (see Figure 1B), which are separated by ca. 16 amu, suggests that B12H11‒ is produced and subsequently undergoes reaction with residual water in the ion trap.65 Ultimately, IRMPD of the [Cu(I)•B12H12]− and [Ag(I)•B12H12]− complexes seems likely to occur via both the charge-transfer and hydride abstraction pathways.


Page 9 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


9

Figure 1. Experimental mass spectra recorded following isolation of [Ag(I)•B12H12]−. (A) The mass spectrum observed during non-resonant IR interrogation at 1375 cm‒1 and (B) resonant IR interrogation at 1050 cm‒1.

The observed IRMPD peak widths (see Figure 2), which are on the order of 50 cm−1, are significantly broader than the 25 cm−1 peak widths typically observed at the CLIO facility. 84

69, 83-

We attribute this to the presence of multiple isotopologues and isotopomers in the probed

sample. For example, the [Cu(I)•10B211B10H12]− complex has fifteen different arrangements of two

10

B atoms under the symmetry constraints of the cluster, each of which has a slightly

different vibrational spectrum. Similar observations were made in our studies of [Cu(I)•B12F12]− and [Ag(I)•B12F12]−.63, 68 The intense vibrational band at ca. 1050 cm−1 is associated with the triply degenerate T1u B–H stretching mode of the B12H122− cage. Owing to the presence of the metal cations, the degeneracy of this mode is lifted to produce two bands corresponding to B–H stretching along and perpendicular to the TM+•••B12H122− axis. This splitting is most easily observed in the calculated spectrum of the [63Cu(I)•11B12H12]− species, where the two vibrational



Page 10 of 34

10

transitions are separated by 25 cm−1 (red trace in Figure 2B). In the [107Ag(I)•11B12H12]− cluster, these transitions are calculated to be split by 13 cm−1.

Figure 2. Experimental IRMPD spectra (black traces) and calculated harmonic vibrational spectra (red traces) for (A) B12H122−, (B) [Cu(I)•B12H12]−, and (C) [Ag(I)•B12H12]−. Calculated spectra are unscaled. Calculations were conducted at the B3LYP/6-311++G(d,p) level of theory for the Cu-containing species. The Def2−TZVPPD/ECP−28 basis set and effective core potential combination was employed for Ag(I).

Experimental observation of B12H12• − formation upon IRMPD of [Ag(I)•B12H12]− and [Cu(I)•B12H12]− implies that charge-transfer occurs from the quadruply degenerate B12H122− gu HOMO to the valence s orbital of the TM cation during IRMPD of the parent cluster. The charge-transfer dissociation process for these species is analogous to that of NaCl, which exhibits charge separation in its ground electronic state (rNaCl = 2.36 Å, µNaCl = 9.0 D),85 but which


Page 11 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


11

dissociates via its lowest thermodynamic threshold to form neutral radical products in the gas phase. This behaviour is due to the imbalance between the ionization energy of Na (5.14 eV) and the electron affinity of Cl (3.51 eV), which results in a relatively low energy charge-transfer threshold.63, 85 Similar arguments can be made for the charge-transfer process in [TM•B12X12]− (X = H, F; TM = Cu(I), Ag(I)) where the metal centers have ionization energies of IECu = 7.73 eV and IEAg = 7.58 eV, respectively, and the electron affinities of B12H12− and B12F12− are ca. 1.0 eV and 1.6 eV, respectively.63, 66 However, for the [TM•B12X12]− (X = H, F; TM = Cu(I), Ag(I)) species, charge-transfer must occur over a distance of ca. 3.5 Å and via the intervening H or F layer that separates the B12X122− (X = H, F) cage HOMO and the TM cation. This has important bearing on the stabilization energy due to charge-transfer, which decays as e‒ γr

, where γ is proportional to the square root of the ionization potential of the donor and r is the

distance between the center of masses for the two particles in question.81, 86 If one compares the Ag complexes of cyclopentadienyl (IP = 1.789 eV)87 versus B12F122−, the increase in interparticle separation from ca. 2.85 Å to 3.5 Å yields a ca. 50 % reduction in stabilization energy due to charge-transfer. However, this same coarse approximation indicates that the charge-transfer stabilization energy is comparable in the B12H122− complex compared to the cyclopentadienyl complex owing to the lower IP of the cage moiety. Consequently, a more detailed investigation is warranted. Electronic structure calculations of [Cu(I)•B12H12]− show that the atomic orbitals of the Cu(I) center contribute to the HOMO, suggesting that there is a charge-transfer component to the electronic ground state (see Figure 3). Complexation with the Cu+ cation also serves to lift the four-fold degeneracy of the B12H122− gu HOMO, resulting in level splitting that spans a range of 90 meV. The [Ag(I)•B12H12]− complex exhibits similar level splitting for the highest occupied



Page 12 of 34

12

orbitals, but the ordering of the four split MOs varies slightly from that observed for [Cu(I)•B12H12]− and occurs over a slightly larger energy range (140 meV) (see Supporting Information). NBO population analyses of the electronic ground states for the geometrically optimized [Cu(I)•B12H12]− and [Ag(I)•B12H12]− clusters shows that the metal centers carry a partial charge of +0.9 e, that is, 0.1 e of electron density is transferred from the from B12H122− to the TM+ cation. The relatively minor shift observed for the B12H122‒ vibrational band upon complexation with Cu(I) or Ag(I) (ca. 5 cm‒1 to lower wavenumber) also suggests that interaction with the metal centers results in only a minor perturbation to the cage structure. In comparison, NBO analysis of [Ag(I)•B12F12]− indicates that the Ag(I) center also carries a partial charge of +0.9 e in the fluorinated analogue, but that the Cu(I) center has a partial charge of +0.4 e in [Cu(I)•B12F12]−.63 This accords with expectations based on the relatively strong interactions between the Cu(I) center and the F lone pairs in [Cu(I)•B12F12]−.63 The four highest energy occupied MOs of the fluorinated species are analogous to those calculated for the hydrogenated species, but include contributions from the F lone pairs closest to the metal centers (see Supporting Information).


Page 13 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


13

Figure 3. Molecular orbital energies relative to the HOMO for (left) B12H122− and (right) [Cu(I)•B12H12]−. Blue lines indicate the MOs with large contributions from Cu+ atomic s orbital. The two lowest thermodynamic dissociation thresholds are indicated with dashed lines. Calculations were conducted at the B3LYP/6-311++G(d,p) level of theory.

Figure 3 also shows the LUMO of B12H122−, which is composed of the anti-bonding B–H σ* orbitals arising from the combination of H 1s and B 2pz atomic orbitals. HOMO-LUMO gaps are commonly used as an index of stability, with larger gaps typically being associated with more stable, unreactive species.88-89 The calculated HOMO-LUMO gap for B12H122−, ∆EH-L = 5.06 eV, agrees with previous work.90-91 For [Cu(I)•B12H12]−, ∆EH-L = 3.57 eV, indicating that the relative stability of the cluster decreases upon complexation with Cu+.91 Examination of the low-lying unoccupied molecular orbitals of [Cu(I)•B12H12]− shows that these MOs are predominantly associated with the valence s atomic orbital of the Cu(I) center, with a minor contribution from



Page 14 of 34

14

the anti-bonding B–H σ* orbitals of the B12H122− cage (see Figure 3). Table 1 provides the calculated HOMO-LUMO gaps for [Ag(I)•B12H12]− and the fluorinated analogues. Similar electronic structures are calculated for all four [TM•B12H12]− (X = H, F; TM = Cu(I), Ag(I)) complexes (see Supporting Information). DFT calculations suggest that substitution of Ag(I) for Cu(I) and F for H further narrows the HOMO-LUMO gap in these complexes. Note, though, that calculations conducted for Ag(I)-containing species employed a different basis set than those conducted for Cu(I)-containing species, so care should be taken in making a direct comparison. Table 1 also provides the thermodynamic thresholds for the formation of B12X12− and B12X122− (X=H, F) from the Cu(I) and Ag(I) complexes. Unsurprisingly, production of TM+ and the B12X122− dianion is a relatively high energy process owing to the Coulombic attraction between the cation and the dianion. In contrast, the charge-transfer dissociation thresholds (TM0 + B12X12• −

) are at relatively low energies and below the LUMOs for all complexes. This is consistent with

the experimental observation of B12X12• − (X=H, F) formation via IRMPD of the [TM•B12X12]− (X = H, F; TM = Cu(I), Ag(I)) clusters, and suggests that excitation and dissociation occurs on the diabatic ground state potential energy surface. Table 1. Calculated HOMO-LUMO gaps and standard Gibbs’ energies of dissociation for [TM•B12H12]− (X=H, F; TM=Cu(I), Ag(I)). Calculations were conducted at the B3LYP/6311++G(d,p) level of theory for the Cu(I)-containing species. The Def2−TZVPPD/ECP−28 basis set and effective core potential combination was employed for Ag(I). Species

∆EH-L / eV

∆G° (B12X12• ‾ production) / eV

∆G° (B12X122‾ production) / eV

B12H122−

5.06

/

/

[Cu(I)•B12H12]−

3.57

2.80

10.15

−

2.89

2.02

9.26

[Ag(I)•B12H12] B12F122− [Cu(I)•B12F12]

4.83

/

/

−

2.56

1.66

8.18

−

1.72

1.16

7.58

[Ag(I)•B12F12]


Page 15 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


15

To estimate the thermodynamic thresholds for hydride abstraction, the Gibbs’ energies of the parent complex, e.g., [Cu(I)•B12H12]−, were subtracted from the summed Gibbs’ energies of the associated geometry optimized fragments (e.g., CuH + B12H11−). This resulted in hydride abstraction thresholds of 1.63 eV and 1.12 eV for the Cu and Ag complexes, respectively. In both cases, the thermodynamic threshold for hydride abstraction is lower than the threshold for charge-transfer. This supports the interpretation that the minor product channels observed to higher mass of the m/z 140 region are associated with formation of B12H11On− via hydrogenhydroxyl substitution upon reaction of B12H11− with residual water vapor in the ion trap.65 A third, low energy dissociation process whereby nascent B12H12• – anions eject a neutral hydrogen atom to form B12H11–. This threshold is calculated to occur 1.93 eV above the charge-transfer threshold for all hydrogenated clusters.

ii. Double Cage Clusters, [Co(II)•(B12H12)2]2− and [Cd(II)•(B12H12)2]2− To compare with their previously reported fluorinated analogues,63, 68 the [Cd(II)•(B12H12)2]2− and [Co(II)•(B12H12)2]2− metal-bound homodimer clusters were studied. Efforts were also made to record IRMPD spectra for the [Ni(II)•(B12H12)2]2− and [Zn(II)•(B12H12)2]2− clusters, but the presence of isobaric contaminants prevented data acquisition. The IRMPD spectra for [Cd(II)•(B12H12)2]2− and [Co(II)•(B12H12)2]2− in the 900−1300 cm−1 region are plotted in Figures 4A and 4B, respectively. As was the case with the Cu(I) and Ag(I) complexes, very small shifts observed for the B12H122‒ vibrational band upon complexation with Co(II) or Cd(II) (ca. 5 cm‒1 to lower wavenumber). Figure 4 also plots the calculated harmonic spectra for these species. In



Page 16 of 34

16

the case of [Co(II)•(B12H12)2]2−, two low-energy electronic states are identified by electronic structure calculations; the global minimum quartet state, and an excited doublet state at +42.7 kJ mol–1 (443 meV). The calculated spectrum for the quartet state is clearly a better match with the band observed at ca. 1070 cm–1 in the IRMPD spectrum. The optimized global minimum geometries of [Co(II)•(B12H12)2]2− and [Cd(II)•(B12H12)2]2− both have the TM cations located in the center of a distorted octahedron formed by the H atoms associated with two trigonal faces of the B12H122‾ dianions (see Figure 5). The HOMO for these species is composed predominantly of the HOMOs of the B12H122‾ cages, with a minor contribution from the atomic d orbitals of the TM cation. NBO population analysis yields partial charges of 1.3 e and 1.8 e for the Co(II) and Cd(II) centers, respectively. Similar analyses of [Co(II)•(B12F12)2]2− and [Cd(II)•(B12F12)2]2− yields partial charges of 1.4 e and 1.6 e,63 respectively, indicating similar charge-transfer contributions to the electronic ground states in all four [TM•(B12X12)2]2− (X = H, F; TM = Co(II), Cd(II)) clusters. The dominant IRMPD channel for both [Cd(II)•(B12H12)2]2− and [Co(II)•(B12H12)2]2− is production of species with m/z ~140, again consistent with formation of B12H12• − and B12H11−. Minor B12H11On− products associated with reaction between B12H11− and residual water in the ion trap were also observed. In the case of the Cd(II) complex, the m/z ~140 region also exhibited peaks associated with a doublycharged species, likely to be B24H22-242−. Similar cage fusion (and fission) was reported for IRMPD of [Ni(II)•(B12F12)2]2− and [Co(II)•(B12F12)2]2−, and was rationalized in terms of the charge-transfer process.63 The same chemistry is likely occurring for the hydrogenated species; removal of an electron from the B12H122− HOMO yields a radical species (B12H12• −) which, owing to its close proximity, can go on to react with the other B12H122− cage in the metal-bound dimers. It should be noted that in monitoring the observed IRMPD product channels of


Page 17 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


17

[Co(II)•(B12H12)2]2− and [Cd(II)•(B12H12)2]2− as a function of IR-FEL wavenumber, we find that nearly identical IRMPD spectra are observed for all product channels (see Supporting Information for details).

Figure 4. (A) The IRMPD spectrum (black trace) and the calculated vibrational spectra of [Co(II)•(B12H12)2]2− in the low energy doublet spin state (+42.7 kJ mol–1; green trace) and quartet spin state (0.0 kJ mol–1; red trace). (B) The IRMPD spectrum (black trace) and the calculated vibrational spectrum of [Cd(II)•(B12H12)2]2− (red trace). Calculated spectra are unscaled. Calculations were conducted at the B3LYP/6-311++G(d,p) level of theory for the Co(II)containing species. The Def2−TZVPPD/ECP−28 basis set and effective core potential combination was employed for Cd(II). The blue highlighted region indicates the absorption wavenumber of the uncomplexed B12H122− cage.



Page 18 of 34

18

Figure 5. The optimized global minimum geometry of [Co(II)•(B12H12)2]2− Calculations were conducted at the B3LYP/6-311++G(d,p) level of theory.

The calculated HOMO-LUMO gaps and fragmentation thresholds for the four [TM•(B12X12)2]2− (X = H, F; TM = Co(II), Cd(II)) clusters are provided in Table 2. Interestingly, whereas complexation with Co2+ reduces the HOMO-LUMO gap in comparison with bare B12X122− (X = H, F), complexation with Cd2+ results in an appreciable change only for the fluorinated derivative. As was the case with the Cu(I) and Ag(I) complexes, we find that the thermodynamic dissociation threshold associated with charge-transfer is significantly lower than the charge-separated threshold for the [TM•(B12X12)2]2− (X = H, F; TM = Co(II), Cd(II)) clusters. In fact, in the case of the [Cd(II)•(B12F12)2]2− cluster, DFT calculations predict spontaneous charge-transfer and fragmentation at standard temperature and pressure.63 Given that we observe the [Cd(II)•(B12F12)2]2− cluster via ESI mass spectrometry, it is clear that fragmentation is not spontaneous for the conditions employed in the experiment. This discrepancy between calculation and experiment is likely due to a combination of calculation accuracy and the fact that experiment was not run at standard temperature and pressure conditions. As was the case for the Cu(I) and Ag(I) complexes, the charge-transfer thresholds for the double cage species are well below their calculated LUMO energies (see Table 2). Since the NBO calculations show that


Page 19 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


19

the ground electronic states of the double cage clusters are predominantly charge-separated (i.e., partial charges greater than +1 for the metal centers), and assuming that the IRMPD process occurs exclusively on the diabatic ground electronic potential energy surface, the cluster electronic character must change along the charge-transfer dissociative coordinate. Given the apparent production of B12H11On− fragments (which are thought to arise from B12H11− precursors) following IRMPD of the metal-bound dimers, calculations were conducted to estimate the thermodynamic thresholds for hydride abstraction in the parent clusters. Since there was no evidence of [HCo•B12H12]− or [HCd•B12H12]− formation in the associated mass spectra, we must assume that, should this process occur, it results in the formation of the neutral metal dihydride and two B12H11− cages. In employing a similar calculation method to that described above for the Cu and Ag complexes, we arrive at hydride abstraction thresholds of 1.03 eV and 2.89 eV for the Co and Cd metal-bound dimers, respectively. In contrast to the Cu and Ag complexes, the hydride abstraction thresholds for the Co- and Cd-bound dimer species are higher in energy than the associated charge-transfer thresholds (see Table 2). Nevertheless, we expect that these thresholds are accessible in the experiments given the calculated thresholds and experimental observations for the Cu and Ag complexes (see Table 1). It should be noted that a coarse power study was attempted whereby the IR-FEL beam as sequentially attenuated with 3 dB attenuators. However, no significant changes were observed in the relative product distributions.

Table 2. Calculated HOMO-LUMO gaps and standard Gibbs’ energies of dissociation for [TM•(B12H12)2]2− (X = H, F; TM = Co(II), Cd(II)). Calculations were conducted at the B3LYP/6311++G(d,p) level of theory for the Co(II)-containing species. The Def2−TZVPPD/ECP−28 basis set and effective core potential combination was employed for Cd(II). Species

∆EH-L / eV

∆G° (B12X12• ‾ production) / eV


∆G° (B12X122‾ production) / eV


Page 20 of 34

20

B12H122−

5.06

/

/

[Co(II)•(B12H12)2]

2−

3.22

0.83

4.19

[Cd(II)•(B12H12)2]

2−

5.25

0.57

4.41

B12F122−

4.83

/

/

[Co(II)•(B12F12)2]

2−

2.11

0.45

4.04

[Cd(II)•(B12F12)2]

2−

3.05

–0.32

3.65

iii. Mixed-Cage Clusters, [(B12H12)•TM•(B12F12)]2− (TM = Co(II), Ni(II), Zn(II), Cd(II)) To further explore the structures and charge-transfer properties of [TM•(B12X12)n]n− (X = H, F) species, the mixed-cage clusters [TM(B12H12)(B12F12)]2− (TM = Co(II), Ni(II), Zn(II), Cd(II)) were also investigated. The [Co(II)(B12H12)(B12F12)]2− cluster (shown in Figure 6), which has a geometry similar to that of the [Co(II)•(B12H12)2]2− cluster, is typical of all four mixed-cage species studied. The Co(II)•••H distances in the [Co(II)(B12H12)(B12F12)]2− cluster, which are all ca. 1.94 Å, are shorter than the ca. 2.22 Å Co(II) ••• F internuclear distances. This is a consistent trend across all the [TM•(B12X12)]− and [TM•(B12X12)2]2− (X = H, F) clusters studied to date; TM–H distances are shorter than TM–F distances in analogous complexes. The cluster geometries have important bearing on the charge-transfer properties. In the case of the fluorinated analogues, [TM•(B12F12)]− and [TM•(B12F12)2]2−, the interaction between the metal center and boron cage is supplemented by additional interactions between the cation and F lone pairs.63 In the hydrogenated species, where there are no TM / lone pair interactions, the metal center can more closely approach the boron cage, thereby increasing the overlap between cagebased MOs and the valence atomic orbitals of the metal, thus facilitating charge-transfer.


Page 21 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


21

Figure 6. The optimized global minimum geometry of [Co(II)(B12H12)(B12F12)]2− Calculations were conducted at the B3LYP/6-311++G(d,p) level of theory.

By creating the mixed-cage clusters, one can pit two charge-transfer processes against one another, i.e., charge-transfer to the TM cation from B12H122− versus B12F122−. Computationally, we find that charge-transfer from the fluorinated cage is favoured by ca. 1 eV over chargetransfer from the hydrogenated cage, and that the charge-transfer dissociation thresholds are again below the respective LUMOs (see Table 3). Moreover, the highest occupied frontier MOs of the mixed-cage species are predominantly associated with the B12F122− cage-centered orbitals, with minor contribution from the TM atomic d-orbitals (e.g., see the [Co(II)(B12H12)(B12F12)]2− HOMO-1 orbital shown in Figure 6). NBO population analysis yields natural partial charges of +1.4 [Co(II)], +1.5 [Ni(II)], +1.8 [Zn(II)], and +1.7 [Cd(II)], respectively, indicating a relatively high degree of charge-separation in the ground electronic states of the mixed-cage clusters, and suggesting that the electronic character of the complex changes as it dissociates on the diabatic ground state potential energy surface.



Page 22 of 34

22 Table 3. Calculated HOMO-LUMO gaps and standard Gibbs’ energies of dissociation for [TM(B12H12)(B12F12)]2− (TM = Co(II), Ni(II), Zn(II), Cd(II)). Calculations were conducted at the B3LYP/6-311++G(d,p) level of theory for the Co(II)-, Ni(II)-, and Zn(II)-containing species. The Def2−TZVPPD/ECP−28 basis set and effective core potential combination was employed for Cd(II).

∆G° / eV

Species

∆EH-L / eV

B12F12• −

B12H12• −

B12H122−

5.06

/

/

/

/

B12F122−

4.83

/

/

/

/

[Co(II)(B12H12)(B12F12)]2−

2.63

0.40

1.44

2.93

5.86

[Ni(II)(B12H12)(B12F12)]2−

2.64

0.11

1.14

3.67

5.53

[Zn(II)(B12H12)(B12F12)]2−

4.72

0.36

1.20

3.18

6.18

[Cd(II)(B12H12)(B12F12)]2−

3.86

0.00

0.59

3.01

5.39

B12F122‾ B12H122‾

The prediction that the mixed-cage species should form B12F12• − + [(B12H12)•TM]− upon IRMPD is borne out by experiment; IR-induced dissociation of all four [TM(B12H12)(B12F12)]2− (TM = Co, Ni(II), Zn(II), Cd(II)) mixed-cage clusters yields B12F12• −. However, the observed photochemistry is much richer than might be expected based on the view that during the IRMPD process clusters are “heated by one photon at a time” until the lowest thermodynamic threshold is surpassed. Although formation of B12F12• − + [(B12H12)•TM]− was the major IRMPD product channel for the two lightest members of the series, the B12F12• − and [(B12H12)•TM]− ions only account for ca. 80 % of the anionic fragments for the Co(II) complex and ca. 65 % of anionic fragments for the Ni(II) complex. The other anionic fragments produced via IRMPD of [Co(II)(B12H12)(B12F12)]2− are B12H12• − and [(B12F12)•Co(II)]−, suggesting that the IR excitation process also accesses the second lowest-energy charge-transfer threshold. Interestingly, production of B12H12• − via IRMPD of the mixed-cage Ni(II) complex is a very weak product channel, accounting for < 1 % of the observed anionic fragments. Approximately one third of the IRMPD fragments observed for [(B12H12)•Ni(II)•(B12F12)]2− are associated with singly-charged


Page 23 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


23

species in the m/z 230 – 235 range, consistent with production of B11F6−. Similar BnFm− fragments are produced by the [Ni(II)•(B12X12)2]2− (X = H, F) clusters (vide supra).63 In monitoring the observed IRMPD product channels of [Co(II)(B12H12)(B12F12)]2− as a function of IR-FEL wavenumber, we find that nearly identical IRMPD spectra are observed for all product channels. The same is true for [Ni(II)(B12H12)(B12F12)]2−. Figure 7 plots the IRMPD spectra for [TM(B12H12)(B12F12)]2− (TM = Co(II), Ni(II)) in the 950 – 1550 cm–1 region. The green highlighted regions in Figure 7 indicate the calculated positions of B12F122− cage vibrational bands, while the blue region indicates the calculated positions of the most intense B12H122− cage vibrational bands in the 950 – 1550 cm–1 region. The bands observed experimentally are all associated with vibration of the B12F122− cage. The weak feature at ca. 1125 cm–1 is associated with B–F stretching of the three BF units closest to the metal center, whereas the band at ca. 1210 cm–1 is associated with B–F stretching of the three BF units furthest from the metal center. The most intense feature (ca. 1240 cm–1) involves B–F stretching perpendicular to the TM–B12F12 axis, and the weak feature at ca. 1300 cm–1 is associated with the B12F122− cage breathing mode.



Page 24 of 34

24

Figure 7. The Experimental IRMPD spectra (black) and calculated harmonic vibrational spectra (red) for (A) [Co(II)(B12H12)(B12F12)]2− and (B) [Ni(II)(B12H12)(B12F12)]2−. The green highlighted regions are associated with B12F122− vibrations in the complexes, whereas the blue highlighted region is associated with B12H122− vibrations in the complexes. Calculated spectra are unscaled. Calculations were conducted at the B3LYP/6−311++G(d,p) level of theory.

The IRMPD spectra of [Zn(II)(B12H12)(B12F12)]2− and [Cd(II)(B12H12)(B12F12)]2− exhibit the same vibrational bands as were observed in the Ni- and Co-containing complexes (see Figure 8). However, in contrast to the IRMPD behavior of the [Ni(II)(B12H12)(B12F12)]2− and [Co(II)(B12H12)(B12F12)]2− clusters, different product channels displayed different IRMPD spectra for the Zn(II) and Cd(II) mixed-cage complexes. Table 4 gives the IRMPD product channels exhibited by the [Zn(II)(B12H12)(B12F12)]2− and [Cd(II)(B12H12)(B12F12)]2− clusters. Whereas channels I – V displayed identical IRMPD spectra, the IRMPD spectra recorded via channel VI exhibited significantly increased relative intensities for the bands at ca. 1125 cm–1


Page 25 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


25

(B–F stretching of the three BF units closest to the metal center) and ca. 1300 cm–1 (B12F122− cage breathing mode). It is worth noting that product channel VI (m/z 248) is associated with a doubly-charged species that is consistent with the molecular formula B24H8F122–. By necessity, formation of this species requires the fusion of the B12H12 and B12F12 cages. The mechanism and energetics of this process are currently not known. It is possible that this behavior is an example of IR mode-selective chemistry (i.e., different product channels are accessed to different degrees via excitation of different vibrational modes) owing to incomplete IVR at the metal center.92-93 However, electronic excitation and subsequent fragmentation, or fragmentation of hot nascent ions are possible (simpler) alternative explanations. To determine which (if either) of these explanations is correct, a detailed quantum chemical computational study is necessary. Table 4. The major IRMPD fragments observed for [TM(B12H12)(B12F12)]2− (TM = Zn(II), Cd(II)).

[TM(B12H12)(B12F12)]2− IRMPD Fragments I II III IV

B12H12• − (m/z 142) B12F12

•−

Branching Ratio TM = Zn(II)

TM = Cd(II)

19 %

5%

(m/z 358)

4%

5%

−

B7H4F4 (m/z 156)

17 %

13 %

−

19 %

13 %

−

B7H5F5 (m/z 176)

V

B7H3F6 (m/z 193)

0%

5%

VI

B24H8F122− (m/z 248)

34 %

47 %



Page 26 of 34

26

Figure 8. The Experimental IRMPD spectra (black: channels I–V; blue: channel VI) and calculated harmonic vibrational spectra (red) for (A) [Zn(II)(B12H12)(B12F12)]2− and (B) [Cd(II)(B12H12)(B12F12)]2−. The green highlighted regions are associated with B12F122− vibrations, whereas the blue highlighted region is associated with B12H122− vibrations. Calculated spectra are unscaled. Calculations were conducted at the B3LYP/6−311++G(d,p) level of theory. The Def2−TZVPPD/ECP−28 basis set and effective core potential combination was employed for Cd(II).

IV. Conclusions The IRMPD spectra of [TM•(B12H12)n]n− (TM = Co(II), Cu(I), Ag(I), Cd(II); n = 1, 2) have been recorded. DFT calculations show that the dominant spectral feature at approximately 1050 cm-1 corresponds to the triply degenerate T1u B-H stretching mode of B12H122−, which is split into an on-axis component and a doubly degenerate off-axis component of cage vibration. Frequency shifts of this band upon complexation with metal ions is negligible. Excitation of this


Page 27 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


27

mode predominantly leads to production of B12H12• − and B12H11− as evidenced by formation of B12H11On− due to reaction with residual water vapor in the ion trap. In the case of [Cd(II)•(B12H12)2]2−, a doubly-charged species consistent with formation of B24H22-242− was also observed, indicating that charge-transfer and subsequent inter-cage reaction occurs upon IR excitation. In the analogous fluorinated clusters, the charge-transfer process is mediated by relatively strong B–F•••TM interactions. Although analogous interactions are not possible in the hydrogenated clusters, the absence of H lone pair electron density enables a closer approach of the TM center to the boron cage, thereby improving the overlap between the B12H122− HOMO and the TM cation valence orbitals, thus facilitating charge-transfer. To further explore the charge-transfer properties of B12H122− and B12F122−, mixed cage clusters of the form [TM(B12H12)(B12F12)]2− were also studied. IRMPD spectra of these species displayed dominant spectral features at approximately 1250 cm-1, corresponding to excitation of the triply degenerate T1u mode of B12F122−, which is split into an on-axis component and a doubly degenerate off-axis component upon complexation with the TM cation. The photochemistry associated with excitation via this mode varied across the series of TM cations studied. The dominant fragmentation channel for the Co(II) and Ni(II) mixed-cage complexes was production of B12F12• −, consistent with the calculated threshold for impulsive charge-transfer dissociation. In contrast, the Zn(II) and Cd(II) mixed-cage complexes preferentially produce fragments of the form BxHyFz‾/2‾ upon IRMPD. The mechanism for production of these species requires H/F scrambling and/or fusion of the dodecaborate cages, and the exact pathway and energetics of this process is not known. The B24H8F122– fragment is particularly interesting because the IRMPD spectra observed via this product channel differed from those observed via all other product channels. This suggests that production of B24H8F122– occurs via a mechanism which is



Page 28 of 34

28

significantly different to those resulting in the other observed IRMPD product channels. The photochemical process which results in the production of B24H8F122– is currently an open question. Associated Content Supporting Information. Cluster Cartesian atomic coordinates, thermochemical data, channel specific IRMPD data, mass spectra, and IRMPD product channel branching ratios are provided. This information is available free of charge via the Internet at http://pubs.acs.org Acknowledgements The authors gratefully acknowledge high performance computing support from the SHARCNET consortium of Compute Canada and generous financial support from the Natural Sciences and Engineering Research Council (NSERC) of Canada in the form of a Discovery Grant. IDV gratefully acknowledges funding from the NSERC USRA program. References 1. Alexandrova, A. N.; Boldyrev, A. I.; Zhai, H. J.; Wang, L. S. All-Boron Aromatic Clusters as Potential New Inorganic Ligands and Building Blocks in Chemistry. Coord. Chem. Rev. 2006, 250, 28112866. 2. Alexandrova, A. N.; Zhai, H. J.; Wang, L. S.; Boldyrev, A. I. Molecular Wheel B82- as a New Inorganic Ligand. Photoelectron Spectroscopy and Ab Initio Characterization of LiB8. Inorg. Chem. 2004, 43, 3552-3554. 3. Boere, R. T.; Derendorf, J.; Jenne, C.; Kacprzak, S.; Kessler, M.; Riebau, R.; Riedel, S.; Roemmele, T. L.; Ruhle, M.; Scherer, H.; Vent-Schmidt, T.; Warneke, J.; Weber, S. On the Oxidation of the ThreeDimensional Aromatics B12X122- (X=F, Cl, Br, I). Chem. Eur. J. 2014, 20, 4447-4459. 4. Boustani, I.; Quandt, A. Nanotubules of Bare Boron Clusters: Ab Initio and Density Functional Study. Europhys. Lett. 1997, 39, 527-532. 5. Bukovsky, E. V.; Lui, K. W.; Peryshkov, D. V.; Strauss, S. H. Monovalent metal salts of the superweak anion B12F122-: Crystal structure transformations during reversible binding of solvent molecules. Abstr. Pap. Am. Chem. Soc. 2011, 242, 1. 6. Gindulyte, A.; Krishnamachari, N.; Lipscomb, W. N.; Massa, L. Quantum Chemical Calculations of Proposed Multicage Boron Fullerenes. Inorg. Chem. 1998, 37, 6546-6548.


Page 29 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


29 7. Hansen, B. R. S.; Paskevicius, M.; Li, H. W.; Akiba, E.; Jensen, T. R. Metal Boranes: Progress and Applications. Coord. Chem. Rev. 2016, 323, 60-70. 8. Hawthorne, M. F.; Huertas, R.; Maderna, A.; Li, T. J.; Peymann, T. Closomers: Alkyl and Acyl Derivatives of Closo-B12(OH)122- as Icosahedral Scaffolding. Abstr. Pap. Am. Chem. Soc. 2003, 225, U86U86. 9. Her, J. H.; Yousufuddin, M.; Zhou, W.; Jalisatgi, S. S.; Kulleck, J. G.; Zan, J. A.; Hwang, S. J.; Bowman, R. C.; Udovic, T. J. Crystal Structure of Li2B12H12: A Possible Intermediate Species in the Decomposition of LiBH4. Inorg. Chem. 2008, 47, 9757-9759. 10. Huang, W.; Sergeeva, A. P.; Zhai, H. J.; Averkiev, B. B.; Wang, L. S.; Boldyrev, A. I. A Concentric Planar Doubly Pi-Aromatic B19- Cluster. Nat. Chem. 2010, 2, 202-206. 11. Kiran, B.; Bulusu, S.; Zhai, H. J.; Yoo, S.; Zeng, X. C.; Wang, L. S. Planar-to-Tubular Structural Transition in Boron Clusters: B20 as the Embryo of Single-walled Boron Nanotubes. Proc. Natl. Acad. Sci. U. S. A. 2005, 102, 961-964. 12. Moreno, D.; Pan, S.; Liu-Zeonjok, L.; Islas, R.; Osorio, E.; Martinez-Guajardo, G.; Chattaraj, P. K.; Heine, T.; Merino, G. B182-: A Quasi-planar Bowl Member of the Wankel Motor Family. Chem. Commun. 2014, 50, 8140-8143. 13. Oger, E.; Crawford, N. R. M.; Kelting, R.; Weis, P.; Kappes, M. M.; Ahlrichs, R. Boron Cluster Cations: Transition from Planar to Cylindrical Structures. Angew. Chem. Int. Ed. 2007, 46, 8503-8506. 14. Peymann, T.; Knobler, C. B.; Hawthorne, M. F. Synthesis of Alkyl and Aryl derivatives of ClosoB12H122- by the Palladium-catalyzed Coupling of Closo-B12H11I2- with Grignard Reagents. Inorg. Chem. 1998, 37, 1544-1548. 15. Peymann, T.; Knobler, C. B.; Hawthorne, M. F. An Icosahedral Array of Methyl Groups Supported by an Aromatic Borane Scaffold: The closo-B12(CH3)122- Ion. J. Am. Chem. Soc. 1999, 121, 5601-5602. 16. Peymann, T.; Knobler, C. B.; Hawthorne, M. F. A Study of the Sequential Acid-catalyzed Hydroxylation of Dodecahydro-closo-dodecaborate 2-. Inorg. Chem. 2000, 39, 1163-1170. 17. Peymann, T.; Knobler, C. B.; Khan, S. I.; Hawthorne, M. F. Dodecahydroxy-closo-dodecaborate2-. J. Am. Chem. Soc. 2001, 123, 2182-2185. 18. Peymann, T.; Knobler, C. B.; Khan, S. I.; Hawthorne, M. F. Dodecamethyl-closo-dodecaborate2-. Inorg. Chem. 2001, 40, 1291-1294. 19. Peymann, T.; Knobler, C. B.; Khan, S. I.; Hawthorne, M. F. Dodeca(benzyloxy)dodecaborane, B12(OCH2Ph)12: A stable Derivative of Hypercloso-B12H12. Angew. Chem. Int. Ed. 2001, 40, 1664-1667. 20. Peymann, T.; Shelly, K.; Hawthorne, M. F. Recent Developments in the Chemistry of B12H122-. Kluwer Academic/Plenum Publ: New York, 2001; p 775-778. 21. Pham, H. T.; Duong, L. V.; Pham, B. Q.; Nguyen, M. T. The 2D-to-3D Geometry Hopping in Small Boron Clusters: The Charge Effect. Chem. Phys. Lett. 2013, 577, 32-37. 22. Piazza, Z. A.; Hu, H. S.; Li, W. L.; Zhao, Y. F.; Li, J.; Wang, L. S. Planar Hexagonal B36 as a Potential Basis for Extended Single-atom Layer Boron Sheets. Nat. Commun. 2014, 5, 6. 23. Pitochelli, A. R.; Hawthorne, M. F. The Isolation of the Icosahedral B12H12-2 Ion. J. Am. Chem. Soc. 1960, 82, 3228-3229. 24. Quandt, A.; Boustani, I. Boron Nanotubes. Chemphyschem 2005, 6, 2001-2008. 25. Rao, M. H.; Muralidharan, K. Closo-Dodecaborate B12H122- Salts with Nitrogen Based Cations and their Energetic Properties. Polyhedron 2016, 115, 105-110. 26. Szwacki, N. G.; Sadrzadeh, A.; Yakobson, B. I. B80 Fullerene: An Ab Initio Prediction of Geometry, Stability, and Electronic Structure. Phys. Rev. Lett. 2007, 98, 4.



Page 30 of 34

30 27. Tiritiris, I.; Schleid, T. The Dodecahydro-closo-dodecaborates M2B12H12 of the Heavy Alkali Metals (M = K+, Rb+, NH4+, Cs+) and their Formal Iodide Adducts M3IB12H12 (MI * M2B12H12 ). Z. Anorg. Allg. Chem. 2003, 629, 1390-1402. 28. Tiritiris, I.; Schleid, T. The Crystal Structure of Solvent-free Silver Dodecachloro-closododecaborate Ag2B12Cl12 from Aqueous Solution. Z. Anorg. Allg. Chem. 2003, 629, 581-583. 29. Tiritiris, I.; Schleid, T.; Muller, K.; Preetz, W. Structural investigations on Cs2B12H12. Z. Anorg. Allg. Chem. 2000, 626, 323-325. 30. Udovic, T. J.; Matsuo, M.; Unemoto, A.; Verdal, N.; Stavila, V.; Skripov, A. V.; Rush, J. J.; Takamura, H.; Orimo, S. Sodium Superionic Conduction in Na2B12H12. Chem. Commun. 2014, 50, 37503752. 31. Zhai, H. J.; Zhao, Y. F.; Li, W. L.; Chen, Q.; Bai, H.; Hu, H. S.; Piazza, Z. A.; Tian, W. J.; Lu, H. G.; Wu, Y. B.; Mu, Y. W.; Wei, G. F.; Liu, Z. P.; Li, J.; Li, S. D.; Wang, L. S. Observation of an All-Boron Fullerene. Nat. Chem. 2014, 6, 727-731. 32. Li, W.-L.; Chen, X.; Jian, T.; Chen, T.-T.; Li, J.; Wang, L.-S. From Planar Boron Clusters to Borophenes and Metalloborophenes. Nat. Rev. Chem. 2017, 1, 0071. 33. Chen, Q.; Li, W.-L.; Zhao, Y.-F.; Zhang, S.-Y.; Hu, H.-S.; Bai, H.; Li, H.-R.; Tian, W.-J.; Lu, H.-G.; Zhai, H.-J.; Li, S.-D.; Li, J.; Wang, L.-S. Experimental and Theoretical Evidence of an Axially Chiral Borospherene. ACS Nano 2015, 9, 754-760. 34. Popov, I. A.; Li, W. L.; Piazza, Z. A.; Boldyrev, A. I.; Wang, L. S. Complexes between Planar Boron Clusters and Transition Metals: A Photoelectron Spectroscopy and Ab Initio Study of CoB12- and RhB12. J. Phys. Chem. A 2014, 118, 8098-8105. 35. Romanescu, C.; Harding, D. J.; Fielicke, A.; Wang, L. S. Probing the Structures of Neutral Boron Clusters using Infrared/Vacuum Ultraviolet Two Color Ionization: B11, B16, and B17. J. Chem. Phys. 2012, 13, 6. 36. Sergeeva, A. P.; Popov, I. A.; Piazza, Z. A.; Li, W. L.; Romanescu, C.; Wang, L. S.; Boldyrev, A. I. Understanding Boron through Size-Selected Clusters: Structure, Chemical Bonding, and Fluxionality. Accounts Chem. Res. 2014, 47, 1349-1358. 37. Zhai, H. J.; Alexandrova, A. N.; Birch, K. A.; Boldyrev, A. I.; Wang, L. S. Hepta- and octacoordinate boron in molecular wheels of eight- and nine-atom boron clusters: Observation and confirmation. Angew. Chem.-Int. Edit. 2003, 42, 6004-6008. 38. Luo, X. M.; Jian, T.; Cheng, L. J.; Li, W. L.; Chen, Q.; Li, R.; Zhai, H. J.; Li, S. D.; Boldyrev, A. I.; Li, J.; Wang, L. S. B26: The Smallest Planar Boron Cluster with a Hexagonal Vacancy and a Complicated Potential Landscape. Chem. Phys. Lett. 2017, 683, 336-341. 39. Kroto, H. W.; Heath, J. R.; Obrien, S. C.; Curl, R. F.; Smalley, R. E. C60 - Buckminsterfullerene. Nature 1985, 318, 162-163. 40. Wang, Y. J.; Zhao, Y. F.; Li, W. L.; Jian, T.; Chen, Q.; You, X. R.; Ou, T.; Zhao, X. Y.; Zhai, H. J.; Li, S. D.; Li, J.; Wang, L. S. Observation and Characterization of the Smallest Borospherene, B28- and B28. J. Chem. Phys. 2016, 144, 7. 41. Prasad, D.; Jemmis, E. D. Stuffing Improves the Stability of Fullerenelike Boron Clusters. Phys. Rev. Lett. 2008, 100, 4. 42. Li, H.; Shao, N.; Shang, B.; Yuan, L. F.; Yang, J. L.; Zeng, X. C. Icosahedral B12-containing Core-shell Structures of B80. Chem. Commun. 2010, 46, 3878-3880. 43. Zhao, J. J.; Wang, L.; Li, F. Y.; Chen, Z. F. B80 and Other Medium-Sized Boron Clusters: Core Shell Structures, Not Hollow Cages. J. Phys. Chem. A 2010, 114, 9969-9972.


Page 31 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


31 44. De, S.; Willand, A.; Amsler, M.; Pochet, P.; Genovese, L.; Goedecker, S. Energy Landscape of Fullerene Materials: A Comparison of Boron to Boron Nitride and Carbon. Phys. Rev. Lett. 2011, 106, 4. 45. Li, F. Y.; Jin, P.; Jiang, D. E.; Wang, L.; Zhang, S. B. B.; Zhao, J. J.; Chen, Z. F. B80 and B101-103 Clusters: Remarkable Stability of the Core-shell Structures Established by Validated Density Functionals. J. Chem. Phys. 2012, 136, 8. 46. Kirk, R. W.; Timms, P. L.; Smith, D. L.; Airey, W. Perhalogenated Polyboron and Silicon-Boron Analogs of Borane. Dalton Trans. 1972, 13, 1392-1396. 47. Maier, A.; Hofmann, M.; Pritzkow, H.; Siebert, W. A Planar, Aromatic Bicyclo-tetraborane. Angew. Chem. Int. Ed. 2002, 41, 1529-1532. 48. Morrison, J. A. Chemistry of the Polyhedral Boron Halides and the Diboron Tetrahalides. Chem. Rev. 1991, 91, 35-48. 49. Pardoe, J. A. J.; Norman, N. C.; Timms, P. L.; Parsons, S.; Mackie, I.; Pulham, C. R.; Rankin, D. W. H. The Surprising Structures of B8F12 and B10F12. Angew. Chem. Int. Ed. 2003, 42, 571-573. 50. Szwacki, N. G.; Tymczak, C. J. B12Hn and B12Fn: Planar vs Icosahedral Structures. Nanoscale Res. Lett. 2012, 7, 1-6. 51. Timms, P. L.; Norman, N. C.; Pardoe, J. A. J.; Mackie, I. D.; Hinchley, S. L.; Parsons, S.; Rankin, D. W. H. The Structures of Higher Boron Halides B8X12 (X = F, Cl, Br and I) by Gas-phase Electron Diffraction and Ab Initio Calculations. Dalton Trans. 2005, 3, 607-616. 52. Trefonas, L.; Lipscomb, W. N. Crystal and Molecular Structure of Diboron Tetrafluoride, B2F4. J. Chem. Phys. 1958, 28, 54-55. 53. Knoth, W. H.; Muetterties, E. L.; Miller, H. C.; Chia, Y. T.; Sauer, J. C.; Balthis, J. H. Chemistry of Boranes .9. Halogenation of B10H10-2 + B12H12-2. Inorg. Chem. 1964, 3, 159-167. 54. Wunderlich, J. A.; Lipscomb, W. N. Structure of B12H12-2 Ion. J. Am. Chem. Soc. 1960, 82, 44274428. 55. Ivanov, S. V.; Peryshkov, D. V.; Miller, S. M.; Anderson, O. P.; Rappe, A. K.; Strauss, S. H. Synthesis, Structure, and Reactivity of AlMe2(1-Me-CB11F11): An AlMe2+ Cation-like Species Bonded to a Superweak Anion. J. Fluor. Chem. 2012, 143, 99-102. 56. Naganawa, H.; Suzuki, H.; Noro, J.; Kimura, T. Selective Separation of Am(III) from Lanthanides(III) by Solvent Extraction with Hydrophobic Field of "Superweak'' Anion. Chem. Commun. 2005, 23, 2963-2965. 57. Peryshkov, D. V. Direct Fluorination of K2B12H12 and Synthesis and Characterization of Metal Salts of B12F122-. PhD Thesis, Colorado State University, Fort Collins, Colorado, 2011. 58. Peryshkov, D. V.; Bukovsky, E. V.; Folsom, T. C.; Strauss, S. H. Solid-state Solvation and Anion Packing Patterns in X-ray Structures of Crystalline K2(solv)nB12F12 (solv = H2O2(aq), CH3OH, CH3NO2, and CH3CN). Polyhedron 2013, 58, 197-205. 59. Plesek, J. Potential Applications of the Boron Cluster Compounds. Chem. Rev. 1992, 92, 269-278. 60. Rohdenburg, M.; Mayer, M.; Grellmann, M.; Jenne, C.; Borrmann, T.; Kleemiss, F.; Azov, V. A.; Asmis, K. R.; Grabowsky, S.; Warneke, J. Superelectrophilic Behavior of an Anion Demonstrated by the Spontaneous Binding of Noble Gases to B12Cl11-. Angew. Chem.-Int. Edit. 2017, 56, 7980-7985. 61. Roll, M. F. Ionic Borohydride Clusters for the Next Generation of Boron Thin-films: Nano-building Blocks for Electrochemical and Refractory Materials. J. Mat. Res. 2016, 31, 2736-2748. 62. Soloway, A. H.; Tjarks, W.; Barnum, B. A.; Rong, F. G.; Barth, R. F.; Codogni, I. M.; Wilson, J. G. The Chemistry of Neutron Capture Therapy. Chem. Rev. 1998, 98, 1515-1562.



Page 32 of 34

32 63. Hopkins, W. S.; Carr, P. J. J.; Huang, D.; Bishop, K. P.; Burt, M.; McMahon, T. B.; Steinmetz, V.; Fillion, E. Infrared-Driven Charge Transfer in Transition Metal B12F12 Clusters. J. Phys. Chem. A 2015, 119, 8469-8475. 64. Lecours, M. J.; Marta, R. A.; Steinmetz, V.; Keddie, N.; Fillion, E.; O'Hagan, D.; McMahon, T. B.; Hopkins, W. S. Interaction of B12F122- with All-cis 1,2,3,4,5,6 Hexafluorocyclohexane in the Gas Phase. J. Phys. Chem. Lett. 2017, 8, 109-113. 65. Warneke, J.; Dulcks, T.; Knapp, C.; Gabel, D. Collision-induced Gas-phase Reactions of Perhalogenated Closo-dodecaborate Clusters - A Comparative Study. Phys. Chem. Chem. Phys. 2011, 13, 5712-5721. 66. Warneke, J.; Hou, G.-L.; Aprà, E.; Jenne, C.; Yang, Z.; Qin, Z.; Kowalski, K.; Wang, X.-B.; Xantheas, S. S. Electronic Structure and Stability of [B12X12]2– (X = F–At): A Combined Photoelectron Spectroscopic and Theoretical Study. J. Am. Chem. Soc. 2017, 139, 14749-14756. 67. Warneke, J.; Jenne, C.; Bernarding, J.; Azov, V. A.; Plaumann, M. Evidence for an Intrinsic Binding Force between Dodecaborate Dianions and Receptors with Hydrophobic Binding Pockets. Chem. Commun. 2016, 52, 6300-6303. 68. Hopkins, W. S. Determining the Properties of Gas-Phase Clusters. Mol. Phys. 2015, 113, 31513158. 69. Mac Aleese, L.; Simon, A.; McMahon, T. B.; Ortega, J. M.; Scuderi, D.; Lemaire, J.; Maitre, P. MidIR Spectroscopy of Protonated Leucine Methyl Ester Performed with an FTICR or a Paul Type Ion-Trap. Int. J. Mass Spectrom. 2006, 249, 14-20. 70. MacAleese, L.; Maitre, P. Infrared Spectroscopy of Organometallic Ions in the Gas Phase: From Model to Real World Complexes. Mass Spectrom. Rev. 2007, 26, 583-605. 71. Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci, B.; Petersson, G. A.; al., e. Gaussian 09 Revision D.01. In Gaussian, Inc. Wallingford CT 2009. 72. Becke, A. D. Density-functional Exchange-energy Approximation with Correct Asyptotic Behavior. Phys. Rev. A 1988, 38, 3098-3100. 73. Becke, A. D. Density-Functional Thermochemistry .3. The Role of Exact Exchange. J. Chem. Phys. 1993, 98, 5648-5652. 74. Andrae, D.; Haussermann, U.; Dolg, M.; Stoll, H.; Preuss, H. Energy-adjusted Ab Initio Pseudopotentials for the 2nd and 3rd Row Transition Elements. Theor. Chim. Acta 1990, 77, 123-141. 75. Rappoport, D.; Furche, F. Property-optimized Gaussian basis sets for molecular response calculations. J. Chem. Phys. 2010, 133, 11. 76. Dreuw, A.; Weisman, J. L.; Head-Gordon, M. Long-range charge-transfer excited states in timedependent density functional theory require non-local exchange. J. Chem. Phys. 2003, 119, 2943-2946. 77. Hay, P. J. Theoretical studies of the ground and excited electronic states in cyclometalated phenylpyridine Ir(III) complexes using density functional theory. J. Phys. Chem. A 2002, 106, 1634-1641. 78. Khomyakov, P. A.; Giovannetti, G.; Rusu, P. C.; Brocks, G.; van den Brink, J.; Kelly, P. J. Firstprinciples study of the interaction and charge transfer between graphene and metals. Phys. Rev. B 2009, 79, 12. 79. Glendening, E. D.; Landis, C. R.; Weinhold, F. NBO 6.0: Natural Bond Orbital Analysis Program. J. Comput. Chem. 2013, 34, 1429-1437.


Page 33 of 34 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


33 80. Zhang, G. Q.; Li, X. W.; Li, Y.; Chen, D. Z. Electron density characteristics and charge transfer effect of hydrogen bond O-H center dot center dot center dot Pt(II): atoms in molecules study and natural bond orbital analysis. Mol. Phys. 2013, 111, 3276-3282. 81. Cappelletti, D.; Ronca, E.; Belpassi, L.; Tarantelli, F.; Pirani, F. Revealing Charge-Transfer Effects in Gas-Phase Water Chemistry. Accounts of Chemical Research 2012, 45, 1571-1580. 82. Fagiani, M. R.; Zeonjuk, L. L.; Esser, T. K.; Gabel, D.; Heine, T.; Asmis, K. R.; Warneke, J. Opening of an icosahedral boron framework: A combined infrared spectroscopic and computational study. Chemical Physics Letters 2015, 625, 48-52. 83. Ortega, J. M.; Glotin, F.; Prazeres, R. Extension in Far-infrared of the CLIO Free-electron Laser. Infrared Phys. Technol. 2006, 49, 133-138. 84. Fu, W.; Carr, P. J. J.; Lecours, M. J.; Burt, M.; Marta, R. A.; Steinmetz, V.; Fillion, E.; McMahon, T. B.; Hopkins, W. S. Intramolecular Cation-Pi Interactions in Protonated Phenylalanine Derivatives. Phys. Chem. Chem. Phys. 2017, 19, 729-734. 85. Kramida, A.; Ralchenko, Y.; Reader, J. NIST Atomic Spectra Database (version 5.2). National Institute of Standards and Technology: Gaithersburg, MD, 2014. 86. Pirani, F.; Giulivi, A.; Cappelletti, D.; Aquilanti, V. Coupling by charge transfer: role in bond stabilization for open-shell systems and ionic molecules and in harpooning and proton attachment processes. Mol. Phys. 2000, 98, 1749-1762. 87. McDonald, R. N.; Bianchina, E. J.; Tung, C. C. Electron photodetachment of cyclopentadienylidene anion radical in a flowing afterglow apparatus: EA and .DELTA.Hf.degree. of cyclopentadienylidene. J. Am. Chem. Soc. 1991, 113, 7115-7121. 88. Lecours, M. J.; Chow, W. C. T.; Hopkins, W. S. Density Functional Theory Study of RhnS0,+/- and Rhn+10,+/- (n=1-9). J. Phys. Chem. A 2014, 118, 4278-4287. 89. Zhang, G.; Musgrave, C. Comparison of DFT Methods for Molecular Orbital Eigenvalue Calculations. J. Phys. Chem. A 2007, 111, 1554-1561. 90. McKee, M. L.; Wang, Z. X.; Schleyer, P. V. Ab Initio Study of the Hypercloso Boron Hydrides BnHn and BnHn-. Exceptional Stability of Neutral B13H13. J. Am. Chem. Soc. 2000, 122, 4781-4793. 91. Shen, Y.-F.; Xu, C.; Cheng, L.-J. Deciphering Chemical Bonding in BnHn2- (n = 2-17): Flexible Multicenter Bonding. RSC Adv. 2017, 7, 36755-36764. 92. Carr, P. J. J.; Lecours, M. J.; Burt, M.; Marta, R. A.; Steinmetz, V.; Fillion, E.; Hopkins, W. S. ModeSelective Laser-Control of Palladium Catalyst Decomposition. J. Phys. Chem. Lett. 2018, 9, 157-162 93. Shaffer, C. J.; Revesz, A.; Schroder, D.; Severa, L.; Teply, F.; Zins, E. L.; Jasikova, L.; Roithova, J. Can Hindered Intramolecular Vibrational Energy Redistribution Lead to Non-Ergodic Behavior of Medium-Sized Ion Pairs? Angew. Chem. Int. Ed. 2012, 51, 10050-10053.



Page 34 of 34

34

TOC Graphic


Infrared-Driven Charge-Transfer in Transition Metal-Containing

Recommend Documents