Planar Octagonal Tetranuclear Cobaltacarborane Macrocycle [(Î·5

Subscriber access provided by READING UNIV

Article 5

Planar Octagonal Tetranuclear Cobaltacarborane Macrocycle [(#CMe)Co(2,3-EtCBH-5-C#C-7-C#/C)] as 2D Nonlinear Optics: UltraHigh-Response and Multistate Controlled Cubic NLO Switch 5

5

2

2

4

3

4

Hong-Qiang Wang, Li Wang, Jin-Ting Ye, Haiming Xie, and Yongqing Qiu J. Phys. Chem. C, Just Accepted Manuscript • DOI: 10.1021/acs.jpcc.7b10144 • Publication Date (Web): 30 Nov 2017 Downloaded from http://pubs.acs.org on December 6, 2017

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 free 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 accessible to all readers and 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.

The Journal of Physical Chemistry C 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 46 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

Planar

Octagonal

Tetranuclear

Cobaltacarborane

[(η5-C5Me5)Co(2,3-Et2C2B4H3-5-C≡C-7-C≡C)]4

Macrocycle

for 2D Nonlinear

Optics: Ultra-High-Response and Multistate Controlled Cubic NLO Switch

Hong-Qiang Wang,† Li Wang,† Jin-Ting Ye,† Hai-Ming Xie†‡ and Yong-Qing Qiu*†‡

†

Institute of Functional Material Chemistry, Faculty of Chemistry, Northeast Normal University,

Changchun 130024, Jilin, People’s Republic of China ‡

National & Local United Engineering Laboratory for Power Battery, Faculty of Chemistry,

Northeast Normal University, Changchun 130024, Jilin, People’s Republic of China

1

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 46

ABSTRACT Owing to the potential application in the development of new nonlinear optical (NLO) materials, metallomacrocycles have currently attracted considerable attention. The

unusual

24

atoms

{C16B8}

cobaltacarborane

(Cp*=η5-C5Me5)

[Cp*Co(2,3-Et2C2B4H3-5-C≡C-7-C≡/C)]4

featured

ring

4

highly

symmetrical, 2D planar, tetratruncated square architectures have been investigated and characterized compared to its 1D rod-like dinuclear building blocks 2a [Cp*Co(2,3-Et2C2B4H3-7-C≡C)]2, 2b [Cp*Co(2,3-Et2C2B4H3-5-C≡C)]2 and the 0D sandwich monomer 1 Cp*Co(Et2C2B4H4) by density functional theory. Calculations of geometric and electronic structures, UV-Vis absorption spectra, polarizabilities (αave) and second hyperpolarizabilities (γtot) have been performed herein with the aim of rationalizing the structure-property relationship and providing a novel high-performance NLO molecular materials. It is found that the tetranuclear species present long-range bidirectional charge transfer behaviors, leading to an excellent 2D NLO character along with a very large γtot value approached 639.8 ×10-36 esu. Furthermore, because of the multipath of redox process, related molecules can also be used as efficient multistate controlled cubic NLO switches. Overall, we envision that the fascinating architectures introduced in the present work will paves the way toward the rational design of such kind metallomacrocycles for novel functional NLO materials.

2


Page 3 of 46 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


1. INTRODUCTION Metallacarboranes are a class of polyhedral clusters comprising a few to several dozens of carbon, boron, hydrogen, and metal atoms in various combinations.1 It can be generally recognized as carboranes with one or more B(H) vertices being replaced by metal ones (endo-metallacarboranes), or linked to the periphery of the cage framework (exo-metallacarboranes).2,

3

Owing to their unique physicochemical

properties (e.g., aesthetically appealing structures, synthetic versatility, chemical and thermal stability, and well-developed derivative chemistry, etc.), metallacarborane chemistry have received a great deal of attention over the last several decades.4-8 Now a mature field, these cluster complexes are finding a wide range of applications in materials science, encompassing molecular motor,9 dye-sensitized solar cells (DSSCs),10 luminescent materials,11-13 boron neutron capture therapy (BNCT),14-16 nonlinear optical (NLO) materials,17-19 and others. Cobaltacarborane metallacarborane

Cp*Co(Et2C2B4H4)

sandwich

complex,

(Cp*=η5-C5Me5)

which

is

analogue

is of

a

typical

metallocene.

Alternatively, it can also be regarded as organometallic complex in which a metal ion is facially coordinated to carborane and cyclopentadienyl ligand to form a stable closed-shell diamagnetic system with 18-electron (double-decker sandwich), as in ferrocene (Fc) and ferracarborane (chart 1). On the basis of preceding publications, Russell N. Grimes’ research group have used this stable sandwich unit as useful synthon in the construction of a variety of polynuclear metallacarborane systems.5, 20-22

Yao et al. described the stepwise assembly of a tetranuclear complex 3



[Cp*Co(2,3-Et2C2B4H3-5-C≡C-7-C≡/C)]4

that

contains

Page 4 of 46

four

identical

cobaltacarborane clusters and features a planar octagonal (tetratruncated square) macrocycle.23 Notably, it has been reported that, in this fascinating architecture, there are significant intramolecular electronic interactions and metal-metal communication between the four cobalt centers. In view of the distinguishing characteristics, it shows great potential to serve as a novel NLO material with high-performance. Prior to our study, we have proposed a new strategy for explore a series of multinuclear “staircase” ferracarborane oligomers.24 From the calculated results,

we

found

that,

increasing

sandwich

units

n

in

H-[(Et2C2B4H3)Fe(η6-C6H5)]n-H (n=1, 2, 3) from 1 to 2 or 3, their second order NLO response can be significantly enhanced. The first hyperpolarizabilities (βtot) approach 26119.9 × 10-30 esu and the “ON/OFF” redox switching ratio is as large as 916.9. Based on the above, there are several questions: (i) Could these cobaltacarboranes also underlying appreciable dramatic hyperpolarizabilities? (ii) If the NLO properties for these complexes can be manipulated by the arrangement of sandwich unit and its numbers? From these guidelines, it prompted us to use the macrocycle as a parent platform to probe into the molecular electronic structures and NLO activities of such complexes, which can help the experimentalists to modify the structure of these cobaltacarboranes to get novel optical materials.

4


Page 5 of 46 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


Chart 1. Chemical structures of cobaltacarborane, ferrocene and ferracarborane sandwich complexes with formal charges shown for each part.

In the present paper, the tetranuclear cobaltacarborane (24 atoms {C16B8} ring) [Cp*Co(2,3-Et2C2B4H3-5-C≡C-7-C≡/C)]4 was named as complex 4 (Figure 1a). Attempts to further unravel the origin of these electrochemical and photophysical behaviors, we extend our electrochemical studies to a wider series of dinuclear species. Because both of diethynyl-linked isomers can be regarded as building blocks of the tetramer, having different molecular architectures (connection through the apical B(7) atoms [Cp*Co(2,3-Et2C2B4H3-7-C≡C)]2 as 2a; intercluster connection occurs through the equatorial B(5) atoms [Cp*Co(2,3-Et2C2B4H3-5-C≡C)]2 as 2b). And, the small sandwich monomer Cp*Co(Et2C2B4H4) (1) was also prepared as a counterpart to trace the nature of electron-transfer within the individual unit. From another point of view, the presence of redox-active metal centers provides extensive opportunities for switching of NLO responses. Therefore, their oxide (1+, 2a+, 2a2+, 2b+, 2b2+, 4+, and 44+) and reduced states (1-, 2a-, 2a2-, 2b-, 2b2-, 4-, 42-, and 44-) were further investigated. Herein, we performed theoretical studies on these unusual molecules, to describe the geometric and electronic structures, electronic absorption spectra, polarizability, third order NLO response and second hyperpolarizability density of the complexes. The specific aim in this work is to rationalize the 5



relationship between the structures and NLO properties, and propose a smart member of NLO materials with unusual architectures.

Figure 1. (a) Calculation models of the studied neutral complexes. (b) Overlay of the molecular scaffolds for DFT-optimized structure (red) with the structure determined by X-ray crystallography from ref. 23 (white) of complex 4. (c) The molecular structure (thermal ellipsoids) diagram of complex 4 showing the atom labeling scheme.

2. COMPUTATIONAL DETAILS Unless otherwise stated, all the density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations reported herein were carried out using Gaussian 09W program package.25 The equilibrium structures of all complexes were obtained from the geometry optimization using B3LYP functional 6


Page 6 of 46

Page 7 of 46 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


with no constraints for symmetry. B3LYP uses well-known three parameters functional of Becke’s, including 20% Hatree-Fock exchange contribution with non-local correlation suggested by Lee, Young, and Parr.26 We have adopted the 6-31G* basis set for C, B and H atoms and the Los Alamos double-ξ (LANL2DZ) effective core potential (ECP) basis set for Co atom.27-29 At the microscopic level, the response of a molecule to a homogeneous static electric field can be represented by the following Taylor expansions:30 E ( F ) = E 0 − µ i Fi −

1 1 1 α ij Fi F j − β ijk F i F j F k − γ ijkl F i F j F k Fl − ⋅ ⋅ ⋅ 2 6 24

(1)

In this expression, E0 is the energy of the molecule in the absence of an electric field,

µi is permanent dipole moment along the i direction of the molecule, α ij is polarizability, β ijk is first hyperpolarizability, γ ijkl is second hyperpolarizability. And i, j, k, and l designate the different components along the x, y and z directions, respectively. The isotropic average polarizability ( α ave ) was calculated according to the equation:

α = α ave =

1 (α xx + α yy + α zz ) 3

(2)

Anisotropy of polarizability can be obtained by

∆α = [(α xx − α yy ) 2 + (α xx − α zz ) 2 + (α yy − α zz ) 2 + 6(α xy2 + α xz2 + α yz2 )] 2

(3)

The total averaged second hyperpolarizability ( γ tot ) was defined as:

γ = γ tot =

1 (γ xxxx + γ yyyy + γ zzzz + 2γ xxyy + 2γ xxzz + 2γ yyzz ) 5

(4)

With regard to the calculation of the hyperpolarizability, choosing a proper method is crucial. Functionals and basis sets have to be incorporated to meet the requirements of both precision and computational efficiency. Therefore, in this 7



Page 8 of 46

chapter, we have calculated the (hyper)polarizabilities using six functionals, including four conventional hybrid functional B3LYP, PBE1PBE,31,

32

BHandHLYP,33

M062X34 and two range-separated (RSE) exchange functionals CAM-B3LYP35 and ωB97XD36. It is worthy of note that the theoretically calculated values of (hyper)polarizabilities are also basis set sensitive. Various basis sets, (i.e., 6-31G*, 6-31+G*, 6-31++G*, 6-31G**, 6-31+G**, 6-31++G**, 6-311G*, 6-311+G* and 6-311++G* incorporate LANL2DZ and Stuttgart/Dresden double-ζ (SDD)37 basis set for Co atom have been used to check the consistency of our calculations. The TD-DFT method has been confirmed to be an effective candidate for the understanding and predicting the behavior of electronic transition properties in quantum chemistry owing to its efficiency and accuracy. To find a suitable methods for computing the excitation energies of the current systems, the absorption spectra were simulated by means of various methods (TD-B3LYP, TD-PBE1PBE, TD-BHandLYP ，

TD-M062X, TD-CAMB3LYP and TD-ωB97XD). Integral

equation polarizable continuum model (IEPCM) has been account for the dichloromethane solution.

3. RESULTS AND DISCUSSION 3.1. Geometric and Electronic Structures. DFT calculations employing the B3LYP/6-31G(d)/LANL2DZ method were performed for the geometry optimization. Equilibrium structures of complexes 1-4 are shown in Figure S1-S3 (in Supporting Information) and Figure 1c. Intriguingly, 8


Page 9 of 46 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


complex 4 is centrosymmetric and essentially planar which can be deemed as two-dimensional (2D) structure. The edge lengths for this planar octagon are 6.841 Å (-C≡C-C≡/C- linkage, B5~B17), 1.749 Å (-B-B- linkage, B5-B7) and 6.832 Å (-C≡C-C≡/C- linkage, B7~B12), respectively (Table S1). And the edge lengths for the rectangle defined by the centroids of the four {C2B3} carborane rings are as large as 9.141 Å (d1) and 9.490 Å (d2). A comparative analysis of geometrical parameters reveal that the primary bond lengths and distances (d1 and d2) are nearly equal to the X-ray crystallographic study,23 which the absolute deviation △l1 are 0.001-0.023 Å and 0.005-0.022 Å, respectively (cf. Figure 1b). The small deviations indicate that the geometrical calculations are qualitatively reliable for our current systems. Furthermore, we have also compared the optimized geometry of one-dimensional (1D) dinuclear species 2a and 2b to the complex 4. For complex 2a, the differences of selected bond lengths and distance values △l2 are only less than 0.003 Å and 0.091 Å with respect to tetranuclear species. And the differences △l3 are less than 0.003 Å and 0.022 Å for complex 2b. These results can further demonstrate that the geometry structures for such metallacarborane sandwich systems are sufficiently robust and hardly changed in the synthesis progress.

9



Figure 2. Graphical representation for MEP distributions of complexes 1-4.

Molecular electrostatic potential (MEP) is simple quantitative three dimensions (3D) plots of the measurement of electrostatic potential on constant electron density surface. It is a very efficient method to provide comprehensive intuitive about the polarization and charge distribution within molecules by color-coded maps. In this context, the MEP using the Bader charge model was plotted on the van der Waals (vdW) surface (the isodensity surface of ρ=0.001 e/bohr3).38 As graphically depicted in Figure 2, in the individual sandwich complex 1, the maximum negative potential (red) region is mainly located on carborane moiety, while maximum positive potential (blue) region is largely found on the Cp* moiety. It exhibits a nearly identical behavior with the ferracarborane monomer (Et2C2B4H4)Fe(η6-C6H6).24 However, when coming to the diethynyl-linked polynuclear metallacarboranes 2a-4, the region with more negative charge is visualized in the diethynyl bridges primarily and carborane moieties secondarily, whereas the electropositive potential is largely 10


Page 10 of 46

Page 11 of 46 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


distributed at the Cp* groups. In addition, it is worth noting that, for complex 4, the difference between minima and maxima values of MEP is larger with respect to complexes 1-2b. This conspicuous charge separation means that complex 4 is more likely to present an obvious intramolecular charge transfer during electronic excitation. The highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) were usually regarded as a vital reference to reflect the charge transfer characters of a system, and will be helpful for understanding structure-property relations.39,

40

Nevertheless, the visual study on the frontier

molecular orbitals (FMOs) diagram can only draw qualitative conclusion. To evaluate it in a quantitative way, we further proposed the composition analysis as a supportive method which is computed by Multiwfn 3.4.41 Let us first start from the complex 1. As depicted in Figure 3a, the HOMO is delocalized over the carborane and Co moieties, whereas the LUMO is predominantly centered on the whole molecule. From the compositions analysis, the contribution for each parts are Cb: 63.65%, Co: 31.13%, Cp*:5.21% in HOMO (Figure 3b and Table S2), while LUMO is contributed by Cb: 32.00%, Co: 43.49%, Cp*:24.51% (Figure 3c and Table S3), respectively. (In this literature, Cb, Co, Cp*, x-bridge and y-bridge represent the carborane, Co atom,

η5-C5Me5 and the two -C≡C-C≡C- linker along the x-axis and y-axis, respectively.) It reveals that the electron density would flow from the metallacarborane cluster to the Co and Cp* moieties within the individual sandwich unit. With regard to 1D complexes 2a and 2b, they have the similar distributions for HOMO and LUMO, 11



notwithstanding the different vertexes linked type. The HOMO located on the diethynyl linker and carborane moieties with the 80.23% (2a) and 91.26% (2b) compositions. LUMO spread over the Co and Cp* moieties contributed by 58.54% (2a) and 67.41% (2b). Thus, the diethynyl linker and carborane fragments display the electron donor character, and Co and Cp* fragments display the electron acceptor character. Coming to the 2D complex 4, some interesting insights can be perceived from the FMOs. Electron density of the HOMO is largely located on the the y-bridge and carborane fragments with 90.94% percentage (y-bridge: 57.68%, Cb: 33.26%). On the contrary, for the LUMO, the x-bridge, Co and Cp* moieties are the mainly contribution as 70.95%. It suggests that, compared to the 0D and 1D complexes, 2D complex 4 can obviously enlarge the amplitude of electron distribution between HOMO and LUMO, leading to a long-range intramolecular charge transfer. Typically, the energy levels of the FMOs and HOMO-LUMO energy gap (Egap) were important parameters which could properly effect the NLO properties.42, 43 For complexes 1-4, noteworthy is that the HOMO energy levels is significantly enhanced from -5.80 eV to -4.46 eV (Table S4). By contrast, there is little difference on the LUMO energy levels (-1.28 eV ~ -1.59 eV). Thus, their Egap values were decreased in the following order: Egap (1) > Egap(2a) > Egap(2b) > Egap(4) (Figure 3d). It forecasts that, for current systems, their relevant NLO response may be optimized by increasing the numbers of sandwich unit.

12


Page 12 of 46

Page 13 of 46 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


Figure 3. (a) Contour surface diagrams of FMOs of complexes 1-4. (b) Percentage composition of HOMO in terms of carborane, Co atom, Cp*, x-bridge and

y-bridge fragments. (c) Percentage composition of LUMO in terms of carborane, Co atom, Cp*, x-bridge and y-bridge fragments. (d) Schematic energy levels of HOMO and LUMO for the studied complexes.

3.2. Absorption Spectrum. In order to test the hypothesis discussed above and shed light on the nature of the charge transfer characteristic, we present herein UV-Vis spectroelectrochemical analysis on the studied complexes by TD-DFT calculation. To choose a reliable functional for reasonably improve our calculations, six different functionals B3LYP, PBE1PBE, BHandHLYP, M06-2X, CAM-B3LYP and ωB97XD with the same basis set were employed in dichloromethane solution and gas phase. Obviously, although 13



they give different values for the oscillator strength (fos), all of these functionals contain two strong absorption peaks (Figure 4). Turning our attention to the maximal absorption wavelengths (λmax), it can be seen that the λmax values for different functionals increase as the order of ωB97XD (495 nm) < CAM-B3LYP (496 nm) < B3LYP (504 nm) < PBE1PBE (507 nm) < BHandHLYP (583 nm) < M06-2X (664 nm) (Table S5). All of the global hybrid functional (B3LYP, PBE1PBE, BHandHLYP and M06-2X) contain relative larger values in comparision to the RSE exchange functionals (CAM-B3LYP and ωB97XD). It shown closely related to the amount of Hartree-Fock (HF) exchange weighting. Increasing the percentage of HF exchange, there is a substantial bathochromic shift of the absorption spectrum. (Noteworthy is that the HF exchange weighting for each functionals are B3LYP (20%), PBE1PBE (25%), BHandHLYP (50%) and M062X (54%), respectively.) Actually, this overestimation is because of the over-polarisation problem caused by traditional global hybrid functionals within the TD-DFT framework.44, 45 To solve this problem, the RSE exchange functionals that include nonconstant percentage of HF exchange were properly introduced.46-48 As expected, the simulated UV-Vis absorption spectra archived from CAM-B3LYP (λmax = 496 nm) and ωB97XD (λmax = 495 nm) are in satisfactorily agreement with the available experimental data (λmax = 464 nm).23 Hence, in the following discussion, we employed the reliable TD-ωB97XD method to studied the remaining complexes.

14


Page 14 of 46

Page 15 of 46 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


Figure 4. Comparison of the absorption spectra of complexes 4 computed by various functionals of theory.

The principal TD-DFT electronic transition parameters along with charge density difference (CDD) maps for the crucial singlet excited states were compiled in Table 1. To verify the definition of crucial excited state is trustworthy, sum-over-state (SOS) investigation has been further conducted within the framework of the SOS perturbation theory.49-51 In this paper, we employed the full SOS expression for evaluating second hyperpolarizability. The explicit SOS equation for second hyperpolarizability γ is (all units are in a.u.):

γ ABCD (− ωσ ; ω1 , ω 2 , ω 3 ) = P[ A(− ωσ ), B(ω1 ), C (ω 2 ), D (ω 3 )](γ I − γ II ) ∧

γI =∑ i ≠0

∑ j ≠0

µ 0Ai µ ijB µ Cjk µ kD0 ∑ k ≠ 0 (∆ i − ωσ )(∆ j − ω 2 − ω 3 )(∆ k − ω 3 ) 15



µ0Ai µiB0 µ0Cj µ Dj0 γ = ∑∑ i ≠ 0 j ≠ 0 (∆ i − ωσ )(∆ i − ω1 )(∆ j − ω3 ) II

Page 16 of 46

(5)

∧

where, µijA = 〈i µ A j 〉 , µijA = µ ijA − µ 00A δ ij and ωσ = ∑ ωi ; A,B,C... denote one of i

directions {x, y, z}; ω is energy of external fields, ω=0 corresponds to static electric ∧

field; ∆ i stands for excitation energy of state i with respect to ground state 0. P is permutation operator. µ ijA is A component of transition dipole moment between state ∧

i and j; when i=j the term simply corresponds to electric dipole moment of state i. µ is dipole moment operator. The advantage for the SOS method is that it can separate the contribution to the hyperpolarizabilities from different excited states. The quantitative variations and convergent behaviors of the γtot values with the number of excited states have been rendered in Figure 5. In this paper, we performed 100 excited states for avoiding undesirable truncation error. One can see that, when the number of states increased to 100, the γtot values have mostly converged to a constant value following the order of 1 (4.81 × 104 a.u.) < 2b (6.92 × 105 a.u.) < 2a (1.72 × 106 a.u.)
PBE1PBE > M06-2X ≈ CAM-B3LYP ≈ ωB97XD > BHandHLYP. Obviously, the B3LYP and PBE1PBE method provide the largest numerical outcomes accompanied by 2.04% and 1.19% overestimation for αave, as well as 36.25% and 22.56% for γtot amplitudes, respectively (Figure 7b). On the contrary, BHandHLYP produced the smallest results along with -2.45% (αave) and -7.57% (γtot) underestimations. Nearly equal quantitive values can be observed for the remaining three functionals M06-2X, CAM-B3LYP and ωB97XD. Furthermore, γ one can easily seen that the magnitude of RDFunc (-7.57% ~ 36.25%) is much larger α than the RDFunc (-2.45% ~ 2.04%) values, suggesting that γ is more sensitive to

functional as compared to α quantity. This is on account of the polarizability is the second derivative of the molecular energy with respect to the strength of the applied electric field, whereas second hyperpolarizability is a fourth rank tensor (according to eq. 1 given in 2. COMPUTATIONAL DETAILS section ). To the end, we can safely conclude that, the M06-2X, CAM-B3LYP and ωB97XD functionals are more suitable to evaluate the NLO properties for our current systems.

22


Page 22 of 46

Page 23 of 46 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


α Figure 7. Comparisons of αave and γtot values (a.u.) (a), as well as RDFunc and γ results (b) of complex 1 calculated by the 6-31+G*/LanL2DZ basis set using RDFunc

various functionals.

The choice of appropriate basis sets for theoretical computations is another major issue in modern. Hence, at the background, we calculated the αave and γtot values at the CAM-B3LYP level of theory using various basis sets (compiled in Table S8 and S9). In a similar way, the relative deviation of αave and γtot values computed by different α γ basis sets ( RDBS and RDBS ) are also presented for comparison. The quantity can be

obtained by α RDBS =

α BS − α 6−31+G* × 100% α 6−31+G*

(9)

γ RDBS =

γ BS − γ 6−31+ G* × 100% γ 6−31+G*

(10)

As proposed in Figure 8, we divided all the results into four groups to distinguish the role of polarization functions, diffuse functions, split valence and effective core potential in influencing the numerical outcomes, respectively. The first thing comes into sight is that the values obtained by 6-31G*, 6-31G** and 6-311G** are much 23



α smaller than other results (Figure 8a). This catastrophic deviation ( RDBS : -7.32%, γ -6.40% and -1.78%; RDBS : -75.62%, -75.64% and -54.79%) is ascribed to the

absence of diffuse functions (Figure 8b). Secondly, as the number of diffuse functions goes up, the magnitude of both the αave and γtot also present a monotonic increase. However, there are no significant changes taking place with the diffuse functions from single to double (6-31+G* vs. 6-31++G*, 6-31+G** vs. 6-31++G**, and 6-311+G** vs. 6-311++G**), indicating that the single diffuse functions is indispensable and adequate. Compared between Group 1 with Group 2 separately, the absolute difference of 6-31G**, 6-31+G** and 6-31++G** with respect to the 6-31G*, 6-31+G* and 6-31++G* are 2.26 a.u., 2.15 a.u. and 2.14 a.u. for the αave amplitudes; and -6.73 a.u., 293.02 a.u. and 311.88 a.u for γtot values, respectively. It reveals that the calculated results depend little on the choice of polarization functions for the studied case. Coming to the comparison between Group 1 with Group 3, the results for the triple-ζ basis set are slightly smaller than relative double split ones. But, the αave and γtot for large 6-311++G* basis set are approximately equal to 6-31+G* ones with 1.41% and 1.40% relative deviations, demonstrated the 6-31+G* basis set is reliability enough. Moreover, to addressed the performance of LanL2DZ ECP for Co atom, the SDD basis set was further employed for comparative analysis. Inspection of α Figure 8, the results of SDD and LanL2DZ are very close to each other ( RDBS : γ -0.01% and RDBS : 0.17%), suggesting that the choice of ECP basis set have little

influence on the (hyper)polarizabilities. Consequently, the 6-31+G*/LanL2DZ basis set has proved to be a promising tool in treating the NLO properties in our case. 24


Page 24 of 46

Page 25 of 46 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


α γ Figure 8. Comparisons of αave and γtot values (a.u.) (a), as well as RDBS and RDBS

results (b) of complex 1 calculated by CAM-B3LYP functional with various basis sets.(SDD represents the 6-31+G*/SDD basis set; others are in combination with LanL2DZ basis set)

To sum up, taken together these results demonstrated above, the excellent coupling of functionals and basis sets can give credit to choose a desired method for evaluating the NLO response. Considering the calculation cost, the particularly advantageous CAM-B3LYP/6-31+G*/LanL2DZ will be employed in this work for the subsequent calculations. 25



3.3.2. Polarizability. Turning our attention to the quantitive magnitude, the data shows that both αave and △α results increase as the order of 1 < 2b < 2a < 4 (Table 2; components of α are summed in Table S10). The αave value of complex 4 approached 188.2 × 10-24 esu, which is 1.9 times higher than the known large values for C72 fullerene (677 a.u.)56 and 2.3 times larger than the boron-heterofullerene-(super)alkali dyad (K3O-BC59) (560 a.u.).57 (It should be mentioned that the conversion relation between atomic units and electrostatic units for α is 1 a.u. = 1.4818 × 10-25 esu.) Besides, the αave values of

2a (92.2 × 10-24 esu) and 2b (89.5 × 10-24 esu) are much of a size, which are almost half the magnitude of complex 4. For understanding the origin of the αave values, a physical property of the relative electronic spatial extent was introduced. characterizes the electron density volume around the molecule.58 Hence, the more diffuse electron density, the larger values lead to a larger αave result. Increasing the molecular size from 1 to 4, are following as 1 (7164.6 a.u.) < 2b (45814.5 a.u.) < 2a (53731.2 a.u.) < 4 (176908.1 a.u.), which shows near-perfect linear correlation with the polarizabilities αave.

26


Page 26 of 46

Page 27 of 46 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


Table 2. The electronic spatial extents (103 a.u.), isotropic average polarizability α ave (10-24 esu), anisotropy of polarizability △α (10-24 esu), second hyperpolarizabilities γtot (10-36 esu) and components of γ values (10-36 esu) of the studied complexes computed at the CAM-B3LYP/6-31+G* (LanL2DZ for Co atom) level. complex

αave

△α

γxxxx

γyyyy

γzzzz

γtot

1

7.2

36.4

6.4

16.7

23.2

23.0

23.8

2a

53.7

92.2

69.5

1164.1

43.7

41.8

278.1

2b

45.8

89.5

45.8

872.6

29.6

42.5

241.0

4

176.9

188.2

106.4

1620.6

1258.5

61.3

639.8

3.3.2. Second Hyperpolarizability. Coming the second hyperpolarizability results (Table 2), as expected from earlier prediction, the calculated γtot values of complexes 1-4 increase as the order of γtot (1) < γtot (2b) < γtot (2a) < γtot (4), which is also found favorable identical to the SOS calculations. The magnitude γtot values of complexes 2a (278.1 × 10-36 esu) and 2b (241.0 ×10-36 esu) are much larger than that of complex 1 (23.8 × 10-36 esu), which means that introducing the diethynyl π-conjugation extension can significantly improve the cubic NLO response. (Notably，the calculated values in atomic units for γ are converted into electrostatic units according to 1 a.u. = 5.0367 × 10-40 esu.) Further, the difference between the two dinuclear isomers of 2a and 2b demonstrate that the second hyperpolarizabilities are strongly influenced by the type of different vertex 27



Page 28 of 46

connection. It may be caused by the discrepancy of the CT behavior. Among them, tetranuclear cobaltacarborane 4 possesses the largest γtot result, almost 2.3 and 2.7 times with respect to dinuclear species 2a and 2b, as well as 27.0 times compared to sandwich monomer 1, respectively. To address the original contribution to the hyperpolarizability, we make the focus on the tensorial components (Table S11). For 1D complexes 2a and 2b, γxxxx is the principal component with respect to the rest, resulting from the major unidirectional CT transition and their linear molecule structure paralleled to the dipolar x axis (Figure S2 and S3). Significantly, due to 2D planar construction of complex 4, it shows that both the γxxxx and γyyyy present the dominant contributions, while the other tensorial components point to z axis like γzzzz are negligible. This phenomenon is primarily attributable to its bidirectional CT behavior. These properties suggest tetranuclear cobaltacarborane macrocycle 4 has the special potential to form high-performance 2D NLO materials. In order to examine the spatial contributions of electrons to the third-order NLO response, we performed the second hyperpolarizability density analysis in this context. The γ-density, ρxxx and ρyyy, are the third-order derivative of the electron density for each part with respect to the electric field along the x and y direction, respectively. They are defined according to eq. 11:59, 60 ρxxx (r ) = ( 3)

∂ 3 ρ (r ) ∂Fx ∂Fx ∂Fx

F =0

ρ yyy(3) (r ) =

∂ 3 ρ (r ) ∂Fy ∂Fy ∂Fy

F =0

(11)

And the γ values are given by:

γ xxxx = −

1 3） − ρ（xxx (r )xdr 3! ∫

γ yyyy = −

1 3） − ρ（yyy (r ) ydr 3! ∫

28


(12)

Page 29 of 46 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


In this section, we only focus on the description of local contributions of electrons to the primary tensorial components γxxxx and γyyyy. The isosurface maps of ( 3) ( 3) ( 3) ( 3) ρ xxx and ρ yyy combined with as well as − xρ xxx and − yρ yyy plots rendered by

VMD 1.9.1 program61 together with corresponding γ values for the neutral complexes

1-4 have been provided in Figure 9. At the first glance of Figure 9a, the positive (cyan) and negative (orange) γ densities give nearly equivalent allocations. In complex 2a-4, ( 3) the positive γ-density ρ xxx primarily located on the left sides, whereas the negative

( 3) ones is mainly distributed in the right sides. For the ρ yyy of complex 4, the positive

and negative allocations are mainly from the top and bottom edges. Specifically, it must be borne in mind that, when calculate the γ values, the positive γ-densities are closely correlated with the coordinate position of origin. For all of the complexes, the negative densities are pointed to the positive direction of the coordinate axis, i.e. x+ ( 3) ( 3) ( 3) ( 3) for ρ xxx and y+ for the ρ yyy . Consequently, their results of − xρ xxx and − yρ yyy

function would be principally positive values. To get a more intuitive insight, the ( 3) ( 3) and − yρ yyy plots were further introduced (shown in Figure 9b). It is clearly − xρ xxx

found that, for all of the complexes, the region of positive contributions (cyan) ( 3) ( 3) dominate the − xρ xxx and − yρ yyy function, spreading all over the molecule and

prevailing over relevant negative parts (orange). As a consequence, the components γxxxx and γyyyy present a relative large positive values. On the other side, with increasing the sandwich units from 1 to 4, the magnitude of positive contribution going much larger. It would be undoubtedly enlarged the γ values. Hence, the

29



difference between the positive and negative of γ-density distributions can be deemed as an efficient auxiliary approach to evaluate the relative amplitudes of the γ values.

( 3) ( 3) ( 3) ( 3) Figure 9. The ρ xxx and ρ yyy plots (a), as well as the − xρ xxx and − yρ yyy

plots (b) for primary tensorial components of complexes 1-4. (Cyan color represents positive value, while orange color represents negative value.)

3.5. Potential Redox Switchability. According to the previous literatures, it has been demonstrated that such sandwich metallacarboranes of transition-metal elements are generally air-stable, 30


Page 30 of 46

Page 31 of 46 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


soluble in common solvents, and highly robust materials which can undergo reversible redox processes and survive chemical modification without structural degradation.3, 5 Significantly, these attractive features can meet the basic requirements of NLO materials and offer special opportunities for reversibly modulating or switching the NLO response. All of the possible redox states observed by cyclic voltammetry (one-, two- and four-electron oxidation/reduction)21 were considered in our current work (Figure S4-S11). For the open-shell calculations, the square of total spin values were found quite close to their eigenvalue (Table S12), meaning the spin-contamination effect can be negligible. From the comparatively studied on the total electronic energies for each complexes, their triplet states of all two-electron oxidized/reduced species are more stable than singlet states; quintuplet states are more stable than singlet and triplet states at the +4/-4 valence (Table S13 in the Supporting Information; conversion relations for energy is 1 a.u.= 627.51 kcal/mol). Hence, herein, we only focus on the γtot magnitudes of relative stable states 1+, 1-, 2a+, 2a2+, 2a-, 2a2-, 2b+, 2b2+, 2b-, 2b2-,

4+, 44+, 4-, 42-, and 44- and exploring the switching ratios of cubic nonlinearities (Figure 10). It can be seen that, after the oxidation and reduction process, almost all of the third-order NLO properties have been enhanced except for 1+. In comparision to the neutral complexes 1-4, the γtot values of complexes 1-, 2a+, 2a-, 2b- and 4+ increase to 71.0 ×10-36 esu, 1805.4 ×10-36 esu, 1851.1 ×10-36 esu, 940.9 ×10-36 esu and 55387.6 ×10-36 esu, respectively. Especially for 4+, to the best of our knowledge, the biggest γtot gain is 15.8 times larger than the giant known γ values for macromolecule salts 31



[FeII{(2,4-DNPh)2bbpe2+}3][PF6]8 synthesized by Benjamin J. Coe’s group,62 and 1.3 times larger than that of open-shell singlet s-indaceno[1,2,3-cd;5,6,7-c’d’]diphenalene diradical compound reported by Masayoshi Nakano et al.61 The γ-ratios of 1 → 1-, 2a → 2a+, 2a → 2a- and 2b → 2b- are 2.99, 6.49 and 6.66, respectively. They contain the relative larger modulating ratios with respect to other forms (Table S11). For complex

4+, the γ-ratio approached as large as 86.58, which presents a significant difference on the corresponding third-order NLO properties. Subsequently, the multiple redox states make it possible to develop an efficient multistate controlled cubic NLO switches, which can be addressed independently to achieve molecular switching properties.

Figure 10. Schematic diagram of the switching ratios for the second hyperpolarizability γtot values.

Why did the γ value of complex 4+ can be significantly enhanced from that of neutral counterpart compared to other redox states? To unveil the origin of this 32


Page 32 of 46

Page 33 of 46 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


significant enhancement, we also performed the TD-DFT computation on the complex 4+. As visualized in Figure 11, there is a strong absorption in the near infrared region absorbing at 1090.5 nm. A distinct bathochromic shift of the major absorption peak is observed with respect to the neutral species 4 (271.7 nm), which effectively give rise to a lower excited energy. The two-level model is considered a reliable technique for analyze the hyperpolarizabilities, which is the linkage between the γtot and electronic transition of crucial excited state.63, 64 The expression is as 5 follow: γ ∝ f os2 / ∆E ge , which the γ is proportional to the quadratic power of f os but

inversely proportional to the fifth power of ∆E ge . Hence, the ∆E ge displays as decisive factor for determining the γ value. In comparision to neutral state 4, complex

4+ contains a much lower transition energy 0.0418 a.u. (1.14 e.V.), no doubt leading 5 to very large f os2 / ∆E ge results in spite of its relative small oscillator strength 5 (0.5750). According to the two-level model, the calculated f os2 / ∆E ge results have

been calculated as the order: 4 (1.03 ×105 a.u.) < 4+ (2.60 ×106 a.u.), which is in quantitative agreement with the order of γtot values (Table S11). To sum up, it is not much to say that the decrement of excited energy played a decisive role to the remarkable NLO switchable behaviors for 4 → 4+.

33



Figure 11. Comparison of aborption spectra between the one-electron-oxidized complex 4+ (blue line) and its neutral counterpart 4 (red line) along with the TD-ωB97XD results corresponding to the crucial excited states.

4. CONCLUSIONS In the present work, by means of quantum chemistry methods, a series of unusual mono-, di-, and tetranuclear cobaltacarboranes with Cp*Co(Et2C2B4H4) connected by diethynyl linker were systematically and comparatively studied. Our calculations demonstrated that, increasing the molecular size from 1 to 4 sandwich units, their geometric structures are hardly changed, but electronic properties varied drastically. The electron distribution and energy gap between HOMO and LUMO are significantly enlarged and narrowed. Noteworthy is that, the 24-atoms {C16B8} macrocycle (complex 4) present an excellent 2D NLO character resulting from its fascinating planar octagonal architectures. The exceptionally large second order hyperpolarizabilities approached an unprecedented 639.8 ×10-36 esu, which is 2.3 and 34


Page 34 of 46

Page 35 of 46 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


2.7 times larger than the 1D rod-like dinuclear building blocks (2a and 2b) and 27.0 times with respect to the 0D sandwich monomer (1). The observation is ascribed to the long-range intramolecular bidirectional charge transfer pattern. In addition, this series of sandwich model complexes, owing to their a variety of modes of redox behaviors, can be regarded as efficient multistate control cubic NLO switches, which can designedly achieve the specific hyperpolarizabilities. Especially for complex 4, the γtot value is as large as 55387.6 ×10-36 esu and high ON/OFF ratios for one-electron oxidation reached to 86.58. This work not only provides a novel member of excellent NLO materials underlying exceptionally large hyperpolarizabilities, but also propose new insight

into macrocycle molecule rational design for

high-performance electronic and optoelectronic applications. How large such planar macrocycle systems can be expanded and what hyperpolarizabilities can be achieved are our forward main objective and explored actively in progress.

ASSOCIATED CONTENT Supporting Information. Calculated and experimental geometric parameters. Percentage composition of HOMO and LUMO. Frontier molecular orbital energy levels. Simulated wavelengths of complex 4 calculated by various functionals. Components of α, average polarizabilities αave, components of γ, the second α γ hyperpolarizabilities γtot, and relative deviation of αave and γtot values RDFunc , RDFunc ,

α γ , RD BS of complex 1 calculated by various functionals and basis sets. RD BS

Tensorial components of γ, the second hyperpolarizabilities γtot and the γ-ratio r for all 35



of the studied complexes. Calculated square of total spin. Total electronic energies containing zero-point correction. Optimized geometrical structure of complex 1, 2a and 2b. Overlay of the optimized molecular structures of neutral complexes with their oxidized and reduced species.

AUTHOR INFORMATION Corresponding Author * E-mail: [email protected] (Y. Q. Qiu) Telephone: +86 0431 85099291

Notes The authors declare no competing financial interest.

ACKNOWLEDGMENTS The authors gratefully acknowledge the financial support from the “12th Five-Year” Science and Technology Research Project of the Education Department of Jilin Province ([2016] 494) and the National Natural Science Foundation of China (21173035).

REFERENCES (1) Núñez, R.; Tarrés, M.; Ferrer-Ugalde, A.; De Biani, F. F.; Teixidor, F. Electrochemistry and Photoluminescence of Icosahedral Carboranes, Boranes, Metallacarboranes, and Their Derivatives. Chem. Rev. 2016, 116, 14307-14378.

36


Page 36 of 46

Page 37 of 46 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


(2) Farras, P.; Juarez-Perez, E. J.; Lepsik, M.; Luque, R.; Nunez, R.; Teixidor, F. Metallacarboranes and Their Interactions: Theoretical Insights and Their Applicability. Chem. Soc. Rev. 2012, 41, 3445-3463. (3) Grimes, R. N. Metallacarboranes in the New Millennium. Coord. Chem. Rev. 2000, 200, 773-811. (4) Hawthorne, M. F.; Dunks, G. B. Metallocarboranes That Exhibit Novel Chemical Features. Science 1972, 178, 462-471. (5) Grimes, R. N. Boron-Carbon Ring Ligands in Organometallic Synthesis. Chem. Rev. 1992, 92, 251-268. (6) Pathak, B.; Pandian, S.; Hosmane, N.; Jemmis, E. D. Reversal of Stability on Metalation

of

1-M-2,4-C2B4H7)

Pentagonal-Bipyramidal and

(1-MB6H72-,

(1-MB11H122-,

Icosahedral

1-M-2-CB5H71-,

and

1-M-2-CB10H121-,

and

1-M-2,4-C2B9H12) Boranes (M = Al, Ga, In, and Tl): Energetics of Condensation and Relationship to Binuclear Metallocenes. J. Am. Chem. Soc. 2006, 128, 10915-10922. (7) Grimes, R. N. Carboranes in the Chemist's Toolbox. Dalton Trans. 2015, 44, 5939-5956. (8) Yao, Z. J.; Deng, W. Half-Sandwich Late Transition Metal Complexes Based on Functionalized Carborane Ligands. Coord. Chem. Rev. 2016, 309, 21-35. (9) Hawthorne, M. F.; Zink, J. I.; Skelton, J. M.; Bayer, M. J.; Liu, C.; Livshits, E.; Baer, R.; Neuhauser, D. Electrical or Photocontrol of the Rotary Motion of a Metallacarborane. Science 2004, 303, 1849.

37



Page 38 of 46

(10) Li, T. C.; Spokoyny, A. M.; She, C.; Farha, O. K.; Mirkin, C. A.; Marks, T. J.; Hupp, J. T. Ni(III)/(IV) Bis(dicarbollide) as a Fast, Noncorrosive Redox Shuttle for Dye-Sensitized Solar Cells. J. Am. Chem. Soc. 2010, 132, 4580-4582. (11) Mukherjee, S.; Thilagar, P. Boron Clusters in Luminescent Materials. Chem. Commun. 2016, 52, 1070-1093. (12) Li, X.; Yan, H.; Zhao, Q. Carboranes as a Tool to Tune Phosphorescence. Chem. Eur. J. 2016, 22, 1888-1898. (13) Wee, K.-R.; Cho, Y.-J.; Jeong, S.; Kwon, S.; Lee, J.-D.; Suh, I.-H.; Kang, S. O. Carborane-Based Optoelectronically Active Organic Molecules: Wide Band Gap Host Materials for Blue Phosphorescence. J. Am. Chem. Soc. 2012, 134, 17982-17990. (14) Miyajima, Y.; Nakamura, H.; Kuwata, Y.; Lee, J.-D.; Masunaga, S.; Ono, K.; Maruyama, K. Transferrin-Loaded nido-Carborane Liposomes: Tumor-Targeting Boron Delivery System for Neutron Capture Therapy. Bioconjugate Chem. 2006, 17, 1314-1320. (15) Hao, E.; Sibrian-Vazquez, M.; Serem, W.; Garno, J. C.; Fronczek, F. R.; Vicente, M.

G.

H.

Synthesis,

Aggregation

and

Cellular

Investigations

of

Porphyrin-Cobaltacarborane Conjugates. Chem. - Eur. J. 2007, 13, 9035-9042. (16) Valliant, J. F.; Guenther, K. J.; King, A. S.; Morel, P.; Schaffer, P.; Sogbein, O. O.; Stephenson, K. A. The Medicinal Chemistry of Carboranes. Coord. Chem. Rev. 2002, 232, 173-230.

38


Page 39 of 46 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) Ma, N. N.; Li, S. J.; Yan, L. K.; Qiu, Y. Q.; Su, Z. M. Switchable NLO Response Induced

by

Rotation

of

Metallacarboranes

[NiIII/IV(C2B9H11)2]-/0

and

C-,

B-Functionalized Derivatives. Dalton Trans. 2014, 43, 5069-5075. (18) Muhammad, S.; Xu, H. L.; Liao, Y.; Kan, Y. H.; Su, Z. M. Quantum Mechanical Design and Structure of the Li@B10H14 Basket with a Remarkably Enhanced Electro-Optical Response. J. Am. Chem. Soc. 2009, 131, 11833-11840. (19) Wang, H. Q.; Wang, L.; Li, R. R.; Ye, J. T.; Chen, Z. Z.; Chen, H.; Qiu, Y. Q.; Xie, H. M. Second-Order Nonlinear Optical Properties of Carboranylated Square-Planar Pt(II) Zwitterionic Complexes: One-/Two-Dimensional Difference and Substituent Effect. J. Phys. Chem. A 2016, 120, 9330-9340. (20) Fabrizi De Biani, F.; Fontani, M.; Ruiz, E.; Zanello, P.; Russell, J. M.; Grimes, R. N. Electronic Interactions in (η6-Arene) Ferracarboranes. Organometallics 2002, 21, 4129-4137. (21) Fabrizi De Biani, F.; Corsini, M.; Zanello, P.; Yao, H. J.; Bluhm, M. E.; Grimes, R. N. Electronic Properties of Mononuclear, Dinuclear, and Polynuclear Cobaltacarboranes: Electrochemical and Spectroelectrochemical Studies. J. Am. Chem. Soc. 2004, 126, 11360-11369. (22)

Russell,

J.

Metallacarboranes.

M.; 59.1

Sabat,

M.;

Synthesis

Grimes, and

R.

Linkage

N.

Organotransition-Metal

of

Ferracarborane Clusters. Organometallics 2002, 21, 4113-4128.

39


Boron-Functionalized


(23) Yao H. J.; Sabat M.; Grimes R. N.; Fabrizi De Biani, F.; Zanello, P. Metallacarborane-Based Nanostructures: A Carbon-Wired Planar Octagon. Angew. Chem. Int. Ed. 2003, 42, 1001-1005. (24) Wang, H. Q.; Wang, L.; Xia, Y. Y.; Ye, J. T.; Zhao, H. Y.; Qiu, Y. Q. Multinuclear “Staircase” Oligomers Based on the (Et2C2B4H4)Fe(η6-C6H6) Sandwich Unit: Quantitative Tailorable and Redox Switchable Nonlinear Optics. J. Phys. Chem. C

2017, 121, 16470-16480. (25) 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., et al. Gaussian 09, Revision D.01; Gaussian, Inc.: Wallingford, CT, 2009. (26) Becke, A. D. Density-Functional Thermochemistry. III. The Role of Exact Exchange. J. Chem. Phys. 1993, 98, 5648-5652. (27) Hay, P. J.; Wadt, W. R. Ab Initio Effective Core Potentials for Molecular Calculations. Potentials for the Transition Metal Atoms Sc to Hg. J. Chem. Phys. 1985, 82, 270-283. (28) Hay, P. J.; Wadt, W. R. Ab Initio Effective Core Potentials for Molecular Calculations. Potentials for K to Au Including the Outermost Core Orbitals. J. Chem. Phys. 1985, 82, 299-310. (29) Wadt, W. R.; Hay, P. J. Ab Initio Effective Core Potentials for Molecular Calculations. Potentials for Main Group Elements Na to Bi. J. Chem. Phys. 1985, 82, 284-298.

40


Page 40 of 46

Page 41 of 46 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


(30) Willetts, A.; Rice, J. E.; Burland, D. M.; Shelton, D. P. Problems in the Comparison of Theoretical and Experimental Hyperpolarizabilities. J. Chem. Phys.

1992, 97, 7590-7599. (31) Perdew, J. P.; Burke, K.; Ernzerhof, M. Generalized Gradient Approximation Made Simple. Phys. Rev. Lett. 1996, 77, 3865-3868. (32) Perdew, J. P.; Burke, K.; Ernzerhof, M. Generalized Gradient Approximation Made Simple [Phys. Rev. Lett. 77, 3865 (1996)]. Phys. Rev. Lett. 1997, 78, 1396-1396. (33) Becke, A. D. A New Mixing of Hartree-Fock and Local Density-Functional Theories. J. Chem. Phys. 1993, 98, 1372-1377. (34) Zhao, Y.; Truhlar, D. G. Comparative DFT Study of van der Waals Complexes: Rare-Gas Dimers, Alkaline-Earth Dimers, Zinc Dimer, and Zinc-Rare-Gas Dimers. J. Phys. Chem. A 2006, 110, 5121-5129. (35) Yanai, T.; Tew, D. P.; Handy, N. C. A New Hybrid Exchange-Correlation Functional Using the Coulomb-Attenuating Method (CAM-B3LYP). Chem. Phys. Lett.

2004, 393, 51-57. (36) Chai, J. D.; Head-Gordon, M. Long-Range Corrected Hybrid Density Functionals with Damped Atom-Atom Dispersion Corrections. Phys. Chem. Chem. Phys. 2008, 10, 6615-6620. (37) Dolg, M.; Wedig, U.; Stoll, H.; Preuss, H. Energy-Adjusted ab Initio Pseudopotentials for the First Row Transition Elements. J. Chem. Phys. 1987, 86, 866-872. 41



Page 42 of 46

(38) Bader, R. F. W.; Carroll, M. T.; Cheeseman, J. R.; Chang, C. Properties of Atoms in Molecules: Atomic Volumes. J. Am. Chem. Soc. 1987, 109, 7968-7979. (39) Wang, L.; Wang, W. Y.; Qiu, Y. Q.; Lu, H. Z. Second-Order Nonlinear Optical Response of Electron Donor-Acceptor Hybrids Formed between Corannulene and Metallofullerenes. J. Phys. Chem. C 2015, 119, 24965-24975. (40) Wang, W. Y.; Ma, N. N.; Sun, S. L.; Qiu, Y. Q. Impact of Redox Stimuli on Ferrocene-Buckybowl Complexes: Switchable Optoelectronic and Nonlinear Optical Properties. Organometallics 2014, 33, 3341-3352. (41) Lu, T.; Chen, F. W. Multiwfn: a Multifunctional Wavefunction Analyzer. J. Comput. Chem. 2012, 33, 580-592. (42) Eisler, S.; Slepkov, A. D.; Elliott, E.; Luu, T.; Mcdonald, R.; Hegmann, F. A.; Tykwinski, R. R. Polyynes as a Model for Carbyne: Synthesis, Physical Properties, and Nonlinear Optical Response. J. Am. Chem. Soc. 2005, 127, 2666-2676. (43) Zhong, R. L.; Zhang, J.; Muhammad, S.; Hu, Y. Y.; Xu, H. L.; Su, Z. M. Boron/Nitrogen Substitution of the Central Carbon Atoms of the Biphenalenyl Diradical π dimer: A Novel 2e-12c Bond and Large NLO Responses. Chem. - Eur. J.

2011, 17, 11773-11779. (44) Dreuw, A.; Head-Gordon, M. Failure of Time-Dependent Density Functional Theory

for

Long-Range

Charge-Transfer

Excited

States:

The

Zincbacteriochlorin-Bacteriochlorin and Bacteriochlorophyll-Spheroidene Complexes. J. Am. Chem. Soc. 2004, 126, 4007-4016.

42


Page 43 of 46 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


(45) Magyar, R. J.; Tretiak, S. Dependence of Spurious Charge-Transfer Excited States on Orbital Exchange in TDDFT: Large Molecules and Clusters. J. Chem. Theory Comput. 2007, 3, 976-987. (46) Gritsenko,

O.;

Baerends,

E.

J.

Asymptotic

Correction

of

the

Exchange-correlation Kernel of Time-Dependent Density Functional Theory for Long-Range Charge-Transfer Excitations. J. Chem. Phys. 2004, 121, 655-660. (47) Wong, B. M.; Piacenza, M.; Sala, F. D. Absorption and Fluorescence Properties of Oligothiophene Biomarkers from Long-Range-Corrected Time-Dependent Density Functional Theory. Phys. Chem. Chem. Phys. 2009, 11, 4498-4508. (48) Peach, M. J. G.; Benfield, P.; Helgaker, T.; Tozer, D. J. Excitation Energies in Density Functional Theory: An Evaluation and a Diagnostic Test. J. Chem. Phys.

2008, 128, 044118. (49) Sasagane, K.; Aiga, F.; Itoh, R. Higher-Order Response Theory Based on the Quasienergy Derivatives: The Derivation of the Frequency-dependent Polarizabilities and Hyperpolarizabilities. J. Chem. Phys. 1993, 99, 3738-3778. (50) Bredas, J. L.; Adant, C.; Tackx, P.; Persoons, A.; Pierce, B. M. Third-Order Nonlinear Optical Response in Organic Materials: Theoretical and Experimental Aspects. Chem. Rev. 1994, 94, 243-278. (51) Geskin, V. M.; Lambert, C.; Brédas, J. L. Origin of High Second- and Third-Order Nonlinear Optical Response in Ammonio/Borato Diphenylpolyene Zwitterions: the Remarkable Role of Polarized Aromatic Groups. J. Am. Chem. Soc.

2003, 125, 15651-15658. 43



Page 44 of 46

(52) Morita, Y.; Suzuki, S.; Sato, K.; Takui, T. Synthetic Organic Spin Chemistry for Structurally Well-Defined Open-Shell Graphene Fragments. Nat. Chem. 2011, 3, 197-204. (53) Maroulis, G. How Large is the Static Electric (Hyper)polarizability Anisotropy in HXeI? J. Chem. Phys. 2008, 129, 044314. (54) Karamanis, P.; Otero, N.; Pouchan, C. Unleashing the Quadratic Nonlinear Optical Responses of Graphene by Confining White-Graphene (h-BN) Sections in Its Framework. J. Am. Chem. Soc. 2014, 136, 7464-7473. (55) Wang, W. Y.; Ma, N. N.; Sun, S. L.; Qiu, Y. Q. Redox Control of Ferrocene-Based Complexes with Systematically Extended π-Conjugated Connectors: Switchable and Tailorable Second Order Nonlinear Optics. Phys. Chem. Chem. Phys.

2014, 16, 4900-4910. (56) Wang, L.; Ye, J. T.; Chen, H.; Chen, Z. Z.; Qiu, Y. Q.; Xie, H. M. A Structure-Property Interplay Between the Width and Height of Cages and the Static Third Order Nonlinear Optical Responses for Fullerenes: Applying Gamma Density Analysis. Phys. Chem. Chem. Phys. 2017, 19, 2322-2331. (57) Tu, C.; Yu, G.; Yang, G.; Zhao, X.; Chen, W.; Li, S.; Huang, X. Constructing (Super)alkali-Boron-Heterofullerene Dyads: an Effective Approach to Achieve Large First Hyperpolarizabilities and High Stabilities in M3O-BC59 (M = Li, Na and K) and K@n-BC59 (n = 5 and 6). Phys. Chem. Chem. Phys. 2014, 16, 1597-1606. (58) Fkyerat, A.; Guelzim, A.; Baert, F.; Zyss, J.; Périgaud, A. Assessment of the Polarizabilities

(α/β)

of

a

Nonlinear 44


Optical

Compound

Page 45 of 46 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


[N-(4-nitrophenyl)-(L)-prolinol] from an Experimental Electronic Density Study. Phys. Rev. B 1996, 53, 16236-16246. (59) Nakano, M.; Minami, T.; Yoneda, K.; Muhammad, S.; Kishi, R.; Shigeta, Y.; Kubo, T.; Rougier, L. A.; Champagne, B. T.; Kamada, K., et al. Giant Enhancement of the Second Hyperpolarizabilities of Open-Shell Singlet Polyaromatic Diphenalenyl Diradicaloids by an External Electric Field and Donor-Acceptor Substitution. J. Phys. Chem. Lett. 2011, 2, 1094-1098. (60) Nakano, M.; Champagne, B. Theoretical Design of Open-Shell Singlet Molecular Systems for Nonlinear Optics. J. Phys. Chem. Lett. 2015, 6, 3236-3256. (61) Humphrey, W.; Dalke, A.; Schulten, K. VMD: Visual Molecular Dynamics. J. Mol. Graphics 1996, 14, 33-38. (62) Coe, B. J.; Fielden, J.; Foxon, S. P.; Brunschwig, B. S.; Asselberghs, I.; Clays, K.; Samoc, A.; Samoc, M. Combining Very Large Quadratic and Cubic Nonlinear Optical Responses in Extended, Tris-Chelate Metallochromophores with Six π-Conjugated Pyridinium Substituents. J. Am. Chem. Soc. 2010, 132, 3496-3513. (63) Oudar, J. L.; Chemla, D. S. Hyperpolarizabilities of the Nitroanilines and Their Relations to the Excited State Dipole Moment. J. Chem. Phys. 1977, 66, 2664-2668. (64) Oudar, J. L. Optical Nonlinearities of Conjugated Molecules. Stilbene Derivatives and Highly Polar Aromatic Compounds. J. Chem. Phys. 1977, 67, 446-457.

45



TOC Graphic

46


Page 46 of 46

Planar Octagonal Tetranuclear Cobaltacarborane Macrocycle [(Î·5

Recommend Documents