Article pubs.acs.org/Organometallics
Electrochemical, Spectroscopic, and Theoretical Studies on Diethynyl Ligand Bridged Ruthenium Complexes with 1,3-Bis(2pyridylimino)isoindolate Dao-Bin Zhang,† Jin-Yun Wang,† Hui-Min Wen,† and Zhong-Ning Chen*,†,‡ †
State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002, People’s Republic of China ‡ State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, People’s Republic of China S Supporting Information *
ABSTRACT: A series of ruthenium acetylide complexes [Ru(BPI)(PPh3)2(CCR)] (BPI = 1,3-bis(2-pyridylimino)isoindolate; R = −C6H5 (2), −Cp2Fe (3a), −C6H4C6H4CCCp2Fe (3b)) and bis(acetylide)-linked binuclear ruthenium complexes [{Ru(BPI)(PPh3)2}2(CCRCC)] (R = none (4), 1,4-benzenediyl (5), 1,4naphthalenediyl (6), 9,10-anthracenediyl (7)) were synthesized and characterized by ESI-MS spectrometry, IR, 1H and 31P NMR, and UV− vis−near-IR spectroscopy, and cyclic and differential pulse voltammetry. Oxidation of 3−7 with 1 equiv of ferrocenium perchlorate afforded the corresponding one-electron-oxidized complexes 3+−7+. In contrast to the case for 3a+, where spin density is localized at the Fe center due to moderate electronic communication between RuII and FeIII centers along the Ru−CC−Cp2Fe backbone, the spin density is primarily populated on Ru for 3b+ without an appreciable electronic interaction between RuIII and FeII across the quite long bridging system RuCCC6H4C6H4CCCp2Fe. For bis(acetylide)-linked binuclear ruthenium complexes 4−7, electrochemical, UV−vis−near-IR spectral and TD-DFT computational studies reveal that electronic delocalization along the bridging RuCCRCCRu backbone is highly dependent on the R spacer. It is demonstrated that with the gradual increase of a π-conjugated system in aromatic R spacer, the electronic delocalization shows progressive enhancement along the Ru−CCRCC−Ru backbone due to an increasing participation of the bridging ligand. 4+ displays highly electronically delocalized behavior, whereas 5+−7+ are on the borderline of electronic delocalization.
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transfer along the molecular backbones.8 The metal−metal electron transfer is dependent on several factors such as the separation between metal centers, the coordination environment of the metal components, and the capability of the bridging ligands to mediate electronic communication.1−6,8 According to the Robin and Day9 classification and Hush10 theoretical analysis, the mixed-valence complexes can be categorized as class I to class III systems, depending on the degree of charge delocalization along the molecular backbone. Electrochemistry and spectroscopy have provided us the approaches to evaluate the capability and mechanism of electronic communication between metal centers. The 1,3-bis(2-pyridylimino)isoindoline (BPI) derivatives exhibit versatile coordination chemistry capable of complexation with a variety of transition-metal ions, including platinum, ruthenium, copper, cobalt etc.11 Because of their thermal
INTRODUCTION Rigid-wire-like metal alkynyl complexes with extensively πconjugated systems along molecular backbones have attracted great interest because of their potential application as structural modules in molecular-scale electronic materials and devices.1 A number of studies in this area have mainly focused on finding redox-active metallic termini as well as modifying the πconjugated spacer between metal centers to modulate metal− metal communication.2−6 It is demonstrated that auxiliary ligands with different electronic effects influence to some extent the redox potential and wave splitting arising from electronic interaction.3−6 As a result, the judicious selection of redoxactive organometallic termini with proper ancillary ligands is indispensable for achieving electronic delocalization along wirelike molecular backbones. Since the discovery of the Ru2II,III complex [(NH3)5Rupyrazine-Ru(NH3)5]5+ by Creutz and Taube,7 mixed-valence metal complexes linked by conjugated organic ligands and capped with redox-active organometallic termini have been intensely investigated, highlighting intramolecular electron © 2014 American Chemical Society
Special Issue: Organometallic Electrochemistry Received: December 29, 2013 Published: March 27, 2014 4738
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Scheme 1. Synthetic Routes to Complexes 1−7
calculated values for all of these complexes. ESI-MS shows that cationic molecular units [M+] were detected as base peaks or fragments with high abundance in most cases. The 31P NMR spectra of complexes 1−7 display one singlet signal at ca. 31.0 ppm, indicating the equivalence of the P donors on the NMR time scale. This signal is shifted to high field (26−30 ppm) in the one-electron-oxidized compounds 3a(ClO4) and 4(ClO4)− 7(ClO4). For the binuclear ruthenium complexes 5(ClO4)− 7(ClO4), two distinctly separated P signals were observed due to partial electronic delocalization along the molecular backbone. It is interesting to note that the P signal shows a more pronounced high-field shift upon one-electron oxidation of 3b (31.0 ppm) to 3b+ (26.2 ppm) in comparison with that of 3a (31.0 ppm) to 3a+ (29.0 ppm). This coincides with the fact that one-electron oxidation occurs most likely at Ru with direct Ru−P bonds for 3b, whereas this occurs at ferrocenyl for 3a without direct Fe−P bonds, as revealed from electrochemical and theoretical studies (vide infra). The ν(CC) bands in the IR spectra of complexes 2−7 occur at 1940−2070 cm−1. Upon one-electron oxidation, the ν(CC) bands of 3a(ClO4) and 4(ClO4)−7(ClO4) show an 80−100 cm−1 shift to lower wavenumber relative to that of the corresponding complexes 3a−7, revealing a decrement of the bond order and an increasing contribution of the cumulenic resonance structure.15 Electrochemical Properties. The electrochemical data are presented in Table 1. The plots of cyclic (CV) and different pulse voltammograms (DPV) of compounds 4−7 in 0.1 M (Bu4N)(PF6)−dichloromethane solutions are shown in Figure 1. Compounds 1 and 2 display reversible oxidation waves at +0.48 and +0.40 V versus Ag/AgCl, respectively. In comparison with compound 1, the substitution of chloride with phenylacetylide in complex 2 results in a negative shift (80 mV) due to the formation of a Ru−acetylide σ bond. Compound 3a exhibits two significantly separated reversible anodic waves at +0.27 and +0.78 V versus Ag/AgCl, ascribable to the oxidations
stability, facile accessibility, and ease of modification and functionalization, BPI derivatives usually serve as monoanionic N∧ N ∧N tridentate ligands to form either 1:1 or 1:2 (metal:ligand) complexes depending on the coordination number and geometrical preference of the metal ions.12,13 In this article, we are devoted to the preparation, characterization, and theoretical studies of a series of wirelike ruthenium complexes utilizing the Ru(BPI)(PPh3)2 moiety as the redox center and the bis(acetylide) ligand as the organic linker. Electronic delocalization along the molecular backbones was estimated by electrochemical, UV−vis−near-IR spectroscopic, and TD-DFT (time-dependent density functional theory) studies. The metal−metal communication is well modulated by changing π-conjugated systems in the organic spacers.
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RESULTS AND DISCUSSION Preparation and Characterization. As shown in Scheme 1, the initial precursor Ru(BPI)(PPh3)2Cl (1) was obtained by a two-step synthetic procedure. BPI reacted first with 1.5 equiv of Ru(PPh3)3Cl2 in ethanol under reflux, followed by the addition of NEt3 as a base for the deprotonation of BPI. It is noteworthy that compound 1 is inaccessible by directly mixing BPI, Ru(PPh3)3Cl2, and NEt3 in ethanol solution under reflux. Compounds 2 and 3a,b were prepared by the reactions of 1 with HCCC6H5, HCCCp2Fe, and HCCC6H4C6H4C CCp2Fe in the presence of NEt3 in refluxing ethanol, respectively. Bis(acetylide)-linked binuclear ruthenium complexes 4−7 were synthesized by the reactions of 1 with Me3SiCCRCCSiMe3 via KF-catalyzed14 desilylation in the presence of potassium fluoride in methanol solutions under reflux. The one-electron-oxidized compounds 3a(ClO4) and 4(ClO4)−7(ClO4) were accessed by the oxidation of 3a and 4−7 with 1 equiv of ferrocenium perchlorate, respectively. The complexes were characterized by elemental analyses, ESI-MS spectrometry, and 1H and 31P NMR spectroscopy. Elemental analyses (C, H, and N) coincide well with the 4739
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Table 1. Electrochemical Data for Compounds 1−7a compound HCCCp2Fe HCCC6H4C6H4C CCp2Fe 1 2 3a 3b 4 5 6 7
E1/2(Fe/ Ru)
E1/2′(Ru)
ΔE1/2b
Kcc
0.48 0.40 0.78 0.43 0.55 0.50 0.50 0.35
0.51 0.21 0.63 0.27 0.30 0.32
4.18 × 108
to ascribe the two redox potentials at 0.64 and 0.43 V to Fc/Fc+ and RuII/RuIII couples, respectively. Such an assignment is supported by TD-DFT studies (vide infra), in which the spin density in one-electron-oxidized species is dominant at Fe for 3a+ and at Ru for 3b+. The oxidation at Ru for 3b+ also coincides with the observation of an obvious shift of the 31P NMR spectrum relative to that of 3b, as mentioned above. As a result, the ferrocenyl is first oxidized in complex 3a with C CCp2Fe, whereas the use of CCC6H4C6H4CCCp2Fe in complex 3b induces the first oxidation at the ruthenium(II) center, followed by the iron(II) center of ferrrocenyl. In striking contrast to the first oxidation of ruthenium(II) center in 3b having minimal electronic communication, the lower oxidation potential of iron(II) in comparison to that of the ruthenium(II) center in 3a originates most likely from the substantial metal− metal electronic interaction through a short RuCCCp2Fe bridging pathway. As shown in Figure 1, binuclear ruthenium complexes 4−7 show two consecutive, distinctly spaced reversible redox waves due to stepwise one-electron-oxidation processes. The potential differences (ΔE1/2 = E1/2 − E1/2′) between the two waves are 0.63, 0.27, 0.30, and 0.32 V for 4−7, respectively. It is demonstrated that the wave separation or potential difference (ΔE1/2) between two successive redox processes due to stepwise metal-centered oxidation is a critical measure to evaluate electronic delocalization along the molecular backbones and thermodynamic stability of the mixed-valence species.29 The potential difference ΔE1/2 of complex 4 is 0.63 V, corresponding to the comproportionation constant Kc of 4.47 × 1010. The considerably large Kc value in complex 4 is suggestive of strong metal−metal electronic communication transmitted through the 1,3-butadiynyl group, comparable to other 1,3-butadiynyl-linked binuclear ruthenium complexes with different ancillary ligands.30−32 In contrast, complexes 5−7 show much smaller ΔE1/2 values (0.27−0.32 V) in comparison with that of complex 4 (0.63 V), owing to the longer intramolecular Ru···Ru distances (ca. 12.4 Å) of 5−7 in comparison to that of 4 (7.8 Å). It is noteworthy that complexes 5−7 exhibit different π-conjugated bridging systems depending on the spacer R in the diethynyl ligand C CRCC but comparable intramolecular Ru···Ru separations (ca. 12.4 Å). With an increase of π-conjugated systems in the spacer R, the potentials of stepwise oxidation processes in complexes 5−7 show gradual cathodic shifts, as depicted in Figure 1. Meanwhile, the potential difference ΔE1/2 due to stepwise redox processes displays a distinctly progressive increase in the order 0.27 V (5) < 0.30 V (6) < 0.32 V (7). From the electrochemical studies, it is thus revealed unambiguously that π-conjugation in the bridging ligands exerts an obvious impact on the stepwise oxidation and consequent electronic delocalization along the molecular backbone. For this series of binuclear ruthenium complexes, it is confirmed that the expansion of π-conjugated systems in the bridging ligands is favorable for electronic communication.31a,33−44 UV−vis−Near-IR Spectra. The UV−vis absorption spectra of complexes 1−7 (Figures S11 and S12, Supporting Information) in dichloromethane at room temperature show intense absorption bands in the UV region, ascribable to ligandcentered π → π* transitions of BPI, PPh3, and acetylide ligands. A broad band at ca. 350−600 nm in the low-energy visible-light region originates from dπ(Ru) → π*(BPI)/π*(CC) metalto-ligand charge transfer (MLCT) transitions. This band shows
0.68 0.63
0.27 0.64 −0.08 0.23 0.20 0.03
4.47 3.67 1.18 2.57
× × × ×
1010 104 105 105
a
Potential data in volts versus Ag/AgCl are from single-scan cyclic voltammograms recorded in a 0.1 M dichloromethane solutions of (Bu4N)(PF6) at 25 °C. Detailed experimental conditions are given in the Experimental Section. bΔE1/2 = |E1/2′ − E1/2| denotes the potential difference between two successively separated redox processes. cThe comproportionation constants Kc were calculated by the formula Kc = exp(ΔE1/2/25.69) at 298 K.16
Figure 1. Cyclic and differential pulse voltammograms of compounds 4−7 in 0.1 M (Bu4N)(PF6) dichloromethane solutions. The scan rate is 100 mV s−1 for CV and 20 mV s−1 for DPV.
of ferrocenyl and ruthenium centers, respectively. Relative to those in ethynylferrocene (E1/2 = 0.68 V) and Ru(BPI)(PPh3)2(CCPh) (E1/2 = 0.40 V), the oxidation potentials of ferrocenyl (E1/2 = 0.27 V) and ruthenium (E1/2 = 0.78 V) centers show significant cathodic and anodic shifts, respectively. Such a shift implies substantial electronic communication between Fe and Ru redox centers, comparable to that found in previously described Fe−Ru heteronuclear complexes with bridging ferrocenylacetylides.17−28 Since the Fe−Ru complex 3a is structurally unsymmetrical, the potential difference or wave separation due to sequential oxidation of ferrocenyl and ruthenium(II) centers should not be totally ascribed to metal− metal electronic interactions. To minimize metal−metal communication, the distance between Fe and Ru centers is extended using HCCC6H4C6H4CCCp2Fe (dFe···Ru = ca. 19.0 Å) instead of HCCCp2Fe (dFe···Ru = ca. 8.0 Å) to space Fe···Ru centers in complex 3b. Although complex 3b also exhibits two sequential oxidation waves at 0.64 and 0.43 V, their origin is strikingly in contrast to that in 3a. On comparison of the oxidation potentials of 3b with those in the corresponding precursors HCCC6H4C6H4CCCp2Fe (E1/2 = 0.63 V) and Ru(BPI)(PPh3)2(CCPh) (2, E1/2 = 0.40 V), it is reasonable 4740
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a slight red shift with the increase of the π-conjugated system in the bridging ligand. Upon one-electron oxidation of complexes 3a and 4−7 to 3a+ and 4−7+, the MLCT bands become obviously weaker, whereas new bands at longer wavelength occur (500−900 nm), attributable to ligand-to-metal charge transfer (LMCT) transitions as a result of the one-electron oxidation. By comparison of the absorption bands of LMCT transitions, it is found that, with the extension of π-conjugated organic bridging systems, the energy of LMCT bands (Figure 2) is not
coupling between FeIII and RuII centers to behave as a class II mixed-valence system. Complex 4 + exhibits an intense composite near-IR absorption, composed of two overlapped sub-bands centered at 1295 nm (ε = 9820 M−1 cm−1) and 1040 nm (ε = 6470 M−1 cm−1) deconvoluted using Gaussian simulation. Such near-IR bands are solvent-independent when measured in different solvents with a wide range of polarity, such as dichloromethane, acetone, and acetonitrile. The observed half-height width Δν1/2 (1193 and 3006 cm−1) is much narrower than the theoretical value (4223 and 4713 cm−1) predicted from Hush’s theoretical analysis.10 From electrochemical and spectroscopic studies which revealed a large comproportionation constant (Kc = 4.47 × 1010), intense near-IR absorption (ε = 9820 M−1 cm−1) with solvent independence, and narrow half-height width (Δν1/2), it is concluded that 4+ is highly electronically delocalized along the molecular backbone, comparable to other 1,3-butadiynyllinked diruthenium complexes with various auxiliary ligands.30−32 The near-IR absorption spectra of 5+−7+ are sensitive to the nature of the bridging ligands. With the increase of πconjugated systems in the aromatic diethynyl ligands, the near-IR absorption bands show progressive blue shifts in the order 5+ → 6+ → 7+ (Figure 2). By assuming the Gaussian shapes, the near-IR absorption bands of 5+−7+ can be deconvoluted into a sum of two or three sub-bands (Figure 3
Figure 2. UV−vis-near-IR electronic spectra of [3](ClO4)−[7](ClO4) in dichloromethane solutions.
only progressively red shifted but the molar extinction coefficient is also significantly enhanced. More importantly, one-electron-oxidized species 3a+ and 4+−7+ (Figure 2) show characteristic low-energy absorption bands in the near-infrared (near-IR) region, ascribed to electronic delocalization along the molecular backbones. In contrast, such a near-IR band was essentially unobserved in the one-electron-oxidized Fe−Ru heteronuclear complex 3b+ that lacks intramolecular electronic communication due to a quite long Fe···Ru separation. The corresponding parameters and analytical data of the near-IR bands are summarized in Table 2. The UV−vis−near-IR spectrum of 3a+ in CH2Cl2 solution displays a broad near-IR band centered at 1941 nm (ε = 4400 M−1 cm−1) with moderate intensity, ascribed most likely to a heterometallic RuII → FeIII intervalence charge transfer (IVCT) transition. Such a low-energy band disappears upon further oxidation of 3a+ to 3a2+, as is found in other mixed-valence Ru−Fe complexes containing both ferrocenyl and ruthenium centers.17−28 The experimentally estimated (2960 cm−1) halfheight width of the near-IR band is comparable to that calculated (3488 cm−1) by Hush model theory (Δν1/2 = (2310νmax)1/2). Moreover, the IVCT bands of 3a+ show solvent-dependent behavior, further implying a moderate
Figure 3. Electronic spectrum of [7](ClO4) in the near-IR absorption region, showing deconvolution into a sum of three Gaussian-shaped sub-bands.
and Table 2). To the best of our knowledge, it is not uncommon that a mixed-valence system exhibits multiple nearIR bands, although they are not always observed. Such multiple charge transfer transitions originate from multiple ligandmediated orbital interactions and level splitting through low symmetry and spin−orbit coupling. 33 For instance, a diaza[2.2]ferrocenophane complex displays two IVCT bands
Table 2. Selected Parameters Derived from Deconvolution of the Near-IR Absorption Band Envelopes in 3a+ and 4+−7+ 3a+ νa/cm−1 (ε/M−1 cm−1) λa/nm νb/cm−1 (ε/M−1 cm−1) λb/nm νIVCT/cm−1 (ε/M−1 cm−1) λIVCT/nm Δν1/2(IVCT) (cm−1) Δν1/2(theor)a (cm−1) a
5433 (4400) 1841 2960 3488
4+
7720 (9820), 9615 (6470) 1295, 1040 1193, 3006 4223, 4713
5+
6+
7+
5225 (11900) 1914
5656 (26400) 1768
6849 (5510) 1460 3094 3978
7192 (8370) 1390 2368 4076
6788 (21000) 1473 5582 (11270) 1791 8028 (8140) 1246 2331 4309
The theoretical Δν1/2 value is calculated using the equation Δν1/2 = (2310νmax)1/2. 4741
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attributable to two stable atropo isomers in poor polar solvents.45 Due to the strong spin−orbit coupling effect of the osmium atom, the number of IVCT bands could be up to five in binuclear osmium mixed-valence complexes.46 Multiple near-IR transitions have been also observed in a few ruthenium mixed-valence complexes,33,47−49 in which the bridging πconjugated systems exhibit strong orbital interaction with the metal centers and participate in the oxidation process so as to bring about multiple near-IR bands. Low and co-workers33 described that the radical cationic binuclear ruthenium complexes [{Ru(dppe)Cp*}2(μ-CCArCC)]+ (dppe = 1,2-bis(diphenylphosphino)ethane, Ar = 1,4-phenylene, 1,4naphthylene, 9,10-anthrylene) exhibited a sum of three subbands in the near-IR region through Gaussian deconvolution, in which the synchronous population of bridge-oxidized and mixed-valence states likely result from different orientations of the aromatic planes in the bridging ligand relative to the metal d orbitals with appropriate π symmetry. Among two or three near-IR sub-bands in complexes 5+−7+, only one broad sub-band is ascribable to an IVCT band (Table 2). This IVCT band is significantly broader than the other one or two sub-bands, in which the half-height bandwidth (Δν1/2) is much narrower than the values calculated (Δν1/2(theor)) by Hush’s theoretical analysis for class II mixed-valence compounds. The near-IR band of 5+ or 6+ can be deconvoluted into two sub-bands centered at 6849 cm−1 (1460 nm) and 5225 cm−1 (1914 nm) for 5+ or 7192 cm−1 (1390 nm) and 5656 cm−1 (1768 nm) for 6+. The broader sub-band at 6849 cm−1 (1460 nm) for 5+ or 7192 cm−1 (1390 nm) for 6+ is likely ascribed to an IVCT absorption. For complex 7+, the near-IR band is deconvoluted into three sub-bands at 8028 cm−1 (1246 nm), 6788 cm−1 (1473 nm), and 5582 cm−1 (1791 nm).33 The subband at 8028 cm−1 with a broad half-height width (2331 cm−1) is assignable to an IVCT transition, which is somewhat sensitive to organic solvents with different polarities such as dichloromethane, acetone, and acetonitrile (Figure S16, Supporting Information), implying partially delocalized behavior of the mixed-valence system. Obviously, the Kc values for 5+ (3.67 × 104), 6+ (1.18 × 105), and 7+ (2.57 × 105) are much lower than that for 4+ (4.47 × 1010), suggesting a weaker coupling between two ruthenium centers across a longer CCRCC spacer. The IVCT spectroscopic behavior also indicates that the 1,3butadiynyl linked binuclear ruthenium complex 4+ is a highly electronically delocalized system, whereas aromatic diethynyl linked complexes 5+−7+ are between electronic delocalization and localization. Theoretical Studies. To get more detailed information concerning electronic structures and transition and spectroscopic properties, (time-dependent) density functional theory (DFT/TD-DFT) was employed for computational studies on the simplified model compounds 1′−7′ along with the oneelectron-oxidized species [3a′]+−[7′]+ using PH3 in place of PPh3 to reduce computation time. The detailed molecular orbital compositions and absorption transitions are summarized in Tables S1−S13 (Supporting Information). Spatial plots of the HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital) of 3a′−7′ are depicted in Figure 4. The LUMO of complex 1′ is predominantly resident on BPI (95.7%), and the HOMO is mainly distributed on Ru (41.7%) and BPI (46.2%) with a minor contribution from Cl (4.3%). Upon chloride being substituted with phenylacetylide (C
Figure 4. Spatial plots of the HOMO and LUMO of complexes 3a′− 7′.
CPh) to form complex 2′, the acetylide ligand (27.7%) is heavily involved in the HOMO with an obviously decreased population on BPI (25.4%). It has been demonstrated that the predominant metal−acetylide bonding character is filled/filled interactions between the occupied acetylide π bonds and the occupied metal dπ orbitals.50 Such a dπ−acetylide-π overlap is distinctly reflected by electronic communication along the metal−CC arrays in acetylide compounds as a result of the substantial coupling between the metal dπ and acetylide π electrons. The HOMO of 2′ is delocalized along the (BPI)RuCCPh backbone and is coplanar with BPI. In contrast, the HOMOs in binuclear ruthenium acetylide complexes 3a′−7′ (Figure 4) are staggered with BPI ligands to form 23−64° dihedral angles between the HOMO and the BPI ligand. The HOMO of 3a′ is distributed along RuCCCp2Fe with significant population on the ferrocenyl moiety (43%) and less contribution on Ru (30%). In contrast, the HOMO of 3b′ is dominated by the RuCCC 6 H 4 − moiety with slight population of the ferrocenyl moiety (2%) but an increased population of Ru (41%). Such a distribution of the HOMO is well in accordance with the oxidation at iron(II) for 3a′ and at ruthenium(II) for 3b′. The spin density for one-electronoxidized species [3a′]+ is primarily resident on the Fe center, whereas that for [3b′]+ is dominantly centered at Ru (Table S14, Supporting Information), further demonstrating that oneelectron oxidation occurs at the ferrocenyl moiety for 3a′ but at ruthenium(II) for 3b′. For the one-electron-oxidized species [3a′]+, both αHOSO and βHOSO (highest occupied spin orbital) are dominant on the Ru(BPI) moiety whereas both αLUSO and βLUSO (lowest unoccupied spin orbital) are populated on the ferrocenyl moiety. The near-IR band arises 4742
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mainly from βHOSO-10 → βLUSO (44%) and βHOSO-12 → βLUSO (21%) with Ru(BPI) → FeCp2 character, which is typical of IVCT and LLCT states. For the binuclear ruthenium(II) complexes 4′−7′, the LUMO is predominantly contributed by one peripheral BPI ligand and the HOMO exhibits delocalized distribution along the bridging Ru−CC−R−CC−Ru backbone, as depicted in Figure 4. With the extension of π-conjugated bridging systems, the Ru-based contribution to the HOMO progressively decreases in the order 4′ (44%) → 5′ (39%) → 6′ (34%) → 7′ (26%), whereas the population of the organic bridging system shows a gradual increase in the order 4′ (41%) → 5′ (46%) → 6′ (52%) → 7′ (63%). The HOMO level (Figure 5) is gradually raised in the order 5′ (−4.57 eV) → 6′
oxidation states,42,43 the one-electron-oxidized species 5+−7+ are not appropriately regarded as true mixed-valence systems, since the bridging aryl moieties in these dinuclear ruthenium complexes are significantly involved in the oxidation process.33,44 Low and co-workers33 have demonstrated that the radical cations of binuclear ruthenium complexes [{Ru(dppe)Cp*}2(μ-CCArCC)] are characteristic of oxidation of the bridging diethynyl aromatic moiety as well as a mixedvalence state. With the gradual extension of π conjugation in the bridging ligands, a significant portion of spin resides on the bridging systems, revealing a progressively enhanced electron delocalization along π-conjugated molecular backbones. The near-IR bands in the one-electron-oxidized complexes 4+−7+ are principally associated with multiple electron promotions from βHOSO and βHOSO-n to βLUSO levels. The βHOSO and βHOSO−n levels are delocalized over the molecular backbones (BPI)Ru−CC−R−CC−Ru(BPI), whereas the βLUSO levels are primarily populated onto the bridging ligands and two Ru centers. The near-IR sub-bands obtained through Gaussian deconvolution are mostly reproduced by TD-DFT calculations, although they are not satisfactorily ascribed as intervalence charge transfer transitions.33,48 Instead, the electronic promotions from βHOSO and βHOSO−n to βLUSO are described as the charge-transfer transitions from Ru and BPI to the bridging π systems and the metal centers as a consequence of the redox-noninnocent behavior for the aromatic diethynyl bridging ligands. The involvement of several βHOSO/βHOSO-n → βLUSO excitations may explain the observation of multiple near-IR bands in these one-electron-oxidized systems.
Figure 5. Plots of the energy level for simplified models of complexes 3a′ and 4′−7′, calculated by the TD-DFT method at the B3LYP level.
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CONCLUSIONS A series of homo- and heterobinuclear ruthenium complexes [Ru(BPI)(PPh3)2(CCR)] (R = −Cp2Fe, −C6H4C6H4C CCp2Fe) and [{Ru(BPI)(PPh3)2}2(CCRCC)] (R = none, 1,4-benzenediyl, 1,4-naphthalenediyl, 9,10-anthracenediyl) together with their one-electron-oxidized complexes were synthesized and fully characterized. While one-electron oxidation of 3a occurs at the FeII center to afford moderate electronic delocalization along the RuII−CC−Cp2FeIII backbone, the RuII is first oxidized for 3b to give the mixed-valence complex 3b+ with total electronic isolation between the RuIII and FeII centers across a quite long bridging system Ru−C CC6H4C6H4CCCp2Fe. Complex 4 with 1,3-butadiynyl as a linker between two Ru centers exhibits substantial electronic delocalization along the Ru−CC−CC−Ru backbone. A combination of electrochemical, spectroscopic, and TD-DFT computational studies on complexes 5−7 demonstrates that πconjugated aromatic diynyl spacers between two ruthenium centers behave as redox-noninnocent ligands that are remarkably involved in the one-electron-oxidation process. It is demonstrated that, with the gradual expansion of πconjugated bridging systems, the aromatic diynyl ligands are more and more involved in electronic delocalization in the order 5 → 6 → 7. The one-electron-oxidized species 5+−7+ exhibit multiple near-IR absorption bands, in which multiple near-IR transitions are relevant to redox-noninnocent bridging ligands that have strong orbital interaction with the metal center and participate significantly in the oxidation processes. These Ru2 or Ru−Fe organometallic complexes with appealing electronic properties will be helpful for promoting further diversity in the design of open-shell bimetallic complexes with potential applications in molecular electronics.
(−4.52 eV) → 7′ (−4.40 eV) → 4′ (−4.25 eV), implying that an electron is progressively readily lost following this order, coinciding well with the gradual lowering of the first oxidation potential in the order 5′ (0.23 V) → 6′ (0.20 V) → 7′ (0.03 V) → 4′ (−0.08 eV). Furthermore, the HOMO−LUMO gap decreases progressively in the order 5′ (2.27 eV) → 6′ (2.21 eV) → 7′ (2.07 eV) → 4′ (1.99 eV). Since the HOMOs of 4′−7′ are delocalized over the Ru− CC−R−CC−Ru backbone, one-electron oxidation is not simply localized at the ruthenium centers but is involved in significant participation of the π-conjugated bridging system CC−R−CC. This is verified by the Mulliken spin density distribution in the one-electron-oxidized species [4′]+−[7′]+, in which Ru-centered spin density shows a gradual decrease in the order [4′]+ (0.52 e) → [5′]+ (0.47 e) → [6′]+ (0.40 e) → [7′]+ (0.30 e), whereas density population along the bridging C C−R−CC exhibits a progressive increase in the order [4′]+ (0.47 e) → [5′]+ (0.52 e) → [6′]+ (0.59 e) → [7′]+ (0.68 e). It is worth mentioning that with the gradual expansion of aromatic R groups in CC−R−CC, the spin density populated onto four C atoms of diacetylide shows a gradual decrease in the order [4′]+ (0.47 e) → [5′]+ (0.32 e) → [6′]+ (0.30 e) → [7′]+ (0.25 e), whereas that onto aromatic R group becomes a progressive increase in the order [4′]+ (0 e) → [5′]+ (0.20 e) → [6′]+ (0.29 e) → [7′]+ (0.43 e). Thus, these oneelectron-oxidized complexes could not be defined as true mixed-valence systems with definite metal oxidation states, particularly for 7+ with 9,10-diethynylanthracene. In fact, the πconjugated CC−R−CC in these dinuclear ruthenium complexes are better described as redox-noninnocent systems.48 In contrast to mixed-valence dinuclear iron complexes of diethynyl aromatic ligands having distinctly identifiable metal 4743
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7.64 (m, 20H), 7.56−7.53 (m, 10H), 7.48−7.44 (m, 18H), 7.12−6.98 (m, 13H), 6.92−6.86 (m, 11H). 31P NMR (CDCl3, ppm): 31.2 (s). {Ru(BPI)(PPh3)2}2(CCC6H4CC) (5). The synthetic procedure of this compound was the same as that of 4, using 1,4bis(trimethylsilylethynyl)benzene instead of bis(trimethylsilyl)-1,3butadiyne to give a green product. Yield: 68%. Anal. Calcd for C118H88N10P4Ru2: C, 71.87; H, 4.50; N, 7.10. Found: C, 71.81; H, 4.53; N, 7.19. IR (KBr, cm−1): 2057 s (CC). ESI-MS: m/z (%) 1971.6 (100) [M]+. 1H NMR (CDCl3, ppm): 10.01−9.99 (m, 4H), 7.77−7.75 (m, 4H), 7.44−7.42 (m, 4H), 7.22−7.14 (m, 32H), 7.05− 7.01 (t, 14H, J = 7.3 Hz), 6.91−6.87 (t, 26H, J = 7.5 Hz), 6.07−6.03 (m, 4H). 31P NMR (CDCl3, ppm), 31.2 (s). {Ru(BPI)(PPh3)2}2(CCC10H6CC) (6). The synthetic procedure of this compound was the same as that of 4, using 1,4bis(trimethylsilylethynyl)naphthalene instead of 1,4-bis(trimethylsilyl)-1,3-butadiyne to give a green product. Yield: 67%. Anal. Calcd for C122H90N10P4Ru2: C, 72.46; H, 4.49; N, 6.93. Found: C, 72.40; H, 4.41; N, 6.84. IR (KBr, cm−1): 2036 s (CC). ESI-MS: m/z (%) 2021.6 (100) [M]+, 1497.9 (91) [M − 2PPh3]+, 661.1 (62) [Ru(BPI)(PPh3)]+. 1H NMR (CDCl3, ppm): 10.29−10.27 (m, 4H), 8.57−8.55 (m, 2H), 7.79−7.77 (m, 4H), 7.45−7.43 (m, 4H), 7.34− 7.32 (m, 4H), 7.25−7.24 (m, 2H), 7.22 (d, 3H, J = 1.5 Hz), 7.18−7.16 (m, 24H), 7.02−6.99 (t, 14H, J = 7.3 Hz), 6.87−6.83 (t, 25H, J = 7.6 Hz), 6.13−6.09 (m, 4H). 31P NMR (CDCl3, ppm): 31.1 (s). {Ru(BPI)(PPh3)2}2(CCC14H8CC) (7). The synthetic procedure of this compound was the same as that of 4, using 9,10bis(trimethylsilylethynyl)anthracene instead of 1,4-bis(trimethylsilyl)1,3-butadiyne to give a purple product. Yield: 70%. Anal. Calcd for C126H92N10P4Ru2: C, 73.03; H, 4.48; N, 6.76. Found: C, 73.11; H, 4.44; N, 6.70. IR (KBr, cm−1): 2010 s (CC). ESI-MS: m/z (%) 2072.3 (57) [M]+, 1546.9 (42) [M − 2PPh3]+, 1130.2 (100) [{Ru(BPI)(PPh3)2}(CCC14H8CCH)]+. 1H NMR (CDCl3, ppm): 10.54 (s, 2H), 10.35−10.33 (m, 2H), 8.63−8.59 (t, 4H, J = 9.6 Hz), 7.82−7.79 (m, 4H), 7.57−7.53 (m, 3H), 7.46−7.43 (m, 5H), 7.37−7.30 (m, 9H), 7.23−7.21 (m, 3H), 7.09 (d, 10H, J = 7.5 Hz), 7.00−6.93 (m, 24H), 6.79−6.71 (m, 21H), 6.17−6.10 (m, 5H). 31P NMR (CDCl3, ppm): 30.3 (s). [{Ru(BPI)(PPh3)2}(CCCp2Fe)](ClO4) (3a(ClO4)). To 20 mL of dichloromethane were added 3a (80.0 mg, 0.071 mmol) and ferrocenium perchlorate (20.1 mg, 0.071 mmol) with stirring for 2 h. After the solvent was removed in vacuo, the crude product was purified by silica gel column chromatography (dichloromethane/ acetone 7/1) to give a green solid. Yield: 45%. Anal. Calcd for C66H51ClFeN5O4P2Ru: C, 64.32; H, 4.17; N, 5.68. Found: C, 64.50; H, 4.30; N, 5.52. IR (KBr, cm−1): 1978 s (CC), 1103 s (ClO4). ESIMS: m/z (%) 1132.5 (100) [M]+. 31P NMR (CDCl3, ppm): 29.0 (s). [{Ru(BPI)(PPh3)2}(CCC6H4C6H4CCCp2Fe)](CO4) (3b(ClO4)). The synthetic procedure of this compound was the same as that of 3a(ClO4), using 3b instead of 3a to give a red product. Yield: 60%. Anal. Calcd for C80H59ClFeN5O4P2Ru·1/2CH2Cl2·H2O: C, 65.81; H, 4.25; N, 4.77. Found: C, 65.81; H, 4.48; N, 4.92. IR (KBr, cm−1): 1953 m (CC), 1103 s (ClO4). 31P NMR (CD2Cl2, ppm): 26.2 (s). [{Ru(BPI)(PPh3)2}2(CCCC)](ClO4) (4(ClO4)). The synthetic procedure of this compound was the same as that of 3a(ClO4), using 4 instead of 3a to give a brown product. Yield: 42%. Anal. Calcd for C112H84ClN10O4P4Ru2: C, 67.41; H, 4.24; N, 7.02. Found: C, 67.51; H, 4.28; N, 7.69. IR (KBr, cm−1): 1847 s (CC), 1090 s (ClO4). ESIMS: m/z (%) 1896.4 (100) [M]+. 31P NMR (CDCl3, ppm): 29.0 (s). [{Ru(BPI)(PPh3)2}2(CCC6H4CC)](ClO4) (5(ClO4)). The synthetic procedure of this compound was the same as that of 3a(ClO4), using 5 instead of 3a to give a brown product. Yield: 45%. Anal. Calcd for C118H88ClN10O4P4Ru2: C, 68.42; H, 4.28; N, 6.76. Found: C, 68.49; H, 4.23; N, 6.70. IR (KBr, cm−1): 1964 s (CC), 1089 s (ClO4). ESI-MS: m/z (%) 1972.0 (100) [M]+. 31P NMR (CDCl3, ppm): 29.2 (s), 26.4 (s). [{Ru(BPI)(PPh3)2}2(CCC10H6CC)](ClO4) (6(ClO4)). The synthetic procedure of this compound was the same as that of 3a(ClO4), using 6 instead of 3a to give a green product. Yield: 45%. Anal. Calcd for C122H90ClN10O4P4Ru2: C, 69.07; H, 4.28; N, 6.60. Found: C, 69.14; H, 4.31; N, 6.66. IR (KBr, cm−1): 1949 s (CC), 1088 s
EXPERIMENTAL SECTION
General Procedures and Materials. All operations were performed under a dry argon atmosphere using Schlenk techniques and a vacuum-line system. Solvents were dried, distilled, and degassed before use, except those for UV−vis−near-IR spectral measurements were of spectroscopic grade. The reagents ruthenium(III) chloride hydrate, 1,4-bis(trimethylsilyl)-1,3-butadiyne, 1,4-dibromobenzene, 1,4-dibromonaphthalene, and 9,10-dibromoanthrancene were commercially available. The compounds Ru(PPh3)3Cl2,51 1,3-bis(2pyridylimino)isoindoline (BPI),52 and ethynylferrocene (Cp2FeC CH)53 were synthesized by the literature methods. 1,4-Bis(trimethylsilylethynyl)benzene, 1,4-bis(trimethylsilylethynyl)naphthalene, and 9,10-bis(trimethylsilylethynyl)anthracene were prepared by procedures modified from those described in the literature.54 Ru(BPI)(PPh3)2Cl (1). An ethanol solution of BPI (0.9 g, 3 mmol) and Ru(PPh3)3Cl2 (4.3 g, 4.5 mmol) in a round-bottom flask was stirred under reflux for 5 h. The solution was filtered upon cooling to room temperature, and to the filtrate was added 5 mL of triethylamine. The solution was stirred at room temperature for 1 h, and then the solvent was removed to give a green product. Yield: 80%. Anal. Calcd for C54H42ClN5P2Ru: C, 67.60; H, 4.41; N, 7.30. Found: C, 67.48; H, 4.37; N, 7.27. ESI-MS: m/z (%) 924.0 (50) [M − Cl]+, 662.5 (100) [M − PPh3 − Cl]+. 1H NMR (CDCl3, ppm): 9.99−9.97 (m, 2H), 7.63−7.62 (m, 2H), 7.35−7.32 (m, 4H), 7.18−7.16 (m, 2H), 7.02− 6.98 (t, 7H, J = 7.2 Hz), 6.95−6.92 (m, 12H), 6.86−6.82 (t, 11H, J = 7.5 Hz), 6.27−6.23 (m, 2H). 31P NMR (CDCl3, ppm): 25.6 (s). Ru(BPI)(PPh3)2(CCPh) (2). To 20 mL of methanol were added Ru(BPI)(PPh3)2Cl (300 mg, 0.32 mmol), phenylacetylene (64 mg, 0.63 mmol), and 2 mL of triethylamine. After the solution was stirred under reflux overnight, the cold solution was filtered to give the crude product, which was crystallized in acetonitrile to give a green product. Yield: 65%. Anal. Calcd for C62H47N5P2Ru: C, 72.64; H, 4.62; N, 6.83. Found: C, 72.60; H, 4.81; N, 6.87. IR (KBr, cm−1): 2054 s (CC). ESI-MS: m/z (%) 1025.4 (100) [M]+. 1H NMR (CDCl3, ppm): 9.90− 9.89 (m, 2H), 7.76−7.74 (m, 2H), 7.43−7.41 (m, 2H), 7.28 (d, 2H, J = 1.8 Hz), 7.20−7.18 (m, 3H), 7.15 (d, 2H, J = 1.6 Hz), 7.13−7.08 (m, 14H), 7.07−6.97 (t, 6H, J = 7.3 Hz), 6.85−6.82 (t, 12H, J = 7.6 Hz), 6.01−5.97 (m, 2H). 31P NMR (CDCl3, ppm): 31.3 (s). Ru(BPI)(PPh3)2(CCCp2Fe) (3a). The synthetic procedure of this compound was the same as that of 2, using ethynylferrocene instead of ethynylbenzene to give a green product. Yield: 68%. Anal. Calcd for C66H51FeN5P2Ru: C, 69.96; H, 4.54; N, 6.18. Found: C, 70.18; H, 4.65; N, 5.99. IR (KBr, cm−1): 2062 s (CC). ESI-MS: m/z (%) 1132.8 (100) [M]+, 871.2 (90) [M − PPh3]+, 609.2 (35) [M − 2PPh3]+. 1H NMR (CDCl3, ppm): 9.93−9.92 (m, 2H), 7.77−7.75 (m, 2H), 7.43−7.41 (m, 2H), 7.20−7.01 (m, 16H), 7.03−6.99 (t, 7H, J = 7.3 Hz), 6.90−6.86 (t, 12H, J = 7.5 Hz), 5.60−5.96 (m, 2H), 4.34 (s, 2H), 4.16−4.14 (m, 6H). 31P NMR (CDCl3, ppm): 31.0 (s). Ru(BPI)(PPh3)2(CCC6H4C6H4CCCp2Fe) (3b). The synthetic procedure of this compound was the same as that of 2, using ((4′ethynyl-[1,1′-biphenyl]-4-yl)ethynyl)ferrocene instead of ethynylbenzene to give a green product. Yield: 70%. Anal. Calcd for C80H59FeN5P2Ru·CH2Cl2: C, 69.78; H, 4.41; N, 5.02. Found: C, 69.98; H, 4.74; N, 5.22. IR (KBr, cm−1): 2053 s (CC). ESI-MS: m/z (%) 1308.2 (30) [M]+, 1046.0 (95) [M − PPh3]+, 662.2 (100) [Ru(BPI)(PPh3)]+. 1H NMR (CD2Cl2, ppm): 9.96−9.95 (d, 2H, J = 5.1 Hz), 7.66−7.64 (d, 2H, J = 8.3 Hz), 7.57−7.55 (d, 4H, J = 8.2 Hz), 7.34−7.31 (m, 4H), 7.08−7.02 (m, 22H), 6.89−6.85 (m, 13H), 6.11(s, 3H), 4.54−4.53 (t, 2H, J = 1.8 Hz), 4.29−4.28 (t, 2H, J = 1.8 Hz), 4.27 (s, 5 H). 31P NMR (CD2Cl2, ppm): 31.0 (s). {Ru(BPI)(PPh3)2}2(CCCC) (4). To 20 mL of methanol were added 1 (300 mg, 0.32 mmol), 1,4-bis(trimethylsilyl)-1,3-butadiyne (36.5 mg, 0.19 mmol), and potassium fluoride (21.8 mg, 0.42 mmol) with stirring. After the solution was refluxed overnight, the solvents were removed in vacuo. The residue was recrystallized in acetonitrile to give a green product. Yield: 60%. Anal. Calcd for C112H84N10P4Ru2: C, 70.95; H, 4.47; N, 7.39. Found: C, 70.69; H, 4.51; N, 7.50. IR (KBr, cm−1): 1942 s (CC). ESI-MS: m/z (%) 1896.5 (100) [M]+. 1H NMR (CDCl3, ppm): 11.29 (s, 4H), 8.36 (s, 4H), 8.26 (s, 4H), 7.70− 4744
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(ClO4). ESI-MS: m/z (%) 2021.8 (70) [M]+. 31P NMR (CDCl3, ppm): 30.0 (s), 26.5 (s). [{Ru(BPI)(PPh3)2}2(CCC14H8CC)](ClO4) (7(ClO4)). The synthetic procedure of this compound was the same as that of 3a(ClO4), using 7 instead of 3a to give a green product. Yield: 45%. Anal. Calcd for C126H92ClN10O4P4Ru2: C, 69.69; H, 4.27; N, 6.45. Found: C, 69.81; H, 4.22; N, 6.41. IR (KBr, cm−1): 1930 s (CC), 1087 s (ClO4). ESI-MS: m/z (%) 2071.3 (100) [M]+. 31P NMR (CDCl3, ppm): 29.0 (s). Physical Measurements. 1H and 31P NMR spectra were obtained on a Bruker Avance III (400 MHz) spectrometer with SiMe4 as the internal reference and H3PO4 as the external reference, respectively. UV−vis absorption spectra were measured on a PerkinElmer Lambda 25 UV−vis spectrophotometer. The UV−vis−near-IR spectra were measured on a Perkin-Elmer Lambda 900 UV−vis−near-IR spectrometer. Infrared spectra (IR) were recorded on a Magna 750 FT-IR spectrophotometer with KBr pellets. Elemental analyses (C, H, and N) were carried out on a Perkin-Elmer Model 240 C elemental analyzer. Electrospray ionization mass spectrometry (ESI-MS) was carried out on a Finnigan DECAX-30000 LCQ mass spectrometer using dichloromethane/methanol as mobile phases. The cyclic voltammograms (CVs) and differential pulse voltammograms (DPVs) were measured using a Model 263A potentiostat/galvanostat in dichloromethane solutions containing 0.1 M (Bu4N)(PF6) as the supporting electrolyte. CV was performed at a scan rate of 100 mV s−1 and DPV at a rate of 20 mV s−1 with a pulse height of 40 mV. Platinum and glassy graphite were used as the counter and working electrodes, respectively, and the potential was measured against an Ag/ AgCl reference electrode. Theoretical Methodology. To get insight into the electronic and spectroscopic properties as well as the nature of absorption origins of complexes 3a and 4−7, along with the corresponding one-electronoxidized species 3a+ and 4+−7+, (time-dependent) density functional theory (DFT/TD-DFT)55,56 with the widely used hybrid Becke threeparameter Lee−Yang−Parr (B3LYP) functional57 was employed for the calculations. First, the ground-state geometrical structures as isolated molecules in the vacuum phase were optimized without symmetry constraints by density functional theory (DFT) at the 321G* level. During the optimization processes, the convergent values of maximum force, root-mean-square (RMS) force, maximum displacement, and RMS displacement were set by default. To analyze the spectroscopic properties, more than 100 singlet excited states were calculated to determine the vertical excitation energies by the TD-DFT method with the same functional used in the geometrical optimization process. In the calculations of excited states, the solvent effects of dichloromethane were taken into account by the conductor-like polarizable continuum model method (CPCM).58 The self-consistent field (SCF) convergence criterions of RMS density matrix and maximum density matrix were set at 10−8 and 10−6 au, respectively, in all of the electronic structure calculations. The iterations of excited states continued until the changes in energies of states were no more than 10−7 au between the iterations so as to reach convergence in all of the excited states. To save computation time, the phenyl groups in the phosphine ligands were replaced by H atoms, affording simplified models. All calculations were performed with the Gaussian 03 program package.59 Visualization of the frontier molecular orbitals was performed by GaussView. The Ros and Schuit method (C-squared population analysis method, SCPA)60 was supported to analyze the partition orbital composition by using the Multiwfn 2.4 program.61
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AUTHOR INFORMATION
Corresponding Author
*E-mail for Z.-N.C.:
[email protected]. Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS The authors are grateful for financial support from the NSFC (20931006, 91122006, and 21390392), the 973 project (2014CB845603) from the MSTC, and the NSF of Fujian Province (2011J01065).
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REFERENCES
(1) (a) Szafert, S.; Gladysz, J. A. Chem. Rev. 2003, 103, 4175. (b) Carroll, R. L.; Gorman, C. B. Angew. Chem., Int. Ed. 2002, 41, 4378. (2) Ren, T. Organometallics 2005, 24, 4854. (3) Low, P. J. Coord. Chem. Rev. 2013, 257, 1507. (4) Halet, J.-F.; Lapinte, C. Coord. Chem. Rev. 2013, 257, 1584. (5) Costuas, K.; Rigaut, S. Dalton Trans. 2011, 40, 5643. (6) Venkatesan, K.; Blacque, O.; Berke, H. Dalton Trans. 2007, 1091. (7) (a) Creutz, C.; Taube, H. J. Am. Chem. Soc. 1969, 91, 3988. (b) Creutz, C.; Taube, H. J. Am. Chem. Soc. 1973, 95, 1086. (8) Aguirre-Etcheverry, P.; O’Hare, D. Chem. Rev. 2010, 110, 4839. (9) Robin, M. B.; Day, P. Adv. Inorg. Chem. Radiochem. 1967, 10, 422. (10) (a) Allen, G.; Hush, N. Prog. Inorg. Chem. 1967, 8, 357. (b) Hush, N. Prog. Inorg. Chem. 1967, 8, 391. (11) (a) Wen, H.-M.; Wu, Y.-H.; Xu, L.-J.; Zhang, L.-Y.; Chen, C.-N.; Chen, Z.-N. Dalton Trans. 2011, 40, 6929. (b) Wen, H.-M.; Wu, Y.-H.; Fan, Y.; Zhang, L.-Y.; Chen, C.-N.; Chen, Z.-N. Inorg. Chem. 2010, 49, 2210. (c) Gagne, R. R.; Marks, D. N. Inorg. Chem. 1984, 23, 65. (d) Balogh-Hergovich, É.; Kaizer, J.; Speier, G.; Huttner, G.; Jacobi, A. Inorg. Chem. 2000, 39, 4224. (e) Tolman, C.; Druliner, J.; Krusic, P.; Nappa, M.; Seidel, W.; Williams, I.; Ittel, S. J. Mol. Catal. 1988, 48, 129. (12) Gagne, R. R.; Marritt, W. A.; Marks, D. N.; Siegl, W. O. Inorg. Chem. 1981, 20, 3260. (13) Wicholas, M.; Garrett, A. D.; Gleaves, M.; Morris, A. M.; Rehm, M.; Anderson, O. P.; la Cour, A. Inorg. Chem. 2006, 45, 5804. (14) Bruce, M.; Hall, B.; Kelly, B.; Low, P.; Skelton, B.; White, A. J. Chem. Soc., Dalton Trans. 1999, 3719. (15) Bruce, M. I.; Ellis, B. G.; Low, P. J.; Skelton, B. W.; White, A. H. Organometallics 2003, 22, 3184. (16) Richardson, D. E.; Taube, H. Inorg. Chem. 1981, 20, 1278. (17) Colbert, M. C. B.; Lewis, J.; Long, N. J.; Raithby, P. R.; White, A. J. P.; Williams, D. J. J. Chem. Soc., Dalton Trans. 1997, 99. (18) Zhu, Y.; Clot, O.; Wolf, M. O.; Yap, G. P. A. J. Am. Chem. Soc. 1998, 120, 1812. (19) (a) Sato, M.; Hayashi, Y.; Kumakura, S.; Shimizu, N.; Katada, M.; Kawata, S. Organometallics 1996, 15, 721. (b) Sato, M.; Shintate, H.; Kawata, Y.; Sekino, M. Organometallics 1994, 13, 1956. (20) Jones, N. D.; Wolf, M. O.; Giaquinta, D. M. Organometallics 1997, 16, 1352. (21) Bruce, M. I.; Low, P. J.; Hartl, F.; Humphrey, P. A.; de Montigny, F.; Jevric, M.; Lapinte, C.; Perkins, G. J.; Roberts, R. L.; Skelton, B. W.; White, A. H. Organometallics 2005, 24, 5241. (22) Wu, S.-H.; Shen, J.-J.; Yao, J.; Zhong, Y.-W. Chem. Asian J. 2013, 8, 138. (23) Li, Z.; Beatty, A. M.; Fehlner, T. P. Inorg. Chem. 2003, 42, 5707. (24) Lebretsn, C.; Touchard, D.; Le Pichon, L.; Daridor, A.; Toupet, L.; Dixneuf, P. H. Inorg. Chim. Acta 1998, 272, 188. (25) Bruce, M. I.; Jevric, M.; Perkins, G. J.; Skelton, B. W.; White, A. H. J. Organomet. Chem. 2007, 692, 1757. (26) Fan, Y.; Liu, I. P.-C.; Fanwick, P. E.; Ren, T. Organometallics 2009, 28, 3959. (27) Lohan, M.; Justaud, F.; Lang, H.; Lapinte, C. Organometallics 2012, 31, 3565.
ASSOCIATED CONTENT
S Supporting Information *
Figures giving additional spectral properties, tables and figures giving details of TD-DFT calculations, and an .xyz file of all computed molecule Cartesian coordinates for convenient visualization. This material is available free of charge via the Internet at http://pubs.acs.org. 4745
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Organometallics
Article
(55) Becke, A. D. J. Chem. Phys. 1993, 98, 5648. (56) (a) Casida, M. E.; Jamorski, C.; Casida, K. C.; Salahub, D. R. J. Chem. Phys. 1998, 108, 4439. (b) Stratmann, R. E.; Scuseria, G. E.; Frisch, M. J. J. Chem. Phys. 1998, 109, 8218. (c) Bauernschmitt, R.; Ahlrichs, R. Chem. Phys. Lett. 1996, 256, 454. (57) (a) Becke, A. D. Phys. Rev. A 1988, 38, 3098. (b) Lee, C. T.; Yang, W. T.; Parr, R. G. Phys. Rev. B 1988, 37, 785. (58) (a) Cossi, M.; Rega, N.; Scalmani, G.; Barone, V. J. Comput. Chem. 2003, 24, 669. (b) Barone, V.; Cossi, M. J. Phys. Chem. A 1998, 102, 1995. (59) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Montgomery, J. A., Jr.; Vreven, T.; Kudin, K. N.; Burant, J. C.; Millam, J. M.; Iyengar, S. S.; Tomasi, J.; Barone, V.; Mennucci, B.; Cossi, M.; Scalmani, G.; Rega, N.; Petersson, G. A.; Nakatsuji, H.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Klene, M.; Li, X.; Knox, J. E.; Hratchian, H. P.; Cross, J. B.; Bakken, V.; Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.; Ayala, P. Y.; Morokuma, K.; Voth, G. A.; Salvador, P.; Dannenberg, J. J.; Zakrzewski, V. G.; Dapprich, S.; Daniels, A. D.; Strain, M. C.; Farkas, O.; Malick, D. K.; Rabuck, A. D.; Raghavachari, K.; Foresman, J. B.; Ortiz, J. V.; Cui, Q.; Baboul, A. G.; Clifford, S.; Cioslowski, J.; Stefanov, B. B.; Liu, G.; Liashenko, A.; Piskorz, P.; Komaromi, I.; Martin, R. L.; Fox, D. J.; Keith, T.; Al-Laham, M. A.; Peng, C. Y.; Nanayakkara, A.; Challacombe, M.; Gill, P. M. W.; Johnson, B.; Chen, W.; Wong, M. W.; Gonzalez, C.; Pople, J. A. Gaussian 03, revision D.02; Gaussian, Inc., Wallingford, CT, 2004. (60) Ros, P.; Schuit, G. C. A. Theor. Chim. Acta 1966, 4, 1. (61) Lu, T.; Chen, F. W. J. Comput. Chem. 2012, 33, 580.
(28) Grelaud, G.; Cifuentes, M. P.; Schwich, T.; Argouarch, G.; Petrie, S.; Stranger, R.; Paul, F.; Humphrey, M. G. Eur. J. Inorg. Chem. 2012, 65. (29) Paul, F.; Lapinte, C. Coord. Chem. Rev. 1998, 178, 431. (30) (a) Bruce, M. I.; Low, P. J.; Costuas, K.; Halet, J.-F.; Best, S. P.; Heath, G. A. J. Am. Chem. Soc. 2000, 122, 1949. (b) Bruce, M. I.; Ellis, B. G.; Low, P. J.; Skelton, B. W.; White, A. H. Organometallics 2003, 22, 3184. (c) Bruce, M. I.; Scoleri, N.; Zaitseva, N. N.; Le Guennic, B.; Halet, J.-F. Organometallics 2012, 31, 4701. (d) Bartlett, M. J.; Hill, A. F.; Smith, M. K. Organometallics 2005, 24, 5795. (31) (a) Gao, L.-B.; Zhang, L.-Y.; Shi, L.-X.; Chen, Z.-N. Organometallics 2005, 24, 1678. (b) Gao, L.-B.; Liu, S.-H.; Zhang, L.-Y.; Shi, L.-X.; Chen, Z.-N. Organometallics 2006, 25, 506. (32) (a) Xu, G.-L.; Zou, G.; Ni, Y.-H.; DeRosa, M. C.; Crutchley, R. J.; Ren, T. J. Am. Chem. Soc. 2003, 125, 10057. (b) Ren, T.; Zou, G.; Alvarez, J. C. Chem. Commun. 2000, 1197. (33) Fox, M. A.; Le Guennic, B.; Roberts, R. L.; Brue, D. A.; Yufit, D. S.; Howard, J. A. K.; Manca, G.; Halet, J.-F.; Hartl, F.; Low, P. J. J. Am. Chem. Soc. 2011, 133, 18433. (34) Olivier, C.; Kim, B.; Touchard, D.; Rigaut, S. Organometallics 2008, 27, 509. (35) Gao, L.-B.; Kan, J.; Fan, Y.; Zhang, L.-Y.; Liu, S.-H.; Chen, Z.-N. Inorg. Chem. 2007, 46, 5651. (36) (a) Xia, J.-L.; Zhu, X.; Zhang, C.; Jin, G.-J.; Yin, J.; Yu, G.-A.; Liu, S. H.; Man, W. Y.; Schauer, P. A.; Fox, M. A.; Low, P. J. Organometallics 2012, 31, 5321. (b) Ou, Y.-P.; Jiang, C.; Wu, D.; Xia, J.; Yin, J.; Jin, S.; Yu, G.-A.; Liu, S. H. Organometallics 2011, 30, 5763. (37) Huang, C.-C.; Lin, Y.-C.; Huang, S.-L.; Liu, Y.-H.; Wang, Y. Organometallics 2003, 22, 1512. (38) Lavastre, O.; Plass, J.; Bachmann, P.; Guesmi, S.; Moinet, C.; Dixneuf, P. H. Organometallics 1997, 16, 184. (39) Wuttke, E.; Pevny, F.; Hervault, Y.-M.; Norel, L.; Drescher, M.; Winter, R. F.; Rigaut, S. Inorg. Chem. 2012, 51, 1902. (40) Field, L. D.; Magill, A. M.; Shearer, T. K.; Colbran, S. B.; Lee, S. T.; Dalgarno, S. J.; Bhadbhade, M. M. Organometallics 2010, 29, 957. (41) Colbert, M. C. B.; Lewis, J.; Long, N. J.; Raithby, P. R.; Younus, M.; White, A. J. P.; Williams, D. J.; Payne, N. N.; Yellowlees, L.; Beljonne, D.; Chawdhury, N.; Friend, R. H. Organometallics 1998, 17, 3034. (42) de Montigny, F.; Argouarch, G.; Costuas, K.; Halet, J.-F.; Roisnel, T.; Toupet, L.; Lapinte, C. Organometallics 2005, 24, 4558. (43) Tanaka, Y.; Shaw-Taberlet, J. A.; Justaud, F.; Cador, O.; Roisnel, T.; Akita, M.; Hamon, J.-R.; Lapinte, C. Organometallics 2009, 28, 4656. (44) Fox, M. A.; Farmer, J. D.; Roberts, R. L.; Humphrey, M. G.; Low, P. J. Organometallics 2009, 28, 5266. (45) Otón, F.; Ratera, I.; Espinosa, A.; Tárraga, A.; Veciana, J.; Molina, P. Inorg. Chem. 2010, 49, 3183. (46) (a) Demadis, K. D.; El-Samanody, E.-S.; Coia, G. M.; Meyer, T. J. J. Am. Chem. Soc. 1999, 121, 535. (b) Kober, E. M.; Goldsby, K. A.; Narayana, D.; Meyer, T. J. J. Am. Chem. Soc. 1983, 105, 4303. (47) Rocha, R. C.; Rein, F. N.; Jude, H.; Shreve, A. P.; Concepcion, J. J.; Meyer, T. J. Angew. Chem., Int. Ed. 2008, 47, 503. (48) Yao, C.-J.; Zhong, Y.-W.; Yao, J. J. Am. Chem. Soc. 2011, 133, 15697. (49) Sikora, D. J.; Rausch, M. D.; Rogers, R. D.; Atwood, J. L. J. Am. Chem. Soc. 1981, 103, 982. (50) (a) Lichtenberger, D. L.; Renshaw, S. K.; Bullock, R. M. J. Am. Chem. Soc. 1993, 115, 3276. (b) Lichtenberger, D. L.; Renshaw, S. K. Organometallics 1993, 12, 3522. (51) Mura, P.; Olby, B. G.; Robinson, S. D. J. Chem. Soc., Dalton Trans. 1985, 2101. (52) Gagne, R. R.; Marritt, W. A.; Marks, D. N.; Siegl, W. O. Inorg. Chem. 1981, 20, 3260. (53) Rosenblum, M.; Brawn, N.; Papenmeier, J.; Applebaum, M. J. Organomet. Chem. 1966, 6, 173. (54) Khan, M. S.; Al-Mandhary, M. R.; Al-Suti, M. K.; Al-Battashi, F. R.; Al-Saadi, S.; Ahrens, B.; Bjernemose, J. K.; Mahon, M. F.; Raithby, P. R.; Younus, M. Dalton Trans. 2004, 2377. 4746
dx.doi.org/10.1021/om401235p | Organometallics 2014, 33, 4738−4746
