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Haiduc I. Inverse coordination metal complexes with oxalate and sulfur, selenium and nitrogen analogues as coordination centers. Topology and systematization. J COORD CHEM 2020. [DOI: 10.1080/00958972.2020.1789120] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- Ionel Haiduc
- Facultatea de Chimie, Universitatea Babeş-Bolyai, Cluj-Napoca, Romania
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2
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Zhu GY, Meng M, Tan YN, Xiao X, Liu CY. Electronic Coupling between Two Covalently Bonded Dimolybdenum Units Bridged by a Naphthalene Group. Inorg Chem 2016; 55:6315-22. [PMID: 27243960 DOI: 10.1021/acs.inorgchem.6b01021] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Using 2,6-naphthalenedicarboxylate and its thiolated derivatives as bridging ligands, three Mo2 dimers of the type [Mo2(DAniF)3](E2CC10H6CE2)[Mo2(DAniF)3] (DAniF = N,N'-di-p-anisylformamidinate; E = O, S) have been synthesized and characterized by X-ray diffraction. These compounds can be generally formulated as [Mo2]-naph-[Mo2], where the complex unit [Mo2] ([Mo2(DAniF)3(μ-E2C)]) functions as an electron donor (acceptor) and the naphthalene (naph) group is the bridge. The mixed-valence (MV) complexes, generated by one-electron oxidation of the neutral precursors, display weak, very broad intervalence charge-transfer absorption bands in the near-to-mid-IR regions. The electronic coupling matrix elements for the MV complexes, Hab = 390-570 cm(-1), are calculated from the Mulliken-Hush equation, which fall between those for the phenyl (ph) and biphenyl (biph) analogues reported previously. The three series consisting of three complexes with the same [Mo2] units exhibit exponential decay of Hab as the bridge changes from ph to biph via naph, with decay factors of 0.21-0.17 Å(-1). Therefore, it is evidenced that while the extent of the bridge conjugacy varies, the electronic coupling between the two [Mo2] units is dominated by the Mo2···Mo2 separation. The absorption band energies for metal-to-ligand charge transfer are in the middle of those for the ph and biph analogues, which is consistent with variation of the HOMO-LUMO energy gaps for the complex series. These results indicate that the interplay of the bridge length and conjugacy is to affect the enegy for charge transfer crossing the intervening moiety, in accordance with a superechange mechanism.
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Affiliation(s)
- Guang Yuan Zhu
- Department of Chemistry, Jinan University , 601 Huang-Pu Avenue West, Guangzhou 510632, China
| | - Miao Meng
- Department of Chemistry, Jinan University , 601 Huang-Pu Avenue West, Guangzhou 510632, China
| | - Ying Ning Tan
- Department of Chemistry, Jinan University , 601 Huang-Pu Avenue West, Guangzhou 510632, China
| | - Xuan Xiao
- Department of Chemistry, Jinan University , 601 Huang-Pu Avenue West, Guangzhou 510632, China
| | - Chun Y Liu
- Department of Chemistry, Jinan University , 601 Huang-Pu Avenue West, Guangzhou 510632, China
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Kang MT, Meng M, Tan YN, Cheng T, Liu CY. Tuning the Electronic Coupling and Electron Transfer in Mo2 Donor-Acceptor Systems by Variation of the Bridge Conformation. Chemistry 2016; 22:3115-26. [PMID: 26807909 DOI: 10.1002/chem.201504033] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2015] [Indexed: 11/12/2022]
Abstract
Assembling two quadruply bonded dimolybdenum units [Mo2 (DAniF)3 ](+) (DAniF=N,N'-di(p-anisyl)formamidinate) with 1,4-naphthalenedicarboxylate and its thiolated derivatives produced three complexes [{Mo2 (DAniF)3 }2 (μ-1,4-O2 CC10 H6 CO2 )], [{Mo2 (DAniF)3 }2 (μ-1,4-OSCC10 H6 COS)], and [{Mo2 (DAniF)3 }2 (μ-1,4-S2 CC10 H6 CS2 )]. In the X-ray structures, the naphthalene bridge deviates from the plane defined by the two Mo-Mo bond vectors with the torsion angle increasing as the chelating atoms of the bridging ligand vary from O to S. The mixed-valent species exhibit intervalence transition absorption bands with high energy and very low intensity. In comparison with the data for the phenylene analogues, the optically determined electronic coupling matrix elements (Hab =258-345 cm(-1) ) are lowered by a factor of two or more, and the electron-transfer rate constants (ket ≈10(11) s(-1) ) are reduced by about one order of magnitude. These results show that, when the electron-transporting ability of the bridge and electron-donating (electron-accepting) ability of the donor (acceptor) are both variable, the former plays a dominant role in controlling the intramolecular electron transfer. DFT calculations revealed that increasing the torsion angle enlarges the HOMO-LUMO energy gap by elevating the (bridging) ligand-based LUMO energy. Therefore, our experimental results and theoretical analyses verify the superexchange mechanism for electronic coupling and electron transfer.
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Affiliation(s)
- Mei Ting Kang
- Department of Chemistry, Jinan University, 601 Huang-Pu Avenue West, Guangzhou, P.R. China
| | - Miao Meng
- Department of Chemistry, Jinan University, 601 Huang-Pu Avenue West, Guangzhou, P.R. China
| | - Ying Ning Tan
- Department of Chemistry, Jinan University, 601 Huang-Pu Avenue West, Guangzhou, P.R. China
| | - Tao Cheng
- Department of Chemistry, Jinan University, 601 Huang-Pu Avenue West, Guangzhou, P.R. China
| | - Chun Y Liu
- Department of Chemistry, Jinan University, 601 Huang-Pu Avenue West, Guangzhou, P.R. China.
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Zhang HL, Zhu GY, Wang G, Meng M, Liu CY, Lei H. Electronic Coupling in [Mo2]-Bridge-[Mo2] Systems with Twisted Bridges. Inorg Chem 2015; 54:11314-22. [PMID: 26579936 DOI: 10.1021/acs.inorgchem.5b01923] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In order to evaluate the impact of bridge conformation on electronic coupling in donor-bridge-acceptor triad systems, two Mo2 dimers, [Mo2(DAniF)3]2[μ-1,4-{C(O)NH}2-Naph] (1, DAniF = N,N'-di(p-anisyl)formamidinate and Naph = naphthalenyl) and [Mo2(DAniF)3]2[μ-1,4-(CS2)2-2,5-Me2C6H2] (2), have been synthesized and structurally characterized. These two compounds feature a large dihedral angle (>60°) between the central aromatic ring and the plane defined by the Mo-Mo bond vectors, which is distinct from the previously reported phenylene bridged analogues [Mo2(DAniF)3]2[μ-1,4-{C(O)NH}2-ph] (I) and [Mo2(DAniF)3]2[μ-1,4-(CS2)2-C6H4] (II), respectively. Unusual optical behaviors are observed for the mixed-valence (MV) species (1(+) and 2(+)), generated by single-electron oxidation. While 2(+) exhibits a weak intervalence charge transfer (IVCT) absorption band in the near-IR region, the IVCT band is absent in the spectrum of 1(+), which is quite different from what observed for I(+) and II(+). Optical analyses, based on superexchange formalism and Hush model, indicate that, in terms of Robin-Day classification, mixed-valence species 1(+) belongs to the electronically uncoupled Class I and complex 2(+), with Hab = 220 cm(-1), is assigned to the weakly coupled Class II. Together with I(+) and II(+), the four MV complexes complete a transition from Class I to Class II-III borderline as a result of manipulating the geometric topology of the bridge. Given the structural and electronic features for the molecular systems, the impacts of electrostatic interaction (through-space) and electron resonance (through-bond) on electronic coupling are discussed.
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Affiliation(s)
- Hong Li Zhang
- Department of Chemistry, Jinan University , 601 Huang-Pu Avenue West, Guangzhou 510632, China
| | - Guang Yuan Zhu
- Department of Chemistry, Jinan University , 601 Huang-Pu Avenue West, Guangzhou 510632, China
| | - Gangyi Wang
- Department of Chemistry, Jinan University , 601 Huang-Pu Avenue West, Guangzhou 510632, China
| | - Miao Meng
- Department of Chemistry, Jinan University , 601 Huang-Pu Avenue West, Guangzhou 510632, China
| | - Chun Y Liu
- Department of Chemistry, Jinan University , 601 Huang-Pu Avenue West, Guangzhou 510632, China
| | - Hao Lei
- Department of Chemistry, Jinan University , 601 Huang-Pu Avenue West, Guangzhou 510632, China
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Ventura K, Veleta JM, Metta-Magaña A, Villagrán D. Stabilization of a W26+ bimetallic complex supported by two N,N′,N″-triphenylguanidinate ligands. Inorganica Chim Acta 2015. [DOI: 10.1016/j.ica.2014.09.019] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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The magic of the delta bonds: How to modulate electronic communication in pairs-of-pairs containing multiple bonded Mo2 species. Inorganica Chim Acta 2015. [DOI: 10.1016/j.ica.2014.03.034] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Cheng T, Tan YN, Zhang Y, Zhang YY, Meng M, Lei H, Chen L, Liu CY. Distinguishing the Strength of Electronic Coupling for Mo2-Containing Mixed-Valence Compounds within the Class III Regime. Chemistry 2014; 21:2353-7. [DOI: 10.1002/chem.201406196] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2014] [Indexed: 11/11/2022]
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Falvello LR, Foxman BM, Murillo CA. Fitting the Pieces of the Puzzle: The δ Bond. Inorg Chem 2014; 53:9441-56. [DOI: 10.1021/ic500119h] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Affiliation(s)
- Larry R. Falvello
- Departamento de Química Inorgánica, ICMA, Universidad de Zaragoza, CSIC, Pedro Cerbuna 12, E-50009 Zaragoza, Spain
| | - Bruce M. Foxman
- Department of Chemistry, MS 015, Brandeis University, Waltham, Massachusetts 02453, United States
| | - Carlos A. Murillo
- Department of Chemistry, Texas A&M University, P.O. Box 30012, College Station, Texas 77842-3012, United States
- Department
of Chemistry, University of Texas at El Paso, El Paso, Texas 79968, United States
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Tanaka S, Tsurugi H, Mashima K. Supramolecular assemblies of multi-nuclear transition metal complexes: Synthesis and redox properties. Coord Chem Rev 2014. [DOI: 10.1016/j.ccr.2014.01.012] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Dalal NS, Murillo CA. The usefulness of EPR spectroscopy in the study of compounds with metal–metal multiple bonds. Dalton Trans 2014; 43:8565-76. [DOI: 10.1039/c4dt00506f] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A discussion of how EPR spectroscopy has contributed to the understanding of the electronic structure of paddlewheel compounds with multiple bonds between metal atoms is presented while commemorating the 50th anniversary of the paper describing the quadruple bond and the identification of the delta bond in the Re2Cl82− anion.
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Affiliation(s)
- Naresh S. Dalal
- Department of Chemistry and Biochemistry
- and National High Magnetic Field
- Florida State University
- Tallahassee, USA
| | - Carlos A. Murillo
- Department of Chemistry
- College Station, USA
- University of Texas at El Paso
- El Paso, USA
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Xiao X, Liu CY, He Q, Han MJ, Meng M, Lei H, Lu X. Control of the charge distribution and modulation of the class II-III transition in weakly coupled Mo2-Mo2 systems. Inorg Chem 2013; 52:12624-33. [PMID: 24151862 DOI: 10.1021/ic4017855] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Three novel dimolybdenum dimers [Mo2(DAniF)3]2(μ-OSCC6H4CSO), [Mo2(DAniF)3]2(μ-O2CC6H4CS2), and [Mo2(DAniF)3]2(μ-S2CC6H4CS2) (DAniF = N,N'-di(p-anisyl)formamidinate) have been synthesized and characterized by single-crystal X-ray diffractions. Together with the terephthalate analogue, the four compounds, denoted as [O2-O2], [OS-OS], [S2-S2], and [O2-S2], have similar molecular skeletons and Mo2···Mo2 separations (∼12 Å), but varying sulfur contents or symmetry. The singly oxidized complexes [O2-O2](+), [OS-OS](+), [S2-S2](+), and [O2-S2](+) display characteristic intervalence transition absorption bands in the near- and mid-IR regions, with differing band energy, intensity, and shape. Applying the geometrical length of the bridging group "-CC6H4C-" (5.8 Å) as the effective electron transfer distance, calculations from the Mulliken-Hush equation yield electronic coupling matrix elements (H(ab)) in the range 600-900 cm(-1). Significantly, this series presents a transition from electron localization to "almost-delocalization" as the carboxylate groups of the bridging ligand are successively thiolated. In terms of Robin-Day's scheme, [S2-S2](+) is best described as an intermediate between Class II and III, while [O2-O2](+) and [OS-OS](+) belong to Class II. It is unusual that the Class II-III transition occurs in such a weakly coupled system (H(ab) < 1000 cm(-1)). This is attributed to the d(δ)-p(π) conjugation between the Mo2 center and bridging ligand. By electrochemical and spectroscopic methods, the internal energy difference for [O2-S2](+) is determined to be 2250 ± 80 cm(-1), which controls the charge distribution of the cation radical. The experimental results and theoretical analyses illustrate that the unsymmetrical geometry leads to unbalanced electronic configurations and asymmetrical redox and optical behaviors.
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Affiliation(s)
- Xuan Xiao
- Department of Chemistry, Tongji University , 1239 Siping Road, Shanghai 200092, China
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Ibarra-Rodríguez M, Rasika Dias HV, Jiménez-Pérez VM, Muñoz-Flores BM, Flores-Parra A, Sánchez S. Dinuclear Tin(II) Complex of a Bulky cis-Oxamide: Synthesis, Characterization, Crystal Structure, and DFT Studies. Z Anorg Allg Chem 2012. [DOI: 10.1002/zaac.201200212] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Cotton FA, Dalal NS, Kaur N, Murillo CA, Young MD, Zhao Q. A Rare Cyclic Dimolybdenum Triad with Three Weakly Interacting Unpaired Electrons. J CLUST SCI 2010. [DOI: 10.1007/s10876-010-0289-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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Cotton FA, Li Z, Murillo CA. Evidence of disruption of conjugation involving delta bonds in intramolecular electronic coupling. Inorg Chem 2009; 48:11847-52. [PMID: 19911818 DOI: 10.1021/ic9018647] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A dimer of dimers containing two quadruply bonded [Mo(2)(DAniF)(3)](+) units (DAniF = N,N'-di(p-anisyl)formamidinate) linked by the S-donor linker, dimethyldithiooxamidate was synthesized, structurally characterized, and electronic communication was probed. The core of [Mo(2)(DAniF)(3)](2)(C(2)S(2)N(2)Me(2)), 1, formed by the Mo(2)NSC(2)SNMo(2) atoms shows two fused but non planar six-membered rings, which differs from that of the beta form of dimethyloxamidate analogue that has a heteronaphthalene-type structure (Cotton, F. A.; Liu, C. Y.; Murillo, C. A.; Villagran, D.; Wang, X. J. Am. Chem. Soc. 2004, 126, 14822). For these two analogous compounds electronic coupling between the two [Mo(2)] units, as determined by electrochemical measurements, diminishes considerably upon replacement of O-donor by S-donor atoms (DeltaE(1/2) = 531 mV and 440 mV, respectively). This suggests that the non planar conformation of the linker in 1 hampers a pathway leading to pi conjugation. Density functional theory (DFT) calculations show that the highest occupied molecular orbitals HOMO-HOMO-1 energy gap of 0.12 eV for 1 is much smaller than that of 0.61 eV for the O-donor analogue, which is consistent with the electrochemical data.
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Affiliation(s)
- F Albert Cotton
- Department of Chemistry, Laboratory for Molecular Structure and Bonding, P.O. Box 30012, Texas A&M University, College Station, Texas 77842-3012, USA
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Cotton FA, Murillo CA, Zhao Q. Influence of Bonding Mode of the Linkers in the Electronic Communication of Molecular Pairs Having Dimolybdenum Units Linked by Pseudohalides. Inorg Chem 2009; 48:11755-66. [DOI: 10.1021/ic901826y] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- F. Albert Cotton
- Department of Chemistry, P.O. Box 3012, Texas A&M University, College Station, Texas 77842-3012
| | - Carlos A. Murillo
- Department of Chemistry, P.O. Box 3012, Texas A&M University, College Station, Texas 77842-3012
| | - Qinliang Zhao
- Department of Chemistry, P.O. Box 3012, Texas A&M University, College Station, Texas 77842-3012
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Lu CC, Bill E, Weyhermüller T, Bothe E, Wieghardt K. Neutral bis(alpha-iminopyridine)metal complexes of the first-row transition ions (Cr, Mn, Fe, Co, Ni, Zn) and their monocationic analogues: mixed valency involving a redox noninnocent ligand system. J Am Chem Soc 2008; 130:3181-97. [PMID: 18284242 DOI: 10.1021/ja710663n] [Citation(s) in RCA: 235] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A series of bis(alpha-iminopyridine)metal complexes featuring the first-row transition ions (Cr, Mn, Fe, Co, Ni, and Zn) is presented. It is shown that these ligands are redox noninnocent and their paramagnetic pi radical monoanionic forms can exist in coordination complexes. Based on spectroscopic and structural characterizations, the neutral complexes are best described as possessing a divalent metal center and two monoanionic pi radicals of the alpha-iminopyridine. The neutral M(L*)2 compounds undergo ligand-centered, one-electron oxidations generating a second series, [(L(x))2M(THF)][B(ArF)4] [where L(x) represents either the neutral alpha-iminopyridine (L)0 and/or its reduced pi radical anion (L*)-]. The cationic series comprise mostly mixed-valent complexes, wherein the two ligands have formally different redox states, (L)0 and (L*)-, and the two ligands may be electronically linked by the bridging metal atom. Experimentally, the cationic Fe and Co complexes exhibit Robin-Day Class III behavior (fully delocalized), whereas the cationic Zn, Cr, and Mn complexes belong to Class I (localized) as shown by X-ray crystallography and UV-vis spectroscopy. The delocalization versus localization of the ligand radical is determined only by the nature of the metal linker. The cationic nickel complex is exceptional in this series in that it does not exhibit any ligand mixed valency. Instead, its electronic structure is consistent with two neutral ligands (L)0 and a monovalent metal center or [(L)2Ni(THF)][B(ArF)4]. Finally, an unusual spin equilibrium for Fe(II), between high spin and intermediate spin (S(Fe) = 2 <--> S(Fe) = 1), is described for the complex [(L*)(L)Fe(THF)][B(ArF)4], which consequently is characterized by the overall spin equilibrium (S(tot) = 3/2 <--> S(tot) = 1/2). The two different spin states for Fe(II) have been characterized using variable temperature X-ray crystallography, EPR spectroscopy, zero-field and applied-field Mössbauer spectroscopy, and magnetic susceptibility measurements. Complementary DFT studies of all the complexes have been performed, and the calculations support the proposed electronic structures.
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Affiliation(s)
- Connie C Lu
- Max-Planck-Institut für Bioanorganische Chemie, Stiftstrasse 34-36, D-45470 Mülheim an der Ruhr, Germany
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Cotton FA, Jin JY, Li Z, Murillo CA, Reibenspies JH. Exceptionally strong electronic coupling between [Mo2] units linked by substituted dianionic quinones. Chem Commun (Camb) 2008:211-3. [DOI: 10.1039/b710804d] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Cotton FA, Murillo CA, Young MD, Yu R, Zhao Q. Very Large Difference in Electronic Communication of Dimetal Species with Heterobiphenylene and Heteroanthracene Units. Inorg Chem 2007; 47:219-29. [DOI: 10.1021/ic701937c] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- F. Albert Cotton
- Department of Chemistry and Laboratory for Molecular Structure and Bonding, P.O. Box 30012, Texas A&M University, College Station, Texas 77842-3012
| | - Carlos A. Murillo
- Department of Chemistry and Laboratory for Molecular Structure and Bonding, P.O. Box 30012, Texas A&M University, College Station, Texas 77842-3012
| | - Mark D. Young
- Department of Chemistry and Laboratory for Molecular Structure and Bonding, P.O. Box 30012, Texas A&M University, College Station, Texas 77842-3012
| | - Rongmin Yu
- Department of Chemistry and Laboratory for Molecular Structure and Bonding, P.O. Box 30012, Texas A&M University, College Station, Texas 77842-3012
| | - Qinliang Zhao
- Department of Chemistry and Laboratory for Molecular Structure and Bonding, P.O. Box 30012, Texas A&M University, College Station, Texas 77842-3012
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Cotton FA, Li Z, Liu CY, Murillo CA. Modulating Electronic Coupling Using O- and S-donor Linkers. Inorg Chem 2007; 46:7840-7. [PMID: 17705370 DOI: 10.1021/ic700932s] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Structures of compounds having two dimolybdenum units Mo2(DAniF)3+ (DAniF = N,N'-di-p-anisylformamidinate) connected by unsubstituted oxamidate (1) and dithiooxamidate (2) linkers are isomorphous, and the cores of the molecules are planar because of two intramolecular hydrogen bonds within the linkers. Molecular mechanics calculations show a barrier of rotation along the C-C bond of approximately 10 kcal x mol(-1), which suggests that planar conformations are also expected in solution. Changing the two oxygen atoms in the linker of 1 to sulfur atoms results in a significant enhancement of the electronic coupling between the dimetal units (Delta(E1/2) = 204 mV for 1 and 407 mV for 2). The electronic spectrum of 2 shows an intense low energy (600 nm) metal-to-ligand charge transfer (MLCT) band, whereas that for 1 shows only a weak absorption band at 460 nm. DFT calculations on models 1' and 2', in which the anisyl groups were replaced by hydrogen atoms, show that the energy of the pi* orbital of the linker is much lower for 2'. This allows dpi-ddelta interactions from the electrons in the delta orbitals of the Mo2 unit to the sulfur atom that in turn facilitates an electron hopping pathway.
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Affiliation(s)
- F Albert Cotton
- Department of Chemistry and Laboratory for Molecular Structure and Bonding, P.O. Box 3012, Texas A&M University, College Station, Texas 77842-3012, USA
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