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Carboxylate Tolerance of the Redox-Active Platform [Ru(mu-tppz)Ru](n), where tppz=2,3,5,6-Tetrakis(2-pyridyl)pyrazine, in the Electron-Transfer Series [(L)CIRu(mu-tppz)RuCl(L)](n), n=2+, +, 0, -, 2-, with 2-Picolinato, Quinaldato, and 8-Quinolinecarboxylato Ligands (L(-))

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Title Carboxylate Tolerance of the Redox-Active Platform [Ru(mu-tppz)Ru](n), where tppz=2,3,5,6-Tetrakis(2-pyridyl)pyrazine, in the Electron-Transfer Series [(L)CIRu(mu-tppz)RuCl(L)](n), n=2+, +, 0, -, 2-, with 2-Picolinato, Quinaldato, and 8-Quinolinecarboxylato Ligands (L(-))
 
Creator KUNDU, T
SARKAR, B
MONDAL, TK
FIEDLER, J
MOBIN, SM
KAIM, W
LAHIRI, GK
 
Subject dinuclear ruthenium complexes
transition-metal-complexes
density-functional theory
intervalence charge-transfer
tridentate bridging ligand
hydrazone-based ligands
dot cellular-automata
mixed-valence isomers
diruthenium complexes
2,3,5,6-tetrakis(2-pyridyl)pyrazine tppz
 
Description The neutral title complexes [(L(1-3))ClRu(II)(mu-tppz)Ru(II)Cl(L(1-3))] [tppz = 2,3,5,6-tetrakis(2-pyridyl)pyrazine with L(1) = 2-picolinate, L(2) = 2-quinolinecarboxylate (quinaldate) and with the hitherto little used L(3) = 8-quinolinecarboxylate] have been structurally characterized as approximately anti- (1 and 3) and syn-configured isomers (2) with L ligand N (1 and 3) or 0 atoms (2) trans to the pyrazine N atoms of tppz. In contrast to 1 and 2 with five-membered chelate rings, complex 3 (which is isomeric with 2) contains six-membered chelate rings. Each system 1-3 thus features a significantly different coordination situation, and all complexes exhibit a considerably distorted tppz bridge, including a twisted central pyrazine ring. In spite of this, double one-electron reduction of the bridge is always possible, as is evident from electron paramagnetic resonance (EPA) and UV/vis spectroelectrochemistry. Two separate (Delta E similar to 0.4 V and K(c) similar to 10(7)) one-electron oxidations occur on the metals, producing invariably EPA-silent (4 K) Ru(III)Ru(II) intermediates with moderately intense near-IR absorptions, ranging from 1500 to 1900 nm. IA spectroelectrochemistry of the carboxylato carbonyl stretching bands did not result in any noticeable shift, in contrast to what was observed with dipyridyl ketones and related coligands. Density functional theory (DFT)/time-dependent OFT calculations confirm the experimental structures and explain the noted spectroscopic trends: destabilized and closer-spaced frontier orbitals for 3 over 2, with the comparison to 1 suggesting that the configuration is a major factor. Nevertheless, the rather unperturbed electronic structure of the [Ru(mu-tppz)Ru](n) entity, despite different coordination situations at the metal sites, is remarkable and suggests further use of this entity as a robust, carboxylate-tolerant redox-active platform in extended frameworks.
 
Publisher AMER CHEMICAL SOC
 
Date 2011-07-13T18:17:45Z
2011-12-26T12:48:01Z
2011-12-27T05:43:18Z
2011-07-13T18:17:45Z
2011-12-26T12:48:01Z
2011-12-27T05:43:18Z
2010
 
Type Article
 
Identifier INORGANIC CHEMISTRY, 49(14), 6565-6574
0020-1669
http://dx.doi.org/10.1021/ic100500p
http://dspace.library.iitb.ac.in/xmlui/handle/10054/3739
http://hdl.handle.net/10054/3739
 
Language en