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Hydroxo-Bridged Dimers of Oxo-Centered Ruthenium(III) Triangle: Synthesis and Spectroscopic and Theoretical Investigations

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Title Hydroxo-Bridged Dimers of Oxo-Centered Ruthenium(III) Triangle: Synthesis and Spectroscopic and Theoretical Investigations
 
Creator UPADHYAY, A
RAJPUROHIT, J
SINGH, MK
DUBEY, R
SRIVASTAVA, AK
KUMAR, A
RAJARAMAN, G
SHANMUGAM, M
 
Subject cluster compounds
density functional calculations
magnetism
NMR spectroscopy
ruthenium
SINGLE-MOLECULE MAGNETS
INTRAMOLECULAR ELECTRON-TRANSFER
N-HETEROCYCLIC LIGANDS
SCHIFF-BASE COMPLEXES
H BOND ACTIVATION
X-RAY-STRUCTURE
TRINUCLEAR RUTHENIUM
TRIRUTHENIUM COMPLEXES
REDOX PROPERTIES
ELECTROCHEMICAL PROPERTIES
 
Description The homometallic hexameric ruthenium cluster of the formula [Ru-6(III)((3)-O)(2)(-OH)(2)((CH3)(3)CCO2)(12)(py)(2)] (1) (py=pyridine) is solved by single-crystal X-ray diffraction. Magnetic susceptibility measurements performed on 1 suggest that the antiferromagnetic interaction between the Ru-III centers is dominant, and this is supported by theoretical studies. Theoretical calculations based on density functional methods yield eight different exchange interaction values for 1: J(1)=-737.6, J(2)=+63.4, J(3)=-187.6, J(4)=+124.4, J(5)=-376.4, J(6)=-601.2, J(7)=-657.0, and J(8)=-800.6cm(-1). Among all the computed J values, six are found to be antiferromagnetic. Four exchange values (J(1), J(6), J(7) and J(8)) are computed to be extremely strong, with J(8), mediated through one -hydroxo and a carboxylate bridge, being by far the largest exchange obtained for any transition-metal cluster. The origin of these strong interactions is the orientation of the magnetic orbitals in the Ru-III centers, and the computed J values are rationalized by using molecular orbital and natural bond order analysis. Detailed NMR studies (H-1, C-13, HSQC, NOESY, and TOCSY) of 1 (in CDCl3) confirm the existence of the solid-state structure in solution. The observation of sharp NMR peaks and spin-lattice time relaxation (T1 relaxation) experiments support the existence of strong intramolecular antiferromagnetic exchange interactions between the metal centers. A broad absorption peak around 600-1000nm in the visible to near-IR region is a characteristic signature of an intracluster charge-transfer transition. Cyclic voltammetry experiments show that there are three reversible one-electron redox couples at -0.865, +0.186, and +1.159V with respect to the Ag/AgCl reference electrode, which corresponds to two metal-based one-electron oxidations and one reduction process.
 
Publisher WILEY-V C H VERLAG GMBH
 
Date 2014-12-28T12:45:08Z
2014-12-28T12:45:08Z
2014
 
Type Article
 
Identifier CHEMISTRY-A EUROPEAN JOURNAL, 20(20)6061-6070
0947-6539
1521-3765
http://dx.doi.org/10.1002/chem.201304826
http://dspace.library.iitb.ac.in/jspui/handle/100/16586
 
Language English