Article,

Low-Valent Cobalt Complexes with Three Different p Acceptor Ligands: Experimental and DFT Studies of the Reduced and the Low-Lying Excited States of (R-DAB)Co(NO)(CO), R-DAB = Substituted 1,4-Diaza-1,4-butadiene

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Inorganic Chemistry, 42 (10): 3340--3346 (2003)
DOI: 10.1021/ic026078t

Abstract

The complexes (RN=CH-CH=NR)Co(NO)(CO) with R = iso-Pr, 2,6-diisopropylphenyl, or p-tolyl are chem. and electrochem. reducible to radical anions at potentials which strongly depend on R. The DFT calcd. structure for the neutral compd. with R = iPr agrees with the expt., and the computed structure of the anion radical reveals changes according to a redn. of the R-DAB ligand. EPR results confirm an (R-DAB)-based singly occupied MO in (RNCHCHNR)Co(NO)(CO).bul.-, with minor but detectable contributions from NO as supported by IR spectroelectrochem. and as quantified by DFT spin d. calcns. The calcns. indicate increasingly stabilized CO, NO, and RNCHCHNR p* acceptor orbitals, in that order. On the basis of TD-DFT (time-dependent d. functional theory) calcns., the lowest-lying excited states are assigned to metal-to-(R-DAB) charge transfer transitions while bands due to the metal-to-nitrosyl charge transfer occur at higher energies but still in the visible region. Resonance Raman studies were used to probe these assignments. on SciFinder(R)

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