Issue 8, 2015

UV-visible spectroscopy of macrocyclic alkyl, nitrosyl and halide complexes of cobalt and rhodium. Experiment and calculation

Abstract

Transition metal complexes (NH3)5CoX2+ (X = CH3, Cl) and L(H2O)MX2+, where M = Rh or Co, X = CH3, NO, or Cl, and L is a macrocyclic N4 ligand are examined by both experiment and computation to better understand their electronic spectra and associated photochemistry. Specifically, irradiation into weak visible bands of nitrosyl and alkyl complexes (NH3)5CoCH32+ and L(H2O)MIIIX2+ (X = CH3 or NO) leads to photohomolysis that generates the divalent metal complex and ˙CH3 or ˙NO, respectively. On the other hand, when X = halide or NO2, visible light photolysis leads to dissociation of X and/or cis/trans isomerization. Computations show that visible bands for alkyl and nitrosyl complexes involve transitions from M–X bonding orbitals and/or metal d orbitals to M–X antibonding orbitals. In contrast, complexes with X = Cl or NO2 exhibit only d–d bands in the visible, so that homolytic cleavage of the M–X bond requires UV photolysis. UV-Vis spectra are not significantly dependent on the structure of the equatorial ligands, as shown by similar spectral features for (NH3)5CoCH32+ and L1(H2O)CoCH32+.

Graphical abstract: UV-visible spectroscopy of macrocyclic alkyl, nitrosyl and halide complexes of cobalt and rhodium. Experiment and calculation

Supplementary files

Article information

Article type
Paper
Submitted
12 Oct 2014
Accepted
08 Jan 2015
First published
22 Jan 2015

Dalton Trans., 2015,44, 3811-3816

UV-visible spectroscopy of macrocyclic alkyl, nitrosyl and halide complexes of cobalt and rhodium. Experiment and calculation

E. A. Hull, A. C. West, O. Pestovsky, K. E. Kristian, A. Ellern, J. F. Dunne, J. M. Carraher, A. Bakac and T. L. Windus, Dalton Trans., 2015, 44, 3811 DOI: 10.1039/C4DT03143A

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