Jump to main content
Jump to site search

Issue 34, 2017
Previous Article Next Article

Low-spin [MII(L)2] and [MIII(L)2]+ (M = Fe and Co) complexes of tridentate azo-containing pyridine/pyrazine amide ligands: structures, properties and redox potential correlations

Author affiliations

Abstract

Using deprotonated forms of tridentate azo-containing pyridine-2-/pyrazine-2-carboxamide 2-[N-(2-phenylazo)carbamoyl]-pyridine/pyrazine, seven bis-ligand complexes of FeII/CoII and FeIII/CoIII have been synthesized. Molecular structures of six of them reveal that these six-coordinate complexes utilize all available donor sites of the ligands and assume MII/IIIN2(pyridine/pyrazine)N′2(amide)N′′2(azo) coordination. Complexes of FeII and CoIII are diamagnetic and those of FeIII and CoII are paramagnetic (S = 1/2; room-temperature magnetic data and EPR spectra). Cyclic voltammetry experiments in CH2Cl2 reveal facile metal-centred FeIII/FeII and CoIII/CoII redox responses, and all complexes display quasireversible-to-irreversible ligand(azo)-centred redox processes. The E1/2 values of MIII/MII redox processes for Fe, Co and Ni (reported earlier) complexes of the pyridine amide ligand linearly correlate with those for six-coordinate [MIII(bpy)3]3+/[MII(bpy)3]2+, [MIII(terpy)2]3+/[MII(terpy)2]2+, [MIII(L)]+/[MII(L)]0 or [MIII(L′)2]+/[MII(L′)2]0 (bpy = 2,2′-bipyridine, terpy = 2,2′:6′,2′′-terpyridine, hexadentate L(2−) = 1,4-bis[o-(pyridine-2-carboxamidophenyl)]-1,4-dithiobutane and tridentate L′(−) = {2-[2-(arylimino)phenylazo]-pyridine}) couples. Density functional theory (DFT) at the B3LYP level and time-dependent (TD)-DFT calculations rationalize the electronic structure of the present complexes and throw light on the origin of observed electronic transitions.

Graphical abstract: Low-spin [MII(L)2] and [MIII(L)2]+ (M = Fe and Co) complexes of tridentate azo-containing pyridine/pyrazine amide ligands: structures, properties and redox potential correlations

Back to tab navigation

Supplementary files

Publication details

The article was received on 29 Apr 2017, accepted on 20 Jul 2017 and first published on 27 Jul 2017


Article type: Paper
DOI: 10.1039/C7DT01577A
Citation: Dalton Trans., 2017,46, 11291-11305
  •   Request permissions

    Low-spin [MII(L)2] and [MIII(L)2]+ (M = Fe and Co) complexes of tridentate azo-containing pyridine/pyrazine amide ligands: structures, properties and redox potential correlations

    A. Sengupta, A. Rajput, S. K. Barman and R. Mukherjee, Dalton Trans., 2017, 46, 11291
    DOI: 10.1039/C7DT01577A

Search articles by author

Spotlight

Advertisements