Synthesis, spectroscopic characterization and reactivity studies of oxovanadium(IV) complexes with bulky N,N'-polymethylenebis(3,5-(t)Bu(2)salicylaldimine) ligands

Spectrochim Acta A Mol Biomol Spectrosc. 2010 Oct 15;77(3):630-7. doi: 10.1016/j.saa.2010.06.040. Epub 2010 Jul 31.

Abstract

A series of new sterically hindered N,N'-polymethylenebis(3,5-(t)Bu(2)salicylaldimine) ligands (H(2)L(x)) VO(IV) complexes, [VO{(2-O-3,5-(t)Bu(2)C(6)H(2))CHN-R-NCH-(3,5-(t)Bu(2)-C(6)H(2)O-2)] (X), where R=-(CH(2))(3)- (3), -(CH(2))(4)- (4), -(CH(2))(5)- (5), -(CH(2))(6)- (6) and -CH(2)C(CH(3))(2)CH(2)- (7) and early reported -(CH(2))(2)- (1) and -CH(2)CH(CH(3))- (2), has been synthesized and characterized by spectroscopic (IR, UV/vis, (1)H NMR, EPR), electrochemical and magnetic susceptibility measurements. Complexes 1-7 are described a trigonal distorted pyramids. All seven compounds give nearly the same parallel hyperfine coupling constant (A(z)) regardless that the geometry of VO(IV) changes from square pyramidal to trigonal distorted pyramids. Chemical oxidation of 1-7 by one equiv Ce(IV) leads to the formation of stable [VO(V)L(x)](+) complexes. Cyclic voltammograms of 2-6 in DMSO along with a quasi-reversible VO(IV)/VO(V) redox couple also showed irreversible phenolate/phenoxyl responses. Each 1 and 7 shows only one reversible VO(IV) centered oxidation waves. Chemical oxidation of H(2)L(x) forms the stable [H(2)L(x)](+) radical species.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Coordination Complexes / chemistry*
  • Electrochemical Techniques
  • Electron Spin Resonance Spectroscopy
  • Magnetics
  • Molecular Structure
  • Nuclear Magnetic Resonance, Biomolecular
  • Oxidation-Reduction
  • Salicylamides / chemistry*
  • Spectrophotometry, Infrared
  • Spectrophotometry, Ultraviolet
  • Vanadates / chemistry*

Substances

  • Coordination Complexes
  • Salicylamides
  • oxovanadium IV
  • Vanadates