Synthesis and characterization of a stable paramagnetic hexacoordinated oxochromium(IV) complex with dianionic tetradentate Schiff base ligand salen

A paramagnetic octahedral oxochromium(IV) complex with dianionic tetradentate ligand salen (where H(2)salen is N,N'-bis(salicylidene)-1,2-ethylenediamine) has been synthesized. This compound [CrO(OH(2)) (salen)] (1) is characterized by elemental analysis, magnetic moment measurement, IR, UV-Vis and EPR spectroscopic studies. Measured room temperature (RT) magnetic moment value is 2.96 BM for 1 indicates a d(2) system with a triplet ground state. The magnetic moment value rules out a large spin-orbit coupling. The RT and LNT powder EPR spectra of 1 in X-band clearly shows two lines, one around g = 1.965 and the other with larger intensity at g = 4.26 +/- 0.10. The first line at g = 1.965 corresponds to the vertical bar 0> <->vertical bar +/- 1> transition from the Kramers doublet vertical bar +/- 1>, while the broad and intense line at low field with the g-value of 4.26 +/- 0.10 is due to the forbidden transition vertical bar-1> <-> vertical bar+1>. Compound 1 displays two successive reductions at -0.76 and -1.63 V (versus Ag/AgCl), respectively, while it undergoes only one irreversible oxidation as evident from the well-defined anodic wave at +1.48 V in its cyclic voltammogram. (c) 2010 Elsevier B.V. All rights reserved.