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 H2salen is N,N′-bis(salicylidene)-1,2-ethylenediamine) has been synthesized. This compound [CrO(OH2)(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 d2 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 |0> ↔ |±1> transition from the Kramers doublet |±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 |−1> ↔ |+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.