Thermochromic behavior of vanadium(IV) alkoxides in solution: a molecular modeling aproach

摘要

The thermochromic behavior exhibited by vanadium(IV) alkoxides, [V2(μ-OPri)2(OPri) 6] and [V2(μ-ONep)2(ONep)6 ], OPri = isopropoxide and ONep = neopentoxide, was studied by molecular modeling using DFT, TDDFT and INDO/S methods. The vibrational and electronic spectra calculated for [V2(μ-OPri)2(OPri) 6] were very similar to the experimental data registered for crystalline samples of the complex and for its solutions at low temperature ( 210 K), while spectra recorded at high temperature ( 315 K) were compatible with those calculated for the monomeric form, [V(OPri)4]. These results consistently point to a monomer/dimer equilibrium as an explanation for the solution thermochromism of {V(OPri)4}n. In spite of the structural similarity between [V2(μ-ONep)2(ONep)6 ] and [V2(μ-OPri)2(OPri) 6] in the solid state, the thermochromic behavior of the former could not be explained by the same model, and the possibility of tetranuclear aggregation at low temperatures was also investigated.