Synthesis, structure, luminescence properties, quantum chemistry and cytotoxic effects of two vanadium(IV) complexes with polypyrazolylborates, HB(pz)3VO(acac) and HB(3,5-Me2pz)3VO(acac)·CH3CN (pz = pyrazole)

The reaction of VO(acac)2 (acac = acetylacetonate) with NaHB(pz)3 (pz = pyrazole) or NaHB(3,5-Me2pz)3 in methanol gave vanadium(IV) complexes HB(pz)3VO(acac) (1) or HB(3,5-Me2pz)3VO(acac)·CH3CN (2), respectively. The complexes 1 and 2 were characterized by elemental analysis, IR, UV-vis, NMR and X-ray diffraction crystallography methods. Complex 1 crystallizes in space group P21/c, a = 7.641(2) Å, b = 17.008(4) Å, c = 13.362(2) Å; β = 92.092(17)°, V = 1735.5(7) Å3, Z = 4. Complex 2 crystallizes in space group P21/c, a = 17.410(13) Å, b = 8.076(16) Å, c = 19.300(13) Å; β = 101.75(5)°, V = 2657(6) Å3, Z = 4. X-ray structure analyses have shown that the complexes 1 and 2 are monomeric with a similar coordination environment of the vanadium atom. Luminescence properties and cytotoxic effects of the complexes are discussed. On CBRH-7919 cells, the complexes 1 and 2 caused a slight stimulation of growth at low doses (1–10 µM) and a significant cytotoxic effect at higher doses (100–1000 µM). The electronic structure and the bonding characters of the two complexes were analyzed with ab initio calculations.