Synthesis and characterization of two oxovanadium (IV) Schiff base complexes derived from amino acids and pyridoxal

Two N-pyridoxylideneamino acidato complexes of oxovanadium (IV), [VO(pyr-D,L-Met)(bipy)] and [VO(pyr-D,L-Thr)(bipy)]⋅H2O with Schiff bases, made from amino acids (DL-methionine and DL-threonine) and pyridoxal, were prepared by an amine-diffusion reaction and characterized by single crystal X-ray diffraction. Both [VO(pyr-D,L-Met)(bipy)] and [VO(pyr-D,L-Thr)(bipy)]⋅H2O crystallize in triclinic P-1P-1 with cell parameters a=9.2605(19) Åa=9.2605(19) Å, b=12.851(3) Åb=12.851(3) Å, c=19.079(4) Åc=19.079(4) Å, α=92.34(3)°α=92.34(3)°, β=93.20(3)°β=93.20(3)°, γ=91.03(3)°γ=91.03(3)°, V=2264.7(8) Å3V=2264.7(8) Å3, Z=2Z=2, and a=9.4513(8) Åa=9.4513(8) Å, b=11.9026(13) Åb=11.9026(13) Å, c=12.7589(12) Åc=12.7589(12) Å, α=66.836(6)°α=66.836(6)°, β=87.171(6)°β=87.171(6)°, γ=67.214(6)°γ=67.214(6)°, V=1207.6(2) Å3V=1207.6(2) Å3, Z=2Z=2, respectively. They contain two diastereomers, donating the chiral vanadium centers as A or C, e.g., [A(pyr-D-Met)(bipy)], [C(pyr-L-Met)(bipy)] and [A(pyr-D-Thr)(bipy)]⋅H2O, [C(pyr-L-Thr)(bipy)]⋅H2O. The complexes were also characterized by elemental analysis, IR and EPR spectroscopy. The EPR spectra illustrate well-resolved coupling of the unpaired electron with V51 nucleus (I=7/2I=7/2).

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