Spectroscopic evidence of chirality in tetranuclear Cu(II)-Schiff base complexes, catalytic potential for oxidative kinetic resolution of racemic benzoin

Abstract

Two chiral Schiff base ligands 2-((1-hydroxy-3-phenylpropan-2-ylimino)methyl)-6-methoxyphenol (L1H2 ) and 2-(4-hydroxy-3-isopropylbut-1-enyl)-6-methoxyphenol (L2H2 ) have been synthesized by the condensation of l-phenylalaninol/l-valinol and o-vanillin (2-hydroxy-3-methoxy benzaldehyde). A tetranuclear homometallic Cu(II) complex [Cu4(L1H)2(L1)2] (ClO4)2 (C1) and a hexanuclear heterometallic complex [Cu4(L2)4Na2(DMF)2(H2O)] (ClO4)2 (C2) have been synthesized with the ligands. Both the complexes possess cubane like Cu4O4 core with interesting structural variations and inherit the chirality of their corresponding ligands. The catalytic potential of the complexes has been explored for the oxidative kinetic resolution of racemic benzoin. The electronic, optical and chiroptical properties of the ligands and the complexes have been studied by DFT and TD-DFT calculations.