Bis-chelates of N-R-1-hydroxy-2-naphthylstyrylketoneimines of copper(II) and nickel(II) [R = H, Me, Et] were synthesised in situ from the ring opening reaction of 7,8-benzoflavanone with the respective metal(II) chlorides and aliphatic monoamines. Likewise, 1,2-ethanediamine (en) and 1,3-propanediamine (pn) afforded N,N′-ethylene-bis(l-hydroxy-2-naphthylstyrylketoneimine) and N,N′-propylene-bis(1-hydroxy-2-naphthylstyrylketoneimine) copper and nickel complexes, respectively. However, 1-hydroxy-2-naphthyl-styrylketone reacts with MeNH2 and CuCl2.2H2O to give bis(N-methyl-1-hydroxy-2-acetonaphthone-imine)copper(II). The complexes were characterised by analytical, IR, electronic and EPR methods and magnetic susceptibility measurements. The copper complexes of N-R-l-hydroxy-2-naphthylstyrylketone-imines have a distorted trans square planar structure. In nickel complexes, when the substituent R changes from H to Et through Me, the geometry changes from trans square planar to tetrahedral through a quasi-octahedral structure. The copper complexes of the tetradentate Schiff bases are square planar. The nickel complex of the en tetradentate Schiff base is cis square planar whereas that of pn is octahedral. EPR study reveals that copper(II) has a distorted square planar geometry, with a trans configuration in the bidentate Schiff base complexes and cis in the tetradentate Schiff base complexes. MO coefficients derived from EPR parameters indicate a high degree of covalency in these complexes.
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Natarajan et al. (1992) studied this question.