Synthesis and spectral studies of cobalt(II), nickel(II) and copper(II) complexes of 1-(2-hydroxy-1-naphthyl)-3-(4-X-phenyl)-2-propen-1-ones and their pyridine adducts

Abstract

Metal(II) chelates of the type ML2nB [M = CoII, NiII and CuII; L = 1-(2-hydroxy-1-naphthyl)-3-(4-X-phenyl)-2-pro-pen-1-one, (X = H, Cl or Me); B = H2O or Py; n = 0, 2] have been prepared by in situ ring opening of 5,6-benzofiavanones and also from the corresponding chalcones. Structures have been assessed by magnetic measurements, i.r., electronic and e.p.r. spectra and by thermal studies. The anhydrous CuII chelates are monomers and possess square-planar geometry, while the corresponding CoII and NiII complexes are polymers with a high-spin trans-octahedral configuration. All the base adducts have a high-spin trans-octahedral configuration. I.r. studies indicate that v(C=O) and v(M-O) frequencies are affected by metal-ion and by phenyl substitution and adduct formation. E.p.r. spectral studies indicate a higher degree of covalency in the in-plane σ-bonded pyridine adducts of the copper complexes than do the parent chalcone complexes. The relatively low ligand field strength of 1-(2-hydroxy-l-naphthyl)-3-(4-X-phenyl)-2-propen-l-ones compared to 2′-hydroxychal-cones is attributed to the inhibition of extensive conjugation arising from deviation of the naphthoyl group from planarity.