Carbonyl compound dependent hydrolysis of mono-condensed Schiff bases: A trinuclear Schiff base complex and a mononuclear mixed-ligand ternary complex of copper(II)

Abstract Two Schiff bases, HL 1 and HL 2 have been prepared by the condensation of N -methyl-1,3-propanediamine (mpn) with salicylaldehyde and 1-benzoylacetone (Hbn) respectively. HL 1 on reaction with Cu(ClO 4 ) 2 ·6H 2 O in methanol produced a trinuclear Cu II complex, [(CuL 1 ) 3 ( μ 3 -OH)](ClO 4 ) 2 ·H 2 O·0.5CH 2 Cl 2 ( 1 ) but HL 2 underwent hydrolysis under similar reaction conditions to result in a ternary Cu II complex, [Cu(bn)(mpn)ClO 4 ]. Both complexes have been characterised by single-crystal X-ray analyses, IR and UV–Vis spectroscopy and electrochemical studies. The partial cubane core [Cu 3 O 4 ] of 1 consists of a central μ 3 -OH and three peripheral phenoxo bridges from the Schiff base . All three copper atoms of the trinuclear unit are five-coordinate with a distorted square–pyramidal geometry. The ternary complex 2 is mononuclear with the square–pyramidal Cu II coordinated by a chelating bidentate diamine (mpn) and a benzoylacetonate (bn) moiety in the equatorial plane and one of the oxygen atoms of perchlorate in an axial position. The results show that the Schiff base (HL 2 ) derived from 1-benzoylacetone is more prone to hydrolysis than that from salicylaldehyde (HL 1 ). Magnetic measurements of 1 have been performed in the 1.8–300 K temperature range. The experimental data clearly indicate antiferromagnetism in the complex. The best-fit parameters for complex 1 are g  = 2.18(1) and J  = −15.4(2) cm −1 .