Designing dicyanamide bridged 1D molecular architecture from a mononuclear copper(II) Schiff base precursor: Syntheses, structural variations and magnetic study

A new tridentate N2O donor Schiff base ligand [(C6H5C(OH)=CHC(CH3)=NCH2C5H4N)=LH] was obtained by 1:1 condensation of benzoylacetone with 2-picolylamine and has been used to synthesise a mononuclear [CuLCl] (1) and an end-to-end dicyanamide bridged polynuclear {[Cu-2(mu-L)(2)(mu(2)-1,5-(CN)(2)N)]ClO4}(n) (2) copper(II) complexes, The ligand, I and 2 were clearly characterised by elemental analysis, FT-IR, H-1 NMR. UV-Vis spectral studies, electrochemical studies and in addition single crystal X-ray diffraction studies were performed for I and 2. The Schiff base ligand [LH] shows a significant variation in its coordination behaviour with copper(II) ion in absence and in presence of dicyanamide ion in I and 2 respectively. In absence of dicyanamide the deprotonated enolato oxygen of the tridentate Schiff base ligand [L](-) coordinates the copper(II) ion in a monodentate fashion generating a mononuclear species (1) whereas in presence of the dicyanamide ion, the deprotonated enolato oxygen of [1](-) bridges two adjacent [CuL(CN)(2)N] units through mu-OL bridges, forming dimers. The dimeric units are further linked to adjacent dimeric units through mu(2)-1,5-dicyanamide bridges to produce 1D polymeric chains in 2. Variable temperature magnetic susceptibility measurements for 2 in the temperature range 2-300 K reveal the presence of weak antiferromagnetic exchange interactions in the polymeric chain. (C) 2008 Elsevier Ltd. All rights reserved.