A new tridentate Schiff base ligand HL (L = C14H19N2O), derived from the condensation of benzoylacetone and 2-dimethylaminoethylamine in a 1:1 ratio, reacts with copper(ii) acetate and cyanate, thiocyanate or azide, to give rise to several end-to-end polymeric complexes of formulae [CuL(mu(1,3)-NCO)]n 1, [CuL(mu(1,3)-NCS)]n 2 and the complex 3 has two crystallographically independent units of formula [CuL(N3)] in the asymmetric unit cell. Complex 3 exists in dimeric form rather than as a polymeric chain. Compound 1 is the first report of a singly end-to-end cyanate bridged polymeric chain of Cu(II) with a Schiff base as a co-ligand. There are many examples of double NCS bridged polymeric chains, but fewer singly bridged ones such as compound 2. We have characterized these complexes by analytical, spectroscopic, structural and variable temperature magnetic susceptibility measurements. The coordination geometry around the Cu(II) centers is distorted square pyramidal for 1 and 2 and square planar for complex 3. The magnetic susceptibility data show slight antiferromagnetic coupling for the polymers having J values -0.19 and -0.57 cm(-1) for complexes 1 and 2 respectively. The low values of J are consistent with the equatorial-axial disposition of the bridges in the polymers.

Keywords: Bridging ligands / Copper / Density functional calculations / Exchange interactions / Hydrogen bondsA rare example of a mono-aqua-bridged copper(II) dimer,, has been synthesised and its structure determined by single-crystal Xray diffraction. Each Cu II centre is in a square-pyramidal surrounding formed by a Schiff base and a terminal H 2 O ligand; a second H 2 O ligand, which acts as a bridge, is common to two metal ions. Hydrogen bonds between the H 2 O ligand and the Schiff base of the adjacent centre complete the intra-

A series of Zn(II), Cd(II), Co(II), Co(III) and Mn(III) complexes with the Schiff base [(CH3)2NCH2CH2N=CHC6H3(OH)(OMe)], LH, derived from 2-dimethylaminoethylamine and o-vanillin, has been synthesised and structures of all the products have been established by X-ray crystallography. In the cases of zinc and cadmium, dimeric complexes [Zn(LH)2(NCS)] [Zn2(L)(mu(1,1)-CH3COO)(NCS)3] (1), [Cd2(L)2(Cl)2] (2) and [Cd2(L)2(NCS)2] (3), and for cobalt and manganese, monomeric complexes [Co(LH)2(NCS)]2 [Co(NCS)4] (4), [Co(LH)2(NCS)]ClO4 (5), [Co(L)(N3)(o-vanillinate)] x 0.5 MeOH (6) and [Mn(LH)2(MeOH)2](ClO4)3 (7), are formed with various terminal ligands. All the complexes have been characterised by elemental analysis and IR spectra. UV-Vis and NMR spectroscopy, magnetic, and electrochemical studies, were also carried out where feasible. The Schiff base functions as a bi-, tri- or tetra-dentate chelating agent and coordinates via the protonated or deprotonated phenolic oxygen, amine and imine nitrogens, and only in case of 1 with the methoxy oxygen atoms, to the metal ion leading to the formation of mono- or bi-metallic complexes.

Two new octahedral Cd(II) complexes [Cd(L) 2 ] (1) and {[Cd(LH) 2 (SCN) 2 ]H 2 O} (2) [where LH = C 14 H 13 N 3 O] are synthesized using a tridentate hydrazone ligand (LH) and they are characterized by elemental analysis, IR spectra, NMR spectra, thermal studies and finally the structures have been determined by single crystal X-ray diffraction. Complex 1 crystallizes in monoclinic system, space group C2/c with a = 22.565(6)Å, b = 10.252(3)Å, c = 12.187(4)Å, β = 118.851(2) • , and Z = 4. Complex 2 also crystallizes in the monoclinic system, space group P2 1 /c with a = 9.257(9)Å, b = 17.809(2)Å, c = 9.548(9)Å, β = 107.439(4) • , and Z = 2. In 1 the ligand binds the Cd(II) ion in tridentate fashion, whereas in 2 it acts as a bidentate ligand.

The title compounds, [Cu(C16H23N2O)SCN] (1) and [Cu(C16H23N2O)N3] (2), containing a tridentate Schiff base ligand, which is the 1:1 condensation product of benzoylacetone and 2- diethylaminoethylamine, have been synthesised and their crystal structures determined. The structure of 1 is based on a four coordinate copper centre with square-planar geometry formed by the N2O donor set of the Schiff base and an N atom of the thiocyanate anion. A similar arrangement occurs in 2 with the N2O donor set of the Schiff base and an N atom of the azide anion. The Cu-N and Cu-O distances are 1.924(8), 2.073(8), 1.927(9) and 1.910(6)Å , for 1 and 1.960(4), 2.050(4), 1.935(4) and 1.907(3) for 2, respectively.