Synthesis, structures and fluorescence of nickel, zinc and cadmium complexes with the N,N,O-tridentate Schiff base N-2-pyridylmethylidene-2-hydroxy-phenylamine Arpi Majumder a , Georgina M. Rosair b, * , Arabinda Mallick c , Nitin Chattopadhyay c , Samiran Mitra a, * a Department of Chemistry, Inorganic Chemistry Section, Jadavpur University, S.C. Mallik Road, Kolkata, West Bengal 700 032, India b Department of Chemistry, Heriot-Watt University, Edinburgh EH14 4AS, UK c Department of Chemistry, Physical Chemistry Section, Jadavpur University, S.C. Mallik Road, Kolkata, West Bengal 700 032, India Received 19 August 2005; accepted 14 November 2005 Available online 18 January 2006 Abstract Mono-, tri- and dinuclear neutral complexes [Ni(HL)(L)] Æ (ClO 4 ) Æ 0.16(H 2 O) (1), [ZnLZn(OOCCH 3 ) 4 ZnL] (2) and [Cd 2 L 2 (OCH 3 - CO) 2 (H 2 O) 2 ](3) have been obtained from the reaction between the potentially tridentate N,N,O-donor Schiff base ligand HL, where HL = N-2-pyridylmethylidene-2-hydroxy-phenylamine with nickel, zinc or cadmium salts, respectively. The ligand has been prepared by 1:1 condensation of pyridine-2-carboxaldehyde and 2-aminophenol. The ligand and metal complexes were characterised by elemental analysis, spectroscopic studies such as IR, UV–Vis, 1 H NMR, fluorescence, electrochemical and magnetic susceptibility measurement. The structures of the three complexes have been determined by single-crystal X-ray diffraction. The nickel ions in 1 show a distorted mer-octahedral geometry. In 2, the terminal zinc ions have coordination geometry midway between square pyramidal and trigonal bipy- ramidal, whilst the central zinc ion has slightly distorted octahedral geometry. The trinuclear unit is held together by bridging deproto- nated phenolic oxygen atoms from the Schiff base and acetate groups. In 3, two monocapped-octahedron cadmium ions are held together by l 2 -diphenoxo bridges. Among the three synthesised complexes, 1 is nonfluorescent while the other two can serve as potential photo- active materials as indicated from their characteristic fluorescence properties. Ó 2005 Elsevier Ltd. All rights reserved. Keywords: Mononuclear Ni(II); Trinuclear Zn(II); Dinuclear heptadentate Cd(II); l 2 -Diphenoxo bridged complexes; Tridentate Schiff base ligand; Crystal structures; Fluorescence 1. Introduction Schiff base ligands have been extensively studied in coor- dination chemistry mainly due to their facile syntheses, eas- ily tunable steric, electronic properties and good solubility in common solvents [1]. Transition metal complexes with oxygen and nitrogen donor Schiff bases are of particular interest [2] because of their ability to possess unusual con- figurations, be structurally labile and their sensitivity to molecular environments [3]. Schiff base ligands have pro- ven to be very effective in constructing supramolecular architectures such as coordination polymers, double helixes, and triple helicates [4]. Schiff bases can accommo- date different metal centres involving various coordination modes allowing successful synthesis of homo- and hetero- metallic complexes with varied stereochemistry [5]. This feature is employed for modelling active sites in biological systems [6]. Additionally, they have wide applications in fields such as antibacterial, antiviral, antifungal agents [7], homogeneous or heterogeneous catalysis [8] and mag- netism [9]. Schiff bases are potential anticancer drugs [10] and when administered as their metal complexes, the anticancer activity of these complexes is enhanced in 0277-5387/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.poly.2005.11.029 * Corresponding authors. Tel.: +91 33 2668 2017; fax: +91 33 2414 6414. E-mail address: smitra_2002@yahoo.com (S. Mitra). www.elsevier.com/locate/poly Polyhedron 25 (2006) 1753–1762