A tetra-nuclear copper(II) complex stabilizes an extended structure of a water nonamer: Synthesis and characterization of [Cu 4 (C 54 H 46 N 4 O 14 )(OH) 2 ] Æ 10H 2 O Chullikkattil P. Pradeep, Sabbani Supriya, Panthapally S. Zacharias, Samar K. Das * School of Chemistry, University of Hyderabad, Hyderabad, Andhra Pradesh 500 046, India Received 14 May 2006; accepted 13 July 2006 Available online 15 July 2006 Abstract A tetra-nuclear copper(II) complex [Cu 4 (C 54 H 46 N 4 O 14 )(OH) 2 ] Æ 10H 2 O(1) has been synthesized starting from L-tyrosine, NaOH, 2,6- diformyl-4-methylphenol (dfp) and CuSO 4 Æ 5H 2 O. Compound 1 crystallizes from an ethanol–water mixture in triclinic P  1 space group. In the crystal of 1, two binuclear copper units, related by a center of symmetry, are bridged by two hydroxo bridges and results in the formation of a tetra-nuclear {Cu 4 } structure. Five lattice water molecules, located in the asymmetric unit, interact among themselves and form an unusual form of a water nonamer. In the crystal, the water nonamer is again hydrogen bonded to the next nonamer forming a chainlike polymer. Each {Cu 4 } complex unit attaches four such water nonamer chains. Variable temperature magnetic data fit to the Bleaney–Bower’s equation with a Curie type of impurity of S = 0.5. The best fit of the magnetic data to this equation yielded 2J = 217, g = 2.019 and a TIP value of 60 · 10 6 cm 3 mol 1 . Ó 2006 Elsevier Ltd. All rights reserved. Keywords: Schiff-base ligand; Tetra-nuclear copper(II) complex; Crystal structure; Extended chainlike structure of water nonamer; Supramolecular hydrogen bonding network; Magnetic studies 1. Introduction Multinuclear copper(II) complexes have received con- siderable interest because of their importance as magnetic materials, bioinorganic model compounds and catalysts [1–7]. Tetra-nuclear copper(II) complexes represent a class of compounds that are partly useful in understand- ing magneto-structural correlations in such compounds [8–10]. Carboxylate bridged copper clusters have been considered as bioinorganic models because the active sites of some copper containing metalloenzymes contain multinuclear copper(II) centers bridged by amino- acid-carboxylates [11]. Carboxylate bridged tetrameric copper(II) complexes, in addition to their significance in magneto-structural research, bioinorganic chemistry and catalysis, play an important role for the design of new designer materials based on supramolecular interac- tions. The flexibility of the coordination sphere around copper(II), in combination with steric and crystal pack- ing forces, leads to its tremendous structural diversity. We wish to describe here synthesis and characterization of a new tetra-nuclear copper(II) complex, [Cu 4 (C 54 H 46 - N 4 O 14 )(OH) 2 ] that stabilizes an extended water structure of an unusual form of water nonamer in the crystal lattice of compound [Cu 4 (C 54 H 46 N 4 O 14 )(OH) 2 ] Æ 10H 2 O (1). We have used L-tyrosine and 2,6-diformyl-4-methyl- phenol as the precursors for the formation of a Schiff- base ligand in situ that subsequently reacts with CuSO 4 Æ 5H 2 O and NaOH resulting in the isolation of compound 1. 0277-5387/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.poly.2006.07.008 * Corresponding author. Tel.: +91 40 2301 1007; fax: +91 40 2301 2460. E-mail address: skdsc@uohyd.ernet.in (S.K. Das). www.elsevier.com/locate/poly Polyhedron 25 (2006) 3588–3592