Chiral supramolecular metal-organic architectures from dinuclear copper complexes Chullikkattil P. Pradeep, Samar K. Das * School of Chemistry, University of Hyderabad, Hyderabad, Andhra Pradesh 500 046, India article info Article history: Received 3 November 2008 Accepted 4 December 2008 Available online 18 January 2009 Keywords: Chiral complexes Copper Chiral amino alcohols Hydrogen bonding Supramolecular chemistry abstract Two new chiral dinuclear Cu(II) complexes [Cu 2 (l-Cl) 2 (HL 1 ) 2 ] Á C 2 H 5 OH (1) and [Cu 2 (l- Cl) 2 (HL 2 ) 2 ] Á CH 3 OH (2), have been synthesized and structurally characterized, where the chiral ligands H 2 L 1 and H 2 L 2 are derived from the chiral amino alcohols (S)-(À)-2-amino-3-phenyl-1-propanol and (S)-(+)-2-phenylglycinol. Single-crystal X-ray crystallographic analyses revealed that in these complexes, the dominant hydrogen bonding property of metal bound chloride anion directs the self assembly of complex molecules through C–HÁÁÁCl hydrogen bonding interactions leading to the formation of intrigu- ing hydrogen bonded metallo-supramolecular architectures in their respective crystal lattices. The supra- molecular systems described here belong to the rare class of metal-organic architectures that are formed as a result of metal directed hydrogen bonding interactions among chiral complex molecules. Complexes 1 and 2 are further characterized by IR, ESR, UV–Vis and CD spectroscopy. Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction The influence of transition metals on hydrogen bonding (H- bonding) is a current topic of fundamental relevance [1]. Transition metals and their primary coordination sphere can exert consider- able control over H-bonds, affecting the nature of intermolecular interactions in synthetic as well as natural systems [2–4]. In nat- ure, the active sites of metalloenzymes exhibit many H-bonding interactions which are influential in deciding their properties [5]. Many interesting synthetic supramolecular systems are being developed in recent years having relevance to host–guest [6–8], bio-inorganic [9], medicinal [10,11], organometallic [12,13] and solid state [14,15] chemistry, by strategically combining the properties of transition metals with that of H-bonding ligands. Nevertheless, the design and synthesis of metallo-supramolecular systems is still a daunting task, as it involves a number of variables such as properties of ligands, metal ions, solvents and counter- ions. Incorporation of a powerful H-bonding functionality into the molecular building unit, capable of directing its supramolecu- lar self-assembly is vital in the design of such systems [16–20]. In this respect, metal bound chlorine (M–Cl) is recognized as a strong H-bond functionality in metallo-supramolecular chemistry [21–27]. Meanwhile, chiral metallo-supramolecular systems are in de- mand for specific applications such as non-linear optics, chiral catalysis, sensing and enantioselective inclusion studies [28–31]. One strategy to ensure the chirality of supramolecular architec- tures is to employ chiral building units [32–36]. Chiral amino alco- hols are a promising class of chiral sources employed for the synthesis of chiral coordination compounds [37–42]. Eventhough chiral amino alcohol based coordination compounds are well known for their applications in asymmetric catalysis [43–46], the number of structurally characterized coordination complexes de- rived from chiral amino alcohol based ligands are limited in the lit- erature [37–42]. Structural studies of such complexes will help to design new systems with improved functionalities. Herein we report the synthesis, structural characterization and properties of two chiral dinuclear copper complexes containing Cu–Cl as the dominant H-bond acceptor, which self assemble through C–HÁÁÁCl–Cu, C–HÁÁÁO, etc. interactions leading to the for- mation of fascinating H-bonded metal-organic architectures in the solid state. 2. Experimental 2.1. Materials and measurements Microanalytical (C, H, N) data were obtained with a FLASH EA 1112 Series CHNS Analyzer. A Shimadzu 3101-PC UV–Vis–NIR spectrophotometer was used to record the electronic spectra. Infrared spectra were recorded by using KBr pellets on a Jasco- 5300 FT-IR spectrophotometer. 1 H NMR spectra in CDCl 3 solutions were recorded with a Bruker DRX-400 spectrometer, using Si(CH 3 ) 4 as an internal standard. Room temperature solid state magnetic susceptibilities were measured by using a Sherwood Scientific 0277-5387/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.poly.2008.12.012 * Corresponding author. Tel.: +91 40 2301 1007; fax: +91 40 2301 2460. E-mail address: skdsc@uohyd.ernet.in (S.K. Das). Polyhedron 28 (2009) 630–636 Contents lists available at ScienceDirect Polyhedron journal homepage: www.elsevier.com/locate/poly