Published: March 10, 2011 r2011 American Chemical Society 1697 dx.doi.org/10.1021/cg101629w | Cryst. Growth Des. 2011, 11, 1697–1704 ARTICLE pubs.acs.org/crystal Interaction of Copper(II) with Ditopic Pyridyl-β-diketone Ligands: Dimeric, Framework, and Metallogel Structures Melanie Dudek, † Jack K. Clegg, ‡ Christopher R. K. Glasson, § Norman Kelly, † Kerstin Gloe, † Karsten Gloe,* ,† Alexandra Kelling, || Hans-J€ urgen Buschmann, ^ Katrina A. Jolliffe, ‡ Leonard F. Lindoy,* ,‡ and George V. Meehan § † Department of Chemistry and Food Chemistry, TU Dresden, 01062 Dresden, Germany ‡ School of Chemistry, University of Sydney, NSW 2006, Australia § School of Pharmacy and Molecular Sciences, James Cook University, Townsville 4811 Queensland, Australia ) Institute of Chemistry, University of Potsdam, 14469 Potsdam, Germany ^ German Textile Research Centre DTNW, 47798 Krefeld, Germany b S Supporting Information ’ INTRODUCTION The synthesis of new metal coordination polymers, including new metal organic frameworks, has been given increasing atten- tion over recent years, in part motivated by their ready prepara- tion via self-assembly processes and by the prospect of generating new materials exhibiting useful and/or unusual properties. 1-11 Thus, systems showing luminescent, 12-14 nonlinear optical, 15 catalytic, 16 magnetic spin-crossover, 17,18 as well as other less common magnetic properties 19 have all been documented. Linear difunctional ligand systems (such as, for example, 4,4 0 - bipyridyl or terephthalic acid) have very commonly been em- ployed to connect metal units in the formation of such materials, while nonlinear bifunctional ligands have received somewhat less attention. Nevertheless, both categories have now been demon- strated to form a range of diverse metallo-polymeric structures. For example, both linear and nonlinear, pyridyl-substituted β-diketonato ligands have been successfully employed for the generation of a range of interesting coordination polymers. In these hetero difunctional ligand systems, the β-diketone frag- ment has the pyridyl substituent attached either to the “central” carbon atom (that is, the carbon between the two keto functions) or in a terminal position with respect to this fragment. Thus, the linear bifunctional derivative, 3-(4-pyridyl)pentane-2,4-dione, has been demonstrated to be an effective ligand for generating a number of one- (1D) and two-dimensional (2D) coordination polymers incorporating a range of metal ions; 20-24 linear poly- meric, ladder, and square-grid architectures have all been ob- served. A corresponding nonlinear ligand in which the pyridyl group is coupled to a β-diketone fragment via a “bent” thioether linkage has also been demonstrated to yield porous 2D and three- Received: December 8, 2010 Revised: February 9, 2011 ABSTRACT: The interaction of Cu(II) with three β-diketone ligands of type R 1 C(O)CH 2 C(O)R 2 (where R 1 = 2-, 3-, or 4-pyridyl and R 2 =C 6 H 5 , respectively), HL 1 -HL 3 , along with the X-ray structures and the pK a values of each ligand, are reported. HL 1 yields a dimeric complex of type [Cu(L 1 ) 2 ] 2 . In this structure, two deprotonated HL 1 ligands coordinate in a trans planar fashion around each Cu(II) center, one oxygen from each CuL 2 unit bridges to an axial site of the second complex unit such that both Cu(II) centers attain equivalent five-coordinate square pyramidal geometries. The two-substituted pyridyl groups in this complex do not coordinate, perhaps reflecting steric factors associated with the closeness of the pyridyl nitrogen to the attached (conjugated) β-diketonato backbone of each ligand. The remaining two Cu(II) species, derived from HL 2 and HL 3 , are both coordination polymers of type [Cu(L) 2 ] n in which the terminal pyridine group of each ligand is intermolecularly linked to an adjacent copper center to generate the respective infinite structures. HL 2 was also demonstrated to form a fibrous metallogel when reacted with CuCl 2 in an acetonitrile/water mixture under defined conditions.