hide
Free keywords:
Crystal engineering; Supramolecular chemistry; Coordination modes; Jahn-Teller distortion; Copper
Abstract:
Attempts to crystal engineer metallosupramolecularcomplexes from Cu(phen)2+ building blocks and the prototypical,rod-like, exo-bidentate ligand 4,4′-bipyridine (4,4′-bipy) by layering techniques are described. Reactions of Cu(phen)2+ (phen = 1,10-phenanthroline) with 4,4′-bipy in the presence of NO3– counterions yielded two distinct, discrete, dinuclear, Ci symmetric, dumbbell-typecomplexes, [{Cu(NO3)2(phen)}2(4,4′-bipy)] (1) and [{Cu(NO3)(phen)(H2O)}2(4,4′-bipy)](NO3)2 (2), depending upon the mixture of solvents used for crystallization. In compound 1, a mono- and a bidentate nitrato group coordinate to Cu2+, whereas in 2 the monodentate nitrato groups are replaced by aqua ligands, which introduce additional hydrogen-bond donor functionality to the molecule. The crystal structure of 1 was determined by single-crystal X-ray analysis at 296 and 110 K. Upon cooling, a disorder-order transition occurs, with retention of the space group symmetry. The crystal structure of 2 at room temperature was reported previously [Z.-X. Du, J.-X. Li, Acta Cryst. 2007, E63, m2282]. We have redetermined the crystal structure of 2 at 100 K. A phase transition is not observed for 2, but the low temperature single-crystal structure determination is of significantly higher precision than the room temperature study. Both 1 and 2 are obtained phase-pure, as proven by powder X-ray diffraction of the bulk materials. Crystals of [Cu(phen)(CF3SO3)2(4,4′-bipy)·0.5H2O]n (3), a one-dimensional coordination polymer, were obtained from [Cu(CF3SO3)2(phen)(H2O)2] and 4,4′-bipy. In 3, Cu(phen)2+ corner units are joined by 4,4′-bipy via the two vacant cis sites to form polymeric zig-zag chains, which are tightly packed in the crystal. Compounds 1–3 were further studied by infrared spectroscopy.
