4,4′-Bipyrazolyl: new bitopic connector for construction of coordination networks

Abstract

New organic bitopic connector 4,4′-bipyrazolyl ( bpz) easily forms complexes with metal ions and produces 1, 2 and 3D coordination polymers of different topology. Ten coordination polymers based upon bpz ligand and octahedral metal centers (Zn 2+, Cd 2+, Cu 2+, Co 2+) have been prepared and characterized by means of X-ray analysis. In all compounds the bipyrazolyl molecules act as bridging neutral groups and connect two metal atoms at the distances of 9.81–10.34 Å. Representative possibilities for the formation of multidimensional metal-organic array include linear chains in [Cu( bpz)(H 2O) 3(SO 4)]·H 2O, ‘ladder chains’ in [M( bpz) 1.5(H 2O) 2(NO 3)](NO 3) (M=Cu, Zn), flat and corrugated square grid layers in 1:2 complexes with cobalt chloride, zinc and cadmium perchlorates and copper trifluoroacetate, parallel/parallel interpenetrated square grid layers in [Cd( bpz) 2(NO 3) 2] and 3D diamondoid net in [Cu( bpz) 2(H 2O) 2](ClO 3) 2·5H 2O. With exception of the latter example the supramolecular architecture of metal-organic polymers may be clearly related with 4,4′-bipyridine derivatives, but more hydrophilic nature of pyrazole nuclei facilitates easy incorporation of different H-bond donors/acceptors—H 2O, CH 3OH, DMF. The 2D coordination arrays may enclathrate also guest molecules of hydrophilic aromatics that appear to be located between successive coordination layers: [Cu( bpz) 2(H 2O) 2](CF 3CO 2) 2·2H 2O·C 6H 5OH.