A new copper(II) tubelike metal-organic framework constructed from P,P '-diphenylmethylenediphosphinic acid and 4,4 '-bipyridine: Synthesis, structure, and thermal behavior

A new tubular metal-organic framework [Cu-2(pcp)(2)(4,4'-bipy)] center dot 5H(2)O (pcp = P,P'-diphenylmethylenediphosphinate) has been synthesized and characterized by single-crystal X-ray analysis, temperature-dependent X-ray powder diffraction (TDXD), thermogravimetric measurements and IR spectroscopy. The structure consists of polymeric nano-sized square channels, whose edges are constituted by infinite chains of metal ions bridged by phosphinate ligands. The chains are linked together by 4,4'-bipyridines, forming the walls of the channels. Solvent water molecules are located inside and outside the channels, all anchored through hydrogen bonds. The cross-section dimensions of the channels are approximately 10 x 10 angstrom(2). The four guest molecules located inside the channels can be eliminated by gentle heating at ca. 80 degrees C, restored in air, or in turn substituted by DMF through vapour exposition. The monohydrated phase [Cu-2(pcp)(2)(4,4'-bipy)] center dot H2O, which maintains the same polymeric framework as the title complex, remains stable till 260 degrees C. Above this temperature the complex undergoes a solid state crystal-to-crystal rapid reaction, via loss of both the 4,4'-bipyridine and the remaining water and rearrangement of the coordinated pcp to give the previously reported [Cu(pcp)] polymeric framework. (c) 2007 Elsevier B.V. All rights reserved.