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Communication | Special issue | Vol 79, No. 1, 2009, pp.331-337
Published online, 29th December, 2008
DOI: 10.3987/COM-08-S(D)9
High Binding Affinity of DABCO with Porphyrin in a Porphyrin-cis-Stilbene-Porphyrin Triad

Md. Wahadoszamen, Takashi Yamamura, Atsuya Momotake, Yoshinobu Nishimura, and Tatsuo Arai*

*Department of Chemistry, Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Ten-nodai, Tsukuba-shi, Ibaraki 305-0006, Japan

Abstract

Porphyrin-stilbene-porphyrin triad (mZnPst) where a central cis-stilbene unit is connected to zinc-tetraphenylporphyrin (ZnTPP) was synthesized and its binding ability with a selected guest ligand DABCO was investigated. The association constant was evaluated to be 2.47 x 108 M-1, from the iterative least squares fitting to a 1:1 binding model, which is larger than that of monomer ZnTPP/DABCO complex (3.50 x 105 M-1). In addition, when a toluene solution of mZnPst is mixed with 1 equivalent of DABCO, the color of the solution was changed abruptly to light purple from bright reddish, providing further a visual evidence of forming strong complex. Such a high association constant suggests mZnPst/DABCO to be a promising photoresponsive supramolecular system.