K. Kano, T. Hayakawa, S. Hashimoto
Mar 1, 1991
Citations
0
Influential Citations
33
Citations
Journal
Bulletin of the Chemical Society of Japan
Abstract
The stability of the molecular complexes between 5,10,15,20-tetraarylporphyrins and quinones in organic solvents has been compared with that in water. 5,10,15,20-Tetrakis(mono-substituted phenyl)porphines (RTPPs) hardly form molecular complexes with p-benzoquinone (BQ), 2,3,5,6-tetramethyl-p-benzoquinone (DQ), and 2,3,5,6-tetrachloro-p-benzoquinone (CQ) in dichloromethane (K>60 mol−1 dm3). In contrast, the stability constants (K<60 mol−1 dm3) for the molecular complexes of cationic porphyrins (TMPyP and TAPP) with BQ in water are much larger than those in methanol. The thermodynamic parameters clearly indicate that complexation in water is an enthalpically favorable process, suggesting that the van der Waals interactions are the main binding forces and that hydrophobic interaction does not play an important role in complex formation in water. The larger stability of the molecular complexes in water can be interpreted in terms of the nature of water, as demonstrated by Smithrud and Diederich (D. B. Smithru...