International Journal of Photoenergy

International Journal of Photoenergy / 2003 / Article

Open Access

Volume 5 |Article ID 346941 |

L. F. M. Ismail, M. S. A. Abdel-Mottaleb, "Fluorescence studies of photoactivated acidity of 2,2-Dihydroxy-1,1-Binaphthalene", International Journal of Photoenergy, vol. 5, Article ID 346941, 6 pages, 2003.

Fluorescence studies of photoactivated acidity of 2,2-Dihydroxy-1,1-Binaphthalene


Linear and multilinear relationships between some solvent polarity parameters and solvatochromic shifts of absorption and fluorescence of 2,2-dihydroxy-1,1-binaphthalene (DHBN) revealed strong charge transfer excitations (formation of S1,CT with higher dipole moment) in this dipolar system. This dihydroxy molecule with pKa(S0) of 10.9 becomes a weak acid with pKa(S1) of 6.8 in its first excited singlet state. We studied the excited state proton-transfer process from DHBN to the base water in acetonitrile solution by means of fluorescence spectroscopy. We found that the process occurs via a 1: 1 very weak (with equilibrium constant K=9×103M1) hydrogen-bonded adduct between the photoacid DHBN and the base. Moreover, the rate constant of fluorescence quenching of DHBN by some Lewis acids; Ag+1, Cu+2, Fe+2 or Fe+3 metal ions in methanol solution as well as the binding constant of the formed complexes are correlated with the size and charge of the metal ion. Furthermore, photostability studies of DHBN in aqueous solutions at different pHs point to photolability of DHBN with formation of different photo-oxidation products similar to simple naphthols.

Copyright © 2003 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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