Interaction of the excited singlet state of 1,4- and 1,8-dimethoxynaphthalene with some organic compounds: A fluorescence-quenching study

The fluoroescence quenching of 1,4-dimethoxynaphthalene (1) and 1,8-dimethoxynaphthalene (2) by tetraphenylporpyrin (3), 9,10-diphenylanthracene (4), and 3-cyano-4-phenyl-6-(p-tolyl)-pyridin-2-one (5) has been studied in chloroform solution. The quenching occurs Dia a resonance energy transfer mechanism. The rate constant for the energy transfer (k(ET)) of donor 2 is slower than that of 1 by the same accepters, indicating that the steric effect dominates the ionization potential effect in all systems. The calculated critical transfer distances (R(0)) are 17-72 Angstrom. In contrast, charge transfer is the predominant pathway of electronic deexcitation in the fluorescence quenching of donors 1 and 2 by 7,7,8,8-tetracyanoquinone-dimethane (6) in chloroform. The roles of temperature and geometrical structure of the donors on the efficiency of fluorescence quenching of 1 and 2 by acceptor 6 have also been studied.