Photoinduced electron transfer (ET) within some novel synthesized derivatives of phenanthrene acting as donors and 9-fluorenone/9-cyanoanthracene behaving as acceptors

With the help of both steady state and time-resolved measurements, possibilities of the occurrences of photoinduced electron transfer (ET) reactions within some novel synthesized derivatives of phenanthrene (1,1-dimethyl-9-methoxy-1,2,3,4-tetrahydrophenanthrene, 9MTHP; 1,1-dimethyl-6,9-dimethoxy-7-isopropyl-1,2,3,4-tetrahydrophenanthrene, 69DMTHP and 1,1-dimethyl-6,7,9-trimethoxy-1,2,3,4-tetrahydrophenanthrene, 679TMTHP) donors and 9-fluorenone/9-cyanoanthracene acceptors in acetonitrile fluid solution were studied at the ambient temperature (296 K). No ground state charge transfer complex was apparent from the observed electronic absorption spectra of the present reacting (D-A) systems. On singlet (S-1) excitation of acceptor moiety, low to moderate exothermic photoinduced ET reactions seem to be primarily responsible for the observed fluorescence quenching phenomena. Occurrence of such process within the excited acceptor and ground state donor was also confirmed from the measurement of transient absorption spectra at different delay times between the exciting and analyzing pulses. An attempt was made to test the Marcus theory both in the normal and inverted region for the photoinduced forward ET reactions within the donor and acceptor systems used in the present investigation. (C) 2001 Elsevier Science B.V. All rights reserved.