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, possibil ities of the occurrences of photoinduced electron transfer (ET) reactions w ithin some novel synthesized derivatives of phenanthrene (1,1-dimethyl-9-me thoxy-1,2,3,4-tetrahydrophenanthrene, 9MTHP; 1,1-dimethyl-6,9-dimethoxy-7-i sopropyl-1,2,3,4-tetrahydrophenanthrene, 69DMTHP and 1,1-dimethyl-6,7,9-tri methoxy-1,2,3,4-tetrahydrophenanthrene, 679TMTHP) donors and 9-fluorenone/9 -cyanoanthracene acceptors in acetonitrile fluid solution were studied at t he ambient temperature (296 K). No ground state charge transfer complex was apparent from the observed electronic absorption spectra of the present re acting (D-A) systems. On singlet (S-1) excitation of acceptor moiety, low t o moderate exothermic photoinduced ET reactions seem to be primarily respon sible for the observed fluorescence quenching phenomena. Occurrence of such process within the excited acceptor and ground state donor was also confir med from the measurement of transient absorption spectra at different delay times between the exciting and analyzing pulses. An attempt was made to te st the Marcus theory both in the normal and inverted region for the photoin duced forward ET reactions within the donor and acceptor systems used in th e present investigation. (C) 2001 Elsevier Science B.V. All rights reserved .