ABSORPTION AND FLUORESCENCE OF A RIGIDLY-BRIDGED DONOR-ACCEPTOR MOLECULE IN LANGMUIR-BLODGETT MIXED FILMS

Thermodynamic analysis of the pressure-area isotherms, of solutions of rigidly-bridged donor-acceptor molecule, D(10)A, in arachidic acid, i ndicates that the solutions behave ideally at low concentrations. The surface area per molecule at high dilutions (mf less than or equal to 0.02) approximates to 27 Angstrom(2) from which it is evident that the long axis of the D(10)A molecule is oriented vertically, and the shor t axis of the 1,4-dimethoxynaphthalene moiety parallel to the monolaye r surface at 25 mN m(-1) surface pressure Evidence from electronic abs orption, static and time-resolved fluorescence spectra led us to concl ude that D(10)A molecules form ground-state dimers, intermolecular exc imers with very short lifetimes which do not photodimerize in Langmuir -Blodgett films, and give long-lived (tau(3) approximate to 29 +/- 3ns ) charge-transfer emissions at 440 nm.