GLOBAL TRICOMPARTMENTAL ANALYSIS OF THE FLUORESCENCE DECAY SURFACE OFTHE CHARGED FLUORESCENT-PROBE N,N,N-TRIMETHYL-3-(1-PYRENYL)-1-PROPANAMINIUM PERCHLORATE

The kinetics of the excited-state processes of the charged fluorescent probe N,N,N-trimethyl-3-(1-pyrenyl)-1-propanaminium perchlorate (PROB E) in tetrahydrofuran are reported. At very low concentrations PROBE d ecays monoexponentially with a lifetime tau of 236 +/- 1 ns, from whic h k(01) = 1/tau = 4.2 x 10(6) s(-1) is obtained. Upon addition of the quaternary ammonium salt N,N,N-trimethyl-1-dodecanaminium perchlorate a biexponential decay function is needed to describe the decay traces. The second excited state is the aggregated PROBE. This aggregation is due to dipole-dipole or ion-dipole interactions. The rate constant va lues of the kinetic Scheme (Scheme 4) are obtained by global bicompart mental analysis: k(01) = k(02), k(21) = (42 +/- 7) x 10(9) M(-1) s(-1) ; k(12) = (5.7 +/- 0.1) x 10(7) s(-1). When the concentration of PROBE itself is varied, a triple-exponential decay function adequately desc ribes the decay surface. The third excited-stale species is a PROBE ex cimer, which can be formed through two different pathways: either inte rmolecularly when a locally excited PROBE molecule encounters a ground -state PROBE molecule or intramolecularly when an aggregate of two PRO BE molecules rearranges. To resolve the kinetics of this system, globa l tricompamnental analysis is developed. Even after including the info rmation available from experiments where N,N,N-trimethyl-1-dodecanamin ium perchlorate is added (k(01) = k(02)), and the information availabl e from the global triple-exponential analysis (k(13) = 0 and k(23) = 0 ) (Scheme 5), the experimental time-resolved data do not allow one to obtain a unique solution for the rate constant values, By scanning the rate constant k31, bounds can be specified for the rate constants: 53 x 10(9) < k(21) < 60 x 10(9) M(-1) s(-1), k(31) < 7 x 10(9) M(-1) s(- 1), 1.5 x 10(8) < k(12) < 1.7 x 10(8) s(-1) and k(32) < 2 X 10(7) s(-1 ). Unique values are obtained for k(01), k(02), and k(O3): k(01) = k(0 2) = (4.25 +/- 0.01) x 10(7) s(-1); k(03) = (1.92 +/- 0.03) x 10(7) s( -1).