No abstract

Comparisons of the temporal characteristics of the transient absorption with those of the delayed fluorescence for dinaphthylmethanes and dinaphthyl ethers provide compelling kinetic evidence for the formation of intramolecular triplet excimers.

No abstract

kJ/m01.~~ Recent theoretical calculations are in fair agreement with this value. Using empirical corrections to ab initio atomization energies, Ho et al. obtained AH?(SiC13) = -318 f 7 k J / m 0 1 .~~-~~ A recent semiempirical calculation yielded -485 kJ/mol,'* but this should probably be disregarded because of grass (30) Steele, W. C.; Nichols, L. D.; Stone, F. G. A. disagreement with other experimental and theoretical results. In the present work we obtain AHfo298(SiC13) = -353 i 12 kJ/mol by combining our theoretical IP,(SiC13) with the experimental recently reported by Fisher and A r m e n t r~u t .~~ Our calculation of LWf0(SiCl3) is based on ion thermochemistry and differs from calculations by previous workers, who used only neutral thermochemistry. The good agreement between Walsh's recommended value and our value indicates that the neutral and ion thermochemical data are mutually consistent.The formation of an intramolecular charge-transfer (CT) exciplex is demonstrated for 1,l'-dinaphthylamine (1,l'-DNA) and 2,2'-dinaphthylamine (2,2'-DNA) in the lowest excited singlet state using steady-state and picosecond time-resolved fluorescence spectroscopy. The exciplex is formed through a mutual reorientation of the two naphthalene rings. Differences in the rate of formation and relaxation of the CT state for 1,l'-DNA and 2,2'-DNA indicate the importance of the bridge position in this process. The comparison of the steady-state fluorescence of 2,2'-DNA with that of its protonated form, as well as the fluorescence of 2,2'-dinaphthyl ether and 2,2'-dinaphthylmethane, show the role of the lone-pair electrons of the nitrogen atom in the exciplex formation.