Charge-transfer interactions of singlet excited trans isomers of n-styrylnaphthalene (n-StN, with n = 1 and 2), 9-styrylanthracene (9-StAn), and n-styrylphenanthrene (n-StPh, with n = 1, 2, and 9) with electron donors (N,N-diethylaniline, DEA, and 4-bromo-N,N-dimethylaniline, BrDMA) and accepters (p-dicyanobenzene, DCNB) were studied in polar and nonpolar solvent at room temperature by absorption picosecond laser flash photolysis. The transient absorption formed within the laser pulse, already attributed to S-1 --> S-n and S-2 --> S-n transitions, were replaced, in the presence of amine quenchers, by the absorption of the exciplex (nonpolar solvent) or of contact radical ion pairs (CRIP, polar solvent). The time evolution of these transients showed the formation of the solvent-separated radical ion pair (SSRIP) and then of the longer-lived absorption of tripler state and/or radical anions. In the presence of DCNB in polar solvent the evolution of the first excited singlet showed the formation of GRIP, SSRIP, and radical cations. The criteria of the transient attribution and the spectral and kinetic characteristics of the transients are reported.
Dynamics of the Singlet Excited States of Diarylethenes in the Presence of Charge-Transfer Interactions. A Picosecond Laser Flash Photolysis Study
LATTERINI, Loredana;ELISEI, Fausto;ALOISI, Gian Gaetano;
1997
Abstract
Charge-transfer interactions of singlet excited trans isomers of n-styrylnaphthalene (n-StN, with n = 1 and 2), 9-styrylanthracene (9-StAn), and n-styrylphenanthrene (n-StPh, with n = 1, 2, and 9) with electron donors (N,N-diethylaniline, DEA, and 4-bromo-N,N-dimethylaniline, BrDMA) and accepters (p-dicyanobenzene, DCNB) were studied in polar and nonpolar solvent at room temperature by absorption picosecond laser flash photolysis. The transient absorption formed within the laser pulse, already attributed to S-1 --> S-n and S-2 --> S-n transitions, were replaced, in the presence of amine quenchers, by the absorption of the exciplex (nonpolar solvent) or of contact radical ion pairs (CRIP, polar solvent). The time evolution of these transients showed the formation of the solvent-separated radical ion pair (SSRIP) and then of the longer-lived absorption of tripler state and/or radical anions. In the presence of DCNB in polar solvent the evolution of the first excited singlet showed the formation of GRIP, SSRIP, and radical cations. The criteria of the transient attribution and the spectral and kinetic characteristics of the transients are reported.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
