Laser flash photolysis was used to produce and investigate the lowest excited triplet state (T1) and radical ions (DAE.+ and DAE.-) of some diarylethylenes (DAE). In particular, the two trans-styrylnaphthalene isomers (n-StN, where n = 1 or 2 on the naphthalene) and four trans-1-(n-naphthyl)-2-(n'-pyridyl)ethylenes (n,n'-NPE, with n,n' = 1,4'; 2,2'; 2,3' and 2,4') were studied. The transients were characterized in terms of their absorption spectra, decay kinetics, molar absorption coefficients (for DAE.+ and DAE.-) and formation quantum yields (for T1 and DAE.+). Except for 1-StN, under direct excitation in the absence of quenchers (lambda(exc) = 308 and 347 nm), T1 --> T(n) absorption was undetectable and DAE.+ was the only transient observed, even though it was produced in low yield (phi(PI) less-than-or-equal-to 0.06). The triplet state T1 of the DAEs was characterized in n-hexane, in the presence of 4-bromo-N, N-dimethylaniline (BrDMA) which enhances the intersystem-crossing quantum yields, while DAE.- was produced and studied in acetonitrile, by laser excitation at 347 nm, in the presence of diethylaniline (DEA) and BrDMA.
Triplet and radical ion properties of styrylnaphthalenes and their aza-derivatives: a laser flash fotolysis study
ALOISI, Gian Gaetano;ELISEI, Fausto;LATTERINI, Loredana
1992
Abstract
Laser flash photolysis was used to produce and investigate the lowest excited triplet state (T1) and radical ions (DAE.+ and DAE.-) of some diarylethylenes (DAE). In particular, the two trans-styrylnaphthalene isomers (n-StN, where n = 1 or 2 on the naphthalene) and four trans-1-(n-naphthyl)-2-(n'-pyridyl)ethylenes (n,n'-NPE, with n,n' = 1,4'; 2,2'; 2,3' and 2,4') were studied. The transients were characterized in terms of their absorption spectra, decay kinetics, molar absorption coefficients (for DAE.+ and DAE.-) and formation quantum yields (for T1 and DAE.+). Except for 1-StN, under direct excitation in the absence of quenchers (lambda(exc) = 308 and 347 nm), T1 --> T(n) absorption was undetectable and DAE.+ was the only transient observed, even though it was produced in low yield (phi(PI) less-than-or-equal-to 0.06). The triplet state T1 of the DAEs was characterized in n-hexane, in the presence of 4-bromo-N, N-dimethylaniline (BrDMA) which enhances the intersystem-crossing quantum yields, while DAE.- was produced and studied in acetonitrile, by laser excitation at 347 nm, in the presence of diethylaniline (DEA) and BrDMA.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
