TY - JOUR
T1 - Effects of alcohols on emission spectra of toluene-triethylamine mixtures in THF
T2 - Separation into polar and hydrogen-bonding interactions
AU - Xie, Guobin
AU - Sueishi, Yoshimi
AU - Yamamoto, Shunzo
N1 - Funding Information:
This work was supported by a Grand-in-Aid for Scientific Research (No. 15550014) from the Ministry of Education, Culture, Sports, Science and Technology.
PY - 2004/3/15
Y1 - 2004/3/15
N2 - The emission spectra of toluene (T)-triethylamine (TEA) systems were measured under conditions of steady-state illumination in some protic and aprotic solvent-THF mixtures. The fluorescence spectrum of the T-TEA system in THF could be separated into three component bands (band A at 279 nm (fluorescence of T), band B at 336 nm (fluorescence of TEA) and band C at 373 nm (emission from an intermolecular exciplex)). The intensities of bands B and C decreased with increasing solvent polarity. The decrease in the intensities of bands B and C is considered to be caused by the enhanced conversion of the exciplex to an ion-pair with increase in solvent polarity. The intensities of bands B and C also decreased owing to the hydrogen-bonding interaction between TEA and protic solvents, but in this case the intensity of band A increased. Acetonitrile only has a polar effect and trichloroacetic acid only has a hydrogen-bonding (or protonation) effect, while alcohols have both effects. The equilibrium constants for the formation of intermolecular hydrogen-bonded complexes of TEA with alcohols were estimated from the changes in the intensity of band A. The hydrogen-bonding and polar effects of alcohols on the intensities of bands B and C could be evaluated separately. The ratio of the hydrogen-bonding effect to the polar effect of alcohols was observed to increase with increasing vol.% of alcohol.
AB - The emission spectra of toluene (T)-triethylamine (TEA) systems were measured under conditions of steady-state illumination in some protic and aprotic solvent-THF mixtures. The fluorescence spectrum of the T-TEA system in THF could be separated into three component bands (band A at 279 nm (fluorescence of T), band B at 336 nm (fluorescence of TEA) and band C at 373 nm (emission from an intermolecular exciplex)). The intensities of bands B and C decreased with increasing solvent polarity. The decrease in the intensities of bands B and C is considered to be caused by the enhanced conversion of the exciplex to an ion-pair with increase in solvent polarity. The intensities of bands B and C also decreased owing to the hydrogen-bonding interaction between TEA and protic solvents, but in this case the intensity of band A increased. Acetonitrile only has a polar effect and trichloroacetic acid only has a hydrogen-bonding (or protonation) effect, while alcohols have both effects. The equilibrium constants for the formation of intermolecular hydrogen-bonded complexes of TEA with alcohols were estimated from the changes in the intensity of band A. The hydrogen-bonding and polar effects of alcohols on the intensities of bands B and C could be evaluated separately. The ratio of the hydrogen-bonding effect to the polar effect of alcohols was observed to increase with increasing vol.% of alcohol.
KW - Exciplex
KW - Fluorescence
KW - Hydrogen-bonding
KW - Polar effect
KW - Solvent effect
UR - http://www.scopus.com/inward/record.url?scp=1342265070&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=1342265070&partnerID=8YFLogxK
U2 - 10.1016/S1010-6030(03)00413-1
DO - 10.1016/S1010-6030(03)00413-1
M3 - Article
AN - SCOPUS:1342265070
SN - 1010-6030
VL - 162
SP - 449
EP - 456
JO - Journal of Photochemistry and Photobiology A: Chemistry
JF - Journal of Photochemistry and Photobiology A: Chemistry
IS - 2-3
ER -