Abstract The spectroscopic and photophysical behavior of a series of six extended arylacetylenes and one 1,3-diyne derivative was studied in solvents of different polarity to gain insight into the relationships between molecular architecture and optical/photophysical properties. The radiative decay channel was revealed to be the most important one for all the compounds, particularly in nonpolar solvents. A notable fluoro-solvatochromism was observed for the 1,3-diyne derivative in line with the large increase of its dipole moment under excitation. A peculiar behavior was observed for nitro-substituted aryl acetylenes on increasing solvent polarity, which was explained by the presence of an upper forbidden singlet state (S2) that is more polar than the allowed S1 state; this was confirmed by quantum mechanical calculations. The large decrease of the S2-S1 energy gap in a moderately polar solvent causes a strong increase of S1-S0 internal conversion to the detriment of fluorescence, which is in agreement with Lim's proximity effect model. Push and pull: The spectroscopic and photophysical properties of a series of six extended arylacetylenes and one 1,3-diyne derivative were studied in solvents of different polarity to gain insight into the relationships between molecular architecture and optical/photophysical properties. A scheme like Lim's proximity effect model was evoked to explain the fluorescence quenching in nitro-substituted systems.
Spectral and photophysical characterization of acetylenic fluorophores: the role of proximity effect on increasing internal conversion
FLAMINI, REBECCA;MARROCCHI, Assunta;SPALLETTI, Anna
2015
Abstract
Abstract The spectroscopic and photophysical behavior of a series of six extended arylacetylenes and one 1,3-diyne derivative was studied in solvents of different polarity to gain insight into the relationships between molecular architecture and optical/photophysical properties. The radiative decay channel was revealed to be the most important one for all the compounds, particularly in nonpolar solvents. A notable fluoro-solvatochromism was observed for the 1,3-diyne derivative in line with the large increase of its dipole moment under excitation. A peculiar behavior was observed for nitro-substituted aryl acetylenes on increasing solvent polarity, which was explained by the presence of an upper forbidden singlet state (S2) that is more polar than the allowed S1 state; this was confirmed by quantum mechanical calculations. The large decrease of the S2-S1 energy gap in a moderately polar solvent causes a strong increase of S1-S0 internal conversion to the detriment of fluorescence, which is in agreement with Lim's proximity effect model. Push and pull: The spectroscopic and photophysical properties of a series of six extended arylacetylenes and one 1,3-diyne derivative were studied in solvents of different polarity to gain insight into the relationships between molecular architecture and optical/photophysical properties. A scheme like Lim's proximity effect model was evoked to explain the fluorescence quenching in nitro-substituted systems.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
