Environment-Sensitive Behavior of DCNP in Solvents with Different Viscosity, Polarity and Proticity.
A pyrazoline derivative, 3-(1,1-dicyanoethenyl)-1-phenyl-4,5-dihydro-1H-pyrazole (DCNP), is studied by using optical spectroscopy methods in several solvents at room and at low temperatures. The DCNP molecule reveals a complex photophysics behavior, which is sensitive to solvent polarity, proticity, temperature and viscosity and arises from the presence of two rotational degrees of freedom of the dicyanovinyl group--the torsion around the double C=C bond and the s-trans-s-cis isomerization around the single C-C bond--that differently behave in various environmental conditions. The fluorescence yield of a few percent and sub-nanosecond decay times observed at room temperature make the compound useful for optical studies of liquid environments. The proticity of polar solvents can be detected with two-exponential fluorescence decays. At low temperatures, DCNP can be used as solvent viscosity or temperature fluorescent sensor.
Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668, Warsaw, Poland. morawo@ifpan.edu.pl.
Olaf
O
Morawski
Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668, Warsaw, Poland.
Boleslaw
B
Kozankiewicz
Advanced Materials Engineering and Modelling Group, Faculty of Chemistry, Wroclaw University of Technology, 50-370, Wroclaw, Poland.
Andrzej
A
Miniewicz
Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668, Warsaw, Poland.
Andrzej L
AL
Sobolewski
charge transfer; cis-trans isomerization; hydrogen bonds; molecular rotor; torsion