Spectral properties of coumarin derivatives substituted at position 3. Effect of polymer matrix

摘要: Abstract The spectral properties of coumarin (2H-1-benzopyran-2-one) derivatives substituted at position 3 with bulky substituents, such as phenyl, phenylthio and benzylthio, were investigated in solvents different viscosity polymer matrices. In order to evaluate the heavy atom effect, some by bromine positions 6 8. absorption spectra exhibit a broad band maximum 340 nm (log e ≈ 4) which is not influenced medium. Coumarin low fluorescence quantum yield 0.005 lifetime shorter than 0.1 ns. higher films, yields are 0.05–0.2 increased approximately 2 On basis data, rate constant radiationless deactivation k nr 10 11 s −1 solution 4 × 8 matrix. activation energy process 3-phenylcoumarin about 34 kJ mol glycerol. change glycerol 72 . This comparison indicates that torsional rotation substituent partially friction