Steric effect on fluorescence quenching.
In this communication we have reported the steric effect on the fluorescence quenching rate constants of the electron transfer (ET) process. We have done a comparative study using donor (D)-acceptor (A) systems with different exergonicity (-deltaG(f)). Different carbazole derivatives (CZ): 1,4-dicyanobenzene (DCB) systems (-deltaG(f) = 0.7-0.8 eV) were found to be among those limiting systems that show a clear-cut steric dominance in the process of fluorescence quenching. It is known that with increasing exergonicity the ET distance increases and hence steric dependence becomes insignificant. On the other hand, with decreasing exergonicity the ET distance decreases and a pronounced steric dominance should be observed. However, in the D-A systems having lower exergonicity compared to CZ-DCB systems, this steric dominance is observed only in polar medium. In non-polar medium due to exciplex formation the D-A distance effectively becomes much longer and therefore no steric dominance is observed.
Chatterjee
Suchandra
S
Department of Chemistry, Serampore College, Serampore, Hooghly 712204, India.
Basu
Samita
S
Ghosh
Nandita
N
Chakrabarty
Manas
M
D002227:Carbazoles / Q000737:chemistry*; D004579:Electron Transport; D005453:Fluorescence; D009570:Nitriles / Q000737:chemistry*; D013050:Spectrometry, Fluorescence
D002227:Carbazoles; D009570:Nitriles; C041514:carbazole; C412619:1,3-dicyanobenzene