Polycyclic Aromatic Hydrocarbon Solute Probes. Part IV: Effect of Solvent Polarity on the Fluorescence Emission Fine Structures of Select Pyrene and Pentaphene Derivatives

Fluorescence properties of benzo[e]pyrene, benzo[a)pyrene, dibenzo[a,ejpyrene (naphtho[1,2,3,4def]chrysene), 1-chloropyrene, tribenzo[de, kl,rst]pentaphene, dinaphtho[2,1,8,7defg,2′,1,8′,7'ijkl]pentaphene, benz [rst]anthra[9,1,2cde]pentaphene, and dibenzo[fg,ij]phenanthro[2,1,10,9,8,7pqrstuv]pentaphene dissolved in solvents of varying polarity are reported. Measurements indicate that emission intensities of benzo[e)pyrene (BePy) and dibenzophenanthropentaphene (DBPP) depend on solvent polarity. Two new polarity scales are defined, BePy = I/IV and DBPP = I/II, on the basis of the ratio of the fluorescence intensities of select vibronic bands. For fluorescence spectra for the remaining six compounds studied, either the spectra were not clearly resolvable or the calculated intensity ratios remained nearly constant, irrespective of solvent polarity.