Triplet state characteristics of 2,2′- and 4,4′-biphenyldiols studied by 248 nm nanosecond laser flash photolysis

Triplet state characteristics of 2,2′- and 4,4′-biphenyldiols have been investigated in different organic solvents using 248 nm nanosecond laser flash photolysis technique. While for 2,2′-biphenyldiol, the triplet state of the molecule is produced as the only transient, for 4,4′-biphenyldiol, some phenoxyl radicals are also formed along with the triplet state following the laser excitation. Triplet quantum yields of 2,2′-biphenyldiol in different solvents are seen to be much lower than those of 4,4′-biphenyldiol. The differences in the laser flash photolysis results of the two diols have been explained on the basis of the presence and the absence of intramolecular hydrogen bonding in the two molecules.