“…19 Recently, we have reported the excited singlet ͑S 1 ͒ and triplet ͑T 1 ͒ state characteristics and the photoionization behavior of 2,2Ј-and 4,4Ј-biphenyldiols in different protic and aprotic solvents, with a special impor-tance to the role of the presence and the absence of intramolecular hydrogen bonding in the two respective molecules. [20][21][22][23] It has been observed that the photochemical behavior of 2,2Ј-biphenyldiol differs significantly from that of its 4,4Ј-analogue due to the presence and the absence of the intramolecular hydrogen bonding in two respective diols. [20][21][22][23] Since the diols are very prone to oxidation, 18,24 in the present work we have investigated the ET interactions of 2,2Ј-and 4,4Ј-biphenyldiols in their S 1 state with chloroalkane ͑CA͒ acceptors, like carbon tetrachloride ͑CCl 4 ͒, chloroform ͑CHCl 3 ͒, and methylene dichloride ͑CH 2 Cl 2 ͒, using both steady-state ͑SS͒ and time-resolved ͑TR͒ fluorescence quenching measurements.…”