THE FORMATION OF BIFURCATED CHARGE-TRANSFER COMPLEXES WITH MOLECULAR-IODINE

I2 complexes with triptycene and several di- and triaryl derivatives of methane and ethane were studied. For these complexes the values of lambda(CT) are virtually identical to those reported for the complexes with the analogous monoaryl donors, while the values of lambda for their blue shifted 12 peaks are significantly lower than those for the monoaryl complexes. Both the equilibrium constants and -DELTAH-0 values for the formation of complexes from the components lead to the conclusion that the complexes with the di- and triaryl compounds are more stable than those with the monoaryl donors. For the diaryl donors, the DELTAS-298(0) values for complex formation are less favorable than those of the monoaryl donors. The dipole moment for 12 in diphenylmethane is larger than the moment of I2 in toluene. All of these observations can be explained by taking into account the transannular effect of one aromatic ring on another and viewing the complexes as bifurcated ones in which the I atom at one end of an I2 molecule simultaneously interacts with two rings in the donor molecules.