THE CHARGE-TRANSFER COMPLEXES OF 1-METHYL -2(1H)-PYRIDINIMINE AND ITSMETHYL-DERIVATIVES WITH IODINE

The molecular interaction of 1-methyl-2(1H)-pyridinimine (1MPI), its m ethyl derivatives (1-methyl-2 (1H)-pyridine (methyimine) (12MPMI), 1,3 -dimethyl-2 (1H)-pyridinimine (13DMPI), 1,4-dimethyl-2 (1H)-pyridinimi ne (14DMPI), 1,5-dimethyl-2 (1H)-pyridinimine (15DMPI) and 1,6-dimethy l-2(1H)-pyridinimine (16DMPI)), with iodine has been studied by UV, H- 1-NMR and IR spectroscopies. The UV spectra of the above pyridinimines /iodine systems indicate that a 1 : 1 charge transfer (CT) complex is formed between pyridinimines and I-2. The IR spectral results of these pyridinimines/iodine systems reveal that the new sharp band appears a t ca. 1510 cm(-1) with increasing I-2 concentration in the CT complexe s except for the 12MPMI/iodine and 13DMPI/iodine systems. The band mea ns that the interaction occurs at the nitrogen of the imino group of p yridinimines and the I-2 molecule. The enthalpy change of complexation of the 15DMPI/iodine complex is the largest among specimens investiga ted to be 54.3 kJ mol(-1). On the other hand, the 12MPMI/iodine and 13 DMPI/iodine systems make a weak interaction because the two methyl gro ups of the 12MPMI and 13DMPI keep away from the nitrogen of the imino group. In addition, from the NOESY spectral results the molecular stru cture of the CT complexes are discussed.