Charge-Transfer Complexes of Iodine with N-Donors.

The spectral and thermodynamic characteristics of iodine complexes with various ether, sulfide and amine donors were examined in the vapor phase and in solution by the constant activity method and /or by a modified Benesi-Hildebr and analysis. The interaction of these donors with iodine covers the complexation range from weak to strong. The dimethyl ether-iodine complex was studied in the vapor phase and in n-heptane solution. The charge-transfer b and and visible iodine b and were characterized. Since the donor is both weak and volatile, the equilibrium constant, K(,C), could only be estimated in solution and could not be determined in the vapor phase. However, the product of the equilibrium constant and the molar absorptivity, (epsilon)(,C), in the vapor phase was determined. The enthalpy of complexation was obtained from the temperature dependence of the absorbance of a single ether-iodine mixture. Ethyl methyl sulfide-iodine and dimethyl sulfide-iodine were studied in n-heptane solution. The former was also studied in the vapor phase. Their spectral properties, e.g., the charge-transfer b and and shifted visible iodine b and , were characterized. For those moderately strong complexes, the equilibrium constant and molar absorptivity could be obtained by employing the usual regression procedure. The enthalpy of complexation for each complex was calculated from a least squares analysis of ln K(,C) (epsilon)(,C) versus 1/T. Studies of iodine complexed with pyridine, ammonia, trimethylamine, dimethylamine and methylamine in the vapor phase showed neither a charge-transfer b and nor a complexed visible iodine b and . In contrast to previous reports, no reaction between the amines (with the exception of methylamine) and iodine was observed. The results with ether and sulfide donors, in conjunction with earlier work reported on similar systems in both phases, give experimental justification for existing theories on solvent effects on the spectral and thermodynamic properties of complexes. A few anomalies still exist, however.PhDInorganic chemistryUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/158300/1/8116287.pd