title: Charge transfer complexes of indole:catechol type II.
abstract: Charge transfer complexes between tryptamine:epinephrine, tryptamine:isoproterenol, tryptamine:catechol, and indole:catechol were demonstrated spectrophotometrically in aqueous solutions containing 0.1 M HCl. It was possible to make precise measurements and to calculate thermodynamic parameters and molar absorptivities. In general, the equilibrium constant was found to be quite low and ranged from 4.00 +/- 0.04 to 0.30 +/- 0.02 M-1. These interactions are exothermic and have relatively large standard enthalpy and entropy changes (delta Ho values ranged from -7.4 +/- 0.3 to -5.2 +/- 0.4 kcal mol-1; delta So ranged from -25 +/- 5.0 to -16 +/- 1.3 cal K-1 mol-1). The similarity in delta Ho and delta So values for all the combinations indicates a similar interacting system. This result has led us to propose the involvement of the charge transfer effect, induced in the indole:catechol system, in the mechanism occurring in nerve conductions.
authors.affiliation: Department of Pharmaceutical Chemistry, College of Pharmacy, University of Baghdad, Republic of Iraq.
authors.forename: H N
authors.initials: HN
authors.lastname: Borazan
authors.forename: Y H
authors.initials: YH
authors.lastname: Ajeena
mesh_terms: D002396:Catechols / Q000032:analysis*; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D007211:Indoles / Q000032:analysis*; D013056:Spectrophotometry, Ultraviolet; D013816:Thermodynamics
chemical_list: D002396:Catechols; D007211:Indoles