عنوان مقاله [English]
In this study the formation of charge transfer complexes between porphyrin free bases such as tetraphenyl porphyrin (TPP) and tetrakis (4-methylphenyl) porphyrin (Me-TPP) as electron donors (D) with some electron acceptors (A) such as 2, 4, and 6-trinitrophenol (Picric acid) and 1-Chloro-2, 4 and 6-trititrobenzene (picryl chloride) were investigated using UV-Vis spectrophotometry in dichloromethane at 293-308K. The porphyrin peak decreased at 418-419 nm and two new absorption bands developed at 441-448 and 654-667 nm. These new bands were characteristic of the charge transfer from HOMO of porphyrin to the LUMO of electron acceptor. The isosbestic point characterized the existence of one equilibrium and two adsorbent species. The Benesi-Hildebrand equation was applied to calculate the equilibrium constants and molar absorption coefficients of the complexes at different temperatures. With considering the temperature dependence of the complex formations, the Vant Hoff equation was used to calculate the thermodynamic constants of the complex formation reactions (ΔH, ΔG, ΔS). The is no deviation linearity at the Vant Hoff equation for all the complexes in different temperatures represented a 1: 1 complex formed between acceptor and donor.