Journal of Inclusion Phenomena and Molecular Recognition in Chemistry 32: 439–451, 1998. © 1998 Kluwer Academic Publishers. Printed in the Netherlands. 439 Spectroscopic Study of the Complexation of 5,6,14,15-Dibenzo-1,4-dioxa-8,12- diazacyclopentadeca-5,14-diene with Some Polynitrophenol Derivatives in Chloroform Solution SUSAN SADEGHI Department of Chemistry, Shahid Beheshti University, Tehran, Iran. MOJTABA SHAMSIPUR ? Department of Chemistry, Razi University, Kermanshah, Iran. (Received: 11 August 1997; in final form: 20 November l997) Abstract. The complex formation between 5,6,14,15-dibenzo-1,4-dioxa-8, 12-diazacyclopentadeca- 5,14-diene (DBDA15C4) and 4-nitrophenol (MNP), 2,4-dinitrophenol (DNP) and 2,4,6- trinitrophenol (TNP) have been studied spectrophotometrically in chloroform solution. The resulting proton transfer-charge transfer complexes are formulated as DBDA15C4·TNP and DBDA15C4·(TNP) 2 , confirming characterizations by microchemical analysis and IR spectroscopy. The equilibrium constants for the resulting complexes (K 1 and K 2 ) were evaluated from the non- linear least-squares fitting of the absorbance–mole ratio data. The overall stability of the resulting complexes was found to vary in the order TNP > DNP > MNP. The enthalpies and entropies of the successive complexation reactions for the DBDA15C4–TNP system were determined from the temperature dependence of the equilibrium constants. Key words: DBDA15C4, polynitrophenol, proton transfer–charge transfer complexes, chloroform, spectrophotometry, IR. 1. Introduction Since the discovery of crown ethers in 1967 [1], most thermodynamic and kinetic studies have been directed toward their complexing ability with different metal ions in aqueous and nonaqueous solvents [2, 3]. Investigations of adduct formation be- tween crown compounds and neutral species are quite recent [4]. The cavity formed by the cyclic disposition of oxygen atoms in crown ethers provides a very exciting feature for studying their molecular encapsulation properties. Recently, there has been increasing interest in the study of the charge transfer complexes between macrocyclic crown ethers and a wide variety of acceptors such as 2,3-dichloro- 5,6-dicyanobenzoquinone (DDQ) [5–7], tetracyanoethylene (TCNE) [5, 6], 7,7,8, ? Author for correspondence.