Journal of Inclusion Phenomena and Macrocyclic Chemistry 34: 431–443, 1999. © 1999 Kluwer Academic Publishers. Printed in the Netherlands. 431 Molecular Complex Formation between Some Azacrown Ethers and 2,4,6-Trinitrophenol SUSAN SADEGHI Department of Chemistry, Shahid Beheshti University, Tehran, Iran NAADER ALIZADEH Department of Chemistry, Tarbiat Modarres University, Tehran, Iran MOJTABA SHAMSIPUR ? Department of Chemistry, Razi University, Kermanshah, Iran (Received: 29 July 1998; in final form: 13 October 1998) Abstract. The formation of molecular complexes with 1 : 1 stoichiometry between 2,4,6-trinitro- phenol and aza-12-crown-4, aza-15-crown-5 and aza-18-crown-6 in chloroform solution was inves- tigated spectrophotometrically. The resulting complexes were isolated and characterized by micro- chemical analysis, IR and NMR spectroscopy. The equilibrium constants of the 1 : 1 adducts were evaluated from the non-linear least-squares fitting of the absorbance-mole ratio data. The overall stability of the 2,4,6-trinitrophenol complexes was found to vary in the order aza-15-crown-5 > aza-18-crown-6 ≈ aza-12-crown-4. The kinetics of complex formation between 2,4,6-trinitrophenol and the aza-substituted crown ethers used were investigated and in all cases the results showed the occurrence of an oscillating chemical reaction in solution. Key words: 2,4,6-trinitrophenol, aza-crown ethers, molecular complexes, spectrophotometry, IR, NMR. 1. Introduction Macrocyclic crown ethers are known to form intermolecular charge-transfer com- plexes with neutral molecules [1, 2], although studies on such molecular interac- tions have been far fewer in number than those on cation-macrocycle interactions. Recent spectroscopic and thermodynamic studies have involved charge-transfer complexes formed between crown ethers and a variety of acceptor molecules such as 2,3-dichloro-5,6-dicycanobenzoquinone (DDQ) [3–5], tetracyanoethylene (TCNE) [3, 4, 6], 7,7,8,8-tetracyanoquinodimethane (TCNQ) [3], p-chloranil (CHL) [3, 7], 2,4,6-trinitrophenol (TNP) [8] and, especially iodine [9–15]. Increas- ing interest in the study of such molecular complexes is mainly due to their possible applications in diverse areas such as separation science, catalysis of chemical re- ? Author for correspondence.