Novel Crown Ethers with a Trithiadiazapentalene–Trithiotriuret Redox System

Abstract

Dedicated to Professor Leonard I;: Lindoy on the occasion of his 60th birthdayThe host-guest chemistry of functionalized macrocycles offers much potential for special applications. For some time now special attention has been paid to macrocyclic compounds whose properties can be changed reversibly by both chemical and physical means. ['] This was achieved by introducing functional units like the reversibly isomerizable azo group''] or the reversible dithiol-disulphide redox systemt3] into the macrocycles. In this way a systematic modification of properties of the guest such as binding strength and binding selectivity offers new possibilities for complexation, separation, or detection of both valuable and toxic species.r41The assembly of heterocyclic trithiadiazapentalene units and diamino polyethers to form pentaleno crown compounds provides a new approach to the above-mentioned modification of macrocyclic host compounds for cations. The exceptional electronic structure of the trithiapentalenes also makes them very interesting building blocks for further synthesis, both in theory and in practice.r51In an earlier publication we showed that 2,5-bis(aryloxy)-3,3aA4,4-trithia-1 ,6-diazapentalene~[~"I are suitable for reaction with nucleophiles. The diphenyl derivative 1 reacts with a,w-diaminopolyethers 2 in a 1 : 3 molar ratio to form bridged bispentalenes in high yields. These compounds can be used as starting materials for designing much larger cyclic molecules.'6b1We now describe the synthesis of pentaleno crown ethers 3a-c and their subsequent reduction to the corresponding thiourea derivatives 4a-c. Furthermore, their complex-forming properties deduced from extraction and transport studies will also be discussed. The synthetic path way leads to a novel class of crown ethers that contains the trithiadiazapentalenetrithiotriuret redox system that can be used to control the recognition properties.The compounds 3 were formed in reactions between 1 and 2 in a 1 : 2 molar ratio. Ring closure only occurred when the chain of the polyethers was long enough (n 2 1). The structures of the pentaleno crown ether compounds 3 a -c have been elucidated