Preparation, Spectroscopic Properties and Characterization of Oxovanadium(IV), Isothiocyanatomanganese(III), Cyanocobalt(III) and Cobalt(II) Complexes with a Bis-Crown Ether Tetraaza[14]Annulene

Abstract

Oxovanadium(IV), isothiocyanatomanganese(III), cyanocobalt(III) and cobalt(II) complexes of tetraaza[14]annulene appended with two crown ethers at 2,3- and 11,12-positions have been prepared. Cation complexation behavior of these cavity-bearing tetraaza[14]annulene complexes has been investigated by optical absorption methods. The cation K + , which necessitates two crown ether cavities for complexation, induces dimerization of the tetraaza[14]annulene complexes, whereas the Na + does not. Formation of the sandwich complexes due to dimerization is hindered by the steric interactions involving the axial ligand as judged by the blue shift of the intense band around 385-425 nm. Judging from its ESR spectrum, the cobalt(II) complex becomes a monomeric dioxygen complex of a 1 : 1 molar ratio in the presence of O 2 and pyridine at 77 K.