NEW DIOXOCYCLAM LIGANDS APPENDED WITH 2-PYRIDYLMETHYL PENDANT(S) - SYNTHESIS, PROPERTIES AND CRYSTAL-STRUCTURE OF THEIR COPPER(II) COMPLEXES (DIOXOCYCLAM = 1,4,8,11-TETRAAZACYCLOTETRADECANE-12,14-DIONE)

Two new dioxocyclam ligands, hyl)-1,4,8,11-tetraazacyclotetradecane-12 ,14-dione (L-1) and hyl)-1,4,8,11-tetraazacyclotetradecane-12,14-dione (L-2), have been synthesized and characterized. The solution chemistr y of the Cu-II complexes with these ligands have been studied by poten tiometric and spectroscopic titration, cyclic voltammetry (CV), UV/VIS and ESR spectral techniques. The Cu-II complex of L-2 has been isolat ed as single crystals and the structure has been determined by X-ray d iffraction analysis to be [CuL2][ClO4](2) 1. In complex 1, the Cu-II a tom is five-co-ordinate with the two pendant pyridyl nitrogens and the two tertiary amines forming a distorted trigonal-bipyramidal configur ation in which the backbone oxygen O(2) co-ordinates to Cu-II while th e two amido nitrogen groups remained non-deprotonated and non-co-ordin ated. To our knowledge, this is the first example of Cu-II complexes o f dioxotetraamines in which the backbone oxygen co-ordinates to the ce ntral metal by twisting the backbone.