Electron paramagnetic resonance and optical spectroscopy study of dibromo diaquo pentaoxa 1,4,7,10,13 cyclopentadecane copper II and dibromo diaquo pentaoxa 1,4,7,10,13 cyclopentadecane zinc (II) doped with copper (II)

ESR parameters of pentaoxa 1,4,7,10,13 cyclopentadecane dibromo diaquo copper (II) have been measured on a single crystal at ambient temperature. In this compound the coordination geometry of the copper-(II) ion is that of a strongly flattened tetrahedron. One finds: /b g//sub z/=2,330, /b g//sub y/=2.057, /b g//sub x /=2.126. These values as well as the optical absorption bands could be reproduced within the framework of an AOM model using: (e/sub sigma /)/sub Ow/=-8000 cm/sup -1/, (/b e//sub sigma /) /sub Br/=-6600 cm/sup -1/, /b e//sub pi ///b e/ /sub sigma /=0,4; /b k//sub z/=0.85, /b k//sub y/=0.90, /b k//sub x/=0.95. The crystallographic structure of pentaoxa 1,4,7,10,13 cyclopentadecane dibromo diaquo zinc (III) could not be completely resolved owing to the disordered character of the rings. This compound is orthorhombic (space group Pbn2/sub 1/) with a=9063, /b b/=15.504, /b c/=13.030 A , /b Z/=4. The general structure is similar to that of the copper compound: chains formed by alternating cycles and ZnBr/sub 2/(H/sub 2/O)/sub 2/ tetrahedrons, the last ones being however less compressed than in the copper compound. ESR parameters, measured on the powder spectrum at 77K of the zinc compound doped with copper (II), are the following: /b g//sub z/=1.991, /b g//sub y/~2.32, /b g//sub x/~2.37, A/sub z/=168 G. These values are interpreted as reflecting a localization of the copper ions at the centre of the rings of crown rather than substituting the zinc ions. ESR spectra have also been recorded on methanolic solutions frozen at 77K. At high metal concentration (5*10/sup -1 / mol.1/sup -1/ in zinc) one observes simultaneously the two paramagnetic species: the tetrahedral one with /b g//sub par />/b g//sub perp / and the centered ring one with /b g//sub par /