Electrochemical and photophysical properties of two-component coordination compounds containing a metallocyclam and an Re-I(bipy)(CO)(3)Cl subunit

The two-component coordination compounds [Re-I(CO)(3)Cl(L)](2+) (L=Ni-II, Cu-II or Zn-II complex of the 1-(2',2"-bipyridyl-5'-yl-methyl)-1,4,8,11-tetraazacyclotetradecane ligand) were synthesized and their electrochemical and photophysical properties investigated and compared with those of the separate components. The influence on the oxidation potential of the ReI centre of the Cu-II and Zn-II neighbouring cations was found to be negligible. However, when Ni-II is coordinated by the cyclam ring (cyclam = 1,4,8,11-tetraazacyclotetradecane),its oxidation precedes that of Re-I, with significant consequences on the oxidation potential of the latter. Finally, the fluorescence of the rhenium-containing component was found to be dependent on the cation coordinated by the proximate cyclam ring: in particular, the Ni-II and Cu-II complexes quench the fluorescence completely, and the Zn-II complex does not. (C) 1998 Elsevier Science S.A. All rights reserved.