Nickel complexation and photophysics of alkylanthracenyl dioxocyclam macrocycle derivatives

Ligands H2L in which (10-R-anthracen-9-yl) methyl moieties (R = H, Me, Et) are covalently joined (6-position) to the 5,7-dioxocyclam macrocycle framew ork have been prepared and their nickel( II) complexes isolated and charact erized. X-Ray crystal structures of (NiL)-L-II (R = H, Me) complexes show t hat in both structures the anthracene moieties are folded around towards th e mean plane of the macrocycles; dihedral angles between the mean anthracen e and macrocyclic planes of c. 22 degrees are subtended. H-1 n.m.r. spectro metry indicates that the folded conformations are retained in solution. Abs orption and fluorescence spectra, fluorescence quantum yields and lifetimes of the anthracenyl macrocycles are reported. Absorption spectra of the met al complexes are red-shifted and the fluorescence is dramatically quenched compared to the metal-free compounds indicating a strong electronic interac tion between the anthracene and the complexed dioxocyclam macrocycle.