A Molecular Antenna Coordination Polymer from Cadmium(II) and 4,4'-Bipyridine Featuring Three Distinct Polymer Strands in the Crystal

Reaction of cadmium perchlorate and the prototypical linear bridging ligand 4,4'-bipyridine (4,4'-bipy) in an ethanol/water mixture affords the one-dimensional coordination polymer, [{Cd(mu-4,4'-bipy)(4,4'-bipy)(2)(H2O) (2)}(ClO4) (2) center dot 2 4,4'-bipy center dot 4.5 H2O](n) (1). The Cd2+ ions adopt an octahedral coordination sphere and are joined into linear chains by 4,4'-bipy via two trans coordination sites. The remaining two trans sites in the equatorial plane carry terminally monodentate-bound 4,4'-bipy ligands, resulting in a molecular antenna arrangement. The two axial sites of each Cd2+ ion are occupied by aqua ligands. Compound 1 crystallizes in the non-centrosymmetric, monoclinic space group C2 with three similar, crystallographically independent, cationic coordination polymer strands in the unit cell, which essentially differ only in the conformations of the 4,4'-bipyridyl ligands. Consistent with the similarity of the local coordination environments of the three independent Cd atoms in the structure, Cd-113 MAS NMR spectroscopy reveals a single resonance line at 89 ppm.