X-ray and NMR study of the fate of the Co(1, 10-phenanthroline-5,6-diketone)3 3+ ion in aqueous solution:: supramolecular motifs in the packing of 1,10-phenanthroline-5,6-diketone and 1,10-phenanthroline-5,6-diol complexes

X-ray structures are presented of three new cobalt complexes prepared from Co(III) and N,N'-1,10-phenanthroline-5,6-dione. The cis-aqua-chloro-bis(N,N'-1,10-phenanthroline-5,6-dione)cobalt(II) nitrate trihydrate (3) and the cis-aqua-bromobis(N,N'-1,10-phenanthroline-5,6-dione)cobalt(II) trifluoro-methanesulfonate tetrahydrate (4), crystalize in the same space group with a similar arrangement of the complex ions. However, on the molecular scale there are important differences. The cobalt complex in 3 has a typical high-spin geometry whereas in 4 the cobalt complex displays a Jahn-Teller distortion characteristic for low-spin compounds. The third structure is di(N,N'-1,10-phenanthroline-5,6-diol)(N,N'-1,10-phenanthroline-5,6-dione)cobalt(III) bromide hexahydrate (5). NMR studies of the hydration of the Co(III)(1,10-phenanthroline-5,6-dione)(3)(3+) ion in water and DMSO are also presented. The various possible transformations of the N,N'-1,10-phenanthroline-5,6-dione ligand are discussed. (C) 2003 Elsevier B.V. All rights reserved.