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

Abstract

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-bromo-bis( 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.