Bis(2,2'-bipyridine)(1,2-diimino-9,10-anthraquinone)ruthenium(II): A complex containing an exceptionally strong pi-accepting alpha-alpha' diimine ligand .1. Synthesis, crystal and electronic structures

The compound 1,2-diamino-9,10-anthraquinone (DAAQ) binds to ruthenium bis-(2,2'-bipyridine) forming a complex containing the oxidized 1,2-diimino-9,10-anthraquinone (DIAQ). The complex was crystallized as [Ru(bpy)(2)DIAQ](1,3-benzenedisulfonate) . 6.5H(2)O. Crystal data: triclinic, space group P (1) over bar, a = 10.095(2) Angstrom, b = 12.035(2) Angstrom, c = 17.652(4) Angstrom, alpha = 97.50(3)degrees, beta = 92.54(3)degrees, gamma = 91.65(3)degrees, Z = 2. The metal is bound to the diimine site of the DIAQ ligand. There is an extensive pi backbonding interaction between the DIAQ ligand and the metal as inferred from theoretical calculations, electrochemical and spectroscopic data. The DIAQ is the best pi accepting neutral alpha-alpha' diimine ligand known to date.