Synthesis, Spectroscopy and Electrochemistry in Relation to DFT Computed Energies of Ferrocene- and Ruthenocene-Containing β-Diketonato Iridium(III) Heteroleptic Complexes. Structure of [(2-Pyridylphenyl)(2)Ir(RcCOCHCOCH(3)]

A series of new ferrocene- and ruthenocene-containing iridium(III) heteroleptic complexes of the type [(ppy)(2)Ir(RCOCHCOR′)], with ppy = 2-pyridylphenyl, R = Fc = Fe(II)(η(5)-C(5)H(4))(η(5)-C(5)H(5)) and R′ = CH(3) (1) or Fc (2), as well as R = Rc = Ru(II)(η(5)-C(5)H(4))(η(5)-C(5)H(5)) and R′ = CH(3) (3), Rc (4) or Fc (5) was synthesized via the reaction of appropriate metallocene-containing β-diketonato ligands with [(ppy)(2)(μ-Cl)Ir](2). The single crystal structure of 3 (monoclinic, P2(1)/n, Z = 4) is described. Complexes 1–5 absorb light strongly in the region 280−480 nm the metallocenyl β-diketonato substituents quench phosphorescence in 1–5. Cyclic and square wave voltammetric studies in CH(2)Cl(2)/[N((n)Bu)(4)][B(C(6)F(5))(4)] allowed observation of a reversible Ir(III/IV) redox couple as well as well-resolved ferrocenyl (Fc) and ruthenocenyl (Rc) one-electron transfer steps in 1−5. The sequence of redox events is in the order Fc oxidation, then Ir(III) oxidation and finally ruthenocene oxidation, all in one-electron transfer steps. Generation of Ir(IV) quenched phosphorescence in 6, [(ppy)(2)Ir(H(3)CCOCHCOCH(3))]. This study made it possible to predict the Ir(III/IV) formal reduction potential from Gordy scale group electronegativities, χ(R) and/or Σχ(R′) of β-diketonato pendent side groups as well as from DFT-calculated energies of the highest occupied molecular orbital of the species involved in the Ir(III/IV) oxidation at a 98% accuracy level.