Terephthalate and Isonicotinate N-Oxide Complexes of the {Mo6I8}4+ Cluster

Abstract

New complexes, (TBA)₂[Mo₆I₈(OOC–C₆H₄–COOH)₆] (I) and (TBA)₂[Mo₆I₈(OOC–C₅H₄NO)₆] (II), were synthesized by the reaction of (TBA)₂[Mo₆I₈(OAc)₆] with terephthalic acid and isonicotinic N-oxide acid, respectively. The optimized synthesis of complex II involves microwave activation of the reaction mixture at 130°C in a Teflon reactor using an ETHOS UP Milestone microwave system. According to X-ray structural analysis, the molybdenum atoms in the cluster cores of I and II are coordinated by carboxylate ligands in a monodentate fashion. The cluster anions [Mo₆I₈(OOC–C₆H₄–COOH)₆]^2– of complex I are arranged into a three-dimensional framework, and the crystal structure contains solvate molecules. Complexes I and II were characterized by elemental analysis for C, H, and N, IR spectroscopy, electrospray mass spectrometry, and proton nuclear magnetic resonance. The powder samples of I and II exhibit intense phosphorescence with emission maxima at ~680 nm, φ = 15%, τ = 125 µs (I) and φ = 12%, τ = 137 µs (II) (under air at λ_exc = 440 nm).