Structures and photophysical properties of homo- and heteronuclear lanthanide(III) complexes with bridging 2-methyl-8-hydroxylquinoline (HMq) in the μ-phenol mode

摘要

Eight new lanthanide(III) complexes, {Ln(hfac)_3} _2(μ-HMq)_2 (Ln = Eu, 1; Tb, 2; Yb, 3; hfac- = hexafluoroacetylacetonate; HMq = 2-methyl-8-hydroxylquinoline), {Eu(hfac) _2(H_2O)-(OC_6H_4CN)} _2(μ-HMq)_2 (4, HOC_6H_4CN = 4-hydroxybenzonitrile), Er_5(hfac)_9(μ-HMq) _2(μ_4-CH3COO)_2(μ_3- CH_3COO)(μ-CH_3COO)(μ_3-OH)_2 (5), and Cr(Mq)(μ-HMq)(μ_3-OH)(μ-OH)(μ-CH3COO) _2{Ln(hfac)_2}_2 (Ln = Eu, 6; Tb, 7; Er, 8), with bridging HMq in the μ-phenol mode were synthesized and characterized by X-ray crystallography, except for 6. Each Ln~(III) center in 1-4 is surrounded by eight O donors to form a distorted square-antiprism, except that two O binding sites from one hfac- in 1-3 are displaced by one H _2O and one OC_6H_4CN- in 4. Complex 5 could be viewed as a combination of two {Er(hfac)_2} _2(μ-HMq) moieties linked to a central Er~(III) ion through bridging acetates and μ3-OH, in which the central Er ~(III) ion is nine-coordinated to give a distorted capped square antiprism whereas the other four Er~(III) ions are eight-coordinated with approximate square antiprisms. CrLn_2 heterotrinuclear complexes 6-8 are ligated by one μ_3-OH~-, one μ-OH~-, one bridging HMq, one chelating-bridging Mq-, and two μ-CH _3COO~-. These complexes display typical linelike emission from the corresponding lanthanide(III) ions with a microsecond range of lifetime. Introducing some amount of fluoride to these lanthanide(III) complexes induces significant enhancement in intensities and lifetimes for both visible and near-infrared (NIR) luminescence from lanthanide centers because strong F?O-H interaction can effectively suppress the O-H vibrational radiationless process.