Luminescent Tris(8-hydroxyquinolates) of Bismuth(III)
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- 作者：Pauline J. Han ; Arnold L. Rheingold ; William C. Trogler
- 刊名：Inorganic Chemistry
- 出版年：2013
- 出版时间：October 21, 2013
- 年：2013
- 卷：52
- 期：20
- 页码：12033-12045
- 全文大小：519K
- 年卷期：v.52,no.20(October 21, 2013)
- ISSN：1520-510X
文摘
Luminescent homoleptic bismuth(III) complexes have been synthesized by adding several functionalized 8-hydroxyquinolate ligands to bismuth(III) chloride in a 3:1 mole ratio in either ethanol or tetrahydrofuran (THF) solvent. These complexes have been characterized by single-crystal X-ray diffraction (XRD) analysis, UV鈥搗is spectroscopy, fluorescence spectroscopy, and density functional theory (DFT) calculations to determine their structures and photophysical properties. Reversible dimerization of the mononuclear tris(hydroxyquinolate) complexes was observed in solution and quantified using UV鈥搗is spectroscopy. The fluorescence spectra show a blue shift for the monomer compared with homoleptic aluminum(III) hydroxyquinolate compounds. Four dimeric compounds and one monomeric isomer were characterized structurally. The bismuth(III) centers in the dimers are bridged by two oxygen atoms from the substituted hydroxyquinolate ligands. The more sterically hindered quinolate complex, tris(2-(diethoxymethyl)-8-quinolinato)bismuth, crystallizes as a monomer. The complexes all exhibit low-lying absorption and emission spectral features attributable to transitions between the HOMO (蟺 orbital localized on the quinolate phenoxide ring) and LUMO (蟺* orbital localized on the quinolate pyridyl ring). Excitation and emission spectra show a concentration dependence in solution that suggests that a monomer鈥揹imer equilibrium occurs. Electronic structure DFT calculations support trends seen in the experimental results with a HOMO鈥揕UMO gap of 2.156 eV calculated for the monomer that is significantly larger than those for the dimers (1.772 and 1.915 eV). The close face to face approach of two quinolate rings in the dimer destabilizes the uppermost occupied quinolate 蟺 orbitals, which reduces the HOMO鈥揕UMO gap and results in longer wavelength absorption and emission spectral features than in the monomer form.