Diorgano-Gallium and -Indium Complexes Derived from Benzoazole Ligands: Synthesis, Characterization, Photoluminescence, and Computational Studies

The reactions of triorgano-gallium and -indium etherate
with benzoazole
ligands 2-(2′-hydroxyphenyl)­benzoxazole (Hhbo) (1a), 2-(2′-hydroxyphenyl)­benzothiazole (Hhbt) (1b), and 2-(2′-hydroxyphenyl)­benzimidazole (Hhbi) (1c) in benzene yielded complexes of the type [R2ML]n with n = 1 for gallium
and 2 for indium (where R = Me, Et; M = Ga, In; L = hbo, hbt, and
hbi) in nearly quantitative yields. These complexes have been characterized
by elemental analysis, IR, UV–vis, and NMR (1H and 13C­{1H}) spectroscopy. Photoluminescence studies
of these complexes showed that the quantum yield is always higher
than that of the corresponding ligands due to reduced intermolecular
interactions in complexes as compared to free ligands. The molecular
structures of [Me2Ga­(hbo)] (2a) and [Me2In­(μ-hbt)]2 (3b) were established
by X-ray crystallography. The analyses revealed that the gallium complex
exists as a four-coordinated monomer, whereas the indium complex forms
a dimer comprising five-coordinated indium atoms. Density functional
calculations have been carried out for computing the structural and
energetic parameters of the complexes, which indicate that the formation
of the monomer is favorable with the Ga3+ ion, whereas
the dimeric structure is preferred with the In3+ ion.

三有机镓与三有机铟醚合物分别与苯并唑类配体2-(2′-羟基苯基)苯并恶唑（Hhbo）(1a)、2-(2′-羟基苯基)苯并噻唑（Hhbt）(1b)及2-(2′-羟基苯基)苯并咪唑（Hhbi）(1c)在苯溶剂中反应，以接近定量的产率得到通式为[R₂ML]ₙ的配合物：其中镓配合物的n=1，铟配合物的n=2（式中R为Me、Et；M为Ga、In；L为hbo、hbt、hbi）。通过元素分析、红外光谱（IR）、紫外-可见光谱（UV–vis）以及核磁共振（NMR，含¹H与¹³C{¹H}谱）对上述配合物进行了结构表征。对该系列配合物的光致发光性能研究表明，相较于游离配体，配合物的分子间相互作用显著减弱，因此其量子产率始终高于对应配体。通过X射线单晶衍射确定了配合物[Me₂Ga(hbo)]（2a）与[Me₂In(μ-hbt)]₂（3b）的分子结构，分析结果显示：镓配合物以四配位单核形式存在，而铟配合物则形成由五配位铟原子构成的二聚体结构。此外，通过密度泛函计算得到了该系列配合物的结构与能量参数，结果表明Ga³+更利于形成单核结构，而In³+则更倾向于形成二聚体结构。