Departamento de Química, Universidade de Coimbra, 3004-535 Coimbra, Portugal.
Dalton Trans. 2013 Mar 14;42(10):3682-94. doi: 10.1039/c2dt32587j. Epub 2013 Jan 8.
Multinuclear ((1)H, (13)C and (71)Ga) magnetic resonance spectroscopy (1D and 2D), DFT calculations and luminescence techniques have been used to study 8-hydroxyquinoline-5-sulfonate (8-HQS) and its complexes with Ga(III) in aqueous solutions. The study combines the high sensitivity of luminescence techniques and the selectivity of multinuclear NMR spectroscopy with the structural details accessible through DFT calculations, and aims to obtain a complete understanding of the complexation between the Ga(3+) ion and 8-HQS, and how this influences the luminescence behaviour. A full speciation study has been performed on this system and three complexes detected, with (metal : ligand) 1 : 1, 1 : 2 and 1 : 3 stoichiometries, the results being consistent with those previously found for the system Al(III)-8-HQS. Complexation in these systems is relevant to their potential biomedical, sensing and optoelectronic applications. On binding to Ga(III), a marked increase is seen in the intensity of the 8-HQS fluorescence band, which is accompanied by changes in the absorption spectra. These support the use of 8-HQS as a sensitive fluorescent sensor to detect Ga(3+) metal ions in surface waters, biological fluids, etc., and its metal complexes as an emitting or charge transport layer in light emitting devices. However, the fluorescence quantum yield of the Ga(III)-8-HQS 1 : 3 complex is about 35% of that of the corresponding system with Al(III). Although this may be due in part to a heavy atom effect favouring S(1)→ T(1) intersystem crossing with Ga(3+), this does not agree with transient absorption measurements on the triplet state yield, which is lower with the Ga(III) system than with Al(III). Instead, it is suggested that photolabilisation of ligand exchange plays a major role in nonradiative decay of the excited state and that this is more efficient with the Ga(3+) complex. Based on these results, suggestions are made of ways of enhancing fluorescence intensity in metal complexes with 8-HQS by inhibiting ligand exchange using surfactant complexation for applications in either sensing or optoelectronics.
采用多核（^1H、^(13)C 和 ^(71)Ga）磁共振波谱（一维和二维）、密度泛函理论（DFT）计算和荧光技术研究了 8-羟基喹啉-5-磺酸（8-HQS）及其与 Ga（III）在水溶液中的配合物。该研究将荧光技术的高灵敏度和多核 NMR 光谱的选择性与 DFT 计算提供的结构细节相结合，旨在全面了解 Ga（3+）离子与 8-HQS 的配合物，以及这种配合物如何影响发光行为。对该体系进行了全配位体研究，检测到三个配合物，具有（金属：配体）1:1、1:2 和 1:3 化学计量比，结果与之前报道的 Al（III）-8-HQS 体系一致。这些体系中的配合物与它们在生物医学、传感和光电应用中的潜在应用有关。与 Ga（III）结合后，8-HQS 荧光带的强度明显增加，同时吸收光谱也发生变化。这些支持将 8-HQS 用作检测地表水、生物体液等中 Ga（3+）金属离子的灵敏荧光传感器，以及其金属配合物作为发光器件中的发射或电荷传输层。然而，Ga（III）-8-HQS 1:3 配合物的荧光量子产率约为相应 Al（III）体系的 35%。尽管这可能部分归因于重原子效应有利于 Ga（III）的 S（1）→ T（1）系间窜越，但这与三重态产率的瞬态吸收测量结果不一致，Ga（III）体系的三重态产率低于 Al（III）体系。相反，建议配体交换的光解在激发态的非辐射衰减中起主要作用，并且 Ga（III）配合物更为有效。基于这些结果，提出了通过使用表面活性剂络合抑制配体交换来增强与 8-HQS 形成的金属配合物中荧光强度的方法，以用于传感或光电应用。
