Precursors of chelate pyridine–N-heterocyclic carbene (N^C:) ligands with methyl- or benzyl-substituted imidazolylidene fragments were synthesized. They were used to obtain 12 iridium bis-cyclometalated complexes of the type [Ir(C^N)₂(N^C:)]⁺ (C^N = 2-(phenyl)pyridinato-C²,N, ppy, 2-(4,6-difluorophenyl)pyridinato-C²,N, dfppy). The ancillary N^C: ligands contain different structural modifications. The aim of the work was to analyze the effect that changes in the two types of ligands have on the photophysical and electrochemical properties and also on the behavior of these materials as photosensitizers. The X-ray crystal structures of five complexes were determined. The complexes emitted in the blue-green region. It was expected that the frontier orbitals and thus the photophysical and electrochemical properties would be controlled by the main C^N ligands, and it was demonstrated that the effect of the modifications in the N^C: ligand, especially the presence of a nitro group in the pyridine ring or the interruption of conjugation between the two rings, also affected these properties. The quenching with O₂ and photostability studies were also performed. Density functional theory calculations were used to explain the behavior of some derivatives. The complexes and other previously reported compounds were employed as photosensitizers (PS) in preliminary studies on the production of H₂ from water using [Co(bpy)₃]Cl₂ (bpy = 2,2′-bipyridine) as catalyst and triethanolamine (TEOA) as the sacrificial reductant. The absence of quenching of the PS with TEOA allowed us to propose an oxidative quenching mechanism.

中文翻译：

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吡啶-碳烯配体的阳离子双（环金属化）Ir（III）配合物。水的光物理性质和光催化产氢

合成了具有甲基或苄基取代的咪唑基亚甲基片段的螯合吡啶-N-杂环卡宾（N ^ C :)配体的前体。它们用于获得12种类型[Ir（C ^ N）₂（N ^ C :)] ⁺（C ^ N = 2-（苯基）吡啶基-C ²，N，ppy，2的铱双环金属化配合物-（4,6-二氟苯基）吡啶并-C ²，N，dfppy）。辅助的N 2 C：配体包含不同的结构修饰。这项工作的目的是分析两种配体类型的变化对光物理和电化学性能以及这些材料作为光敏剂的行为的影响。确定了五个配合物的X射线晶体结构。络合物在蓝绿色区域发射。预期边界轨道以及因此的光物理和电化学性质将由主要的C ^ N配体控制，并且证明了在N ^ C：配体中修饰的影响，特别是硝基的存在。在吡啶环中或两个环之间的共轭的中断，也影响了这些性能。用O ₂淬火并进行了光稳定性研究。密度泛函理论计算用于解释某些导数的行为。所述复合物和其它先前报道的化合物用作在初步研究中的光敏剂（PS）在生产h的₂使用[CO（BPY）从水₃ ]氯₂（BPY = 2,2'-联吡啶）作为催化剂和三乙醇胺（ TEOA）作为牺牲性还原剂。由于没有用TEOA淬灭PS，因此我们提出了一种氧化淬灭机理。