A series of mixed ligand, photoluminescent organometallic Ir(III) complexes have been synthesized to incorporate substituted 2-phenyl-1H-naphtho[2,3-d]imidazole cyclometalating ligands. The structures of three example complexes were categorically confirmed using X-ray crystallography each sharing very similar structural traits including evidence of interligand hydrogen bond contacts that account for the shielding effects observed in the ¹H NMR spectra. The structural iterations of the cyclometalated ligand provide tuning of the principal electronic transitions that determine the visible absorption and emission properties of the complexes: emission can be tuned in the visible region between 550 and 610 nm and with triplet lifetimes up to 10 μs. The nature of the emitting state varies across the series of complexes, with different admixtures of ligand-centered and metal-to-ligand charge transfer triplet levels evident. Finally, the use of the complexes as photosensitizers in triplet–triplet annihilation energy upconversion (TTA-UC) was investigated in the solution state. The study showed that the complexes possessing the longest triplet lifetimes showed good viability as photosensitizers in TTA-UC. Therefore, the use of an electron-withdrawing group on the 2-phenyl-1H-naphtho[2,3-d]imidazole ligand framework can be used to rationally promote TTA-UC using this class of complex.

中文翻译：

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调节铱(III)光敏剂的激发态特性及其对 TTA-UC 的影响


合成了一系列混合配体、光致发光有机金属 Ir(III) 配合物，其中包含取代的 2-苯基-1H-萘并[2,3-d]咪唑环金属化配体。使用 X 射线晶体学明确证实了三个示例配合物的结构，每个配合物都具有非常相似的结构特征，包括配体间氢键接触的证据，这解释了在 ¹ H NMR 谱中观察到的屏蔽效应。环金属化配体的结构迭代提供了对主要电子跃迁的调节，这些电子跃迁决定了配合物的可见光吸收和发射特性：发射可以在550至610 nm之间的可见光区域进行调节，三线态寿命高达10 μs。一系列配合物的发射态性质各不相同，配体中心和金属到配体电荷转移三重态水平的不同混合物很明显。最后，在溶液状态下研究了配合物在三重态-三重态湮没能量上转换（TTA-UC）中作为光敏剂的用途。研究表明，具有最长三线态寿命的配合物在 TTA-UC 中作为光敏剂表现出良好的可行性。因此，在2-苯基-1H-萘并[2,3-d]咪唑配体框架上使用吸电子基团可以合理地促进使用此类络合物的TTA-UC。