Two neutral cyclometalated Ir(III)-tetrazolato complexes that differ by variations of the substituents on either the phenylpyridine or the tetrazolate ligand have been converted into the corresponding methylated and cationic analogues. NMR (¹H and ¹³C) characterization of the Ir(III) complexes provided the results in agreement with the chemo- and regioselective character of methylation at the N-3 position of the Ir(III)-coordinated tetrazolato ring. This evidence was further corroborated by the analysis of the molecular structures of the cationic complexes obtained by X-ray diffraction. In view of the photophysical properties, the addition of a methyl moiety to neutral Ir(III) tetrazolates, which behave as sky-blue or orange phosphors, caused a systematic red shift of their phosphorescence output. The transformation of neutral Ir(III) tetrazolates into cationic Ir(III)-tetrazole complexes was screened for any eventual antimicrobial activity in vitro against Gram negative (E. coli) and Gram positive (D. radiodurans) microorganisms. While both kinds of complexes were not active against E. coli, the conversion of the neutral Ir(III) tetrazolates into the corresponding methylated and cationic Ir(III)tetrazole derivatives determined the turn-on of a good to excellent antimicrobial activity toward Gram positive Deinococcus radiodurans, a non-pathogenic bacterium that is listed as one of the toughest microorganisms in light of its outstanding resistance to radiation and oxidative stress.

中文翻译：

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Ir（III）-四唑络合物的甲基化：调节排放量并转换为抗菌性能的有效途径

通过苯基吡啶或四唑酸酯配体上的取代基的变化而不同的两个中性环金属化的Ir（III）-四唑酸酯络合物已被转化为相应的甲基化和阳离子类似物。Ir（III）配合物的NMR（¹ H和¹³ C）表征提供的结果与Ir（III）配位的四唑酸酯环N-3位置处甲基化的化学和区域选择性特征相符。通过X射线衍射获得的阳离子配合物的分子结构分析进一步证实了这一证据。鉴于光物理性质，在中性Ir（III）表现为天蓝色或橙色磷光体的四唑酸酯导致其磷光输出发生系统性红移。在体外针对革兰氏阴性（E. coli）和革兰氏阳性（D. radiodurans）微生物的任何最终抗微生物活性中，筛选了中性Ir（III）四唑酸盐向阳离子Ir（III）-四唑复合物的转化。虽然两种复合物均未对大肠杆菌具有活性，但将中性四唑Ir（III）转化为相应的甲基化和阳离子Ir（III））四唑衍生物决定了其对革兰氏阳性放线菌（Deinococcus radiodurans）的良好至优异的抗菌活性，这是一种非致病性细菌，由于其对辐射和氧化应激的出色抵抗力，因此被列为最坚韧的微生物之一。