The spectroscopic properties and tautomeric behavior of five novel Rhenium (I) tricarbonyl complexes bearing an azo ligand are presented. The organic ligand is stable in solution as the hydrazone tautomer. It remains as the hydrazone tautomer in different medium conditions (solvent, concentration, pH, etc.) without the formation of detectable amounts of the azo tautomer. However, the complexation of this ligand to the strong electron-withdrawing fragment -Re(CO)₃X (X = Cl⁻, Br⁻) causes tautomerism to appear in the organic moiety. Two well-defined regions in the electronic spectra for both tautomers were observed, allowing the azo/enol-keto/hydrazone equilibrium to be followed. TD-DFT calculations indicate that for the keto/hydrazone form, the main absorption band is attributed to an IL transition. In contrast, the azo/enol species shows a major contribution of the ¹MLCT (dπ(Re) → dπ*(NN)) transition. The tautomeric equilibrium is easily shifted using solvents with different dielectric constant and hydrogen bond donor/acceptor (HBD/HBA) abilities. Also, the tautomerization process is deeply influenced by the electronic properties of the axial ligand. Therefore, this behavior represents a different strategy for the design of novel materials with optical properties. Furthermore, tautomerism is affected by the concentration of complexes and the presence of water in solvents. The acid-base behavior of these compounds in a 50% v/v ethanol-buffer system showed that the azo/enol tautomer is stabilized in acidic media. At the same time, an increase of pH promotes tautomerization toward the keto/hydrazone, followed by forming the anionic form at pH > 8.

介绍了五种带有偶氮配体的新型铼 (I) 三羰基配合物的光谱性质和互变异构行为。有机配体在溶液中作为腙互变异构体是稳定的。它在不同的介质条件（溶剂、浓度、pH 值等）中保持腙互变异构体，而不会形成可检测量的偶氮互变异构体。然而，该配体与强吸电子片段-Re(CO) ₃ X (X = Cl ^- , Br ^-) 导致有机部分出现互变异构现象。观察到两种互变异构体的电子光谱中的两个明确定义的区域，允许遵循偶氮/烯醇-酮/腙平衡。TD-DFT 计算表明，对于酮/腙形式，主要吸收带归因于 IL 转变。相比之下，偶氮/烯醇物种显示出¹MLCT (dπ(Re) → dπ*(NN)) 过渡。互变异构平衡很容易使用具有不同介电常数和氢键供体/受体 (HBD/HBA) 能力的溶剂移动。此外，互变异构化过程深受轴向配体的电子特性的影响。因此，这种行为代表了设计具有光学特性的新型材料的不同策略。此外，互变异构受复合物浓度和溶剂中水的影响。这些化合物在 50% v/v 乙醇缓冲系统中的酸碱行为表明偶氮/烯醇互变异构体在酸性介质中是稳定的。同时，pH 值的增加会促进向酮/腙的互变异构，然后在 pH > 8 时形成阴离子形式。