Four donor-acceptor salicylaldimines with benzoheterocyclic substituents at nitrogen imine were prepared and characterised by means of optical spectroscopy. Their luminescent properties were compared with two isoelectronic carbocyclic analogues. In contrast to the typical salicylaldimines, our reported benzoheterocyclic compounds exhibit solely local emissive behaviour in all media whereas for the carbocyclic analogues we expectedly observe dominant ESIPT emission in the majority of instances. Low temperature (5K - liquid helium) fluorescence measurements revealed the effect of the restriction of the molecular rotation which was manifested by significant increment of the fluorescence intensity. The comprehensive experimental and ab initio study reveal effect of solvent polarity, viscosity and temperature on the complex photophysics of heterocyclic and carbocyclic substituted salicylaldimines with several degrees of freedom for molecular transformations. This work adds considerable insight in emission lifetime data which greatly facilitates understanding of the fluorescence mechanism of the molecules with environmentally dependent restrictions.

制备了四种在氮亚胺上具有苯并杂环取代基的供体-受体水杨醛亚胺，并通过光谱法对其进行了表征。将它们的发光特性与两种等电子碳环类似物进行了比较。与典型的水杨醛亚胺相比，我们报道的苯并杂环化合物在所有介质中仅表现出局部发射行为，而对于碳环类似物，我们预计在大多数情况下观察到主要的 ESIPT 发射。低温（5K - 液氦）荧光测量揭示了分子旋转受限的影响，这表现为荧光强度的显着增加。全面的实验和从头开始研究揭示了溶剂极性、粘度和温度对具有多个分子转化自由度的杂环和碳环取代的水杨醛亚胺的复杂光物理的影响。这项工作增加了对发射寿命数据的深入了解，这极大地促进了对具有环境依赖性限制的分子的荧光机制的理解。