A strategy for designing temperature-sensitive complexes based on ligand vibration rotation mode control

Abstract

Copper(I) and 3,5-dimethyl-1,2,4-triazole ligands construct the isomers α-Cu(mdtz) and β-Cu(mdtz), respectively. In α-Cu(mdtz), the hexagonal ring structure composed of Cu(I) and N atoms restricts the vibrational rotation of the triazole ring structure and reduces the nonradiative transition, achieving a high internal quantum efficiency at room temperature and pressure (IQY = 72.3%). As for β-Cu(mdtz), the triazole ring can rotate back and forth along its own C2 axis within a certain angle. We investigated the comparison of the luminescence spectra of α-Cu(mdtz) and β-Cu(mdtz) at different temperatures, confirmed that the vibrational rotation of the triazole ring improved the sensitivity of the luminescence intensity and spectral broadening to the temperature response, especially at low temperatures. In addition, we found that the decay time of Cu(mdtz)s varies linearly with temperature in a certain temperature interval, which provides strategy for temperature measurement based on the luminescence lifetime. Besides, the non-porous structure of Cu(mdtz)s prevents oxygen from entering the structure and protects the luminescent center from oxygen, thus improving the accuracy of temperature measurement in atmospheric environments.