Synthesis Photophysics and Switchable LuminescenceProperties of a New Class of Ruthenium(II)–Terpyridine ComplexesContaining Photoisomerizable Styrylbenzene Units

摘要

We report here the synthesis and structural characterization of a new class of homoleptic terpyridine complexes of Ru(II) containing styrylbenzene moieties to improve room-temperature luminescence properties. Solid-state structure determination of >2 was done through single-crystal X-ray diffraction. Tuning of photophysical properties was done by incorporating both electron-donating and electron-withdrawing substituents in the ligand. The complexes exhibit strong emission having lifetimes in the range of 10.0–158.5 ns, dependent on the substituent and the solvent. Good correlations were also observed between Hammett σp parameters with the lifetimes of the complexes. Styrylbenzene moieties in the complexes induce trans–trans to trans–cis isomerization accompanied by huge alteration of their spectral profiles upon treating with UV light. Reversal of trans–cis to trans–trans forms was also achieved on interacting with visible light. Change from trans–trans to the corresponding trans–cis form leads to emission quenching, whereas trans–cisto the corresponding trans–trans form leads to restorationof emission. In essence, “on–off” and “off–on”photoswitching of luminescence was observed. Calculations involvingdensity functional theory (DFT) and time-dependent-DFT methods wereperformed to understand the electronic structures as well as for appropriateassignment of the absorption and emission bands.