Thioureido Cymantrene Derivatives: Synthesis and Photochromic Properties

Photolysis of thioureido derivatives of cymantrene in solution and solvent-free affords stable six-membered dicarbonyl chelates due to coordination of sulfur of the C=S group to manganese. The process is accompanied by a color change and the appearance of new bands at 400 and 500 nm in the UV-vis spectra. In the presence of carbon monoxide, these chelates enter the reverse thermal reaction to give the parent tricarbonyl complexes thus forming photochromic systems. In the air, dicarbonyl chelates are oxidized to form stable dicarbonyl Mn-based radicals, which were isolated, and their structure was proved by electron paramagnetic resonance spectra and density functional theory calculations. The irradiation of these dark violet radicals, in turn, also results in formation of stable photochromic systems. Dicarbonyl olefin chelates were synthesized; upon photolysis of these compounds, stable intramolecular photochromic systems with high quantum yield were obtained. The reverse thermal reaction occurs via dissociative isomerization of the substituent.