Synthesis and Photochemical Study of Thiazolidine Derivatives of Cymantrene and the Corresponding Dicarbonyl Chelates

Isomeric 4,5-dihydro-2-[(cymantrenylmethyl)thio]thiazole (1) and 3-(cymantrenylmethyl)-1,3-thioazolidine-2-thione (2) were synthesized and photochemical behavior and spectral characteristics of tricarbonyl and dicarbonyl complexes were studied. Irradiation of compounds 1 and 2 results in the formation of stable chelates due to coordination of manganese to the donor nitrogen and sulfur atoms of the thiazolidine substituent. Photolysis is accompanied with a colour change and the corresponding changes in the UV/Vis spectra depending on the solvent used. In the presence of CO, the dicarbonyl chelates enter the dark reaction to give the parent tricarbonyl complexes thus forming intermolecular photochromic systems. Photolysis of the dicarbonyl chelate 5 gives the isomeric chelate 6, which in the course of the dark isomerization transforms into complex 5. Chelates 5 and 6 form an intramolecular photochromic pair.