Synthesis and photochemical study of tricarbonyl and dicarbonyl derivatives of 3-cymantrenylalkylisothioureas

Abstract A series of 3-cymantrenylalkylisothioureas (2) was synthesized. DFT calculations showed that compounds 2 in solutions are dimers. The photolysis of 2 was studied by IR, UV-vis and NMR spectroscopic methods. Irradiation of compounds 2 results in the formation of two type chelates, in which the manganese atom is coordinated to the S (3) or N (4) atoms of a substituent. The color of solutions sharply changes giving in the UV-vis spectra two new bands at 485 and 590 nm, respectively. In the presence of CO, dicarbonyl chelates enter the reverse thermal reaction to give the starting tricarbonyl complexes thus forming intermolecular photochromic systems. A quantum yield of the photolysis of 2a in benzene equals 0.63 ± 0.07. In the absence of СО, intramolecular linkage isomerization of 4 to 3 occurs. It was found that the bulkiness of a substituent at the sulfur atom insignificantly influences the reaction rate of the reverse thermal reaction. Chelate 3a was isolated; its photolysis gives orange chelate 4a, which isomerizes to violet chelate 3a forming an intramolecular photochromic pair.