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Sulfur‐containing cymantrene derivatives having one or two organometallic moieties were studied by NMR, IR, UV/Vis spectroscopic methods and CVA under irradiation conditions. Photolysis of compounds 1–3 leads to the formation of rare 4‐membered chelates 4, 5 and 8. In the presence of external ligand (L), dissociation of the Mn−S bond occurred to form new dicarbonyl complexes with the Mn−L bond, which demonstrates the hemilabile character of the chelates obtained. The results were confirmed by DFT calculations. CVA method showed manganese oxidation potential value increased in the case of dicarbonyls (1313 mV for 4) as compared to that of tricarbonyls (1067 mV for 1). [ABSTRACT FROM AUTHOR]

For the first time, the photochemical properties of compounds 1–4 containing a cymantrene fragment at the 2‐ or 3‐position of the quinazolinone have been studied. It was found that the ‐NC=O group in compounds 1 and 2 is capable of coordinating to the Mn atom with the formation of intramolecular chelates. The influence of the nature of the solvent and substituent in the side‐chain of cymantrene on the thermodynamic and kinetic stability of the dicarbonyl complexes was studied. For the first time, the olefin chelate 9 was isolated; its structure was established by X‐ray diffraction analysis and its photochemical and fluorescence properties were studied. The photolysis of compound 4 gave only stable intermolecular dicarbonyl complexes, in which the solvent can be easily replaced by n‐ and π‐donor ligands. [ABSTRACT FROM AUTHOR]

Four monosubstituted cymantrene derivatives ( 5- 8) containing two functional groups (allyl and amide) in a dendritic substituent were synthesized. The irradiation of these compounds with an Hg lamp in solution and under solvent-free conditions gives two types of dicarbonyl chelates with Mn-olefin or Mn-amide coordination bonds. Olefin chelates ( 19 and 21) were isolated for the first time, and they undergo reverse photochemical intramolecular isomerization to the amide chelates in solution and as pure liquids. For the first time, it was shown that the photochromism of cymantrene functional derivatives can be observed without the use of a solvent. [ABSTRACT FROM AUTHOR]

• Study of photochemical behavior of di(cymantrenylalkyl)disulfide. • Preparation of stable bicyclic dicarbonyl chelates. • Preparation in situ of unstable fulvenes. • Study electrochemical properties of symmetrical disulfides. Photolysis of di(cymantrenylalkyl)disulfides was studied by IR, 1H NMR and UV-vis spectroscopy. Irradiation of cymantrenes with a disulfide bridge results in the formation of two type dicarbonyl chelates with Mn-S bond. The first type is formed due to removal of one CO ligand from one cymantrenyl moiety to give a 5-membered chelate cycle; the other is formed due to removal of two CO ligands from two cymantrenyl moieties to form a bicyclic chelate. The latter was isolated and characterized by X-ray analysis. For the first time, unstable fulvenes were prepared in situ by irradiation of cymantrenyl derivatives or their dicarbonyl complexes. Electrochemical properties of disulfides were studied before and after photolysis in acetonitrile. The manganese oxidation potential value increased on going from tricarbonyls to dicarbonyls. [Display omitted] [ABSTRACT FROM AUTHOR]

1N- and 2N-cymantrenylalkylsubstituted 1,2,3-triazoles were for the first time synthesized. It was found that irradiation by a mercury lamp light with λ = 365 nm of cymantrenylalkyl-1,2,3-triazoles 3, 5 – 8 gives stable dicarbonyl chelates 4, 9 – 12 . In a closed system without CO removal, intermolecular photochromic systems between tricarbonyl and dicarbonyl complexes were formed; half-conversion time for the dark reaction was more than 10 h. The effect of a substituent position in dicarbonyl chelates 4, 9 – 12 on the parameters of their spectra, coordination ability of the N atom and chemical stability was studied. It was found that coordination ability of the nitrogen atoms markedly depends on steric hindrances, which are significantly different in 1N- and 2N-substituted triazoles. [ABSTRACT FROM AUTHOR]