Spectroscopic Studies of Photochemical Transformations of Cymantrenylquinazolinone Derivatives

Abstract

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 thermo-[a] A. N. Nesmeyanov Institute of Organoelement Compounds,

Photochemical anti–syn isomerization around the –N–N bond in heterocyclic imines

“…[27][28][29] Recently, photochemically-induced isomerization of a quinazolinone derivative containing a large p-system (consisting of two C 6 rings linked by a reduced quinazolinone moiety and a N ring -N]CH-C aromatic bridge) has been described. 30 Unlike previous studies describing isomerization around a C-C linkage [27][28][29] or a N]N linkage (in the case of azobenzene and its derivatives), 31,32 isomerization proceeded around a N-N linkage in the N-N]CH array of this system. This nding prompted us to study similar molecular systems, and in this paper we present experimental data and in-depth theoretical analysis to identify the excited states that are likely to be involved in the photochemically-induced isomerization process.…”

CO‐Preserving Photoinduced Transfer of Cymantrenyl Moiety: a Tandem Experimental and Computational Investigation

“…In more detail, IR monitoring (Figure 1a) of tricarbonyl complex 4 photolysis in the benzene solution for 4 min using monochromatic light of a Hg lamp with λ =365 nm showed the disappearance of ν (MCO) bands of the initial complex, corresponding to symmetric and degenerate stretching vibrations. At the same time, two new ν (MCO) bands of equal intensity appeared in the region of 1932 and 1862 cm −1 with a simultaneous low‐frequency shift of the ν(O=CN) band by 56 cm −1 , which is typical for formation of chelates with the Mn−O bond from the O=CN fragment of quinazoline‐4‐one [36] ( 6 in Scheme 1). The 1 H NMR spectrum (Figure 1cA, B) of the resulting dicarbonyl complex differed significantly from the spectrum of the starting tricarbonyl compound 4 and was in good agreement with the structure of the proposed six‐membered chelate with the Mn−O=CN bond [36] .…”

“…At the same time, two new ν (MCO) bands of equal intensity appeared in the region of 1932 and 1862 cm −1 with a simultaneous low‐frequency shift of the ν(O=CN) band by 56 cm −1 , which is typical for formation of chelates with the Mn−O bond from the O=CN fragment of quinazoline‐4‐one [36] ( 6 in Scheme 1). The 1 H NMR spectrum (Figure 1cA, B) of the resulting dicarbonyl complex differed significantly from the spectrum of the starting tricarbonyl compound 4 and was in good agreement with the structure of the proposed six‐membered chelate with the Mn−O=CN bond [36] . In particular, upon conversion of compound 4 into the corresponding dicarbonyl chelate 6 , the signals from the α‐protons of the Cp‐ring underwent a downfield shift, while the signals from β‐protons was shifted upfield, so that the difference in chemical shifts increased to 0.6 ppm on average.…”

“…[32][33][34] Previously we have studied [35] the alkylation reaction of methyl-and styrylquinazolin-4-ones with bromomethylcymantrene in the presence of sodium hydride, which led to N-substituted products containing quinazolinone and cymantrene fragments within one molecule exhibiting notable photochromic and fluorescent properties. [36] At the same time, identical alkylation of quinazolinone 1 (Scheme 1, see Experimental Section for details) led to the formation of a mixture of products of 4O-and 3 N-substituted quinazolines (3 and 4) in a ratio of approximately 1 : 1. 3 and 4 are easily distinguishable in 1 H and 13 C NMR thanks to their CH 2 groups, see Figure 1.…”

“…Previously we have studied [35] the alkylation reaction of methyl‐ and styrylquinazolin‐4‐ones with bromomethylcymantrene in the presence of sodium hydride, which led to N‐substituted products containing quinazolinone and cymantrene fragments within one molecule exhibiting notable photochromic and fluorescent properties [36] …”