Electronic structure and NH-tautomerism of a novel metal-free phenanthroline-annelated phthalocyanineстатья
Статья опубликована в высокорейтинговом журнале
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Дата последнего поиска статьи во внешних источниках: 9 июня 2017 г.
Аннотация:A novel low-symmetry A(3)B-type phthalocyanine annelated with a pyrazino[2,3-f]phenanthroline ring system and substituted with six solubilizing diisoptopylphenoxy-groups (1) was synthesized by metal free DBU-promoted cross-condensation of diiminoisoindolines derived from 4,5-bis(diisopropylphenoxy)phthalonitrile and pyrazino[2,3-f][1,10]phenarithroline-2,3-dicarbonitrile. The use of these particular precursors affords A(3)B phthalocyanine in 15% yield, while cross-condensation of the corresponding dinitriles yields only trace amounts of the target compound. Comparative studies of the A(3)B-type phthalocyanine and its symmetrical octa(diisopropylphenoxy)-substituted counterpart 2 reveal striking differences in the Q band regions of their UV visible absorption (UV Vis) spectra, which could be readily rationalized through a comparison with calculated TD-DFT spectra. Since 1 can have two NH-tautomers with equivalent and non-equivalent NH-groups, and DFT calculations predict that the former tautomer is only 2.3 kcal/mol more stable than the latter one, a comprehensive analysis of C-13 NMR spectra was carried out through the application of H-1-C-13 HMBC and HSQC techniques. It demonstrated that only the tautomer with equivalent NH-groups is present in solution.