New expanded porphyrinoids: Synthesis, structure and properties of hemihexaphyrazines and their reduced metal containing derivatives
| Autor: | Mikhail K. Islyaikin, Evgenii N. Ivanov, Oskar I. Koifman, Dmitri V. Konarev |
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| Rok vydání: | 2023 |
| Předmět: | |
| Zdroj: | Journal of Porphyrins and Phthalocyanines. 27:55-67 |
| ISSN: | 1099-1409 1088-4246 |
| Popis: | Hemihexaphyrazines can be considered as hexamembered porphyrinoids of the ABABAB type, where thiadiazole rings (A) and pyrrole-containing subunits (B) joined via aza bridges to form a macrocyclic system with an expanded coordination cavity capable of holding at once three atoms of transition metals that are formed a triangular cluster. It was established for the first time that unsubstituted hemihexaphyrazine and its metal complexes can be reduced to form crystalline salts. These salts were characterized by UV-Vis-NIR and IR spectroscopy, MS, and X-Ray diffraction data. The magnetic properties of these compounds were studied for the first time using EPR and SQUID techniques within the [Formula: see text] K temperature range. It was shown that the three-electron reduction of starting [Formula: see text] yields [Formula: see text] and [Formula: see text] crystalline salts. An unusual doublet-quartet transition was found for the [Formula: see text] dianions. Salt [Formula: see text] also shows an unusually strong low energy NIR absorption, which was observed at 1000–2200 nm with maxima located at 1283 and 1980 nm. A phenomenon consisting of equalization of bond lengths among exocyclic nitrogen atoms ([Formula: see text] and neighboring atoms C(pyrrole) and C(thiadiazole) was observed under reduction conditions. |
| Databáze: | OpenAIRE |
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