{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,12]],"date-time":"2025-10-12T02:32:53Z","timestamp":1760236373373,"version":"build-2065373602"},"reference-count":23,"publisher":"MDPI AG","issue":"22","license":[{"start":{"date-parts":[[2021,11,17]],"date-time":"2021-11-17T00:00:00Z","timestamp":1637107200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Molecules"],"abstract":"<jats:p>Cyclic 6-membered aromatic compounds such as benzene and azabenzenes (pyridine, pyridazine, and pyrazine) are known to be light-sensitive, affording, in particular, the Dewar benzene type of intermediates. Pyridine is known to provide the only Dewar pyridine intermediate that undergoes reversible ring-opening. We found that irradiation of photosensitive gels prepared from poly(4-vinyl pyridine) and pyridine at 254 or 312 nm leads to pyridine ring-opening and subsequent formation of 5-amino-2,4-pentadienals. We show that this light-induced process is only partially reversible, and that the photogenerated aminoaldehyde and aminoaldehyde-pending groups undergo self-condensation to produce cross-linked, conjugated oligomers that absorb light in the visible spectrum up to the near-infrared range. Such a sequence of chemical reactions results in the formation of gel with two distinct morphologies: spheres and fiber-like matrices. To gain deeper insight into this process, we prepared poly(4-vinyl pyridine) with low molecular weight (about 2000 g\/mol) and monitored the respective changes in absorption, fluorescence, 1H-NMR spectra, and electrical conductivity. The conductivity of the polymer gel upon irradiation changes from ionic to electronic, indicative of a conjugated molecular wire behavior. Quantum mechanical calculations confirmed the feasibility of the proposed polycondensation process. This new polyacetylene analog has potential in thermal energy-harvesting and sensor applications.<\/jats:p>","DOI":"10.3390\/molecules26226925","type":"journal-article","created":{"date-parts":[[2021,11,17]],"date-time":"2021-11-17T09:16:11Z","timestamp":1637140571000},"page":"6925","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":5,"title":["Light-Induced Reactions within Poly(4-vinyl pyridine)\/Pyridine Gels: The 1,6-Polyazaacetylene Oligomers Formation"],"prefix":"10.3390","volume":"26","author":[{"given":"Evgenia","family":"Vaganova","sequence":"first","affiliation":[{"name":"Department of Molecular Chemistry and Materials Science, Weizmann Institute of Science, Rehovot 7610001, Israel"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Dror","family":"Eliaz","sequence":"additional","affiliation":[{"name":"Department of Molecular Chemistry and Materials Science, Weizmann Institute of Science, Rehovot 7610001, Israel"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Ulyana","family":"Shimanovich","sequence":"additional","affiliation":[{"name":"Department of Molecular Chemistry and Materials Science, Weizmann Institute of Science, Rehovot 7610001, Israel"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6749-6667","authenticated-orcid":false,"given":"Gregory","family":"Leitus","sequence":"additional","affiliation":[{"name":"Chemical Research Support Department, Weizmann Institute of Science, Rehovot 7610001, Israel"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8907-7391","authenticated-orcid":false,"given":"Emad","family":"Aqad","sequence":"additional","affiliation":[{"name":"DuPont Electronics & Industrial, Marlborough, MA 01752, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Vladimir","family":"Lokshin","sequence":"additional","affiliation":[{"name":"Aix Marseille Univ, CNRS UMR 7325, Centre Interdisciplinaire de Nanoscience de Marseille (CINaM) Campus de Luminy, CEDEX 09, 13288 Marseille, France"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9091-6837","authenticated-orcid":false,"given":"Vladimir","family":"Khodorkovsky","sequence":"additional","affiliation":[{"name":"Aix Marseille Univ, CNRS UMR 7325, Centre Interdisciplinaire de Nanoscience de Marseille (CINaM) Campus de Luminy, CEDEX 09, 13288 Marseille, France"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2021,11,17]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"1309","DOI":"10.1016\/0040-4020(76)85002-8","article-title":"The Organic Photochemistry of Benzene-I","volume":"32","author":"Gilbert","year":"1976","journal-title":"Tetrahedron"},{"key":"ref_2","first-page":"1","article-title":"Photoisomerization of Some Nitrogen-Containing Hetero-Aromatic Compounds","volume":"Volume 97","author":"Horspool","year":"2004","journal-title":"CRC Handbook of Organic Photochemistry and Photobiology"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"1659","DOI":"10.2174\/1385272825666210706124855","article-title":"Photochemical Isomerization of Hexatomic Heterocyclic Compounds","volume":"25","year":"2021","journal-title":"Curr. 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