Light-Induced Reactions within Poly(4-vinyl pyridine)/Pyridine Gels: The 1,6-Polyazaacetylene Oligomers Formation
Authors: Vladimir Lokshin
Gregory Leitus
Dror Eliaz
Emad Aqad
Vladimir Khodorkovsky
Evgenia Vaganova
Ulyana Shimanovich
Journal: Molecules (2021)
Discipline: CHEMISTRY
Keywords: aromatic heterocycle; electroconducting polymer; photochemistry; pyridine.
Affiliations: Department of Molecular Chemistry and Materials Science, Weizmann Institute of Science, Rehovot 7610001, Israel., Chemical Research Support Department, Weizmann Institute of Science, Rehovot 7610001, Israel., DuPont Electronics & Industrial, Marlborough, MA 01752, USA., Aix Marseille Univ, CNRS UMR 7325, Centre Interdisciplinaire de Nanoscience de Marseille (CINaM) Campus de Luminy, CEDEX 09, 13288 Marseille, France.

Abstract:  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. 

Retracted: No

PubPeer comments:
 Das RKI hat 1426 COVID-19 mit Aufnahme KW 10 bis 18 mit 69573 SARI-CV-Fu00e4llen mit Aufnahme KW 3 bis 11 verglichen. Nun sind in dieser Auswertung 21% der COVID-19 und 12% der SARI-CW-Fu00e4lle verstorben. Wirkt zunu00e4chst schlimm fu00fcr COVID-19. War das vielleicht die eigentliche Absicht dieser Artikels? Man muss sich aber unbedingt die absoluten Zahlen anschauen. Die hat das RKI entgegen den wissenschaftlichen Usancen nicht genannt. Man kann sie aber ungefu00e4hr nachrechnen. Und das ergibt rund 300 C-Tote und 8349 SARI-CW-Tote; letztere allerdings aufsummiert u00fcber 5 Jahre. Also muss die letzte Zahl durch 5 geteilt werden, das ergibt 1670 SARI-CW-Tote im Durchschnitt pro Jahr. Also 300 gegen 1670, also machen die COVID-Toten nicht einmal ein fu00fcnftel der  normalen Pneumonietoten aus. Kann man da noch von Gefu00e4hrlichkeit von COVID-19 sprechen? Es ist auch einiges andere zu kritisieren. Da 2018 der grou00dfe Influenzapeak in der KW 11 lag (laut Euromomo), hat man mit Schneiden bei KW 11 womu00f6glich eine Menge Influenzafu00e4lle nicht beru00fccksichtigt. Auch das war schon nicht fair. Der Ausschluss der Kinder und Jugendlicher ist unfair! Man hu00e4tte alle 3 Kohorten fu00fcr dei Jahre 2015-19 zeigen sollen, also 1. alle, 2. 15 Jahre, 3. 15 Jahre. Den Vergleich zur Gruppe 2 hu00e4tte man danch (so oder so retrospektiv!) als primu00e4r bezeichnen ku00f6nnen. Die Unterdru00fcckung der Daten geht aber gar nicht! Die Unterteiung der COVID-10 Kohorte erscheint dagegen mu00fcu00dfig, weil dann praktisch die gleichen Zahlen herausku00e4men. Hu00f6chstwahrscheinlich ku00e4me beim Vergleich mit von COVID-19 mit allen Altersklassen COVID-19 noch weit harmloser raus. Passt diese Aussage den Autoren nicht ins Konzept? Und u00fcberhaupt: Warum vergleichen die nur relative Zahlen? Weil die Botschaft nur dann dramatisch klingt? , 
 The authors selected the Calendar Weeks 3 to 11 of the years 2015 to 2019 as reference. Unfortunately, they did not provide a rationale for this selection. The only stated that 58% of all hospitalisations fell in the selected weeks. Why not Weeks 4 to 12 or Weeks 5 to 13? It would have been more confinable if having provided additional data on the tails and more arguments for the selection. , 
 Since it wasn`t clear to me from what Prosopis wrote in comment #2: The authors compare the COVID19 cases in 2020 weeks 10 - 18 with the influenza cases in 2015-2019 weeks 3 - 11. The reasoning might be the sentence  In diesen Zeitraum fielen 58 % der stationu00e4ren Aufnahmen von SARI- GW-Fu00e4llen. which translates to  in this time frame occured 58% of the hospital admissions for SARI-GW-cases [influenza]. Maybe they wanted to compare the 8 consecutive weeks in germany with the most Covid19 cases with the 8 consecutive weeks with the most influenza cases in 2015-2019. , 
 The authors selected 1426 COVID-19 cases who were hospitalised for serious acute respiratory infection (SARI, SARI-COVID) between Calendar Week 10 to 18 and compared them with 69573 SARI cases with certain ICD-codes who were hospitalised between Calendar Weeks 3 to 11 in 2015 to 2019; those Calendar Weeks were said to have covered the u201cGrippewelleu201d (GW, influenza wave) in these years. The latter figure should be divided by 5 to provide a reasonable estimate for the same time window, yielding 13915 cases or about 10 times more control cases than COVID-19 cases. A difference by the factor 10 raises two questions. 1. Were the cohorts comparable? 2. Are the absolute figures not more important than the relative figures the authors highlighted? Regarding 1: Apart from the u201cAbb. 2u201d the authors provide nothing to support the similarity of both cohorts. Could it be that the selected ICD codes diluted the SARI-GW cohort by less serious cases? Regarding 2: The data presented in Table 1 allows to roughly estimate the absolute numbers of deaths in both cohort. This yields 299 deaths in the SARI-COVID cohort (21% of 1426) and 1670 death in the SARI-GW cohort (12% of 13915). If both cohorts were somehow comparable, then the estimates 299 and 1670 deaths would be the striking information, indicating that the mortality in the COVID-19 season was less than 1 5 of that in a typical influenza season. However, this contradicts the authorsu2019 claims given in the title that COVID-19 yields higher mortality than severely progressing respiratory infections during influenza waves. ,