Breaking and Formation of Intramolecular Hydrogen Bonds in Dihydroxybenzaldehydes through UV-Induced Conformational Changes in a Low-Temperature Matrix


Doddipatla S., Ferreira G. I., Sidir Y. G., Nunes C. M., Fausto R.

JOURNAL OF PHYSICAL CHEMISTRY A, vol.126, no.46, pp.8645-8657, 2022 (SCI-Expanded) identifier identifier identifier

  • Publication Type: Article / Article
  • Volume: 126 Issue: 46
  • Publication Date: 2022
  • Doi Number: 10.1021/acs.jpca.2c05839
  • Journal Name: JOURNAL OF PHYSICAL CHEMISTRY A
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Academic Search Premier, Applied Science & Technology Source, Aqualine, Aquatic Science & Fisheries Abstracts (ASFA), Artic & Antarctic Regions, Chemical Abstracts Core, Chimica, Compendex, Computer & Applied Sciences, EMBASE, INSPEC, MEDLINE
  • Page Numbers: pp.8645-8657
  • Istanbul Kültür University Affiliated: Yes

Abstract

Hydrogen bonding (HB) has been receiving attention from both experimental and theoretical researchers since its discovery in the 1920s due to its impact on many chemical and biological processes. However, despite the large number of investigations conducted on this topic, the nature of the HBs and, in particular, the estimation of intramolecular HB energies are still very active subjects of research. In this context, here we report a matrix isolation infrared spectroscopy study of 2,3-dihydroxybenzaldehyde (2,3-DHBA) and 2,4-dihydroxybenzaldehyde (2,4DHBA), which contain two [one resonance-assisted HB (RAHB) and one conventional HB] and one (RAHB) intramolecular hydrogen bonds, respectively, in their most stable conformer. After isolation of the compounds in cryogenic (15 K) krypton matrices, ultraviolet irradiation led to the formation of higher-energy conformers (by a 180 degrees rotation of the hydroxyl and aldehyde groups), which implies breaking of the intramolecular HBs initially existing in the isolated species and, in the case of 2,3DHBA, to the formation of a new intramolecular HB. In this way, we were able to manipulate the structure of the molecules, allowing to characterize a diversity of intramolecular HBs in which the OH groups participate (from strong intramolecular RAHBs to weaker conventional HBs, and also no intramolecular HBs) through the corresponding vibrational signatures. The spectroscopic studies were complemented by natural bond orbital analysis and the molecular tailoring approach method, in order to estimate the relative intramolecular HB energies and explore the substitution effects on HB strength.