{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,18]],"date-time":"2026-02-18T23:11:12Z","timestamp":1771456272369,"version":"3.50.1"},"reference-count":64,"publisher":"MDPI AG","issue":"9","license":[{"start":{"date-parts":[[2021,5,10]],"date-time":"2021-05-10T00:00:00Z","timestamp":1620604800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Bitlis Eren University Research Foundation","award":["(Project BEBAP-2013.05"],"award-info":[{"award-number":["(Project BEBAP-2013.05"]}]},{"name":"LaserLab Coimbra","award":["s\/n"],"award-info":[{"award-number":["s\/n"]}]},{"DOI":"10.13039\/501100001871","name":"Funda\u00e7\u00e3o para a Ci\u00eancia e a Tecnologia","doi-asserted-by":"publisher","award":["UI0313B\/QUI\/2020 and UI0313P\/QUI\/2020; and Project PTDC\/QUI-QFI\/1880\/2020"],"award-info":[{"award-number":["UI0313B\/QUI\/2020 and UI0313P\/QUI\/2020; and Project PTDC\/QUI-QFI\/1880\/2020"]}],"id":[{"id":"10.13039\/501100001871","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Molecules"],"abstract":"<jats:p>A new Schiff base compound, 3-(5-bromo-2-hydroxybenzylideneamino)phenol (abbreviated as BHAP) was synthesized and characterized by 1H- and 13C- nuclear magnetic resonance and infrared spectroscopies. DFT\/B3LYP\/6-311++G(d,p) calculations were undertaken in order to explore the conformational space of both the E- and Z- geometrical isomers of the enol-imine and keto-amine tautomers of the compound. Optimized geometries and relative energies were obtained, and it was shown that the most stable species is the E-enol-imine form, which may exist in four low-energy intramolecularly hydrogen-bonded forms (I, II, V, and VI) that are almost isoenergetic. These conformers were concluded to exist in the gas phase equilibrium with nearly equal populations. On the other hand, the infrared spectra of the compound isolated in a cryogenic argon matrix (10 K) are compatible with the presence in the matrix of only two of these conformers (conformers II and V), while conformers I and VI convert to these ones by quantum mechanical tunneling through the barrier associated with the rotation of the OH phenolic group around the C\u2013O bond. The matrix isolation infrared spectrum was then assigned and interpreted with help of the DFT(B3LYP)\/6-311++G(d,p) calculated infrared spectra for conformers II and V. In addition, natural bond orbital (NBO) analysis was performed on the most stable conformer of the experimentally relevant isomeric form (E-enol-imino conformer V) to shed light on details of its electronic structure. This investigation stresses the fundamental structural relevance of the O\u2013H\u00b7\u00b7\u00b7N intramolecular H-bond in o-hydroxyaryl Schiff base compounds.<\/jats:p>","DOI":"10.3390\/molecules26092814","type":"journal-article","created":{"date-parts":[[2021,5,10]],"date-time":"2021-05-10T10:49:51Z","timestamp":1620643791000},"page":"2814","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":19,"title":["Structural Relevance of Intramolecular H-Bonding in Ortho-Hydroxyaryl Schiff Bases: The Case of 3-(5-bromo-2-hydroxybenzylideneamino) Phenol"],"prefix":"10.3390","volume":"26","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-4410-0831","authenticated-orcid":false,"given":"\u0130sa","family":"S\u0131d\u0131r","sequence":"first","affiliation":[{"name":"Department of Physics, Faculty of Science and Arts, Bitlis Eren University, 13000 Bitlis, Turkey"},{"name":"CQC, Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5329-2815","authenticated-orcid":false,"given":"Yadigar","family":"G\u00fclseven S\u0131d\u0131r","sequence":"additional","affiliation":[{"name":"Department of Physics, Faculty of Science and Arts, Bitlis Eren University, 13000 Bitlis, Turkey"},{"name":"CQC, Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7039-8099","authenticated-orcid":false,"given":"S\u00e1ndor","family":"G\u00f3bi","sequence":"additional","affiliation":[{"name":"CQC, Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal"},{"name":"MTA-ELTE Lend\u00fcl the Four Most Stable Conformers of the et Laboratory Astrochemistry Research Group, Institute of Chemistry, ELTE E\u00f6tv\u00f6s Lor\u00e1nd University, H-1518 Budapest, Hungary"}]},{"given":"Halil","family":"Berber","sequence":"additional","affiliation":[{"name":"Department of Chemistry, Faculty of Science, Eski\u015fehir Technical University, 26470 Eski\u015fehir, Turkey"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8264-6854","authenticated-orcid":false,"given":"Rui","family":"Fausto","sequence":"additional","affiliation":[{"name":"CQC, Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal"}]}],"member":"1968","published-online":{"date-parts":[[2021,5,10]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"506","DOI":"10.1016\/j.cplett.2004.10.129","article-title":"Biological Nano-Ceramic Materials for Holographic Data Storage","volume":"400","author":"Wu","year":"2004","journal-title":"Chem. 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