{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,6]],"date-time":"2026-07-06T23:13:09Z","timestamp":1783379589122,"version":"3.54.6"},"reference-count":43,"publisher":"MDPI AG","issue":"6","license":[{"start":{"date-parts":[[2026,3,23]],"date-time":"2026-03-23T00:00:00Z","timestamp":1774224000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Science Committee of the Ministry of Science and Higher Education of the Republic of Kazakhstan","award":["AP23488935"],"award-info":[{"award-number":["AP23488935"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Molecules"],"abstract":"<jats:p>The utilization and chemical transformation of carbon dioxide remains a pressing problem in modern chemistry. Numerous experimental and theoretical studies have focused on the interaction of CO2 with amines. In this work, quantum chemical density functional theory (DFT) calculations of equilibrium geometries, energies, electronic and vibrational characteristics of CO2-sensitive mono-, di-, tris-hydroxyamidines and their associates were carried out by the B3LYP\/6-31G(d, p) method. The harmonic vibrational frequencies were scaled and compared with the experimental FTIR spectra for supporting wavenumber assignments. Natural bond orbital (NBO) analysis of the atomic charges and charge delocalization was employed to investigate the nature of hydrogen bonding in hydroxyamidine associates. We also used the intrinsically polarizable continuum model (IEFPCM), and the DFT-D3 method was applied to account for dispersion effects during associate formation. Using the 6-311+G(2d, p) basis set for tris-hydroxyamidine, and its adducts, a comparative analysis of the experimental and calculated 1H NMR spectra was performed. Here, we considered non-trivial sites of carbon dioxide absorption and hydroxyamidine protonation, which, to our knowledge, have hardly been considered by other authors. Present DFT results agree rather well with the experimental data and support new insight into the formation of the PIL structure.<\/jats:p>","DOI":"10.3390\/molecules31061055","type":"journal-article","created":{"date-parts":[[2026,3,23]],"date-time":"2026-03-23T11:59:36Z","timestamp":1774267176000},"page":"1055","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Molecular Structure, Theoretical NBO Analysis, Vibrational Spectrum of CO2-Responsive Hydroxyamidine-Based Ionic Liquid: A Combined Computational and Experimental Approach"],"prefix":"10.3390","volume":"31","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-7530-3378","authenticated-orcid":false,"given":"Lyazzat","family":"Abulyaissova","sequence":"first","affiliation":[{"name":"Chemistry Department, Buketov National Research University, Karaganda 100028, Kazakhstan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2494-9248","authenticated-orcid":false,"given":"Nikolay","family":"Barashkov","sequence":"additional","affiliation":[{"name":"Micro-Tracers, Inc., 1370 Van Dyke Avenue, San Francisco, CA 94124, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5432-1200","authenticated-orcid":false,"given":"Irina","family":"Irgibaeva","sequence":"additional","affiliation":[{"name":"Department of Chemistry, L.N. Gumilyov Eurasian National University, Astana 010008, Kazakhstan"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9982-4629","authenticated-orcid":false,"given":"Yerbolat","family":"Tashenov","sequence":"additional","affiliation":[{"name":"Department of Chemistry, L.N. Gumilyov Eurasian National University, Astana 010008, Kazakhstan"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,3,23]]},"reference":[{"key":"ref_1","first-page":"1","article-title":"CO2 capture: A concise, comprehensive overview of recent research trends","volume":"2","author":"Rathi","year":"2025","journal-title":"Acad. Environ. Sci. Sustain."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"6058","DOI":"10.1002\/anie.201000431","article-title":"Carbon dioxide capture: Prospects for new materials","volume":"49","author":"Smit","year":"2010","journal-title":"Angew. Chem. Int. Ed."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"630","DOI":"10.1016\/j.pecs.2012.03.003","article-title":"The outlook for improved carbon capture technology","volume":"38","author":"Rubin","year":"2012","journal-title":"Prog. Energy Combust. Sci."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"745","DOI":"10.4209\/aaqr.2012.05.0132","article-title":"A review of CO2 capture by absorption and adsorption","volume":"12","author":"Yu","year":"2012","journal-title":"Aerosol Air Qual. Res."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"7281","DOI":"10.1039\/c2ee03403d","article-title":"Worldwide innovations in the development of carbon capture technologies and the utilization of CO2","volume":"5","author":"Markewitz","year":"2012","journal-title":"Energy Environ. Sci."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"22739","DOI":"10.1039\/c3ra43965h","article-title":"Review of recent advances in carbon dioxide separation and capture","volume":"3","author":"Kenarsari","year":"2013","journal-title":"RSC Adv."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"10","DOI":"10.1016\/j.apenergy.2015.03.026","article-title":"A comparative review between amines and ammonia as sorptive media for post-combustion CO2 capture","volume":"148","author":"Shakerian","year":"2015","journal-title":"Appl. Energy"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"55","DOI":"10.15377\/2410-3624.2021.08.5","article-title":"Towards Computational CO2 Capture and Storage Models: A Review","volume":"8","author":"Makul","year":"2021","journal-title":"Glob. Environ. Eng."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"3363","DOI":"10.1021\/ie403280h","article-title":"Theoretical Investigation on the Different Reaction Mechanisms of Aqueous 2-Amino-2-methyl-1-propanol and Monoethanolamine with CO2","volume":"53","author":"Xie","year":"2014","journal-title":"Ind. Eng. Chem. Res."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"2244","DOI":"10.1021\/jp212225r","article-title":"Proton Transfer Step in the Carbon Dioxide Capture by Monoethanol Amine: A Theoretical Study at the Molecular Level","volume":"116","author":"Iida","year":"2012","journal-title":"Phys. Chem. B"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"1491","DOI":"10.1080\/01496395.2020.1784943","article-title":"Rigorous rate-based model for CO2 capture via monoethanolamine-based solutions: Effect of kinetic models, masstransfer, and holdup correlations on prediction accuracy","volume":"56","author":"Amirkhosrow","year":"2020","journal-title":"Sep. Sci. Technol."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"2137","DOI":"10.1021\/am507465f","article-title":"Amine-based CO2 capture technology development from the beginning of 2013: A review","volume":"7","author":"Dutcher","year":"2015","journal-title":"ACS Appl. Mater. Interfaces"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"764","DOI":"10.1021\/je400886w","article-title":"Equilibrium total pressure and CO2 solubility in binary and ternary aqueous solutions of 2-(diethylamino) ethanol (DEEA) and 3-(methylamino) propylamine (MAPA)","volume":"59","author":"Arshad","year":"2014","journal-title":"J. Chem. Eng. Data"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"1535","DOI":"10.1007\/s11224-014-0431-5","article-title":"Experimental and theoretical evidence suggests carbamate intermediates play a key role in CO2 sequestration catalysed by sterically hindered amines","volume":"25","author":"Jackson","year":"2014","journal-title":"Struct. Chem."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"9274","DOI":"10.1021\/jp406636a","article-title":"Ab initio study of CO2 capture mechanisms in aqueous monoethanolamine: Reaction pathways for the direct interconversion of carbamate and bicarbonate","volume":"117","author":"Matsuzaki","year":"2013","journal-title":"J. Phys. Chem. A"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"635","DOI":"10.1021\/je200731v","article-title":"Sterically hindered amine-based absorbents for the removal of CO2 from gas streams","volume":"57","author":"Bougie","year":"2012","journal-title":"J. Chem. Eng. Data"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"147","DOI":"10.1021\/ef2011113","article-title":"Selection of blended solvents for CO2 absorption from coal-fired flue gas. Part 1: Monoethanolamine (MEA)-based solvents","volume":"26","author":"Zhu","year":"2012","journal-title":"Energy Fuels"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"931","DOI":"10.1002\/cssc.201000060","article-title":"Computational comparison of the reactions of substituted amines with CO2","volume":"3","author":"Mindrup","year":"2010","journal-title":"ChemSusChem"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"3079","DOI":"10.1021\/jp109851k","article-title":"Density Functional Theory Study on Carbon Dioxide Absorption into Aqueous Solutions of 2-Amino-2-methyl-1-propanol Using a Continuum Solvation Model","volume":"115","author":"Yamada","year":"2011","journal-title":"J. Phys. Chem. A"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"24067","DOI":"10.1039\/C7CP03803H","article-title":"Understanding CO2 capture mechanisms in aqueous hydrazine via combined NMR and first-principles studies","volume":"19","author":"Lee","year":"2017","journal-title":"Phys. Chem. Chem. Phys."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"5022","DOI":"10.1021\/jp810564z","article-title":"Kinetics and mechanism of carbamate formation from CO2 (aq), carbonate species, and monoethanolamine in aqueous solution","volume":"113","author":"McCann","year":"2009","journal-title":"J. Phys. Chem. A"},{"key":"ref_22","doi-asserted-by":"crossref","unstructured":"Ma, C., Pietrucci, F., and Andreoni, W. (2023). CO2 Capture and Release in Amine Solutions: To What Extent Can Molecular Simulations Help Understand the Trends?. Molecules, 28.","DOI":"10.3390\/molecules28186447"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"3404","DOI":"10.1002\/pola.26737","article-title":"Capture and release of CO2 by polyamidine","volume":"51","author":"Furusho","year":"2013","journal-title":"J. Polym. Sci. Part A Polym. Chem."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"1523","DOI":"10.1021\/acs.macromol.5b02483","article-title":"Amidinefunctionalized Poly(2-vinyl-4,4-dimethylazlactone) for selective and efficient CO2","volume":"49","author":"Barkakaty","year":"2016","journal-title":"Fixing Macromol."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"363","DOI":"10.1080\/15685551.2016.1270027","article-title":"A CO2-switchable amidine monomer: Synthesis and characterization","volume":"20","author":"Liu","year":"2017","journal-title":"Des. Monomers Polym."},{"key":"ref_26","unstructured":"Barashkov, N., Irgibayeva, I., Zhapakova, A., Eralinov, A., and Sakhno, T. (2022, January 20\u201324). FTIR and fluorescent control of interaction between hydroxy-containing amidines and carbon dioxide. Proceedings of the ACS Meeting, San Diego, CA, USA. Available online: https:\/\/acs.digitellinc.com\/acs\/sessions\/463141\/view."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"102594","DOI":"10.1016\/j.jcou.2023.102594","article-title":"FTIR and NMR spectra of polymeric ionic liquids\u2014Products of reaction between hydroxycontaining amidines and carbon dioxide","volume":"77","author":"Irgibaeva","year":"2023","journal-title":"J. CO2 Util."},{"key":"ref_28","doi-asserted-by":"crossref","unstructured":"Calva, V., J\u00e1tiva, N., and Ricaurte, M. (2025). CO2 Capture Using Amine-Based Solvents: Identification of Additives to Improve the Kinetics and Thermodynamics of CO2 Sorption at High-Pressure Conditions. Gases, 5.","DOI":"10.3390\/gases5010004"},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"102753","DOI":"10.1016\/j.jcou.2024.102753","article-title":"CO2 capture and in-situ conversion to organic molecules","volume":"82","author":"Zhao","year":"2024","journal-title":"J. CO2 Util."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"46648","DOI":"10.1021\/acsomega.5c03663","article-title":"Steering amine\u2013CO2 chemistry: A molecular insight into the amino site relationship of carbamate and protonated amine","volume":"10","author":"Nguyen","year":"2025","journal-title":"ACS Omega"},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"e202402288","DOI":"10.1002\/cssc.202402288","article-title":"Evaluation of Aliphatic Alcohols for CO2 Capture Using the Characteristic Carbonate Frequency","volume":"18","author":"Delibas","year":"2025","journal-title":"ChemSusChem"},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"1085","DOI":"10.1524\/zpch.217.9.1085.20405","article-title":"Intramolecular Hydrogen Bond Interaction in Selected Diols","volume":"217","author":"Plass","year":"2003","journal-title":"Z. Phys. Chem."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"399","DOI":"10.1016\/S0009-2614(00)00352-3","article-title":"Torsional barriers in biphenyl, 2,2\u2032-bipyridine and 2-phenylpyridine","volume":"321","author":"Grummt","year":"2000","journal-title":"Chem. Phys. Lett."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"16502","DOI":"10.1021\/jp960976r","article-title":"Harmonic vibrational frequencies: An evaluation of Hartree\u2212Fock, M\u00f8ller\u2212Plesset, quadratic con-figuration interaction, density functional theory, and Semiempirical scale factors","volume":"100","author":"Scott","year":"1996","journal-title":"J. Phys. Chem."},{"key":"ref_35","doi-asserted-by":"crossref","unstructured":"Irgibaeva, I., Barashkov, N., Tarikhov, F., Aldongarov, A., Salkeeva, L., Dzhardimalieva, G., and Tashenov, Y. (2025). Methanol-Assisted CO2 Fixation by Hydroxyl-Containing Amidine Leading to Polymeric Ionic Liquid and Cross-Linked Network Formation. Polymers, 17.","DOI":"10.3390\/polym17243306"},{"key":"ref_36","doi-asserted-by":"crossref","unstructured":"Pretsch, E., Buhlmann, P., and Affolter, C. (2000). Structure Determination of Organic Compounds, Springer. [3rd ed.].","DOI":"10.1007\/978-3-662-04201-4"},{"key":"ref_37","unstructured":"Frisch, M.J., Trucks, G.W., Schlegel, H.B., Scuseria, G.E., Robb, M.A., Cheeseman, J.R., Scalmani, G., Barone, V., Petersson, G.A., and Nakatsuji, H. (2026, January 10). Gaussian 16, Available online: https:\/\/gaussian.com\/."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"5105","DOI":"10.1021\/acs.chemrev.5b00533","article-title":"Dispersion-Corrected Mean-Field Electronic Structure Methods","volume":"116","author":"Grimme","year":"2016","journal-title":"Chem. Rev."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"899","DOI":"10.1021\/cr00088a005","article-title":"Intermolecular interactions from a natural bond orbital, donor-acceptor view-point","volume":"88","author":"Reed","year":"1988","journal-title":"Chem. Rev."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"7211","DOI":"10.1021\/ja00544a007","article-title":"Natural hybrid orbitals","volume":"102","author":"Foster","year":"1980","journal-title":"J. Am. Chem. Soc."},{"key":"ref_41","unstructured":"Dennington, R.D., Keith, T.A., and Millam, J.M. (2025, December 28). GaussView, Available online: https:\/\/gaussian.com\/gaussview6\/."},{"key":"ref_42","unstructured":"(2026, January 15). Chemcraft\u2014Graphical Software for Visualization of Quantum Chemistry Computations, Version 1.8, build 682. Available online: https:\/\/www.chemcraftprog.com\/."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"082503","DOI":"10.1063\/5.0216272","article-title":"A comprehensive electron wavefunction analysis toolbox for chemists, Multiwfn","volume":"161","author":"Lu","year":"2024","journal-title":"J. Chem. Phys."}],"container-title":["Molecules"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1420-3049\/31\/6\/1055\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,3,23]],"date-time":"2026-03-23T11:59:44Z","timestamp":1774267184000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1420-3049\/31\/6\/1055"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,3,23]]},"references-count":43,"journal-issue":{"issue":"6","published-online":{"date-parts":[[2026,3]]}},"alternative-id":["molecules31061055"],"URL":"https:\/\/doi.org\/10.3390\/molecules31061055","relation":{},"ISSN":["1420-3049"],"issn-type":[{"value":"1420-3049","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,3,23]]}}}