{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,30]],"date-time":"2026-07-30T14:08:37Z","timestamp":1785420517960,"version":"3.56.0"},"reference-count":47,"publisher":"American Chemical Society (ACS)","issue":"30","license":[{"start":{"date-parts":[[2026,7,16]],"date-time":"2026-07-16T00:00:00Z","timestamp":1784160000000},"content-version":"stm-asf","delay-in-days":0,"URL":"https:\/\/doi.org\/10.15223\/policy-029"},{"start":{"date-parts":[[2026,7,16]],"date-time":"2026-07-16T00:00:00Z","timestamp":1784160000000},"content-version":"stm-asf","delay-in-days":0,"URL":"https:\/\/doi.org\/10.15223\/policy-037"},{"start":{"date-parts":[[2026,7,16]],"date-time":"2026-07-16T00:00:00Z","timestamp":1784160000000},"content-version":"stm-asf","delay-in-days":0,"URL":"https:\/\/doi.org\/10.15223\/policy-045"}],"funder":[{"DOI":"10.13039\/100000997","name":"Arnold and Mabel Beckman Foundation","doi-asserted-by":"publisher","award":["NA"],"award-info":[{"award-number":["NA"]}],"id":[{"id":"10.13039\/100000997","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100002445","name":"Calvin University","doi-asserted-by":"publisher","award":["NA"],"award-info":[{"award-number":["NA"]}],"id":[{"id":"10.13039\/501100002445","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/na","name":"National Science Foundation","doi-asserted-by":"publisher","award":["RUI-1956223"],"award-info":[{"award-number":["RUI-1956223"]}],"id":[{"id":"10.13039\/na","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"published-print":{"date-parts":[[2026,7,30]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                  <jats:p>We report the pKa values for 15 mono- and disubstituted hydroxycoumarins determined using UV\u2013vis absorbance spectroscopy and computational methods. Six of these values, including the pKa of 5-hydroxycoumarin, are reported for the first time. While the primary focus is on the effects of hydroxyl substitution on the benzene ring, we also examine how a 4-methyl substituent may influence acidity in a subset of four coumarin pairs. The experimental results are supported by two kinds of density functional theory calculations. Time-dependent DFT (TD-DFT) models of the UV\u2013vis spectra show strong agreement with experimental observations of 30 species and facilitate spectral interpretation. In addition, pKa values are predicted through a thermodynamic-cycle calculation that combines gas-phase Gibbs free energies with solvation free energies. This computational method accurately reproduces pKa values for a training set (mean absolute error, MAE = 0.37) and yields predictions for the full experimental data set (MAE = 0.65). Together, the experimental and computational results provide a comprehensive view of the structure\u2013acidity relationships in a diverse series of simple hydroxycoumarins.<\/jats:p>","DOI":"10.1021\/acs.jpca.6c02005","type":"journal-article","created":{"date-parts":[[2026,7,16]],"date-time":"2026-07-16T14:43:11Z","timestamp":1784212991000},"page":"5802-5821","source":"Crossref","is-referenced-by-count":0,"title":["Acidity Determination\nby Spectroscopic and Modeling\nMethods in Monohydroxy- and Dihydroxy-Substituted Coumarins"],"prefix":"10.1021","volume":"130","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-7628-8264","authenticated-orcid":true,"given":"George R.","family":"Du Laney","sequence":"first","affiliation":[{"name":"Calvin University , , , ,","place":["Grand Rapids, Michigan, United States, 49546-4403"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Caleb","family":"Gatlin","sequence":"additional","affiliation":[{"name":"Calvin University , , , ,","place":["Grand Rapids, Michigan, United States, 49546-4403"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Isaac","family":"Jonker","sequence":"additional","affiliation":[{"name":"Calvin University , , , ,","place":["Grand Rapids, Michigan, United States, 49546-4403"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0009-6576-5446","authenticated-orcid":true,"given":"Andrea","family":"VanEngen-VerBeek","sequence":"additional","affiliation":[{"name":"Calvin University , , , ,","place":["Grand Rapids, Michigan, United States, 49546-4403"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Leah H.","family":"Knoor","sequence":"additional","affiliation":[{"name":"Calvin University , , , ,","place":["Grand Rapids, Michigan, United States, 49546-4403"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Joy","family":"Yoo","sequence":"additional","affiliation":[{"name":"Calvin University , , , ,","place":["Grand Rapids, Michigan, United States, 49546-4403"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Michael","family":"VandenBerg","sequence":"additional","affiliation":[{"name":"Calvin University , , , ,","place":["Grand Rapids, Michigan, United States, 49546-4403"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yukun","family":"Tu","sequence":"additional","affiliation":[{"name":"Calvin University , , , ,","place":["Grand Rapids, Michigan, United States, 49546-4403"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jinsung","family":"Dho","sequence":"additional","affiliation":[{"name":"Calvin University , , , ,","place":["Grand Rapids, Michigan, United States, 49546-4403"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Hyemin","family":"Seo","sequence":"additional","affiliation":[{"name":"Calvin University , , , ,","place":["Grand Rapids, Michigan, United States, 49546-4403"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Lauren","family":"Timmer","sequence":"additional","affiliation":[{"name":"Calvin University , , , ,","place":["Grand Rapids, Michigan, United States, 49546-4403"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jonathan","family":"Holdridge","sequence":"additional","affiliation":[{"name":"Calvin University , , , ,","place":["Grand Rapids, Michigan, United States, 49546-4403"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Liam P.","family":"Hoogewerf","sequence":"additional","affiliation":[{"name":"Calvin University , , , ,","place":["Grand Rapids, Michigan, United States, 49546-4403"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Elizabeth A.","family":"Doty","sequence":"additional","affiliation":[{"name":"Calvin University , , , ,","place":["Grand Rapids, Michigan, United States, 49546-4403"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4190-7384","authenticated-orcid":true,"given":"Hunter T.","family":"Pham","sequence":"additional","affiliation":[{"name":"Calvin University , , , ,","place":["Grand Rapids, Michigan, United States, 49546-4403"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yejin","family":"Chung","sequence":"additional","affiliation":[{"name":"Calvin University , , , ,","place":["Grand Rapids, Michigan, United States, 49546-4403"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Mariana","family":"Dykstra","sequence":"additional","affiliation":[{"name":"Calvin University , , , ,","place":["Grand Rapids, Michigan, United States, 49546-4403"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ephraim","family":"Lee","sequence":"additional","affiliation":[{"name":"Calvin University , , , ,","place":["Grand Rapids, Michigan, United States, 49546-4403"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6315-4515","authenticated-orcid":true,"given":"Mark A.","family":"Muyskens","sequence":"additional","affiliation":[{"name":"Calvin University , , , ,","place":["Grand Rapids, Michigan, United States, 49546-4403"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"316","published-online":{"date-parts":[[2026,7,16]]},"reference":[{"key":"2026073009071419600_cit1","doi-asserted-by":"publisher","first-page":"1495","DOI":"10.1016\/j.jct.2006.05.002","article-title":"Calculations of pKa Values of Carboxylic Acids in Aqueous\nSolution Using Density Functional Theory","volume":"38","author":"Namazian","year":"2006","journal-title":"J.\nChem. 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Insights"},{"key":"2026073009071419600_cit4","first-page":"113","volume-title":"Annual Reports in\nComputational Chemistry","author":"Alongi","year":"2010"},{"key":"2026073009071419600_cit5","doi-asserted-by":"publisher","first-page":"14683","DOI":"10.1021\/acs.jpcb.5b08439","article-title":"Photoprotolytic Processes of Umbelliferone\nand Proposed\nFunction in Resistance to Fungal Infection","volume":"119","author":"Simkovitch","year":"2015","journal-title":"J. Phys. Chem. B"},{"key":"2026073009071419600_cit6","doi-asserted-by":"publisher","first-page":"307","DOI":"10.1007\/s10895-021-02842-w","article-title":"Aesculetin Exhibits\nStrong Fluorescent Photoacid Character","volume":"32","author":"Knoor","year":"2022","journal-title":"J. Fluoresc."},{"key":"2026073009071419600_cit7","doi-asserted-by":"publisher","first-page":"71","DOI":"10.1007\/s10895-019-02471-4","article-title":"Fluorescence of Scopoletin Including\nIts Photoacidity and Large Stokes Shift","volume":"30","author":"Pham","year":"2020","journal-title":"J.\nFluoresc."},{"key":"2026073009071419600_cit8","doi-asserted-by":"publisher","first-page":"3","DOI":"10.1007\/s00214-009-0667-0","article-title":"A Universal Approach\nfor Continuum Solvent pKa Calculations: Are We There\nYet?","volume":"125","author":"Ho","year":"2010","journal-title":"Theor. Chem. Acc."},{"key":"2026073009071419600_cit9","doi-asserted-by":"publisher","first-page":"218","DOI":"10.1016\/j.cplett.2013.08.002","article-title":"TD-DFT Study of\nthe pK*a for Coumarins","volume":"583","author":"Houari","year":"2013","journal-title":"Chem. 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Chem."},{"key":"2026073009071419600_cit13","first-page":"21A","article-title":"Acid Dissociation\nConstants of Electronically\nExcited Coumarins","author":"Arora","year":"1982","journal-title":"Indian J. Chem.-A"},{"key":"2026073009071419600_cit14","doi-asserted-by":"publisher","first-page":"149","DOI":"10.1016\/j.chroma.2016.03.084","article-title":"Determination\nof Acid Dissociation Constant of 20 Coumarin Derivatives by Capillary\nElectrophoresis Using the Amine Capillary and Two Different Methodologies","volume":"1446","author":"Nowak","year":"2016","journal-title":"J. Chromatogr. A"},{"key":"2026073009071419600_cit15","doi-asserted-by":"publisher","first-page":"1028","DOI":"10.1016\/j.ejmech.2006.12.023","article-title":"Relationship between\nQuantum-Chemical Descriptors of Proton Dissociation and Experimental\nAcidity Constants of Various Hydroxylated Coumarins. Identification\nof the Biologically Active Species for Xanthine Oxidase Inhibition","volume":"42","author":"Ferrari","year":"2007","journal-title":"Eur. J. Med. Chem."},{"key":"2026073009071419600_cit16","first-page":"152","article-title":"Fluorescence of Coumarin Derivatives as a Function\nof pH","volume":"27","author":"Goodwin","year":"1950","journal-title":"Arch. Biochem."},{"key":"2026073009071419600_cit17","doi-asserted-by":"publisher","first-page":"1184","DOI":"10.1039\/tf9565201184","article-title":"Absorption\nand Fluorescence Spectra of Coumarins","volume":"52","author":"Mattoo","year":"1956","journal-title":"Trans.\nFaraday Soc."},{"key":"2026073009071419600_cit18","doi-asserted-by":"publisher","first-page":"19","DOI":"10.1039\/tf9585400019","article-title":"Dissociation\nConstants of Hydroxy Coumarins","volume":"54","author":"Mattoo","year":"1958","journal-title":"Trans. Faraday\nSoc."},{"key":"2026073009071419600_cit19","first-page":"400","article-title":"Ultraviolet absorption\nspectra of coumarins","volume":"1","author":"Shah","year":"1963","journal-title":"Indian J. Chem."},{"key":"2026073009071419600_cit20","doi-asserted-by":"publisher","first-page":"114286","DOI":"10.1016\/j.jphotochem.2022.114286","article-title":"Spectral Properties and Modeling\nof Knightletin, a Novel Aminocoumarin with Intramolecular Hydrogen\nBonding","volume":"435","author":"Knoor","year":"2023","journal-title":"J. Photochem. Photobiol., A"},{"key":"2026073009071419600_cit21","doi-asserted-by":"publisher","first-page":"163","DOI":"10.1016\/j.cplett.2007.11.088","article-title":"Accurate Calculation\nof the pKa of Trifluoroacetic Acid Using High-Level Ab Initio Calculations","volume":"451","author":"Namazian","year":"2008","journal-title":"Chem. Phys. Lett."},{"key":"2026073009071419600_cit22","doi-asserted-by":"publisher","first-page":"2275","DOI":"10.1002\/qua.23211","article-title":"Theoretical\nCalculation of the pKa Values of Some Drugs in Aqueous Solution","volume":"112","author":"Ghalami-Choobar","year":"2012","journal-title":"Int. J. Quantum Chem."},{"key":"2026073009071419600_cit23","doi-asserted-by":"publisher","first-page":"426","DOI":"10.1016\/j.cplett.2018.06.044","article-title":"First Principles Prediction of Aqueous\nAcidities of Some Benzodiazepine Drugs","volume":"706","author":"Ghalami-Choobar","year":"2018","journal-title":"Chem.\nPhys. Lett."},{"key":"2026073009071419600_cit24","doi-asserted-by":"publisher","DOI":"10.26434\/chemrxiv\u20132024\u20138489b","article-title":"Efficient and Accurate\npKa Prediction Enabled by Pre-Trained Machine-Learned\nInteratomic Potentials","author":"Wagen","year":"2024","journal-title":"arXiv"},{"key":"2026073009071419600_cit25","volume-title":"Gaussian\n16 Revision B.01","author":"Frisch","year":"2016"},{"key":"2026073009071419600_cit26","doi-asserted-by":"publisher","DOI":"10.1002\/wcms.1554","article-title":"webmo: Web-based\nComputational Chemistry Calculations\nin Education and Research","volume":"12","author":"Polik","year":"2022","journal-title":"Wiley Interdiscip.\nRev. Comput. Mol. Sci."},{"key":"2026073009071419600_cit27","doi-asserted-by":"publisher","first-page":"51","DOI":"10.1016\/j.cplett.2004.06.011","article-title":"A New Hybrid\nExchange-Correlation\nFunctional Using the Coulomb-attenuating Method (CAM-B3LYP)","volume":"393","author":"Yanai","year":"2004","journal-title":"Chem. Phys. Lett."},{"key":"2026073009071419600_cit28","doi-asserted-by":"publisher","first-page":"1593","DOI":"10.1002\/cphc.200800131","article-title":"Influence of Solvent Polarity and\nHydrogen Bonding on the Electronic Transition of Coumarin 120: A TDDFT\nStudy","volume":"9","author":"Zhao","year":"2008","journal-title":"ChemPhysChem"},{"key":"2026073009071419600_cit29","doi-asserted-by":"publisher","first-page":"215","DOI":"10.1007\/s00214-007-0310-x","article-title":"The M06 Suite of Density Functionals for Main Group\nThermochemistry, Thermochemical Kinetics, Noncovalent Interactions,\nExcited States, and Transition Elements: Two New Functionals and Systematic\nTesting of Four M06-class Functionals and 12 Other Functionals","volume":"120","author":"Zhao","year":"2008","journal-title":"Theor. Chem. Acc."},{"key":"2026073009071419600_cit30","doi-asserted-by":"publisher","first-page":"6378","DOI":"10.1021\/jp810292n","article-title":"Universal\nSolvation Model Based on\nSolute Electron Density and on a Continuum Model of the Solvent Defined\nby the Bulk Dielectric Constant and Atomic Surface Tensions","volume":"113","author":"Marenich","year":"2009","journal-title":"J. Phys. Chem. B"},{"key":"2026073009071419600_cit31","doi-asserted-by":"publisher","first-page":"154104","DOI":"10.1063\/1.3382344","article-title":"A Consistent and Accurate Ab Initio Parametrization\nof Density Functional Dispersion\nCorrection (DFT-D) for the 94 Elements H-Pu","volume":"132","author":"Grimme","year":"2010","journal-title":"J. Chem. Phys."},{"key":"2026073009071419600_cit32","doi-asserted-by":"publisher","first-page":"1456","DOI":"10.1002\/jcc.21759","article-title":"Effect of\nthe Damping Function in\nDispersion Corrected Density Functional Theory","volume":"32","author":"Grimme","year":"2011","journal-title":"J. Comput. Chem."},{"key":"2026073009071419600_cit33","doi-asserted-by":"publisher","first-page":"3866","DOI":"10.1021\/ct200644w","article-title":"Performance of the\nvan Der Waals Density Functional\nVV10 and (Hybrid)GGA Variants for Thermochemistry and Noncovalent\nInteractions","volume":"7","author":"Hujo","year":"2011","journal-title":"J. Chem. Theory Comput."},{"key":"2026073009071419600_cit34","doi-asserted-by":"publisher","first-page":"034112","DOI":"10.1063\/1.4993215","article-title":"Extension of the D3 Dispersion Coefficient\nModel","volume":"147","author":"Caldeweyher","year":"2017","journal-title":"J. Chem. 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Soc."},{"key":"2026073009071419600_cit38","doi-asserted-by":"publisher","first-page":"2094","DOI":"10.1021\/j100636a013","article-title":"Barriers to Internal\nRotation in\nSome M-Substituted Phenols","volume":"77","author":"Manocha","year":"1973","journal-title":"J. Phys. Chem."},{"key":"2026073009071419600_cit39","doi-asserted-by":"publisher","first-page":"7314","DOI":"10.1021\/ja010534f","article-title":"Accurate pKa Calculations for Carboxylic\nAcids Using\nComplete Basis Set and Gaussian-n Models Combined with CPCM Continuum\nSolvation Methods","volume":"123","author":"Liptak","year":"2001","journal-title":"J. Am. Chem. Soc."},{"key":"2026073009071419600_cit40","doi-asserted-by":"publisher","first-page":"616","DOI":"10.1016\/j.molliq.2019.01.083","article-title":"Characterization of 4-Methylesculetin and of Its Mono- and Di-Methoxylated\nDerivatives in Water and Organic Solvents in Its Ground, Singlet and\nTriplet Excited States","volume":"278","author":"Pina","year":"2019","journal-title":"J. Mol. Liq."},{"key":"2026073009071419600_cit41","doi-asserted-by":"publisher","first-page":"123","DOI":"10.1007\/BF00911952","article-title":"Fluoreszenzspektren,\nPhotodissoziation und Phototautomerie einiger\n4-Hydroxycumarine Lumineszierende Heterocyclen, 5. Mitt","volume":"109","author":"Wolfbeis","year":"1978","journal-title":"Monatshefte fu\u0308r Chemie"},{"key":"2026073009071419600_cit42","doi-asserted-by":"publisher","first-page":"143","DOI":"10.1007\/s10534-004-4256-3","article-title":"Studies on Structure\nActivity Relationship of Some Dihydroxy-4-Methylcoumarin Antioxidants\nBased on Their Interaction with Fe(III) and ADP","volume":"18","author":"Sharma","year":"2005","journal-title":"BioMetals"},{"key":"2026073009071419600_cit43","unstructured":"Rowan Scientific. 2026; https:\/\/rowansci.com\/ (accessed\n2026-07-07)."},{"key":"2026073009071419600_cit44","doi-asserted-by":"crossref","DOI":"10.1002\/9783527650002","volume-title":"Molecular Fluorescence:\nPrinciples and Applications","author":"Valeur","year":"2012","edition":"2nd"},{"key":"2026073009071419600_cit45","doi-asserted-by":"publisher","first-page":"10297","DOI":"10.1021\/acs.jpcb.6b01383","article-title":"Comparison\nof the Photoprotolytic Processes of Three 7-Hydroxycoumarins","volume":"120","author":"Simkovitch","year":"2016","journal-title":"J. Phys. Chem. B"},{"key":"2026073009071419600_cit46","doi-asserted-by":"publisher","first-page":"65","DOI":"10.1021\/acs.jpca.0c08283","article-title":"On the Accuracy of the Direct Method\nto Calculate pKa from Electronic Structure\nCalculations","volume":"125","author":"Dutra","year":"2021","journal-title":"J. Phys. Chem. A"},{"key":"2026073009071419600_cit47","doi-asserted-by":"publisher","first-page":"8590","DOI":"10.3390\/molecules27238590","article-title":"An Accurate Approach\nfor Computational\npKa Determination of Phenolic Compounds","volume":"27","author":"Pezzola","year":"2022","journal-title":"Molecules"}],"container-title":["The Journal of Physical\nChemistry A"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/pubs.acs.org\/doi\/pdf\/10.1021\/acs.jpca.6c02005","content-type":"application\/pdf","content-version":"vor","intended-application":"unspecified"},{"URL":"https:\/\/pubs.acs.org\/jpcafh\/article-pdf\/130\/30\/5802\/65980056\/acs.jpca.6c02005.pdf","content-type":"application\/pdf","content-version":"vor","intended-application":"syndication"},{"URL":"https:\/\/pubs.acs.org\/jpcafh\/article-pdf\/130\/30\/5802\/65980056\/acs.jpca.6c02005.pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,7,30]],"date-time":"2026-07-30T13:17:31Z","timestamp":1785417451000},"score":1,"resource":{"primary":{"URL":"https:\/\/pubs.acs.org\/jpcafh\/article\/130\/30\/5802\/5212198\/Acidity-Determination-by-Spectroscopic-and"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,7,16]]},"references-count":47,"journal-issue":{"issue":"30","published-online":{"date-parts":[[2026,7,16]]},"published-print":{"date-parts":[[2026,7,30]]}},"URL":"https:\/\/doi.org\/10.1021\/acs.jpca.6c02005","relation":{},"ISSN":["1089-5639","1520-5215"],"issn-type":[{"value":"1089-5639","type":"print"},{"value":"1520-5215","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,7,16]]}}}