{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,29]],"date-time":"2026-03-29T06:00:41Z","timestamp":1774764041834,"version":"3.50.1"},"reference-count":49,"publisher":"MDPI AG","issue":"13","license":[{"start":{"date-parts":[[2025,6,28]],"date-time":"2025-06-28T00:00:00Z","timestamp":1751068800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Portuguese Foundation for Science and Technology (FCT)","award":["UID\/00686"],"award-info":[{"award-number":["UID\/00686"]}]},{"name":"Portuguese Foundation for Science and Technology (FCT)","award":["UID\/04650"],"award-info":[{"award-number":["UID\/04650"]}]},{"name":"Portuguese Foundation for Science and Technology (FCT)","award":["No. 022161"],"award-info":[{"award-number":["No. 022161"]}]},{"name":"FEDER through COMPETE 2020, POCI, and PORL, and FCT through PIDDAC","award":["UID\/00686"],"award-info":[{"award-number":["UID\/00686"]}]},{"name":"FEDER through COMPETE 2020, POCI, and PORL, and FCT through PIDDAC","award":["UID\/04650"],"award-info":[{"award-number":["UID\/04650"]}]},{"name":"FEDER through COMPETE 2020, POCI, and PORL, and FCT through PIDDAC","award":["No. 022161"],"award-info":[{"award-number":["No. 022161"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Molecules"],"abstract":"<jats:p>Eugenol-based azo dyes illustrate how bio-sourced compounds like eugenol can be transformed through synthetic processes into functional and colorful compounds. The main purpose of the present work was to develop new responsive colorimetric sensors for metal cations based on eugenol-derived azo compounds. The incorporation of the azo group into the eugenol framework allows for strong electronic interactions with metal cations, leading to distinct color changes observable to the naked eye. These azo-eugenol dyes exhibit shifts in their UV-Vis absorption spectra upon complexation with metal cations such as copper (Cu2+) and lead (Pb2+), making them effective sensors for environmental and analytical applications. The eugenol-based azo dyes were subjected to photophysical studies to understand selectivity, response time, and stability in relation to metal cations, which will be a starting point for the monitoring of toxic metal contaminants in aqueous environments.<\/jats:p>","DOI":"10.3390\/molecules30132788","type":"journal-article","created":{"date-parts":[[2025,6,30]],"date-time":"2025-06-30T11:37:51Z","timestamp":1751283471000},"page":"2788","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":3,"title":["New Cation Sensors Based on Eugenol-Derived Azo Dyes"],"prefix":"10.3390","volume":"30","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-9453-4529","authenticated-orcid":false,"given":"Jos\u00e9 R. A.","family":"Coelho","sequence":"first","affiliation":[{"name":"Chemistry Centre of the University of Minho (CQ-UM), Department of Chemistry, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal"}]},{"given":"Ana Rita F.","family":"Pacheco","sequence":"additional","affiliation":[{"name":"Physics Centre of Minho and Porto Universities (CF-UM-UP), Department of Physics, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal"},{"name":"Associate Laboratory LaPMET, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0009-0009-7509-2855","authenticated-orcid":false,"given":"Diogo C.","family":"Domingues","sequence":"additional","affiliation":[{"name":"Chemistry Centre of the University of Minho (CQ-UM), Department of Chemistry, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6094-1713","authenticated-orcid":false,"given":"Ana Rita O.","family":"Rodrigues","sequence":"additional","affiliation":[{"name":"Physics Centre of Minho and Porto Universities (CF-UM-UP), Department of Physics, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal"},{"name":"Associate Laboratory LaPMET, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal"}]},{"given":"Akani A.","family":"Temitope","sequence":"additional","affiliation":[{"name":"Chemistry Centre of the University of Minho (CQ-UM), Department of Chemistry, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4426-9207","authenticated-orcid":false,"given":"Paulo J. G.","family":"Coutinho","sequence":"additional","affiliation":[{"name":"Physics Centre of Minho and Porto Universities (CF-UM-UP), Department of Physics, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal"},{"name":"Associate Laboratory LaPMET, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal"}]},{"given":"Maria Jos\u00e9 G.","family":"Fernandes","sequence":"additional","affiliation":[{"name":"Chemistry Centre of the University of Minho (CQ-UM), Department of Chemistry, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5829-6081","authenticated-orcid":false,"given":"Elisabete M. S.","family":"Castanheira","sequence":"additional","affiliation":[{"name":"Physics Centre of Minho and Porto Universities (CF-UM-UP), Department of Physics, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal"},{"name":"Associate Laboratory LaPMET, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2048-1190","authenticated-orcid":false,"given":"M. Sameiro T.","family":"Gon\u00e7alves","sequence":"additional","affiliation":[{"name":"Chemistry Centre of the University of Minho (CQ-UM), Department of Chemistry, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal"}]}],"member":"1968","published-online":{"date-parts":[[2025,6,28]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"110050","DOI":"10.1016\/j.dyepig.2021.110050","article-title":"Miscellaneous azo dyes: A comprehensive review on recent advancements in biological and industrial applications","volume":"199","author":"Alsantali","year":"2022","journal-title":"Dyes Pigm."},{"key":"ref_2","first-page":"3632","article-title":"Naturalized dyes: A new opportunity for the wood colouring","volume":"15","author":"Vespignani","year":"2023","journal-title":"Polym. J."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"5954","DOI":"10.3390\/molecules28165954","article-title":"Advancements in sustainable natural dyes for textile applications: A review","volume":"28","author":"Pizzicato","year":"2023","journal-title":"Molecules"},{"key":"ref_4","first-page":"56","article-title":"New azo carboxylic dyes derived from eugenol: Synthesis and preliminary application to polyamide","volume":"14","author":"Coelho","year":"2023","journal-title":"Chem. Proc."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"25932","DOI":"10.1039\/D2RA04934A","article-title":"Synthesis and pharmacological activities of azo dye derivatives incorporating heterocyclic scaffolds: A review","volume":"12","author":"Mezgebe","year":"2022","journal-title":"RSC Adv."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"e52340","DOI":"10.1002\/app.52340","article-title":"Synthesis and properties of new siloxane with terminal azo dyes functions based on eugenol","volume":"139","author":"Ryzhkov","year":"2022","journal-title":"J. Appl. Polym. Sci."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"109367","DOI":"10.1016\/j.dyepig.2021.109367","article-title":"Review of NLOphoric azo dyes\u2014Developments in hyperpolarizabilities in last two decades","volume":"191","author":"Ghanavatkar","year":"2021","journal-title":"Dyes Pigment."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"8162","DOI":"10.3390\/ma15228162","article-title":"Synthesis, characterization, DFT study and antifungal activities of some novel 2-(phenyldiazenyl)phenol based azo dyes","volume":"15","author":"Marinescu","year":"2022","journal-title":"Materials"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"100890","DOI":"10.1016\/j.rechem.2023.100890","article-title":"Recent review on synthesis, spectral studies, versatile applications of azo dyes and its metal complexes","volume":"5","author":"Khanum","year":"2023","journal-title":"Results Chem."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"e5883","DOI":"10.1002\/aoc.5883","article-title":"Metal complexes of tetradentate azo-dye ligand derived from 4,4\u2032-oxydianiline: Preparation, structural investigation, biological evaluation and MOE studies","volume":"34","author":"Deghadi","year":"2020","journal-title":"Appl. Organomet. Chem."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"897","DOI":"10.3390\/ma16030897","article-title":"Design, synthesis, spectroscopic inspection, DFT and molecular docking study of metal chelates incorporating azo dye ligand for biological evaluation","volume":"16","author":"Khalaf","year":"2023","journal-title":"Materials"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"6","DOI":"10.1039\/D3NP00012E","article-title":"Simple phenylpropanoids: Recent advances in biological activities, biosynthetic pathways, and microbial production","volume":"41","author":"Zhu","year":"2024","journal-title":"Nat. Prod. Rep."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"7078","DOI":"10.3390\/ijms21197078","article-title":"Monoterpenes and their derivatives\u2013recent development in biological and medical applications","volume":"21","year":"2020","journal-title":"Int. J. Mol. Sci."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"282","DOI":"10.1080\/00397911.2023.2297952","article-title":"An efficient synthesis, characterization, antimicrobial and anticancer activities of azo dyes derived from eugenol","volume":"54","author":"Dandge","year":"2023","journal-title":"Synth. Commun."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"1317","DOI":"10.3390\/ph16091317","article-title":"Nature-inspired compounds: Synthesis and antibacterial susceptibility testing of eugenol derivatives against H. pylori strains","volume":"16","author":"Carradori","year":"2023","journal-title":"Pharmaceuticals"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"346","DOI":"10.1039\/D4MD00511B","article-title":"Azo derivatives of monoterpenes as anti-Helicobacter pylori agents: From the synthesis to a structure-based target investigation","volume":"16","author":"Melfi","year":"2025","journal-title":"RSC Med. Chem."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"350","DOI":"10.1021\/acsfoodscitech.2c00378","article-title":"Antioxidant and cytotoxic activity of essential oils and their principal components: Spectrophotometric, voltammetric, and theoretical investigation of the chelating effect of eugenol and carvacrol","volume":"3","author":"Ferreira","year":"2023","journal-title":"ACS Food Sci. Technol."},{"key":"ref_18","first-page":"42","article-title":"Eugenol [2-Methoxy-4-allylphenol (MAP)] a colorimetric sensing probe for selective determination of Iron(III)","volume":"13","author":"Sadaphal","year":"2022","journal-title":"J. Mater. Environ. Sci."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"65","DOI":"10.1016\/j.tox.2011.03.001","article-title":"Advances in metal-induced oxidative stress and human disease","volume":"283","author":"Jomova","year":"2011","journal-title":"Toxicology"},{"key":"ref_20","doi-asserted-by":"crossref","unstructured":"Ruiz, L.M., Libedinsky, A., and Elorza, A.A. (2021). Role of copper on mitochondrial function and metabolism. Front. Mol. Biosci., 8.","DOI":"10.3389\/fmolb.2021.711227"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"32","DOI":"10.1016\/j.ctrv.2008.07.004","article-title":"Elevated copper and oxidative stress in cancer cells as a target for cancer treatment","volume":"35","author":"Gupte","year":"2009","journal-title":"Cancer Treat. Rev."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"71","DOI":"10.1186\/s12964-018-0277-3","article-title":"Copper signalling: Causes and consequences","volume":"16","author":"Kardos","year":"2018","journal-title":"Cell Commun. Signal."},{"key":"ref_23","unstructured":"Texas Commission on Environmental Quality (TCEQ) (2025, March 01). Lead Poisoning: What Are the Sources? What Are the Risks? TCEQ Publication GI-069, Available online: https:\/\/www.tceq.texas.gov\/downloads\/toxicology\/publications\/lead-poisoning-gi-69.pdf."},{"key":"ref_24","first-page":"100094","article-title":"Bioaccumulation of lead (Pb) and its effects on human: A review","volume":"7","author":"Collin","year":"2022","journal-title":"J. Hazard. Mater."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"110881","DOI":"10.1016\/j.dyepig.2022.110881","article-title":"Small molecule sensors for the colorimetric detection of Copper(II): A review of the literature from 2010 to 2022","volume":"214","author":"Trevino","year":"2023","journal-title":"Dyes Pigment."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"213691","DOI":"10.1016\/j.ccr.2020.213691","article-title":"Small molecular fluorescent probes for the detection of lead, cadmium and mercury ions","volume":"429","author":"Chen","year":"2021","journal-title":"Coord. Chem. Rev."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"101","DOI":"10.1016\/j.jphotochem.2017.10.027","article-title":"A colorimetric Pb2+ chemosensor: Rapid naked-eye detection, high selectivity, theoretical insights, and applications","volume":"355","author":"Wang","year":"2018","journal-title":"J. Photochem. Photobiol. A Chem."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"115580","DOI":"10.1016\/j.optmat.2024.115580","article-title":"A fluorescein conjugate as colorimetric and red-emissive fluorescence chemosensor for selective recognition Cu2+ ions","volume":"153","author":"Zavalishin","year":"2024","journal-title":"Opt. Mater."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"4807","DOI":"10.1007\/s11696-023-02836-x","article-title":"Recent advancements in organic chemosensors for the detection of Pb2+: A review","volume":"77","year":"2023","journal-title":"Chem. Pap."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"111740","DOI":"10.1016\/j.dyepig.2023.111740","article-title":"Recent progress in organic fluorescence and colorimetric chemosensors for Cu2+ detection: A comprehensive review (2018\u20132023)","volume":"220","author":"Alyami","year":"2023","journal-title":"Dyes Pigment."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"102174","DOI":"10.1016\/j.rechem.2025.102174","article-title":"Spectrophotometric method for detecting lead (II) ions using a chemosensor of the thiosemicarbazone-linked phenyl sulphone moiety","volume":"15","author":"Mohammed","year":"2025","journal-title":"Results Chem."},{"key":"ref_32","first-page":"1","article-title":"The UV and FTIR fingerprint of ocimum kilimandscharicum guerke essential oil: A eugenol-rich chemo type","volume":"5","author":"Ayoubi","year":"2022","journal-title":"Int. J. Innov. Res. Sci. Stud."},{"key":"ref_33","unstructured":"World Health Organization (2008). Guidelines for Drinking-Water Quality: Second Addendum, World Health Organization. [3rd ed.]."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"797S","DOI":"10.1093\/ajcn\/63.5.797","article-title":"Copper biochemistry and molecular biology","volume":"63","author":"Linder","year":"1996","journal-title":"Am. J. Clin. Nutr."},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"17","DOI":"10.1016\/j.snb.2015.12.041","article-title":"Naphthalenediimide amphiphile based colorimetric probe for recognition of Cu2+ and Fe3+ ions","volume":"227","author":"Ghule","year":"2016","journal-title":"Sens. Actuators B Chem."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"111982","DOI":"10.1016\/j.jphotochem.2019.111982","article-title":"A novel fluorescent and colorimetric dual-channel sensor for the fast, reversible and simultaneous detection of Fe3+ and Cu2+ based on terthiophene derivative with high sensitivity and selectivity","volume":"383","author":"Wang","year":"2019","journal-title":"J. Photochem. Photobiol. A Chem."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"6995","DOI":"10.3390\/s23156995","article-title":"Colorimetric chemosensor for Cu2+ and Fe3+ based on a meso-triphenylamine-BODIPY derivative","volume":"23","author":"Pinto","year":"2023","journal-title":"Sensors"},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"129248","DOI":"10.1016\/j.matchemphys.2024.129248","article-title":"Silicone films with azo dyes moieties based on eugenol with response to Cu2+ metal ions","volume":"318","author":"Vasilyeva","year":"2024","journal-title":"Mater. Chem. Phys."},{"key":"ref_39","unstructured":"World Health Organization (2023). Exposure to Lead: A Major Public Health Concern: Preventing Disease Through Healthy Environments, World Health Organization. [3rd ed.]."},{"key":"ref_40","unstructured":"(2024, November 22). Available online: https:\/\/www.who.int\/campaigns\/international-lead-poisoning-prevention-week."},{"key":"ref_41","unstructured":"World Health Organization (2021). Guideline for Clinical Management of Exposure to Lead, World Health Organization."},{"key":"ref_42","unstructured":"(2024, November 22). Available online: https:\/\/www.cdc.gov\/lead-prevention\/about\/."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"849","DOI":"10.1016\/j.snb.2014.10.110","article-title":"A novel phenol-based BODIPY chemosensor for selective detection of Fe3+ with colorimetric and fluorometric dual-mode","volume":"207","author":"Wang","year":"2015","journal-title":"Sens. Actuators B Chem."},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"2703","DOI":"10.1021\/ja01176a030","article-title":"A spectrophotometric investigation of the interaction of iodine with aromatic hydrocarbons","volume":"71","author":"Benesi","year":"1949","journal-title":"J. Am. Chem. Soc."},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"e1606","DOI":"10.1002\/wcms.1606","article-title":"Software update: The ORCA program system, version 5.0","volume":"12","author":"Neese","year":"2022","journal-title":"WIRES Comput. Molec. Sci."},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"3297","DOI":"10.1039\/b508541a","article-title":"Balanced basis sets of split valence, triple zeta valence and quadruple zeta valence quality for H to Rn: Design and assessment of accuracy","volume":"7","author":"Weigend","year":"2005","journal-title":"Phys. Chem. Chem. Phys."},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"1740","DOI":"10.1002\/jcc.10318","article-title":"An improvement of the resolution of the identity approximation for the formation of the Coulomb matrix","volume":"24","author":"Neese","year":"2003","journal-title":"J. Comp. Chem."},{"key":"ref_48","doi-asserted-by":"crossref","first-page":"1057","DOI":"10.1039\/b515623h","article-title":"Accurate coulomb-fitting basis sets for H to Rn","volume":"8","author":"Weigend","year":"2006","journal-title":"Phys. Chem. Chem. Phys."},{"key":"ref_49","doi-asserted-by":"crossref","first-page":"154122","DOI":"10.1063\/1.5090222","article-title":"A generally applicable atomic-charge dependent London dispersion correction","volume":"150","author":"Caldeweyher","year":"2019","journal-title":"J. Chem. Phys."}],"container-title":["Molecules"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1420-3049\/30\/13\/2788\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,9]],"date-time":"2025-10-09T18:00:45Z","timestamp":1760032845000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1420-3049\/30\/13\/2788"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2025,6,28]]},"references-count":49,"journal-issue":{"issue":"13","published-online":{"date-parts":[[2025,7]]}},"alternative-id":["molecules30132788"],"URL":"https:\/\/doi.org\/10.3390\/molecules30132788","relation":{},"ISSN":["1420-3049"],"issn-type":[{"value":"1420-3049","type":"electronic"}],"subject":[],"published":{"date-parts":[[2025,6,28]]}}}