Synthesis, Characterization, and Antimicrobial Activity of a Schiff Base Derived from 2-Pyridinecarboxaldehyde and 5-Amino-2-Methoxypyridine and Its Mn(II), Co(II), and Ni(II) Complexes

Synthesis, Characterization, and Antimicrobial Activity of a Schiff Base Derived from 2-Pyridinecarboxaldehyde and 5-Amino-2-Methoxypyridine and Its Mn(II), Co(II), and Ni(II) Complexes | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Synthesis, Characterization, and Antimicrobial Activity of a Schiff Base Derived from 2-Pyridinecarboxaldehyde and 5-Amino-2-Methoxypyridine and Its Mn(II), Co(II), and Ni(II) Complexes Samira Shehu Muhammad, Junaidu Na’aliya, Shehu Jibril, Ibrahim Idris Uba This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8487271/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract A new pyridyl Schiff base ligand, L (C 12 H 11 N 3 O), was synthesized by condensation of 2-pyridinecarboxaldehyde with 5-amino-2-methoxypyridine, and its Mn(II), Co(II), and Ni(II) complexes of the type [M(L) 2 Cl 2 ].xH 2 O were prepared. The ligand and its complexes were characterized by melting/decomposition temperature, elemental analysis, solubility, molar conductance, magnetic susceptibility, FTIR and UV-Vis spectroscopy. L is a coffee-brown solid with a melting point of 90 ˚C and forms dark brown/black non-electrolytic complexes with Mn(II), Co(II) and Ni(II) in good yields (63–77%), all soluble in DMSO and DMF. FTIR spectra show a ⱱ(C = N) band at 1622 cm − 1 in L, shifting to 1568–1626 cm − 1 in the complexes, together with new bands assigned to M-N and coordinated water, consistent with coordination via the azomethine nitrogen and pyridyl nitrogen. Electronic spectra and effective magnetic moments (Mn: 5.66 BM; Co: 3.94 BM; Ni: 2.78 BM) support octahedral geometries around the metal centers. Antimicrobial activity of L and its complexes was evaluated by the agar well diffusion method against Gram-positive bacteria ( Streptococcus mutans , and Staphylococcus aureus ), Gram-negative bacteria ( Escherichia coli ) and fungal strains ( Candida albicans, Trichophyton rubrum, Trichophyton sp. Associated with Tinea pedis ). All compounds exhibited concentration-dependent activity (250–2000 µg/mL). Notably, the free Schiff base ligand generally displayed higher antimicrobial activity than its corresponding metal complexes, with inhibition zones reaching up to 18 mm against Streptococcus mutans and Trichophyton rubrum at 2000 µg/mL. These results demonstrate that metal coordination does not universally enhance antimicrobial efficacy and highlight the critical influence of ligand structure and metal ion identity on biological activity. Pyridyl Schiff base Transition metal complexes Spectral characterization Octahedral geometry Antimicrobial activity Full Text Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8487271","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":582027048,"identity":"ea118f0a-8962-4f85-ada8-c7ded882e9bd","order_by":0,"name":"Samira Shehu Muhammad","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA9klEQVRIiWNgGAWjYJCCA0CcwMDeABcwIFILzwEStDCAtUgkEKlFvv104uGKGrs83ZmPH3/4UWEjz8DevE2CcUctTi0GZ3I3HDxzLLnY7HaamWTPmTTDBp5jZRKMZ47j1sIA1NLAdiBx2+0EM2bGtsOMDRI5ZhKMbcdwO6z/LVDLP6CWm8c/f2Zs+2/fIP8GvxaGG0BbGtuAWm7wGEgzAhkNEjwgLTW4HXYDaEtjX3LitjM5ZUC/JCe38aQVWyS2HcDjsNzNHxu+2SVuO358MzDE7Gz72Q9vvPGxrQ63wzAAG4hIYDhMghYoIMWWUTAKRsEoGOYAAAfCXq7z1BxhAAAAAElFTkSuQmCC","orcid":"","institution":"Aminu Saleh College of Education, Azare","correspondingAuthor":true,"prefix":"","firstName":"Samira","middleName":"Shehu","lastName":"Muhammad","suffix":""},{"id":582027049,"identity":"b133a466-aefb-459b-b7bf-f44b505b85c5","order_by":1,"name":"Junaidu Na’aliya","email":"","orcid":"","institution":"Bayero University, Kano","correspondingAuthor":false,"prefix":"","firstName":"Junaidu","middleName":"","lastName":"Na’aliya","suffix":""},{"id":582027050,"identity":"e808ebe2-a00f-469f-9dea-fae2ab6f0e2e","order_by":2,"name":"Shehu Jibril","email":"","orcid":"","institution":"Aminu Saleh College of Education, Azare","correspondingAuthor":false,"prefix":"","firstName":"Shehu","middleName":"","lastName":"Jibril","suffix":""},{"id":582027051,"identity":"c6ca9fda-4cfa-4698-9c7d-9061e5d2eb4d","order_by":3,"name":"Ibrahim Idris Uba","email":"","orcid":"","institution":"Bayero University, Kano","correspondingAuthor":false,"prefix":"","firstName":"Ibrahim","middleName":"Idris","lastName":"Uba","suffix":""}],"badges":[],"createdAt":"2025-12-31 07:53:11","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8487271/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8487271/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":106588058,"identity":"563e85d1-3ac2-47d4-8ca7-d7b24a655b93","added_by":"auto","created_at":"2026-04-10 07:58:15","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":615084,"visible":true,"origin":"","legend":"","description":"","filename":"ACSDiscoverChemistryJournalsubmission.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8487271/v1_covered_de639261-d353-4b41-805f-fc78398cba5b.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Synthesis, Characterization, and Antimicrobial Activity of a Schiff Base Derived from 2-Pyridinecarboxaldehyde and 5-Amino-2-Methoxypyridine and Its Mn(II), Co(II), and Ni(II) Complexes","fulltext":[],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":false,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":true,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":true,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Pyridyl Schiff base, Transition metal complexes, Spectral characterization, Octahedral geometry, Antimicrobial activity","lastPublishedDoi":"10.21203/rs.3.rs-8487271/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8487271/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eA new pyridyl Schiff base ligand, L (C\u003csub\u003e12\u003c/sub\u003eH\u003csub\u003e11\u003c/sub\u003eN\u003csub\u003e3\u003c/sub\u003eO), was synthesized by condensation of 2-pyridinecarboxaldehyde with 5-amino-2-methoxypyridine, and its Mn(II), Co(II), and Ni(II) complexes of the type [M(L)\u003csub\u003e2\u003c/sub\u003eCl\u003csub\u003e2\u003c/sub\u003e].xH\u003csub\u003e2\u003c/sub\u003eO were prepared. The ligand and its complexes were characterized by melting/decomposition temperature, elemental analysis, solubility, molar conductance, magnetic susceptibility, FTIR and UV-Vis spectroscopy. L is a coffee-brown solid with a melting point of 90 ˚C and forms dark brown/black non-electrolytic complexes with Mn(II), Co(II) and Ni(II) in good yields (63\u0026ndash;77%), all soluble in DMSO and DMF. FTIR spectra show a ⱱ(C\u0026thinsp;=\u0026thinsp;N) band at 1622 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e in L, shifting to 1568\u0026ndash;1626 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e in the complexes, together with new bands assigned to M-N and coordinated water, consistent with coordination via the azomethine nitrogen and pyridyl nitrogen. Electronic spectra and effective magnetic moments (Mn: 5.66 BM; Co: 3.94 BM; Ni: 2.78 BM) support octahedral geometries around the metal centers. Antimicrobial activity of L and its complexes was evaluated by the agar well diffusion method against Gram-positive bacteria (\u003cem\u003eStreptococcus mutans\u003c/em\u003e, and \u003cem\u003eStaphylococcus aureus\u003c/em\u003e), Gram-negative bacteria (\u003cem\u003eEscherichia coli\u003c/em\u003e) and fungal strains (\u003cem\u003eCandida albicans, Trichophyton rubrum, Trichophyton\u003c/em\u003e sp. Associated with \u003cem\u003eTinea pedis\u003c/em\u003e). All compounds exhibited concentration-dependent activity (250\u0026ndash;2000 \u0026micro;g/mL). Notably, the free Schiff base ligand generally displayed higher antimicrobial activity than its corresponding metal complexes, with inhibition zones reaching up to 18 mm against \u003cem\u003eStreptococcus mutans\u003c/em\u003e and \u003cem\u003eTrichophyton rubrum\u003c/em\u003e at 2000 \u0026micro;g/mL. These results demonstrate that metal coordination does not universally enhance antimicrobial efficacy and highlight the critical influence of ligand structure and metal ion identity on biological activity.\u003c/p\u003e","manuscriptTitle":"Synthesis, Characterization, and Antimicrobial Activity of a Schiff Base Derived from 2-Pyridinecarboxaldehyde and 5-Amino-2-Methoxypyridine and Its Mn(II), Co(II), and Ni(II) Complexes","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-01-29 15:38:43","doi":"10.21203/rs.3.rs-8487271/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"836bf661-39ed-4fce-bc87-b0cd934b6723","owner":[],"postedDate":"January 29th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-04-10T07:57:16+00:00","versionOfRecord":[],"versionCreatedAt":"2026-01-29 15:38:43","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8487271","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8487271","identity":"rs-8487271","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}