Publicação
Copper(II) complex with a redox-noninnocent Schiff base bearing a tetraphenyldisiloxane unit: synthesis, structure and catalytic oxidation of cyclohexane
| authorProfile.email | biblioteca@isel.pt | |
| datacite.subject.fos | Engenharia e Tecnologia::Engenharia Química | |
| dc.contributor.author | Wittmann, Christopher | |
| dc.contributor.author | Palamarciuc, Oleg | |
| dc.contributor.author | Dascalu, Mihaela | |
| dc.contributor.author | Cazacu, Maria | |
| dc.contributor.author | Nesterov, Dmytro S. | |
| dc.contributor.author | Pombeiro, Armando | |
| dc.contributor.author | Rapta, Peter | |
| dc.contributor.author | Arion, Vladimir B. | |
| dc.date.accessioned | 2026-02-18T10:40:31Z | |
| dc.date.available | 2026-02-18T10:40:31Z | |
| dc.date.issued | 2025-06-17 | |
| dc.description | This work was funded by a grant from the Ministry of Research, Innovation and Digitalization, project no. PNRR-III-C9-2023-I8-99/31.07.2023 within the National Recovery and Resilience Plan (Romania), as well as by the Slovak Research and Development Agency under contract no. APVV-19-0024 and APVV-23-0195 (P. R.) and the grant agency VEGA (contract no. 1/0392/24). The authors acknowledge the Fundação para a Ciência e a Tecnologia (FCT), Portugal, through the projects UIDB/00100/2020 (https://doi.org/10.54499/UIDB/00100/2020), UIDP/00100/2020 (https://doi.org/10.54499/UIDP/00100/2020), LA/P/0056/2020 (https://doi.org/10.54499/LA/P/0056/2020) of Centro de Química Estrutural. We thank Mr Alexander Prado-Roller for X-ray diffraction measurements. | |
| dc.description.abstract | Abstract An organic–inorganic diamine, 1,3-bis(aminopropyl)tetraphenyldisiloxane, was prepared and introduced as a flexible spacer into the structure of a salen-type Schiff base (H2L7) extending the available small library of similar compounds derived from 1,3-bis(aminopropyl)tetramethyldisiloxane and substituted 2-hydroxybenzaldehydes (H2L1–H2L6). Like the previously reported mononuclear copper(II) complexes [CuL1]–[CuL6], the new copper(II) complex [CuL7], obtained by reaction of Cu(OAc)2·H2O with H2L7 in a mixture of organic solvents, has a tetrahedrally distorted square-planar (N2O2) coordination geometry. X-ray crystallography has shown that compared to [CuL1]–[CuL6] the Si–O–Si angle in [CuL7] is even closer to linear due to stronger intramolecular interactions between Ph groups than between Me groups in the central–R2Si–O–SiR2– fragment (R = Ph and Me, respectively). [CuL7] can be electrochemically reversibly oxidised by two successive one-electron processes, generating stable phenoxyl mono- and diradicals. Both oxidations are ligand-centred, leading to the formation of coordinated phenoxyl radicals. The UV spectrum of [CuL7] consists of π → π* and LMCT σ → d transitions. The low-energy d–d absorption is well described by AILFT CAS(9,5)/NEVPT2 calculations. The one-electron oxidised compound [CuL7]+ should exist in the triplet ground state as 3[CuL7]+ with one unpaired electron located on the dx2−y2 orbital of copper(II) (d9, SCu = ½) and another electron on the molecular orbital (MO) comprising pz oxygen and carbon atoms of the phenoxyl radical (Srad = ½). The broad absorption in the vis-NIR region of the optical spectrum of the one-electron oxidised complex is due to intervalence charge transfer in the triplet species 3[CuL7]+, but not in the [CuL7]2+ one. The doubly oxidised [CuL7] species shows very close doublet and quartet states, where the doublet state has an unpaired electron located on the Cu(II) d-orbital, while the quartet state has one unpaired electron on the Cu(II) d-orbital and two unpaired electrons on π-bonding orbitals. In all state-averaged CASSCF cases, the occupation of the Cu(II) d-orbital is nearly 1.0, indicating its limited involvement in the excited states. Catalytic studies showed that [CuL7] acts as a catalyst for the oxidation of alkanes with peroxides under very unusual solvent-free conditions, converting cyclohexane into cyclohexanol and cyclohexanone (with hydrogen peroxide or tert-butyl hydroperoxide as the oxidant) or into cyclohexanol and ε-caprolactone (with m-chloroperoxybenzoic acid as the oxidant). Theoretical investigations of the catalytic reaction mechanisms disclosed the principal intermediates. | eng |
| dc.identifier.citation | Wittmann, C., Palamarciuc, O. Dascalu, M., Cazacu, M., Nesterov, D. S., Pombeiro, A. J. L., Rapta, P., & Arion, V. B. (2025). Copper(II) complex with a redox-noninnocent Schiff base bearing a tetraphenyldisiloxane unit: synthesis, structure and catalytic oxidation of cyclohexane. Dalton Transactions, 54, 10984-11005. https://10.1039/d5dt01028d | |
| dc.identifier.doi | 10.1039/d5dt01028d | |
| dc.identifier.eissn | 1477-9234 | |
| dc.identifier.issn | 1477-9226 | |
| dc.identifier.uri | http://hdl.handle.net/10400.21/22665 | |
| dc.language.iso | eng | |
| dc.peerreviewed | yes | |
| dc.publisher | Royal Society of Chemistry | |
| dc.relation | Centro de Química Estrutural | |
| dc.relation.hasversion | https://pubs.rsc.org/en/content/articlelanding/2025/dt/d5dt01028d | |
| dc.rights.uri | http://creativecommons.org/licenses/by-nc-nd/4.0/ | |
| dc.subject | Tetraphenyldisiloxane unit | |
| dc.subject | Catalytic oxidation of cyclohexane | |
| dc.subject | UIDB/00100/2020 | |
| dc.subject | UIDP/00100/2020 | |
| dc.title | Copper(II) complex with a redox-noninnocent Schiff base bearing a tetraphenyldisiloxane unit: synthesis, structure and catalytic oxidation of cyclohexane | eng |
| dc.type | research article | |
| dspace.entity.type | Publication | |
| oaire.awardTitle | Centro de Química Estrutural | |
| oaire.awardURI | info:eu-repo/grantAgreement/FCT/6817 - DCRRNI ID/UIDB%2F00100%2F2020/PT | |
| oaire.citation.endPage | 11005 | |
| oaire.citation.startPage | 10984 | |
| oaire.citation.title | Dalton Transactions | |
| oaire.citation.volume | 54 | |
| oaire.fundingStream | 6817 - DCRRNI ID | |
| oaire.version | http://purl.org/coar/version/c_be7fb7dd8ff6fe43 | |
| person.familyName | Pombeiro | |
| person.givenName | Armando | |
| person.identifier.ciencia-id | 8311-38FA-CEFB | |
| person.identifier.orcid | 0000-0001-8323-888X | |
| person.identifier.rid | I-5945-2012 | |
| person.identifier.scopus-author-id | 7006067269 | |
| project.funder.identifier | http://doi.org/10.13039/501100001871 | |
| project.funder.name | Fundação para a Ciência e a Tecnologia | |
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