The observation of very long lifetimes of the metastable states of two cobalt-dioxolene complexes undergoing photoinduced and high T(c) thermally-induced valence tautomer interconversion opens new research perspectives.
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Putting the squeeze on valence tautomerism in cobalt-dioxolene complexes.
Nat Commun
October 2024
School of Molecular Sciences, University of Western Australia, Crowley, Western Australia, Australia.
Molecules that can reversibly switch between electronic states under an external stimulus are of interest to numerous applications. Complexes of open shell metal ions with redox active ligands undergo valence tautomerism, resulting in magnetic, colour and structural switching, relevant to data storage and actuators. However, the precise structural changes occurring during valence tautomerism in the solid state are unclear due to the lack of atomic-resolution characterization.
View Article and Find Full Text PDFThe ability of molecular switches to reversibly interconvert between different forms promises potential applications at the scale of single molecules up to bulk materials. One type of molecular switch comprises cobalt-dioxolene compounds that exhibit thermally-induced valence tautomerism (VT) interconversions between low spin Co(iii)-catecholate (LS-Co-cat) and high spin Co(ii)-semiquinonate (HS-Co-sq) forms. Two families of these compounds have been investigated for decades but have generally been considered separately: neutral [Co(diox)(sq)(NL)] and cationic [Co(diox)(NL)] complexes (diox = generic dioxolene, NL/NL = bidentate/tetradentate N-donor ancillary ligand).
View Article and Find Full Text PDFMolecular Twist-Induced Single-Crystal Isomerization and Valence Tautomeric Transitions in a Cobalt-Dioxolene Complex.
Angew Chem Int Ed Engl
April 2024
Key Laboratory of Cluster Science of Ministry of Education, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Liangxiang Campus, Beijing, 102488, China.
A mononuclear valence tautomeric (VT) complex, [Co(pycz)(Sq)(Cat)] (1-trans), where pycz = 9-(pyridin-4-yl)-9H-carbazole, Sq⋅ = 3,5-di-tert-butyl-semiquinonato, and Cat = 3,5-di-tert-butyl-catecholato, is synthesized in the trans configuration, which undergoes one-step valence tautomeric transition above room temperature. Remarkably, 1-trans can transform into its isomeric structure, [Co(pycz)(Sq)(Sq)] (1-cis), at temperature above 350 K in a single-crystal-to-single-crystal way by in situ molecular twist, and the resulting 1-cis exhibits a pronounced two-step VT transition during magnetic measurements that is rare for mononuclear VT complexes. Such drastic solid-state structural transformation is reported in VT compounds for the first time, which is actuated by a crystal surface's melting-recrystallization induced phase transition process.
View Article and Find Full Text PDFLigand Modifications Produce Two-Step Magnetic Switching in a Cobalt(dioxolene) Complex.
Angew Chem Int Ed Engl
November 2023
Department of Chemistry, Center for Biophysics and Quantitative Biology, Materials Research Laboratory, University of Illinois, Urbana-Champaign, Urbana, Illinois, 61801, USA.
Mononuclear monodioxolene valence tautomeric (VT) cobalt complexes typically exist in their low spin (l.s.) Co (cat ) and high spin (h.
View Article and Find Full Text PDFValence tautomerism in a cobalt-dioxolene complex containing an imidazolic ancillary ligand.
RSC Adv
June 2023
Instituto de Química, Universidade Federal do Rio de Janeiro Rio de Janeiro RJ 21941-909 Brazil
This work reports the synthesis, structural, spectroscopic and magnetic investigation of two complexes, [Co(bmimapy)(3,5-DTBCat)]PF·HO (1) and [Co(bmimapy)(TCCat)]PF·HO (2), where bmimapy is an imidazolic tetradentate ancillary ligand and 3,5-DTBCat and TCCat are the 3,5-di--butyl-catecholate and tetrachlorocatecholate anions, respectively. Their structures have been elucidated using single crystal X-ray diffraction, showing a pseudo-octahedral cobalt ion bound to a chelating dioxolene ligand and the ancillary bmimapy ligand in a folded conformation. Magnetometry displayed an entropy-driven, incomplete, Valence Tautomeric (VT) process for 1 in the 300-380 K temperature range, while 2 displayed a temperature independent, diamagnetic low-spin cobalt(iii)-catecholate charge distribution.
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