title: Solvent-Triggered Cis/Trans Isomerism in Cobalt Dioxolene Chemistry: Distinguishing Effects of Packing on Valence Tautomerism.
abstract: In this article, the synthesis and X-ray crystal structures of two cis/trans isomers of valence tautomeric (VT) cobalt dioxolene compounds are reported. The cis isomer (1) was isolated from the polar protic methanol solvent as a kinetic product, whereas the less polar nonprotic solvent acetone yielded the trans isomer (2). It should be noted that, although some coordination polymers involving cobalt bis(dioxolene) with the cis disposition are known for bridging ancillary ligands, such an arrangement is unprecedented for mononuclear compounds. A careful study of intermocular interactions revealed that the methanol solvent does not have much influence on the crystal growth in 1, whereas acetone forms strong halogen-bonding interactions that are crucial in the solid-state architecture of 2. This behavior can likely be used in crystal engineering to design new organic-inorganic hybrid materials. The energy difference between the two isomers was examined using DFT calculations, confirming that the trans form is in the thermodynamic state whereas the cis isomer is a kinetic product that can be converted into the trans isomer with time. Finally, both isomers exhibit solvent loss at elevated temperatures that is accompanied by a change in magnetic properties, associated with an irreversible valence tautomerism. Our results highlight the crucial role of the solvents for the isolation of cis/trans isomers in cobalt dioxolene chemistry, as well as the distinguishing effects of intermolecular forces and the solid-state packing on VT behavior.
authors.affiliation: Postgraduate Department of Chemistry, Panskura Banamali College , Panskura RS, WB 721152, India.
authors.forename: Anangamohan
authors.initials: A
authors.lastname: Panja
authors.affiliation: Postgraduate Department of Chemistry, Panskura Banamali College , Panskura RS, WB 721152, India.
authors.forename: Narayan Ch
authors.initials: NCh
authors.lastname: Jana
authors.affiliation: Departament de Química, Universitat de les Illes Balears , Carretera de Valldemossa km 7.5, 07122 Palma de Mallorca, Baleares, Spain.
authors.forename: Antonio
authors.initials: A
authors.lastname: Bauzá
authors.affiliation: Departament de Química, Universitat de les Illes Balears , Carretera de Valldemossa km 7.5, 07122 Palma de Mallorca, Baleares, Spain.
authors.forename: Antonio
authors.initials: A
authors.lastname: Frontera
authors.affiliation: CNRS, UPR 9048, Institut de Chimie de la Matière Condensée de Bordeaux (ICMCB) , Pessac F-33600, France.|Université de Bordeaux, ICMCB, UPR 9048 , Pessac F-33600, France.
authors.forename: Corine
authors.initials: C
authors.lastname: Mathonière