The crystal structure of the first oligomeric cobalt dioxolene complex, Co3(3,5-DBSQ)2((t)BuCOO)4(NEt3)2, 1, where DBSQ is 3,5-di-tert-butyl-semiquinonate, has been studied at various temperatures between 20 and 200 K. Despite cobalt-dioxolene complexes being generally known for their extensive ability to exhibit valence tautomerism (VT), we show here that the molecular geometry of compound 1 is essentially unchanged over the full temperature range, indicating the complete absence of electron transfer between ligand and metal. Magnetic susceptibility measurements clearly support the lack of VT between 8 and 300 K. The crystal structure is also determined at elevated pressures in the range from 0 to 2.5 GPa. The response of the crystal structure is surprisingly dependent on the dynamics of pressurisation: following rapid pressurization to 2 GPa, a structural phase transition occurs; yet, this is absent when the pressure is increased incrementally to 2.6 GPa. In the new high pressure phase, Z' is 2 and one of the two molecules displays changes in the coordination of one bridging carboxylate from μ2:κO:κO' to μ2:κ(2)O,O':κO', while the other molecule remains unchanged. Despite the significant changes to the molecular connectivity, analysis of the crystal structures shows that the phase transition leaves the spin and oxidation states of the molecules unaltered. Intermolecular interactions in the high pressure crystal structures have been analysed using Hirshfeld surfaces but they cannot explain the origin of the phase transition. The lack of VT in this first oligomeric Co-dioxolene complex is speculated to be due to the coordination geometry of the terminal Co-atoms, which are trigonal bipyramidally coordinated, different from the more common octahedral coordination. The energy that is gained by a hs-to-ls change in Oh is equal to Δ, while in the case of the trigonal bipyramidal (C3v), the energy gain is equal to the splitting between d(z(2)) and degenerate d(x(2) - y(2))/d(xy), which is significantly less.
We present single-crystal high-pressure studies of the apohost of Dianin's compound (DC), as well as its clathrates with ethanol, acetic acid, and isopropanol, up to a pressure of 8.2(1) GPa. Despite having large cavities, these clathrates of DC are found to be very stable when exposed to high pressure, and even the apohost structure, which contains large void space regions, is stable up to pressures above 6.6(1) GPa. The similarity between the compression of the apohost and the DC clathrates is presumably due to the extraordinary strength of the host framework. Bulk modulus and linear compression values are derived for the apohost and DC/acetic acid clathrate. The observed compression is shown to be more isotropic than what is expected from experimental elastic tensor data in the literature, although the compression along the a-axis is the largest for all the studied clathrates. The pressure evolution of the refined atomic displacement parameters is shown to be a sensitive indicator of the accuracy of the crystal structure refinement.
The structures of thermoelectric ZnSb and ZnSb have been studied extensively as a function of temperature but not in detail as a function of pressure. High pressure single crystal X-ray diffraction data allow structure refinements of ZnSb and ZnSb up to 12.8(2) GPa and 10.6(2) GPa, respectively, and in contrast to previous reports without any signs of phase transitions. At high pressure a redistribution of Zn in ZnSb is present, which is distinctly different from the thermal response of the structure. Fitting of an equation of state resulted in bulk moduli of 45(2) and 48(1) GPa for ZnSb and ZnSb, respectively.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.