Crystal and Molecular Structures and Experimentally Determined Charge Densities of Fluorinated Ethenes

Abstract

Crystals of various fluorinated ethenes were grown by in situ crystallization from their melts on a diffractometer, allowing the structures of tetrafluoroethene (C2F4), trifluoroethene (C2HF)3, 1,1-difluoroethene (C2H2F2), (E)-1,2-difluoroethene (C2H2F2), and (Z)-1,2-difluoroethene (C2H2F2) to be determined by X-ray crystallography. Unexpectedly, the C=C bond lengths show only small variations arising from fluorine substitution. These findings are supported by ab initio calculations at a DFT level of theory and the results of topological analyses of the experimentally determined and theoretically calculated charge densities.

Fluorocarbene, fluoroolefin, and fluorocarbyne complexes of Rh

“…The DFT calculated metrics are in good agreement with crystallographic numbers, giving confidence in the DFT metrics for the unknown complexes. One exception appears in (PNP)Rh(C 2 F 4 ) in which the C–C distance for the coordinated alkene (1.354 Å) is only slightly longer than that in C 2 F 4 itself (1.318 Å) 61 and is much shorter than all other transition metal complexes of this perfluoroalkene in the Cambridge Structure Database. 62 In contrast, the DFT calculated value (1.416 Å) is in good agreement with other crystallographically determined values 62 and is much more sensible with respect to calculated WBI values (see below).…”

Sensing Signatures Mediated by Chemical Structure of Molecular Solids in Laser-Induced Plasmas

“…Although the length and topology of the carbon double bond do not evidence significant changes between the two monomers, 38 the large electronegativity of fluorine atoms causes a strong σ bond polarization, thus leading to a weakening of the C=C bond as compared to a regular C-C bond. Since the dissociation energy for the carbon-carbon double bond in tetrafluoroethylene is 67.5 ± 0.5 kcal mol −1 , 39 the most favored rupture of the vaporized C 2 F 4 monomers proceeds via C=C bond breaking 38 instead of through C-F bond rupture, which requires a much larger dissociation energy (130.6 ± 3 kcal mol -1 ). 40 The direct consequence of these binding energies is a larger abundance of CF 2 radicals in the plasma, that can act as precursors for reaction with atmospheric nitrogen.…”

Permanently hydrophilic, piezoelectric PVDF nanofibrous scaffolds promoting unaided electromechanical stimulation on osteoblasts

“…8,9 In the case of piezoelectric polymers, nanofibrous piezoelectric scaffolds can be obtained by controlling the electrospinning parameters. The most studied piezoelectric polymer is poly(vinylidene fluoride) (PVDF) 10 , and its increasing research interest stems from its fascinating properties due to the high electrical dipole moment. 11 Out of the five crystalline phases of PVDF, the most explored ones are the α, β and γ phases.…”