Zweidimensionales Eis und H₅O₂ ⁺-Ionen. Zur Bildung und Struktur tiefschmelzender molekularer und ionischer Hemi-bis Hexahydrate halogenierter Essigsäuren CCl_nF_3-nCOOH (n = 1 bis 3) [1] / Two-Dimensional Ice and H₅O₂ ⁺ Ions. On Formation and Structure of Low-Melting Molecular and Ionic Hemi-through Hexahydrates of Haloacetic Acids CCl_nF_3-nCOOH (n = 1 to 3) [1]

Abstract

Hydrate formation o f haloacetic acids CCl"F3_"COOH (n = 1, 2, 3) has been studied by D TA and tem perature-dependent X-ray powder diffraction, and evidence obtained for five phases, all melting at temperatures below ambient. The hydrates have been confirmed and further characterized by their crystal structures at -1 5 0 °C. Three lower hydrates, CC12F C O O H 0.5H -> 0 (space group P2,/c and Z = 8 formula unites per unit cell), CC1F2C 0 0 H H 20 (P2,/c, Z = 4), and CC1F2C 0 0 H -4 H 20 (P I, Z = 2), have molecular structures with the acid and water m olecules hydrogen-bonded in two-dimensional arrays. The structures of the remaining hydrates, CCl2F C O O H -6H 20 and CC13C 0 0 H -6 H 20 (sim i lar, but not isotypic, both P 1 and Z = 2), are ionic, as (H s0 2+)(C X 3C 0 Ö ) -4 H 20 , and threedimensional. The neutral water molecules are hydrogen-bonded in ice-like layers rare in crystal chemistry. A lso, CCl2FCOOH is established only as the second acid o f which a lower hydrate is molecular and a higher one ionic. 0 9 3 2 -0 7 7 6 /9 6 /0 4 0 0 -0 5 3 6 $0 6 .0 0 © 1996 V erlag der Z eitschrift für N aturforschung. A ll rights reserved. D

Molecular and supramolecular ionic aggregates HxOyzin organic and organometallic crystalline hydrates

“…The crystal of RABCOI ( Fig. 12; Dahlems et al, 1996) contains a three-dimensional polymeric network in which Zundel cations (green O atoms) link successive two-dimensional sheets of fused hexameric rings of water molecules (red O atoms).…”

Structural modifications of dodecatungstophosphoric acid hexahydrate induced by temperature in the 10–358 K range. In situ high-resolution neutron powder diffraction investigation

“…5b). A rapid survey of the structure of the dioxonium ion obtained from X-ray single crystal diffraction at low temperature [30][31][32][33] or near room temperature [34][35][36][37], where the hydrogen atoms are located give similar results. Therefore, for the H5O2 + detection in a crystal structure, an Ow...Ow distance in the range (2.40-2.46 A˚ ) could be used as the most frequent.…”

Modification of 2D Water That Contains Hexameric Units in Chair and Boat Conformations—A Contribution to the Structural Elucidation of Bulk Water

“…[9,21] Only a few structures that contain solely edge-sharing hexameric rings have been characterized so far by X-ray crystallography and, interestingly, the conformations of the water layers have been different in each case, being allchair, [24] all-boat [25] or an intermediate of them. [26][27][28][29] Of these conformers, only that having an all-boat conformation [25] has a structural motif similar to the one found in ice I h (Figure 1). [30] Although one of the structures has an all-chair conformation, [24] it is apparent that its configuration (all-cis) is different from the one found in ice I h (all-trans).…”