Mg-Al-Cr2O7 Hydrotalcite-Like Catalysts Synthesized at Different pH Values for Styrene Oxidation

Dichromate anions were intercalated between two consecutive hydroxide layers of [Mg0.6Al0.4(OH)2]0.40+ via co-precipitation at different pH conditions. The physico-chemical properties of the obtained solids were examined by physical methods such as X-ray diffraction (XRD), Infrared (IR), Scanning Electron Microscopy (SEM), Brunauer-Emmett-Teller (BET) and Energy-Dispersive Spectroscopy (EDS). The experimental results indicated that the amount of dichromate anions in the catalysts varies with the pH media. Also, the morphology, structure and chemical composition of the materials depends strongly on the preparation conditions. The Mg-Al-Cr2O7 hydrotalcite-like compounds are used as heterogeneous catalysts for the styrene oxidation with H2O2 at mild conditions. The styrene conversion is about 20-50% while styrene selectivity remains rather high.

A luminescent inorganic–organic hybrid, [Cd(C16H10N2O8S)(H2O)], for the selective and recyclable detection of chromates and dichromates in aqueous solution

A three-dimensional inorganic–organic hybrid [Cd(H2L)(H2O)], was shown to exhibit good catalytic activity as well as to detect highly toxic chromate and dichromate anions in aqueous medium with good selectivity.

Crystal structure of 1,4,8,11-tetraazoniacyclotetradecane bis(dichromate) monohydrate from synchrotron data

The asymmetric unit of the hydrated title salt, (C10H28N4)[Cr2O7]2·H2O [C10H28N4= H4(cyclam) = 1,4,8,11-tetraazoniacyclotetradecane], contains two half-cations (both completed by crystallographic inversion symmetry), two dichromate anions and one water molecule. The two [CrO7]2−anions exhibit a nearly staggered conformation, with bridging angles of 133.37 (11) and 136.28 (12)°. The distortions of the dichromate anions are due to their participation in hydrogen-bonding interactions with the water molecule and the cations. Intermolecular hydrogen bonds involving the cyclam N—H groups and water O—H groups as donor groups, and the O atoms of the dichromate anions as acceptor groups give rise to a three-dimensional network.

Bis(3-phenylpropylammonium) dichromate (VI): Synthesis, crystal structure and spectroscopy studies

The structure of bis(3-Phenylpropylammonium) dichromate(VI) was determined from X-ray diffraction data. The compound crystallizes in the monoclinic system (space group P21/c) with the lattice parameters: a = 7.9379(2) Å, b = 36.2439(16) Å, c = 7.5753(3) Å; B = 96.069(2); V= 2167.20(14) Å3 and Z = 4. The structure was solved from 4959 independent reflections with R = 0.043 and Rw = 0.105. The structure consists of discrete dichromate anions (Cr2O72-) with eclipsed conformation stacked in layers parallel to (a, c) plane at y = 0 and ½. These anions are linked via the 3-phenylpropylammonium cations by N—H…O and C—H…O hydrogen bonds, forming a two-dimensional supramolecular network. Crystal structure and spectroscopic studies are reported for the bis(3-phenylpropylammonium) dichromate(VI).