Photocatalysis of Chloroform Decomposition by Tetrachlorocuprate (II) on Dowex 2-X8

Protonation induced redshift in the fluorescence of a pyridine derivative as a potential anti-counterfeiting agent

A simple pyridine-based compound, i.e. (2,4,6-tris(4-(hexyloxy)phenyl)pyridine), was synthesized and exhibited excellent solubility in various organic solvents owing to the presence of three 4-n-hexyloxy chains in its molecular structure. Further, we studied the effect of various solvents on its absorption and emission properties. We observed a greater extent of redshift in the chloroform solvent compared to the rest of the solvents. In fact, the observed redshift was attributed to protonation of the pyridine moiety by HCl (present due to the oxidative photo-decomposition of chloroform) in the solvent. Therefore, we also studied the acidochromic properties of the compound using acetic acid (AA), trifluoroacetic acid (TFA), and hydrochloric acid (HCl). We found that the compound sensed the HCl vapor much more efficiently than the TFA and AA vapours. Additionally, DFT analysis suggested a narrow theoretical bandgap for the protonated molecule when compared to the neutral molecule, explaining the redshift in the absorption and emission spectra of the protonated molecule. Furthermore, the compound exhibited a good level of aggregation induced enhanced emission (AIEE) in the THF-water system. In fact, compounds showing both AIEE and acidochromism are rarely reported in the literature. Finally, we employed it as an anti-counterfeiting agent based on its acid-base vapour sensing capability.

Radical-initiated P,P-metathesis reactions of diphosphanes: evidence from experimental and computational studies

By combining the diphosphanes Ar2P-PAr2, where Ar = C6H5, 4-C6H4Me, 4-C6H4OMe, 3,5-C6H3(CF3)2, it has been shown that P,P-metathesis generally occurs rapidly under ambient conditions. DFT calculations have shown that the stability of unsymmetrical diphosphanes Z2P-PZ'2 is a function of the difference between the Z and Z' substituents in terms of size and electronegativity. Of the mechanisms that were calculated for the P,P-metathesis, the most likely was considered to be one involving Ar2P˙ radicals. The observations that photolysis increases the rate of the P,P-metatheses and TEMPO inhibits it, are consistent with a radical chain process. The P,P-metathesis reactions that involve (o-Tol)2P-P(o-Tol)2 are anomalously slow and, in the absence of photolysis, were only observed to take place in CHCl3 and CH2Cl2. The role of the chlorinated solvent is ascribed to the formation of Ar2PCl which catalyses the P,P-metathesis. The slow kinetics observed with (o-Tol)2P-P(o-Tol)2 is tentatively attributed to the o-CH3 groups quenching the (o-Tol)2P˙ radicals or inhibiting the metathesis reaction sterically.

Halogen-bonded network of trinuclear copper(II) 4-iodo-pyrazolate complexes formed by mutual breakdown of chloro-form and nanojars

Crystals of bis-(tetra-butyl-ammonium) di-μ3-chlorido--tris-(μ2-4-iodo-pyrazolato-κ2N:N')tris-[chlorido-cuprate(II)] 1,4-dioxane hemisolvate, (C16H36N)2[Cu3(C3H2IN2)3Cl5]·0.5C4H8O or (Bu4N)2[CuII3(μ3-Cl)2(μ-4-I-pz)3Cl3]·0.5C4H8O, were obtained by evaporating a solution of (Bu4N)2[{CuII(μ-OH)(μ-4-I-pz)} n CO3] (n = 27-31) nanojars in chloro-form/1,4-dioxane. The decomposition of chloro-form in the presence of oxygen and moisture provides HCl, which leads to the breakdown of nanojars to the title trinuclear copper(II) pyrazolate complex, and possibly CuII ions and free 4-iodo-pyrazole. CuII ions, in turn, act as catalyst for the accelerated decomposition of chloro-form, ultimately leading to the complete breakdown of nanojars. The crystal structure presented here provides the first structural description of a trinuclear copper(II) pyrazolate complex with iodine-substituted pyrazoles. In contrast to related trinuclear complexes based on differently substituted 4-R-pyrazoles (R = H, Cl, Br, Me), the [Cu3(μ-4-I-pz)3Cl3] core in the title complex is nearly planar. This difference is likely a result of the presence of the iodine substituent, which provides a unique, novel feature in copper pyrazolate chemistry. Thus, the iodine atoms form halogen bonds with the terminal chlorido ligands of the surrounding complexes [mean length of I⋯Cl contacts = 3.48 (1) Å], leading to an extended two-dimensional, halogen-bonded network along (-110). The cavities within this framework are filled by centrosymmetric 1,4-dioxane solvent mol-ecules, which create further bridges via C-H⋯Cl hydrogen bonds with terminal chlorido ligands of the trinuclear complex not involved in halogen bonding.

Cube-like Ag/AgCl fabricated via a photoirradiation method and its substantially boosted plasmonic photocatalytic reactivity by an oxidation–chloridization treatment

Cube-like Ag/AgCl species are produced by a photoirradiation method, where substantially boosted plasmonic photocatalytic reactivity has been realized via an oxidation–chloridization treatment.