The Role of Nonbonded Sulfur−Oxygen Interaction in the Dissociative Electron Transfer to Nitro-Substituted Arenesulfenyl Chlorides

Clusteroluminescence from Cluster Excitons in Small Heterocyclics Free of Aromatic Rings

The study of nonconventional luminescence is important for revealing the luminescence of natural systems and has gradually drawn the attention of researchers in recent years. However, the underlying mechanism is still inexplicable. Herein, the luminescence behavior of two series of simple, heteroatom-containing small molecules without aromatic rings, i.e., maleimide and succinimide derivatives, are studied to gain further mechanistic insight into the nonconventional luminescence process. It has been unveiled that all the molecules exhibit bright and visible luminescence in concentrated solution and solid state and the formation of clusters is the root cause for such behaviors, which can effectively increase the possibility of both the nonradiative n-π* and favorable π-π* transitions and stabilize the excitons formed in the excited state. The distinctive luminescent phenomena and intriguing mechanism presented in this work will be significant for understanding the mechanism of clusteroluminescence and provide new strategies for the rational design of novel luminescent materials.

Crystal structure of 1-(2,4,6-trichlorobenzoyloxy) benzotriazole (TCB-OBt): observation of uncommon intermolecular oxygen–oxygen interaction and synthetic application in amidation

A simple active ester (TCB-OBt) has a significant hallmark in synthetic organic chemistry and materials science.

Exploiting the role of stereoelectronic effects to design the antagonists of the human complement C3a receptor

Stereoelectronic effects are crucial in governing the conformational behaviour of small molecules bearing heterocyclic rings adjacent to amides.

Reversible crystal-to-crystal chiral resolution: making/breaking non-bonding S⋯O interactions

Unconventional non-covalent interactions are the key to reversible chiral resolution in polycrystalline samples of a small, achiral molecule.

Breaking bonds with electrons: stepwise and concerted reductive cleavage of C–S, C–Se and Se–CN bonds in phenacylthiocyanates and phenacylselenocyanates

The mechanistic aspects of the electrochemical reduction of phenacylthio- and selenocyanates have been studied.

Observation of novel oxygen⋯oxygen interaction in supramolecular assembly of cobalt(iii) Schiff base complexes: a combined experimental and computational study

Structural features of two newly synthesized mononuclear cobalt(iii) complexes have been examined by DFT calculations.

Hammett correlations as test of mechanism of CO-induced disulfide elimination from dinitrosyl iron complexes

The use of Hammett correlations provide experimental evidence for an unusual role of the frontier molecular orbitals of an iron dinitrosyl unit in CO induced reductive elimination of disulfide.

IR, Raman, SERS and computational study of 2-(benzylsulfanyl)-3,5-dinitrobenzoic acid

FT-IR and FT-Raman spectra of 2-(benzylsulfanyl)-3,5-dinitrobenzoic acid were recorded and analyzed. SERS spectra were recorded in silver colloid, silver electrode and silver substrate. The vibrational wavenumbers were computed using HF and DFT quantum chemical calculation methods. The data obtained from wavenumber calculations are used to assign vibrational bands obtained in infrared and Raman spectra as well as in SERS of the studied molecule. Potential energy distribution was done using GAR2PED program. The geometrical parameters of the title compound are in agreement with the reported similar derivatives. The presence of phenyl ring modes in the SERS spectra suggests a tilted orientation with respect to the metal surface in all cases. In all the three SERS spectra the NO2 moiety shows an enhancement, which indicates the interaction with the metal surface. The first hyperpolarizability is high and the title compound is an attractive object for future studies of nonlinear optics.

Physical structure of standing-up aromatic SAMs revealed by scanning tunneling microscopy

Long-range-ordered aromatic SAMs are formed on Au(111) using 4-nitrophenyl sulfenyl chloride as a precursor. Although the main structure is a √3 × √3 with a molecular density similar to that usually found for aliphatic SAMs, particular spots presenting specific shapes are also observed by STM. These include hexagons, partial hexagons, parallelograms, and zigzags resulting from specific arrangements of adsorbed molecules. These molecular arrangements are reversible as they form and dissociate or "vanish" in various areas on the surface. STM shows that these particular structures provide some order to their surrounding because areas void of these structures look less ordered. More interestingly, STM shows submolecular details of the molecules involved in forming these structures, hence providing direct experimental evidence for the ability of the STM to provide physical structure information of standing up SAMs. This is indeed a heavily debated question, and this work reports the first experimental example where submolecular physical structure is revealed by STM for standing-up SAMs.

Radical/Ion Pair Formation in the Electrochemical Reduction of Arene Sulfenyl Chlorides

Important aspects of the electrochemical reduction of a series of substituted arene sulfenyl chlorides are investigated. A striking change is observed in the reductive cleavage mechanism as a function of the substituent on the aryl ring of the arene sulfenyl chloride. With p-substituted phenyl chlorides a "sticky" dissociative ET mechanism takes place where a concerted ET mechanism leads to the formation of a radical/anion cluster before decomposition. With o-nitropheyl sulfenyl substituted chlorides a stepwise mechanism is observed where through space S...O interactions play an important role stabilizing both the neutral molecules and their reduced forms. Disulfides are generated through a nucleophilic reaction of the two-electron reduction produced anion (arenethiolate) on the parent molecule. The dissociative electron transfer theory, as well as its extension to the case of strong in-cage interactions between the produced fragments, along with the gas phase chemical quantum calculations results helped rationalize both the observed change in the ET mechanism and the occurrence of the "sticky dissociative" ET mechanism. The radical/anion pair interactions have been determined both in solution as well as in gas phase. This study shows that despite the low magnitude of in-cage interactions in acetonitrile as compared to in the gas phase, their existence strongly affects the kinetics of the involved reactions. It also shows that, as expected, these interactions are reinforced by the existence of strong electron-withdrawing substituents.

Sticky Dissociative Electron Transfer to Polychloroacetamides. In-Cage Ion−Dipole Interaction Control through the Dipole Moment and Intramolecular Hydrogen Bond

The reductive cleavage of chloro- and polychloroacetamides in N,N-dimethylformamide gives new insights into the nature of the in-cage ion radical cluster formed upon dissociative electron transfer. Within the family of compounds investigated, the electrochemical reduction leads to the successive expulsion of chloride ions. At each stage the electron transfer is concerted with the breaking of the C-Cl bond and acts as the rate-determining step. The reduction further leads to the formation of the corresponding carbanion with the injection of a second electron, which is in turn protonated by a weak acid added to the solution. From the joint use of cyclic voltammetric data, the sticky dissociative electron-transfer model and quantum ab initio calculations, the interaction energies within the cluster fragments (*R, Cl-) resulting from the first electron transfer to the parent RCl molecule are obtained. It is shown that the stability of these adducts, which should be viewed as an essentially electrostatic radical-ion pair, is mainly controlled by the intensity of the dipole moment of the remaining radical part and may eventually be strengthened by the formation of an intramolecular hydrogen bond, as is the case with 2-chloroacetamide.