Deposition of Phosphate Nanoparticles onto Textile Fabrics via Sol-gel Method and Their Kinetics Desorption Studies

In this paper, phosphate nanoparticles were coated on cotton(CO) and polyester(PES) textile surfaces by sol-gel method using tetraethylorthosilicate(TEOS) and chloropropyltriethoxysilane(CPTS) as silica precursors. The deposited nanoparticles were observed with scanning electronic microscopy energy-dispersive X-ray spectroscopy (SEM-EDX). The release kinetics of phosphorus(P) from these textiles into the aqueous medium(Aq), acid(Ac), and basic(Ba) artificial sweats were then studied. The released amount of phosphorus was evaluated by the inductively coupled plasma(ICP) according to ISO NF EN 16711-2 procedure. The results revealed that the release of P into the aqueous medium is lower than in the artificial sweat. The kinetics data[the phosphorus desorption amount(mg/g) as a function of time] were modeled according to five models:the first order, the second order, the third order, simple Elovich and parabolic diffusion. The suitable model was chosen based on the coefficient of determination(R²) and the calculation of the sum of the absolute errors(EABS), which describes the error between the theoretical and experimental values. SEM observations were also carried out on the fabrics after desorption in order to show the impact of desorption on their morphology. Furthermore, the impact of P release on the tensile strength of CO and PES fabrics was investigated using a uniaxial tensile test. The thermal stability of all samples before and after desorption was assessed by thermogravimetric analysis(ATG).     

Ab initio and density functional theory studies of peri- and regioselectivity in 1,3-dipolar cycloaddition reaction of 1,2-diazepine with nitrile oxide

The first systematic study of all dipolarophile sites of 1,2-diazepine towards nitrile oxide as dipole via 1,3-dipolar cycloaddition reactions has been carried out. To this end, the structural and energetic aspects of seventy-two isomers were determined by means of ab initio and density functional theory methods at different levels of accuracy were performed on all peri- and regio-isomeric forms. The agreement between the calculated and the experimental geometries, regio- and periselectivity of the studied reaction is good in all instances. The dipole condensation with the norcaradiene dipolarophile has been considered seemingly for the first time. The bis-cycloadduct 3a,3b,7,10a-tetrahydro-10 H-[1,2] oxazolo [4,5-d] [1,2,4] oxadiazolo [4,5-b] [1,2] diazepine is the most stable one as predicted by all methods used in this work. However, the tautomerization study of all forms of 1,2-diazepine seems to rule out the existence of the tautomeric form that provides the above mentioned cycloadduct. Consequently, the bis-cycloadduct 5,10-dioxa-1,2,4,11-tetrazatricyclo[7,3,1,0^2,6]trideca-3,7,11-triene is the favored product of this reaction.     

Preparation and coordination complex of the first imine-bridged tetrathiafulvalene-pyridine donor ligand

The first imine-bridged pyridyltetrathiafulvalene building block (TTF-CH=N-Py, 1) has been synthesized via the Schiff base condensation of formyltetrathiafulvalene and 2-aminopyridine. The preparation, X-ray crystal structure, electrochemical and magnetic characterization of a 1:1 copper complex [CuII(hfac)2(TTF-CH=N-Py)] (2) are reported. The crystal structure reveals that the imine N atom participates in chelation to the paramagnetic center, thus making this ligand an attractive precursor for the assembly of pi-d systems.     

Covalent Patterning of 2D MoS2

The development of an efficient method to patterning 2D MoS₂ into a desired topographic structure is of particular importance to bridge the way towards the ultimate device. Herein, we demonstrate a patterning strategy by combining the electron beam lithography with the surface covalent functionalization. This strategy allows us to generate delicate MoS₂ ribbon patterns with a minimum feature size of 2 μm in a high throughput rate. The patterned monolayer MoS₂ domain consists of a spatially well-defined heterophase homojunction and alternately distributed surface characteristics, which holds great interest for further exploration of MoS₂ based devices.     

Activation/driving force relationships for cyclopropylcarbinyl --> homoallyl-type rearrangements of radical anions

By using direct and indirect electrochemical methods, rate constants (ko) for cyclopropane ring opening of radical anions derived from the one-electron reduction of trans-1-benzoyl-2-phenylcyclopropane, trans-1-benzoyl-2-vinylcyclopropane, 2-methylenecyclopropyl phenyl ketone, spiro[anthracene-9,1'-cyclopropan-10-one], 3-cyclopropylcyclohex-2-en-1-one, and 3-(1-methylcyclopropyl)cyclohex-2-en-1-one were determined. Qualitatively, rate constants for ring opening of these (and other cyclopropyl- and cyclobutyl-containing radical anions) can be rationalized on the basis of the thermodynamic stability of the radical anion, the ability of substituents on the cyclopropyl group to stabilize the radical portion of the distonic radical anion, and the stability of the enolate portion of the distonic radical anion. On the basis of this notion, a thermochemical cycle for estimating deltaG(o) for ring opening was presented. For simple cyclopropyl-containing ketyl anions, a reasonable correlation between log(ko) and deltaG(o) was found, and stepwise dissociative electron transfer theory was applied to rationalize the results. Activation energies calculated with density functional theory (UB3LYP/6-31+G*) correlate reasonably well with measured log(ko). The derived log(ko) and deltaG(o) and log(ko) vs E(a) plots provide the basis for a "calibration curve" to predict rate constants for ring opening of radical anions derived from carbonyl compounds, in general.     

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.     

High-level ab initio calculations on CH+2(2A1) + PO(2II) reactions

We present ab initio calculations carried out in the framework of the G 2 theory on the singlet and triplet potential energy surfaces corresponding to the gas-phase between CH⁺₂ and PO. The global minimum of both potential energy surfaces is a cyclic singlet-state cation. Oxygen attachment of PO to CH⁺₂ in a triplet configuration is accompanied by a P(SINGLEBOND)O bond fission, with the result that the corresponding global minimum is an ion-dipole complex between P⁺(³P) and formaldehyde. This is also consistent with the fact that our results predict the formation of formaldehyde to be highly exothermic, either as a neutral or as radical cation. Both charge-transfer processes yielding CH₂(³B₁) or CH₂(¹A₁) are also exothermic. The formation of other carbon and oxygen containing species are endothermic. © 1996 John Wiley & Sons, Inc.     

Experimental and theoretical push‐pull Chemo‐ and regioselectivity in 1,3‐Dipolar cycloaddition reactions: the case of benzotriazepin‐5‐one with mesitylnitrile oxide

A novel heterocyclic compound 3‐mesityl‐5‐methyl‐4,5,11,11a‐tetrahydro‐6H‐[1,2,4]oxadiazolo [5,4‐b][1,3,4]benzotriazépin‐6‐one 4 has been synthesised by a 1,3 dipolar cycloaddition (13DC) reaction of 1,3,4‐benzotriazepin‐5‐one 1 with mesitylnitrile oxide 3 . The reaction, beside its synthetic interest, has shown to be completely chemo‐ and regioselective. The structure of the compound was determined by X‐ray crystallography and analysed by spectral methods (NMR and mass spectrometry). The molecular mechanism for the reaction has been studied using quantum mechanical calculations at the B3LYP/6‐31G* theory level. Two mechanisms are possible for the formation of the cycloadduct 4 . The first one involves a 13DC reaction between 1 , as dipolarophile and 3 , as dipole. Analysis of the results indicates that it takes place along asynchronous concerted bond‐formation process with a very low polar character. The regioselectivity obtained from the calculations are in complete agreement with the unique formation of the cycloadduct 4 . The second mechanism is initiated by the nucleophilic attack of the N3 nitrogen of the tautomer form of 2 , to the C5 carbon of the nitrile oxide 3 to yield an amidoxime. However, the large energy involved in this addition prevents this mechanism. The large energy difference between the tautomers 1 and 2 , makes that only the C?N site of benzotriazepin‐5‐one 1 could act as a dipolarophile site. This fact makes the 13DC reaction to be chemoselective. The analysis of global electrophilicity of the reagents allows explaining the low polar character of these 13DC reactions. Copyright © 2007 John Wiley & Sons, Ltd.     

Cyclopropylcarbinyl --> homoallyl-type ring opening of ketyl radical anions. Structure/reactivity relationships and the contribution of solvent/counterion reorganization to the intrinsic barrier

[reaction: see text] Following a protocol developed by Mathivanan, Johnston, and Wayner (J. Phys. Chem. 1995, 99, 8190-8195), the radical anions of several cyclopropyl- and oxiranyl-containing carbonyl compounds were generated in an effort to measure the rate constants for their ring opening (k(o)) by laser flash photolysis. The results of these experiments are compared to those obtained from earlier electrochemical studies, and the combined data set is used to rationalize the kinetics of radical anion ring opening in a general context by using Saveant's theory pertaining to stepwise dissociative electron transfer (Acc. Chem. Res. 1993, 26, 455-461). Compared to cyclopropylcarbinyl --> homoallyl rearrangements of neutral free radicals, at comparable driving force, the radical anion ring openings are slightly slower. The small difference in rate is attributed to the contribution of an additional, approximately 2 kcal/mol, solvent reorganization component for the radical anion rearrangements. The solvent reorganization energy for ring opening of these radical anions is believed to be small because the negative charge does not move appreciably in the progression reactant --> transition state --> product.