Optimization of polymeric triiodide membrane electrode based on clozapine-triiodide ion-pair using experimental design

Central composite design (CCD) and response surface methodology (RSM) were developed as experimental strategies for modeling and optimization of the influence of some variables on the performance of a new PVC membrane triiodide ion-selective electrode. This triiodide sensor is based on triiodide-clozapine ion-pair complexation. PVC, plasticizers, ion-pair amounts and pH were investigated as four variables to build a model to achieve the best Nernstian slope (59.9 mV) as response. The electrode is prepared by incorporating the ion-exchanger in PVC matrix plasticized with 2-nitrophenyl octal ether, which is directly coated on the surface of a graphite electrode. The influence of foreign ions on the electrode performance was also investigated. The optimized membranes demonstrate Nernstian response for triiodide ions over a wide linear range from 5.0 x 10(-6) to 1.0 x 10(-2)mol L(-1) with a limit of detection 2.0 x 10(-6) mol L(-1) at 25 degrees C. The electrodes could be used over a wide pH range 4-8, and have the advantages of easy to prepare, good selectivity and fast response time, long lifetime (over 3 months) and small interferences from hydrogen ion. The proposed electrode was successfully used as indicator electrode in potentiometric titration of triiodide ions and ascorbic acid.     

An efficient synthesis of 5‐benzoyloxazolines by regio‐ and stereo‐controlled reaction of N‐substituted 2‐benzoylaziridines under microwave irradiation

Several N‐acyl‐2‐benzoylaziridines were prepared conveniently in good to high yields (71‐93%) and used in the preparation of 5‐benzoyloxazolines (76‐91%) by a regio‐ and stereo‐controlled reaction in the presence of Nal as an efficient catalyst under microwave irradiation in short reaction times (5‐10 mins). The structure of the regioisomeric product was confirmed by X‐ray analysis.     

Suppressing Universal Cathode Crossover in High-Energy Lithium Metal Batteries via a Versatile Interlayer Design**

The universal cathode crossover such as chemical and oxygen has been significantly overlooked in lithium metal batteries using high-energy cathodes which leads to severe capacity degradation and raises serious safety concerns. Herein, a versatile and thin (≈25 μm) interlayer composed of multifunctional active sites was developed to simultaneously regulate the Li deposition process and suppress the cathode crossover. The as-induced dual-gradient solid-electrolyte interphase combined with abundant lithiophilic sites enable stable Li stripping/plating process even under high current density of 10 mA cm⁻². Moreover, X-ray photoelectron spectroscopy and synchrotron X-ray experiments revealed that N-rich framework and CoZn dual active sites can effectively mitigate the undesired cathode crossover, hence significantly minimizing Li corrosion. Therefore, assembled lithium metal cells using various high-energy cathode materials including LiNi_0.7Mn_0.2Co_0.1O₂, Li_1.2Co_0.1Mn_0.55Ni_0.15O₂, and sulfur demonstrate significantly improved cycling stability with high cathode loading.     

Addition of mild electrophiles to a Mo[triple bond]N triple bond and nitrile synthesis via metal-mediated N-atom transfer to acid chlorides

The addition of mild electrophiles to the anionic terminal Mo-nitride {[(t)BuOCO]Mo[triple bond]N]Na(DMF)}(2) (1) and the synthesis of nitriles via metal-mediated N-atom transfer is reported. The X-ray structure of a pivaloylimido intermediate indicates the presence of a weakly coordinated DMF molecule. Kinetic studies confirm that cyclometalation and DMF dissociation occur prior to nitrile extrusion.     

Discrete photopatternable pi-conjugated oligomers for electrochromic devices

Three discrete oligomeric systems including an all-thiophene ( T6) system, a thiophene/phenylene ( TPTTPT) system, and a thiophene/EDOT/phenylene ( TPEEPT) system have been constructed and characterized with emphasis on structural, optical, electrochemical, and spectroelectrochemical properties. For all three chromophores, the radical cation, the dication, and the pi-dimer have been identified and characterized. EPR spectroscopy reveals that the radical cations of TPTTPT and TPEEPT have g values of 2.008-2.012 and peak-to-peak widths in the range 4.2-5.3 G. Formation of the radical cation takes place at a lower potential for TPEEPT than for TPTTPT and T6, whereas subsequent oxidation to the dication occurs more easily for TPTTPT than for TPEEPT and T6. We ascribe this observation to more localized charges in the oxidized species of TPEEPT, which is supported by our finding that the radical cation of TPEEPT is less prone to undergo pi-dimerization than the radical cations of TPTTPT and T6. All the oxidized species are sufficiently stable to allow for optical characterization, and the relative positions of all absorption bands are found to be in agreement with the electrochemical data. For further solid-state modifications of these materials, we have effectively modified the synthetic design and grafted terminal functionalities (e.s. acrylates) onto the discrete oligomers. Of these novel materials, TPEEPT proves to be the most promising anodically coloring material for electrochromics, and it undergoes reversible switching between two different colored states (bright yellow and clear blue) and one almost transparent and color neutral state. Contrast ratios, measured as Delta% T at lambda max, are as high as 62.5%, and switching times are in the range 2-5 s for the coloration process, though significantly longer for the bleaching process. As a proof of concept, we have successfully constructed a simple photopatterned electrochromic device by exploiting the terminal acrylate functionalities of the oligomers in a UV-initiated cross-linking process. To the best of our knowledge, this is the first oligomer-based photopatterned electrochromic device reported in the literature.     

High-yield syntheses and reactivity studies of Fe10 "ferric wheels": structural, magnetic, and computational characterization of a star-shaped Fe8 complex

Convenient, high-yield routes have been developed to [Fe 10(OMe) 20(O 2CR) 10] ( 1) "ferric wheels" involving the alcoholysis of [Fe 3O(O 2CR) 6(H 2O) 3] (+) salts in MeOH in the presence of NEt 3. Reactivity studies have established [Fe 10(OMe) 20(O 2CMe) 10] ( 1a) to undergo clean carboxylate substitution with a variety of other RCO 2H groups to the corresponding [Fe 10(OMe) 20(O 2CR) 10] product. In contrast, the reaction with phenol causes a nuclearity change to give a smaller [Fe 8(OH) 4(OPh) 8(O 2CR) 12] ( 2) wheel. Similarly, reactions of [Fe 10(OMe) 20(O 2CR) 10] with the bidentate chelate ethylenediamine (en) cause a structural change to give either [Fe 8O 5(O 2CMe) 8(en) 8](ClO 4) 6 ( 3) or [Fe 2O(O 2CBu (t))(en) 4](NO 3) 3 ( 4), depending on conditions. Complex 3 possesses a "Christmas-star" Fe 8 topology comprising a central planar [Fe 4(mu 4-O)] (10+) square subunit edge-fused to four oxide-centered [Fe 3(mu 3-O)] (7+) triangular units. Variable-temperature, solid-state dc and ac magnetization studies on complexes 1a- 4 in the 5.0-300 K range established that all the complexes possess an S = 0 ground state. The magnetic susceptibility data for 4 were fit to the theoretical chi M versus T expression derived by the use of an isotropic Heisenberg spin Hamiltonian and the Van Vleck equation, and this revealed an antiferromagnetic exchange parameter with a value of J = -107.7(5) cm (-1). This value is consistent with that predicted by a previously published magnetostructural relationship. Theoretically computed values of the exchange constants in 3 were obtained with the ZILSH method, and the pattern of spin frustration within its core and the origin of its S = 0 ground state have been analyzed in detail.     

Synthesis and characterization of diorganohydrazido(2-) tungsten complexes

Diorganohydrazido(2-) complexes of tungsten (L)Cl4W(NNR2) [R2=Me2, Ph2, -(CH2)5-; L=CH3CN, pyridine] were synthesized by reacting the corresponding 1,1-diorganohydrazine with WCl6, followed by reaction with acetonitrile or pyridine. Crystallographic structure determination of (CH3CN)Cl4W(NNMe2) and (CH3CN)Cl4W(NNPh2) allows a comparison of the structural features of the diorganohydrazido(2-) functionality with varying substituents. Mass spectrometry, thermogravimetric analysis, and preliminary chemical vapor deposition experiments were performed to determine the viability of these complexes as single-source precursors for deposition of WNx and WNxCy films.     

Unusual structural types in manganese cluster chemistry from the use of N,N,N',N'-tetrakis(2-hydroxyethyl)ethylenediamine: Mn8, Mn12, and Mn20 Clusters

The syntheses, crystal structures, and magnetochemical characterization are reported for three new mixed-valent Mn clusters [Mn(8)O(3)(OH)(OMe)(O(2)CPh)7(edte)(edteH(2))](2)CPh) (1), [Mn(12)O(4)(OH)(2)(edte)(4)C(l6)(H(2)O)(2)] (2), and [Mn(20)O(8)(OH)(4)(O(2)CMe)(6)(edte)(6)](ClO(4))(2) (3) (edteH(4) = (HOCH(2)CH(2))(2)NCH(2)CH(2)N(CH(2)CH(2)OH)(2) = N,N,N',N'-tetrakis(2-hydroxyethyl)ethylenediamine). The reaction of edteH(4) with Mn(O(2)CPh)(2), MnCl(2), or Mn(O(2)CMe)(2) gives 1, 2, and 3, respectively, which all possess unprecedented core topologies. The core of 1 comprises two edge-sharing [Mn(4)O(4)] cubanes connected to an additional Mn ion by a micro(3)-OH- ion and two alkoxide arms of edteH(22-). The core of 2 consists of a [Mn(12)(micro(4-)O)(4)](24+) unit with S4 symmetry. The core of 3 consists of six fused [Mn(4)O(4)] cubanes in a 3 x 2 arrangement and linked to three additional Mn atoms at both ends. Variable-temperature, solid-state dc and ac magnetization (M) studies were carried out on complexes 1-3 in the 5.0-300 K range. Fitting of the obtained M/Nmicro(B) vs H/T data by matrix diagonalization and including only axial zero-field splitting (ZFS) gave ground-state spin (S) and axial ZFS parameter (D) of S = 8, D = -0.30 cm-1 for 1, S = 7, D = -0.16 cm-1 for 2, and S = 8, D = -0.16 cm-1 for 3. The combined work demonstrates that four hydroxyethyl arms on an ethylenediamine backbone can generate novel Mn structural types not accessible with other alcohol-based ligands.     

Postpolymerization modification of a hydroxy monolith precursor. Part II. Epoxy biphenyl modified poly (hydroxyethyl methacrylate‐co‐pentaerythritol triacrylate) monolithic capillary columns for reversed‐phase capillary electrochromatography based on π–π and hydrophobic interactions

In this second part of the series of investigations involving the postpolymerization modification of a hydroxy monolith (OHM) capillary column, the surface hydroxyl groups were reacted with epoxy biphenyl thus yielding the so‐called Biphenyl OHM capillary column. The modification involved the epoxy ring opening of the 2‐biphenylyl glycidyl ether catalyzed by BF₃ and its subsequent reaction with the hydroxyl groups on the OHM precursor surface. The Biphenyl OHM capillary column thus obtained exhibited the typical reversed phase behavior by primarily hydrophobic interactions vis‐à‐vis the homologous series of alkyl benzenes and in addition by π–π interactions toward nitroalkane homologous series via their π‐electron rich nitro groups. This dual retention mechanism was very distinctly observed with a set of PAH solutes in the sense that the k values of the PAH solutes were comparable to those obtained on a more non polar stationary phase, namely the Epoxy OHM C‐16 reported in the preceding article. Other aromatic solutes showed the dual retention mechanism on the Biphenyl OHM capillary including phenols, anilines derivatives, and phenoxy acid herbicides. The Biphenyl OHM capillary exhibited good reproducibility from run‐to‐run, day‐to‐day, and column‐to‐column.     

A selective,sensitive and label-free visual assay of fructose using anti-aggregation of gold nanoparticles as a colorimetric probe

A new convenient colorimetric sensor for fructose based on anti-aggregation of citrate-capped gold nanoparticles(Au NPs) is presented. 4-Mercaptophenylboronic acid(MPBA) induces the aggregation of Au NPs, leading to a color change from red to blue. Fructose as a potent competitor has strong affinity for MPBA and a borate ester is formed between MPBA and fructose. There is an obvious color change from blue to red with increasing the concentration of fructose. The anti-aggregation effect of fructose on Au NPs was seen by the naked eye and monitored by UV–vis spectra. Our results showed that the absorbance ratio(A_(519)/A_(640)) was linear with fructose concentration in the range of 0.032–0.96 μmol/L(R~2= 0.996), with a low detection limit of 0.01 μmol/L(S/N = 3). Notably, a highly selective recognition of fructose was shown against other monosaccharide and disaccharide(glucose, mannose, galactose,lactose and saccharose). With anti-aggregation assays higher selectivity is achievable. The results of this work provide a rapid method for evaluating the quantitative analysis of fructose in human plasma at physiologically meaningful concentrations and at neutral pH. The proposed procedure can be used as an efficient method for the precise and accurate determination of fructose.