The effect of annealing temperature on structural and optical properties of undoped and Cu doped CdS thin films

Cadmium sulphide (CdS) thin films were prepared chemical bath deposition technique. The films were doped with copper using the direct method consisting in the addition of a copper salt in the deposition bath of CdS. The doped films were annealed in air, at 250, 300 and 350 °C, for 1 h. The deposition films were characterized with X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive analysis by X-rays (EDAX) and optical properties of CdS thin films before and after Cu doping. XRD analysis shows that the films are polycrystalline in nature with cubic crystalline structure. The various parameters such as crystallite size, micro strain and dislocation density were evaluated. SEM study shows that the total substrate surface is well covered by uniformly distributed spherical shaped grains. Optical transmittance study shows the presence of direct transition with band gap energy decrease 2.5–2.2 eV.     

Chelating, bridging, and chain structures within Ag(I) and Cu(I) complexes of bis(nicotinyloxy), bis(isonicotinyloxy), and bis(pyrimidine-5-carboxyloxy)-1,8-disubstituted anthraquinone ligands

Reaction of Ag(I) and Cu(I) [M(NCCH₃)₄]X (X = BF₄⁻ and PF₆⁻) salts with 1,8-bis(nicotinyloxy)anthracene-9,10-dione (1), 1,8-bis(isonicotinyloxy)anthracene-9,10-dione (2), and 1,8-bis(pyrimidine-5-carboxyloxy)anthracene-9,10-dione (3), yield new chelating and bridging complexes and two new coordination polymers. The bridging capabilities of ligands 1 and 2 have not been demonstrated before, and ligand 1, by itself, has the flexibility to produce either chelated or bridged structures and an unusual ladder coordination polymer. The tetradentate ligand 3 also produces a one-dimensional coordination polymer in the presence of one equivalent of Ag(I). All complexes have been characterized by X-ray crystallography.     

Difluorotetrakis(2‐oxypyridine)dirhenium(III) – Preparation,Crystallographic Structure,and Electrochemical Properties

The solid‐state‐melt reaction of (NH₄)₂[Re₂F₈] · 2H₂O with 2‐hydroxypyridine (2‐HOpy) produced dark‐red Re₂(2‐Opy)₄F₂ ( 1 ). This air‐stable compound was obtained in crystalline form as 1· CHCl₃. It was characterized in the solid state by single‐crystal X‐ray diffraction and in solution by UV/Vis spectroscopy and cyclic voltammetry. 1· CHCl₃ forms triclinic crystals with α = 8.3254(5) Å, b = 8.5563(5) Å, c = 11.6784(8) Å, α = 82.723(3)°, β = 75.769(3) °, γ = 64.407(2) °. The Re–Re and Re–F distances were 2.2091(7) and 2.115(6) Å, respectively. The molecule is isostructural with the corresponding chloro derivative.     

The Growth Factors and Cytokines of Dental Pulp Mesenchymal Stem Cell Secretome May Potentially Aid in Oral Cancer Proliferation

Background: Growth factors and cytokines responsible for the regenerative potential of the dental pulp mesenchymal stem cell secretome (DPMSC-S) are implicated in oral carcinogenesis. The impact and effects of these secretory factors on cancer cells must be understood in order to ensure their safe application in cancer patients. Objective: We aimed to quantify the growth factors and cytokines in DPMSC-S and assess their effect on oral cancer cell proliferation. Materials and methods: DPMSCs were isolated from patients with healthy teeth (n = 5) that were indicated for extraction for orthodontic reasons. The cells were characterized using flow cytometry and conditioned medium (DPMSC-CM) was prepared. DPMSC-CM was subjected to a bead-based array to quantify the growth factors and cytokines that may affect oral carcinogenesis. The effect of DPMSC-CM (20%, 50%, 100%) on the proliferation of oral cancer cells ({"type":"entrez-nucleotide","attrs":{"text":"AW123516","term_id":"6099046"}}AW123516) was evaluated using a Ki-67-based assay at 48 h. AW13516 cultured in the standard growth medium acted as the control. Results: VEGF, HCF, Ang-2, TGF-α, EPO, SCF, FGF, and PDGF-BB were the growth factors with the highest levels in the DPMSC-CM. The highest measured pro-inflammatory cytokine was TNF-α, followed by CXCL8. The most prevalent anti-inflammatory cytokine in the DPMSC-CM was IL-10, followed by TGF-β1 and IL-4. Concentrations of 50% and 100% DPMSC-CM inhibited Ki-67 expression in AW13516, although the effect was non-significant. Moreover, 20% DPMSC-CM significantly increased Ki-67 expression compared to the control. Conclusions: The increased Ki-67 expression of oral cancer cells in response to 20% DPMSC-CM indicates the potential for cancer progression. Further research is needed to identify their effects on other carcinogenic properties, including apoptosis, stemness, migration, invasion, adhesion, and therapeutic resistance.     

Complexation,crystallography, and electrochemistry of new chelating nicotinyl and thiazolyl anthraquinone ligands

Chelating anthraquinone ligands that contain nicotinyl and thiazolyl binding units have been synthesized. The complexation chemistry of these new ligands has also been explored using cadmium(II), lead(II), and ruthenium(II). The nicotinic substituted anthraquinone acts as a bidentate ligand, while the thiazolyl substituted anthraquinone binds in a tetradentate arrangement, not previously observed. Due to steric limitations, the number of these ligands that can coordinate to metal centers appears limited to bis-substituted products. Crystallographic data for both the free ligands and the cadmium and lead complexes are reported. Electrochemical data indicate that interaction does not take place between the intraannular carbonyl group and the neighboring metal centers within these complexes.     

Radical-anionic cyclizations of enediynes: remarkable effects of benzannelation and remote substituents on cyclorearomatization reactions

The reasons for large changes in the energetics of C1-C5 and C1-C6 (Bergman) cyclizations of enediynes upon one-electron reduction were studied by DFT and Coupled Cluster computations. Although both of these radical-anionic cyclizations are significantly accelerated relative to their thermal counterparts, the acceleration is especially large for benzannelated enediynes, whose reductive cyclizations are predicted to proceed readily under ambient conditions. Unlike their thermal analogues, the radical-anionic reactions can be efficiently controlled by remote substitution, and the effect of substituent electronegativity is opposite of the effect on the thermal cycloaromatization reactions. For both radical-anionic cyclizations, large effects of benzannelation and increased sensitivity to the properties of remote substituents result from crossing of out-of-plane and in-plane MOs in the vicinity of transition states. This crossing leads to restoration of the aromaticity decreased upon one-electron reduction of benzannelated enediynes. Increased interactions between nonbonding orbitals as well as formation of new aromatic rings (five membered for the C1-C5 cyclization and six membered for C1-C6 cyclizations) are the other sources of increased exothermicity for both radical-anionic cyclizations. The tradeoff between reduction potentials and cyclization efficiency as well as the possibilities of switching of enediyne cyclization modes (exo or C1-C5 vs endo or C1-C6)) under kinetic or thermodynamic control conditions are also outlined.     

Triplet acetylenes as synthetic equivalents of 1,2-bicarbenes: phantom n,pi state controls reactivity in triplet photocycloaddition

Diaryl acetylenes, in which one of the aryl groups is either a pyridine or a pyrazine, undergo efficient triplet state photocycloaddition to 1,4-cyclohexadiene with formation of 1,5-diaryl substituted tetracyclo[3.3.0.0(2,8).0(4,6)]octanes (homoquadricyclanes). In the case of pyrazinyl acetylenes, the primary homoquadricyclane products undergo a secondary photochemical rearangement leading to diaryl substituted tricyclo[3.2.1.0(4,6)]oct-2-enes. Mechanistic and photophysical studies suggest that photocycloaddition proceeds through an electrophilic triplet excited state whereas the subsequent rearrangement to the tricyclooctenes proceeds through a singlet excited state. Chemical and quantum yields for the cycloaddition, in general, correlate with the electron acceptor character of aryl substituents but are attenuated by photophysical factors, such as the competition between the conversion of acetylene singlet excited state into the reactive triplet excited states (intersystem crossing: ISC) and/or to the radical-anion (photoelectron transfer from the diene to the excited acetylene: PET). Dramatically enhanced ISC between pi-pi S(1) state and "phantom" n,pi triplet excited state is likely to be important in directing reactivity to the triplet pathway. The role of PET can be minimized by the judicious choice of reaction conditions (solvent, concentration, etc.). From a practical perspective, such reactions are interesting because "capping" of the triple bond with the polycyclic framework orients the terminal aryl (4-pyridyl, 4-tetrafluoropyridyl, phenyl, etc.) groups in an almost perfect 60 degrees angle and renders such molecules promising supramolecular building blocks, especially in the design of metal coordination polymers.     

Sigma-antiaromaticity in cyclobutane,cubane, and other molecules with saturated four-membered rings

Dissected nucleus-independent chemical shift (NICS) analyses of cycloalkanes and cage hydrocarbons reveal contrasting ring current effects, diatropic in three- and five-membered and paratropic in four-membered ring systems. The large shielding effects of the C-C bonds of the archetypal sigma-aromatic, cyclopropane, are magnified in tetrahedrane and related structures. The remarkable deshielding effect of the cyclobutane C-C(sigma) bonds is general: cubane and cages with four-membered rings are strongly deshielding (i.e., sigma-antiaromatic).[structure--see text]     

Development and validation of a multiresidue method for the simultaneous determination of organophosphorus insecticides and their toxic metabolites in sugarcane juice and refined sugar by gas chromatography with flame photometric detection

A multiresidue method has been developed and validated for the simultaneous determination of organophosphorus insecticides and their toxic metabolites in sugarcane juice and refined sugar by gas chromatography with flame photometric detection. Limits of quantification of the method varied between 0.007 and 0.01 μg/g. Ethyl acetate based extraction followed by dispersive solid‐phase extraction cleanup with primary secondary amine yielded internationally acceptable recoveries of acephate, chlorpyrifos, dichlorvos, monocrotophos, malathion, malaoxon, phorate, phorate‐sulfoxide, phorate‐oxon, phorate‐sulfone, and quinalphos from selected matrices. The recoveries of target analytes from cane juice were 75.55 ± 0.5–102.57 ± 4.2, 77.45 ± 4.7–103.33 ± 3.3, and 80.55 ± 6.6–105.82 ± 9.8% at 0.01, 0.02, and 0.1 μg/g levels of fortification, respectively. The recoveries from cane sugar were 73.24 ± 3.5–104.47 ± 1.9, 75.23 ± 1.5–116.10 ± 3.7, and 70.75 ± 5.7–110.15 ± 2.7%, respectively at 0.01, 0.02, and 0.1 μg/g levels of fortification. Matrix effect and measurement uncertainty were within the permissible limit (less than 20%) as prescribed for pesticide residue analysis.     

Catalytic asymmetric dihydroxylation of substituted trans-stilbene derivatives: implications of the variation of enantioselectivities on the mechanism of OsO4 addition to olefins

The OsO₄ catalyzed asymmetric dihydroxylation of substituted trans-stilbene derivatives using 9-O-acetyldihydrocinchonidine as chiral ligand gives the corresponding diols with lower enantioselectivity in the case of substrates containing electron-donating and electron-withdrawing substituents. The Hammett correlations of the enantiomeric ratios exhibit non-linear plots, in accordance with the conclusion that the reaction involves a 1,3-dipolar type [3+2] cycloaddition transition state.