Sol–gel based thermally stable mesoporous TiO<Subscript>2</Subscript> nanomatrix for fiber optic pH sensing

Thermally stable acid catalyzed mesoporous titania (TiO₂) nanomatrices are obtained by sol–gel method for fiber optic pH sensing. These synthesized nanoparticles are annealed at 300?°C, at two time intervals i.e., 1?h and 2?h, characterized with several analytical techniques such as FE-SEM/EDS, AFM, XRD, FTIR, TGA, and Brunauer–Emmett–Teller (BET) analysis. Microscopic analysis shows that synthesized nanoparticles have crack-free, dense and homogeneous surface with low surface roughness (4.4–5.9?nm). EDS mapping confirms the uniform distribution of Ti in all samples. XRD findings revealed the TiO₂ anatase phase. BET analysis shows that the mesoporous synthesized TiO₂ nanoparticles have surface areas 169?m²/g and average pore diameter 39.2?Å. However, surface area is decreased to 113 and 102?m²/g and average pore diameter increased up to 62.36 and 68.18?Å after 1?h and 2?h heat treatment, respectively. Furthermore, the sensing activity of phenolphthalein (phph) doped mesoporous TiO₂ nanoparticles/matrix is found to be high at pH 12 without any leaching/cracking.

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Structural chemistry of organotin(IV) complexes

The amazing structural diversity in organotin compounds is discussed in the systems containing -O and -S donor ligands. It is demonstrated that there exist a fascinating range of structural diversity for organotin(IV) complexes, including differences in coordination number and molecular geometry. The difference in structure is correlated with the nature of tin and ligand bonded R groups. Despite the large number of different structures found in organotin(IV) carboxylates, there is limited range of coordination geometries about the Sn atom. The four coordinated Sn atom in triorganotin(IV) complexes is invariably distorted tetrahedral and five coordinated Sn is distorted trigonal bipyramidal. A large range has been observed for diorganotin carboxylate structures, where five, six and seven coordinate geometries have been reported. The Sn atom in mono-organotin has only been demonstrated to exist in distorted octahedral geometries (the single exception being a pentagonal bipyramidal geometry). In the case of organotin(IV) complexes of S donor ligands, it has been shown that there exists a rich diversity in Sn atom geometries and coordination modes of the sulfur donor ligands themselves. As in related carboxylate systems, the assignment of coordination numbers to the Sn centers in some compounds is controversial. As a general trend, it has been shown that, the overall coordination number at the Sn atom decreases with the increasing number of organic substituents at the Sn atom. This phenomenon is usually achieved by increased asymmetry in the mode of coordination of the sulfur donor ligands.     

Synthesis, characterization and variable temperature NMR studies on coordination geometry of dimethytin(IV) S(+)-2-(4-isobutylphenyl)propanoate

Dimethytin(IV) S(+)-2-(4-isobutylphenyl)propanoate was synthesized and characterized by elemental analysis and IR and variable temperature NMR spectroscopy. Variable temperature NMR analysis was performed to see the effect of temperature on coordination geometry of organotin complexes in non-coordinating solvent. Spectral data has shown that temperature change does not alter the coordination geometry of the complex, and that it remains greater than four at variable temperatures as well as at room temperature in solution state. This text was submitted by the authors in English.     

Zinc(II) complexes containing N′-aromatic group substituted N,N′,N-bis((1H-pyrazol-1-yl)methyl)amines: Synthesis,characterization, and polymerizations of methyl methacrylate and rac-lactide

A novel series of Zn(II) complexes [L_nZnCl₂] (L_n = L_A ? L_F) based on N,N′,N-bis((1H-pyrazol-1-yl)methyl)amine bidentate ligands, N,N-bis((1H-pyrazol-1-yl)methyl)-3,5-dimethylaniline [L_A], N,N-bis((1H-pyrazol-1-yl)methyl)-2,6-dimethylaniline [L_B], N,N-bis((1H-pyrazol-1-yl)methyl)-2,6-diethylaniline [L_C], N,N-bis((1H-pyrazol-1-yl)methyl)-2,6-diisopropylaniline [L_D], N,N-bis((1H-pyrazol-1-yl)methyl)-4-bromoaniline [L_E] and N,N-bis((1H-pyrazol-1-yl)methyl)benzhydrylamine [L_F], has been synthesized and characterized. X-ray structures of these Zn(II) complexes showed a distorted tetrahedral geometry. No interaction exists between the N_amine and the Zn(II) center in the [L_nZnCl₂] (L_n = L_A ? L_F) complexes, resulting in formation of an eight-membered chelate ring. [L_FZnCl₂] exhibited the highest catalytic activity (3.95 × 10⁴ g PMMA/mol·Zn·h) for the polymerization of methyl methacrylate (MMA) in the presence of modified methylaluminoxane (MMAO) at 60 °C and yielded high molecular weight (M_w) (11.0 × 10⁵ g/mol) of poly(methylmethacrylate) (PMMA). All the complexes resulted in syndiotactic enriched PMMA with high T_g (125–131 °C). The steric bulk of ligand architecture plays an influential role in controlling the catalytic activity and stereoregularity of the resultant PMMA. Further, alkyl derivatives [L_nZnMe₂] (L_n = L_A ? L_F) of synthesized Zn(II) complexes, generated in situ, showed moderate to high activities toward ring opening polymerization (ROP) of rac-lactide (rac-LA) and yielded heterotactic polylactide (PLA) with P_r up to 0.95 at ?50 °C. The activity and stereoselectivity toward ROP of rac-LA by these dimethyl Zn(II) complexes should be considered as a combined effect of steric hindrance and electronic density around the metal center.     

Synthesis, characterization and crystal structure of bis(acetylacetonato)dichlorotin(IV)

The compound bis(acetylacetonato)dichlorotin(IV) [Sn(acac)₂Cl₂] forms a distorted octahedral structure involving both oxygen atoms of the acetylacetone group. The two chlorides occupy the cis position, with Sn-Cl distances of Sn1-Cl1 = 2.380(2) Å, Sn1-O1 = 2.043(2) Å and Sn1-O2 = 2.093(2) Å. We report here a new and simple method for the synthesis of Sn(acac)₂Cl₂, its spectroscopic characterization and, for the first time, we report its crystal structure.     

Coordination chemistry of the transition metal carboxylates synthesized from the ligands containing peptide linkage

Transition metal carboxylates, i.e., 3-[(2,4,6-trichloroanilino)carbonyl]prop-2-enoic acid and 3-[(4-bromoanilino)carbonyl]prop-2-enoic acid have been synthesized. The unimolar and bimolar substituted products have been characterized by elemental analysis, IR, UV-Vis spectroscopy, ¹H NMR, and atomic absorption. IR data show the bidentate nature of the carboxylate group. The transition metal complexes were tested in vitro against a number of microorganisms to assess their biocidal properties. The text was submitted by the authors in English.     

Easy Access to Crystalline Indolines via Hydrogen Bond Transfer

Several indoline derivatives with specific geometries are biologically active and have inhibitor properties. Many indolines are a key part of natural products. Much attention has been focused on the development of synthetic routes for their easy access. Current synthesis depends largely on metal catalysis, iodine reagents, and Oxone. To date, no synthetic route has been established that is metal‐free, reagent‐free, and environmentally friendly and provides a base for green chemistry. Here, we report the first facile metal‐free and reagent‐free synthesis of indoline derivatives, which could potentially be influential in the design of new biologically active compounds. The synthesis proceeds through intramolecular amination between a urea nucleophile and unactivated alkene. The ring closure occurs in a few hours in the presence of pre‐dried silica gel and gives good yields of indolines products, but in the absence of silica gel, the ring closure occurred overnight with stirring in dry solvent. An electron withdrawing group at the substituted aryl moiety of ureas increases the hydrogen bond donor ability of substrates that mediate the internal proton transfer at the terminal alkene and results in facile amination to give the indoline product with an “in plane” orientation of the carbonyl group and aromatic part of indoline framework. Such orientation in indolines is important for potent biological activities.     

Synthesis,spectroscopy, and biological activity of heterobimetallic complexes containing Sn(IV) and Pd(II) with 4-(hydroxymethyl)piperidine-1-carbodithioic acid

4-(Hydroxymethyl)piperidine-1-carbodithioic acid has been synthesized by reacting 4-piperidinemethanol with carbon disulfide at room temperature. The synthesized ligand was treated with organotin(IV) chlorides to yield organotin complexes. These complexes by further treatment with palladium chloride afford heterobimetallic complexes containing Sn(IV) and Pd(II). The synthesized complexes along with ligand has been characterized by elemental analysis, FTIR, NMR (¹H, ¹³C) spectroscopy. The IR data confirmed the complexation through the sulfur and oxygen donor sites of the ligand. NMR data revealed the tetrahedral geometry in the solution. Biological activity was checked against selected bacterial and fungal strains. All complexes along with the ligand were found to be biologically active with few exceptions.     

Anticancer and antibacterial potential of Rhus punjabensis and CuO nanoparticles

Abstract

The present study reports ecofriendly synthesis of CuO nanoparticles (NPs) using an extract of Rhus punjabensis as a reducing agent. NPs structural and composition analysis are evaluated by X-rays diffraction (XRD), Fourier transform infrared, Energy dispersive spectroscopy, Scanning electron microscopy, Transmission electron microscopy, and Thermal analysis. The NPs have pure single phase monoclinic geometry with spherical structure and high stability toward heat and with average particle size of about 36.6 and 31.27?nm calculated by XRD and SEM, respectively. NPs are tested for antibacterial, protein kinase (PK) inhibition, SRB cytotoxic, and NF-κB activities. Antibacterial activity is observed against B. subtilis and E. coli. Significant PK and SRB cytotoxic activity is observed with some NF-κB inhibition. NPs IC₅₀ values against HL-60 and PC-3 prostate cancer cells are 1.82?±?1.22 and 19.25?±?1.55?μg/mL. The results encourage further studies for antibacterial and anticancer drug development of NPs using animal models.     

Pregnane derivatives from Potentilla evestita

A new pregnane derivative, 2,6beta,7beta-trihydroxy-4-methyl-19-norpregna-1,3,5(10)-trien-17-one, has been isolated from the ethyl acetate soluble fraction of Potentilla evestita along with a pregnane derivative, 11alpha,17alpha,21-trihydroxypregna-4,16(22)-diene-3,20-dione, that is reported for the first time as a natural product. Their structures were elucidated with the aid of 1H and 13C NMR spectra and by COSY, HMQC, HMBC and NOESY experiments.