Structural and spectral studies of palladium(II) and platinum(II) complexes derived from N,N,N,N-tetradentate macrocyclic ligands

Palladium(II) and platinum(II) complexes having the general composition [M(L)] X2 (where M=Pd(II) and Pt(II), L=3,4,12,13-tetraphenyl-2,5,11,14,19,20-hexaaza tricyclo [13.3.1.1.(6-10)] cosa-1(19), 2,4,6,8,10,(20),11,13,15,17-decaene (L1); 3,4,13,14-tetraphenyl-2,5,12,15-tetraaza tricyclo [11,0,0,(6-11)] cosa-1(16),2,4,7,9,6(11),12,14,17, 19-decaene (L2); 2,3,8,9-tetraphenyl-1,4,7,10-tetraaza cyclododeca-1,3,7,9-tetraene (L3) and X=Cl(-)) have been synthesized. The ligands were characterized on the basis of elemental analyses, IR, 1H NMR and EI mass spectral studies while that of the complexes were characterized on the basis of elemental analyses, molar conductance measurements, magnetic susceptibility measurements, IR, and electronic spectral techniques. All the complexes were found to be diamagnetic. The structures consist of monomeric units in which the Pd(II) and Pt(II) atoms exhibit square planar geometry.     

Catalytic application of K2Ce(PO4)2 in Knoevenagel condensation -A green protocol

A framework connected phosphate material K₂Ce(PO₄)₂, explored for the first time for the Knoevenagel condensation of aldehydes with malononitrile in water. The catalyst was prepared by newly developed solid-state method and characterized using XRD, RAMAN, FTIR, BET surface area, TPD, XPS, SEM and HRTEM. The developed protocol showed the substrate compatibility along with the catalyst reusability. Moreover, the catalyst was scaled up to 30 g and also showed reusability. The role of predominant Ce(IV) species was also discussed apart from phosphate basic sites.     

Mucoadhesive vaginal film of fluconazole using cross-linked chitosan and pectin

A series of silica gels (Si-40, Si-60, Si-100) and related carbon–silica gels, prepared by carbonization of CH₂Cl₂ at a surface of silica gels at 550 °C, characterized using FTIR/PAS, SEM/EDX, and nitrogen adsorption, was investigated upon interactions with polar (water, dimethylsulfoxide), weakly polar (chloroform), and nonpolar (n-hexane, n-decane, benzene, toluene) adsorbates using adsorption and differential scanning calorimetry methods. Features of confined space effects, such as freezing/melting point depression and melting delay, depend strongly on pore sizes, pore wall structure, type and amount of adsorbates, and the degree of pore filling. Melting curves of both polar and nonpolar adsorbates bound in broad pores (Si-60 and Si-100 based materials) can include two–three peaks around melting point, but for Si-40-based materials, a number of similar peaks is smaller. This occurs due to step-by-step melting of frozen structures located in broader pores and the absence of similar effects in narrower pores. The present study shows that complex carbon–silica gel adsorbents can be more effective adsorbents than simple silica gels due to the presence of a number of surface sites of various polarity and structure.

     

Dithioester-enabled chemodivergent synthesis of acids,amides and isothiazoles via CC bond cleavage and CO/CN/CS bond formations under metal- and catalyst-free conditions

An operationally simple and user-friendly process to access privileged scaffolds such as acids, amides and isothiazoles has been devised employing β-ketodithioesters for the first time. Remarkably, the new protocol involves combination of CC bond cleavage and CO/CN/NS bond formations in one-pot. Aqueous ammonia led to the formation of skeletally distinct amide and isothiazole, whereas aqueous NaOH enabled the formation of aromatic acid near quantitative yield. This practical approach, which can dramatically streamline the synthesis of simple molecules, is highly chemoselective, cost-effective, amenable to gram scale, insensitive to moisture as well as bears high functional group compatibility.     

Recent advances in DFT assisted optimized energy,stability and distortions of optimized topologies of certain biopotent dimethyltin(IV) complexes

The generation, structural elucidation, reactivity, bonding, stability, optimized energy, distortions of optimized topologies of some non-bridged mononuclear and carboxylate bridged binuclear dimethyltin(IV) complexes of N-protected amino acids and 2-aminophenol/2-amino-4-methylphenol were studied experimentally and theoretically with the assistance of density functional theory (DFT). These complexes were synthesized by the reactions of Me₂SnCl₂ with sodium salts of N-protected amino acids and 2-aminophenol/2-amino-4-methylphenol in 1:1:1 ?molar ratio in refluxing dry THF. These complexes were characterized and their plausible structures were suggested with the assistance of spectroscopic [IR and NMR (¹H,¹³C and ¹¹⁹Sn)] evidences, mass studies and DFT investigation. Mass spectral data indicated the tendency of the complexes to undergo dimerization on aging. The ¹¹⁹Sn NMR data demonstrated the presence of penta-coordinated tin centres in these complexes. DFT (B3LYP) was used to study the molecular orbitals, optimized bond lengths and bond angles, optimized energy, stability, distortions of optimized topologies and energy gap of representative complexes. One representative complex, Me₂SnL₍₂₎L’₍₂₎ was screened for its possible antimicrobial activities against gram negative bacteria, E. coli and polymorphic fungal pathogen, Candida albicans, respectively. The structure-activity relationship of this complex has also been investigated.     

Urea nitrate–catalyzed C-N and C-S bond formation: A mechanochemical approach for 5-chloro-2-arylbenzo[d]thiazole derivatives

A series of substituted 5-chloro-2-arylbenzo[d]thiazoles were synthesized using 4-chloro-2-aminothiophenol and aromatic aldehydes in the presence of urea nitrate as a catalyst using the mechanochemical grindstone technique. This protocol was effectively carried out under metal-free conditions at room temperature, and the desired products were obtained in high to excellent yields in short reaction time (30–60 s). The structure of all the synthesized derivatives was confirmed by spectral characterization. The designed protocol has several benefits like eco-friendly, solvent-free, high yields, easy workup, and recyclability of catalyst. The catalyst was reusable at least four times without significant loss of activity. The good functional group tolerance with a series of derivatives has been demonstrated.     

Oxygen Functionalization of Hexagonal Boron Nitride on Ni(111)

The interaction of single-layer hexagonal boron nitride (h-BN) on Ni(111) with molecular oxygen from a supersonic molecular beam led to a covalently bonded molecular oxygen species, which was identified as being between a superoxide and a peroxide. This is a rare example of an activated adsorption process leading to a molecular adsorbate. The amount of oxygen functionalization depended on the kinetic energy of the molecular beam. For a kinetic energy of 0.7 eV, an oxygen coverage of 0.4 ML was found. Near-edge X-ray adsorption fine structure (NEXAFS) spectroscopy revealed a stronger bond of h-BN to the Ni(111) substrate in the presence of the covalently bound oxygen species. Oxygen adsorption also led to a shift of the valence bands to lower binding energies. Subsequent temperature-programmed X-ray photoelectron spectroscopy revealed that the oxygen boron bonds are stable up to approximately 580 K, when desorption, and simultaneously, etching of h-BN set in. The experimental results were substantiated by density functional theory calculations, which provided insight to the adsorption geometry, the adsorption energy and the reaction pathway.     

Synthesis of composite gold/tin-oxide nanoparticles by nano-soldering

Composite Au–SnO₂ nanoparticles (NPs) are synthesized by nano-soldering of pure Au and SnO₂ NPs. The multi-step process involves synthesis of pure Au and SnO₂ NPs separately by nanosecond pulse laser ablation of pure gold and pure tin targets in deionized water and post-ablation laser heating of mixed solution of Au colloidal and SnO₂ colloidal to form nanocomposite. Transmission Electron Microscopy (TEM) and High-Resolution Transmission Electron Microscopy (HRTEM) were used to study the effect of laser irradiation time on morphology of the composite Au–SnO₂ NPs. The spherical particles of 4 nm mean size were obtained for 5 min of post-laser heating. Increased mean size and elongated particles were observed on further laser heating. UV–vis spectra of Au–SnO₂ nanocomposites show red shift in the plasmon resonance absorption peak and line shape broadening with respect to pure Au NPs. The negative binding energy shift of Au 4f_7/2 peak observed in X-ray Photoelectron Spectra (XPS) indicates charge transfer in the nano-soldered Au–SnO₂ between gold and tin oxide and formation of soldered nanocomposite.