Ab Initio Study of Structures,Metallotropic 1,2-Shifts and Prototropic 1,2-Shifts of Cyclopentadienyl(trimethyl)silane, -germane and -stannane

Molecular structures, metallotropic and prototropic shifts of cyclopentadienyl(trimethyl)silane ( 1 ), cyclopentadienyl(trimethyl)germane ( 2 ), and cyclopentadienyl(trimethyl)stannane ( 3 ) were investigated using ab initio molecular orbital and the Becke, Lee, Yang, and Parr density functional (B3LYP) methods. The results show that the most stable structure of compounds 1-3 has the (CH 3 ) 3 M fragment in the allylic position. The energy barrier of metallotropic shifts in compound 1 is higher than in 2 , and in compound 2 higher than in 3 , in good agreement with experimental data. The cyclopentadienyl rings in compounds 1-3 are found to be planar but this result contradicts the reported experimental data.     

A novel inorganic–organic nanohybrid material SBA-15@triazine/H<Subscript>5</Subscript>PW<Subscript>10</Subscript>V<Subscript>2</Subscript>O<Subscript>40</Subscript> as efficient catalyst for the one-pot multicomponent synthesis of multisubstituted pyridines

A novel inorganic–organic nanohybrid material SBA-15@triazine/H₅PW₁₀V₂O₄₀ (SBA-15@ADMPT/H₅PW₁₀V₂O₄₀) was prepared and used as an efficient, eco-friendly, and highly recyclable catalyst for the one-pot multicomponent synthesis of multisubstituted pyridines from the reaction of aldehydes, cyclic ketones, malononitrile, and ammonium acetate with good to excellent yields (77–97%). The nanohybrid catalyst was prepared by the chemical anchoring of Keggin heteropolyacid H₅PW₁₀V₂O₄₀ onto the surface of SBA-15 mesoporous silica modified with 2-APTS -4,6-bis(3,5-dimethyl-1H-pyrazol-1-yl)-1,3,5-triazine (ADMPT) linker. Standard characterization data such as FT-IR, XRD, SEM, TEM, BET, EDX, and DTA-TGA spectroscopy confirmed that the heteropolyacid H₅PW₁₀V₂O₄₀ is well dispersed on the surface of the solid support and its structure is preserved after immobilization on the SBA-15 mesoporous silica modified with ADMPT. Furthermore, the nanocatalyst can be recovered easily and reused five times without considerable loss of catalytic activity. In general, these advantages highlight this protocol as an attractive and useful methodology, among the other methods reported in the literature, for the eco-friendly and rapid synthesis of biologically active multisubstituted pyridines.     

One-pot three-component process for the synthesis of substituted pyrano[2,3-<Emphasis Type="Italic">c</Emphasis>]pyrazoles catalyzed by nanostructured FSM-16-SO<Subscript>3</Subscript>H

A three-component process for the one-pot synthesis of 6-amino-4-aryl-5-cyano-3-methyl-1-phenyl-1,4-dihydropyrano[2,3-c]pyrazoles by the reaction of aldehydes, 3-methyl-1-phenyl-1H-pyrazol-5(4H)-one, and malononitrile in the presence of FSM-16-SO₃H as an efficient mesoporous catalyst. The FSM-16-SO₃H was prepared and characterized by SEM, XRD, BET, and FT-IR techniques. The advantages of the presented method are high yields, short reaction times, easy purification of products, easy work-up, and reusability of the catalyst.     

Boron nitride nanotube (BNNT) as a sensor of hydroperoxyl radical (HO<Subscript>2</Subscript>): A DFT study

In this present study, the adsorption behavior of HO₂ radical on the exterior surface of (5, 0) zigzag boron nitride nanotube (BNNT) has been investigated. The electronic structures and geometries of studied complexes were calculated at B3LYP-D3/6-31++G (d, p) computational level. The value of adsorption energy for the most stable configuration (A) is obtained ?0.68 eV, indicating physisorption process. Meaningful change of HOMO–LUMO gap after adsorption confirming BNNT can be introduced as a promising sensor for sensing of HO₂ radical.     

Cu(II) immobilized on mesoporous organosilica as an efficient and reusable nanocatalyst for one‐pot Biginelli reaction under solvent‐free conditions

Cu(II) immobilized on mesoporous organosilica nanoparticles (Cu²⁺@MSNs‐(CO₂^?)₂) has been synthesized, as a inorganic–organic nanohybrid catalyst, through a post‐grafting approach. Its characterization is carried out by Fourier transform infrared spectroscopy (FT‐IR), X‐ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Energy dispersive X‐ray (EDX), Thermogravimetric/differential thermal analyses (TGA‐DTA), and Nitrogen adsorption–desorption analysis. Cu²⁺@MSNs‐(CO₂^?)₂ exhibits high catalytic activity in the Biginelli reaction for the synthesis of a diverse range of 3, 4‐dihydropyrimidin‐2(1H)‐ones, under mild conditions. The anchored Cu(II) could not leach out from the surface of the mesoporous catalyst during the reaction and it has been reused several times without appreciable loss in its catalytic activity.