No abstract

Ionic liquid N,N,N',N'-tetramethylguanidinium trifluoroacetate (TMGT) has been applied as a green and reusable catalyst for the one-pot synthesis of 10-aryl substituted-9,10-dihydropyrano[2,3-h]chromene-2,8-diones via reaction of various aromatic aldehydes, 5,7-dihydroxycoumarin derivatives and Meldrum's acid. The reactions were rapid, clean and the products were prepared in good yield. The ionic liquid was stable during the reaction process and reused without significant loss of its activity. The synthesised compounds were evaluated for their antioxidant activity by a 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay.

The nano NaY zeolite‐supported copper‐amine complex was prepared by postmodification of the nano NaY zeolite with 3‐chloropropyl trimethoxysilane (CPTMS) and [2‐({3‐[(2‐aminoethyl)thio]propyl}thio)ethyl]amine followed by coordination with Cu (I) ion. Various techniques such as Fourier transform infrared spectroscopy (FT‐IR), X‐ray powder diffraction (XRD), dynamic light scattering (DLS), thermogravimetric analysis (TGA),  differential thermal analysis (DTA), scanning electron micrograph (SEM), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET), t‐plot, energy dispersive spectroscopy (EDS), inductively coupled plasma (ICP), and elemental analyses were used to characterize the structure of the synthesized catalyst. The catalytic activity of the synthesized nano‐sample was evaluated in a three‐component synthesis of 2‐amino‐4H‐chromene derivatives, which resulted in high reaction yields and short reaction times under green conditions. The catalyst is separated by filtration and can be reused for at least seven consecutive runs without significant loss of catalytic activity. The nature of the supported [2‐({3‐[(2‐aminoethyl)thio]propyl}thio)ethyl]amine (NN) on the zeolite's surface improved the catalytic activity of the zeolite, provided homogeneity to the catalyst, and enhanced the capability of coordination with copper ions. Facile catalyst recovery and reuse, simple setup procedure and generality of the method, high turnover number (TON), and aqueous ethanol as a green solvent make this procedure an environmentally benign approach for preparing the titled heterocycles. The findings in this work revealed that the introduced catalytic system could be used to prepare other beneficial heterocyclic compounds under environmentally benign conditions.

No abstract

Some researchers obtained the phonon dispersion relation of carbon nanotube by considering harmonic oscillation of carbon atoms. Recently, we could find an alternative method for determining carbon nanotube band energy by modifying orthogonalized-plane-wave method and combining it with tight binding method. Here, we did some calculations based on these methods and solved the dynamical matrix of carbon nanotube by referring the above methods and using force constant model. Some necessary adjustments are made in order to take into account the effect of the second nearest neighbor atoms which are not harmonic vibrations.