Mechanochemical formation of a 1:1 C60: tert-butylcalix[4]azulene supramolecular complex: solid-state NMR and DFT computational studies

Abstract

Solid-state NMR data are presented to clearly support the formation of a 1:1 supramolecular complex between C₆₀ and the tetra-tert-butylated analogue of calix[4]azulene by a simple mechanochemical hand-grinding of host and guest in a mortar and pestle. The experimental results are supported by a DFT study.     

Synchronization structures in the chain of rotating pendulums

Nonlinear Dynamics - The collective behavior of the ensembles of coupled nonlinear oscillator is one of the most interesting and important problems in modern nonlinear dynamics. In this paper, we...     

A meglumine catalyst–based synthesis,molecular docking,and antioxidant studies of dihydropyrano[3, 2-b]chromenedione derivatives

A simple method was employed for the synthesis of dihydropyrano[3, 2-b]chromenedione derivatives ( 4a-o) in high yields by condensation of 5, 5-dimethylcyclohexane-1, 3-dione( 1 ), different aromatic aldehydes ( 2a-o ), and 5-hydroxy-2-(hydroxymethyl)-4H-pyran-4-one( 3 ), using meglumine as a stable and reusable catalyst. Meglumine, an amino sugar, was employed as an environmentally benign catalyst, due to its splendid properties such as being inexpensive, recyclable, and biodegradable. The accomplished protocol employs low catalyst loading and easy work-up for the synthesis of 5-hydroxy-2-(hydroxymethyl)-4H-pyran-4-one derivatives. A great asset is that without any significant loss, the catalyst could be recovered and reused for extended synthetic steps. This offer huge advantage to overcome recyclability issues. Our synthesized compounds were analyzed by IR, ¹H, ¹³C NMR, mass spectra and evaluated for their antioxidant properties by 1, 1-diphenyl-2-picryl hydrazyl radical (DPPH), hydrogen peroxide(H₂O₂), and nitric oxide (NO) scavenging methods. The correlation in exhibition of antioxidant activity was effective at all doses. The binding interactions and molecular docking studies for entitled compounds were studied against 3MNG protein; 4k exhibited marked binding affinity with excellent docking score of −7.6 Kcal/mol and emerged as a lead compound.     

Rectifiable Curves in Proximally Smooth Sets

Set-Valued and Variational Analysis - In this article we study some geometric properties of proximally smooth sets. First, we introduce a modification of the metric projection and prove its...     

Phase synchronization of chaotic oscillations in terms of periodic orbits

We consider phase synchronization of chaotic continuous-time oscillator by periodic external force. Phase-locking regions are defined for unstable periodic cycles embedded in chaos, and synchronization is described in terms of these regions. A special flow construction is used to derive a simple discrete-time model of the phenomenon. It allows to describe quantitatively the intermittency at the transition to phase synchronization. (c) 1997 American Institute of Physics.     

Palladium and platinum catalyzed hydroselenation of alkynes: SeH vs SeSe addition to CC bond

A mechanistic study of the hydroselenation of alkynes catalyzed by Pd(PPh₃)₄ and Pt(PPh₃)₄ has shown that the palladium complex gives products of both SeH and SeSe bond addition to the triple bond of alkynes, while the platinum complex selectively catalyzes SeH bond addition. The key intermediate of PhSeH addition to the metal center, namely Pt(H)(SePh)(PPh₃)₂, was detected by ¹H-NMR spectroscopy. The analogous palladium complex rapidly decomposes with evolution of molecular hydrogen. A convenient method was developed for the preparation of Markovnikov hydroselenation products H₂CC(SePh)R, and the scope of this reaction was investigated. The first X-ray structure of the Markovnikov product H₂CC(SePh)CH₂N⁺HMe₂·HOOCCOO⁻ is reported.     

Sensing and fixation of NO2/N2O4 by calix[4]arenes

An approach toward visual detection and chemical utilization of NO(2)/N(2)O(4) is proposed, which employs simple calix[4]arenes. Exposure of tetra-O-alkylated calix[4]arenes 1 and 2, possessing either a cone or a 1,3-alternate conformation, to NO(2)/N(2)O(4), both in chloroform solution and in the solid state, results in deeply colored calixarene-nitrosonium (NO(+)) complexes. In the presence of a Lewis acid, such as SnCl(4), stable calixarene-NO(+) complexes 7 and 8 were isolated in a quantitative yield and characterized by UV-vis, FTIR, high-resolution (1)H NMR spectroscopy and elemental analysis. NO(+) is found encapsulated within the calixarene cavity, and stable charge-transfer complexes result with K(ass) > 10(6) M(-1) (CDCl(3)). The NO(+) encapsulation was also demonstrated in titration experiments with calixarenes 1, 2, and 5 and commercially available NO(+)SbF(6)(-) salt in chloroform. The complexation process is reversible, and the complexes dissociate upon addition of water and alcohol, recovering the parent calixarenes. Attachment of functionalized calix[4]arenes to silica gel was demonstrated, which afforded a solid material 15 capable of visual detection and entrapment of NO(2)/N(2)O(4). Calixarene-NO(+) complexes can be utilized for the NO(+) transfer processes and nitrosation reactions. The NO(+) guest transfer between two calixarene containers 2 and 5 was achieved and studied by UV-vis and (1)H NMR spectroscopy. Chemical fixation of NO(2)/N(2)O(4) was demonstrated through their quantitative transformation into the calixarene-NO(+) complex and its use as a nitrosonium transfer agent in the synthesis of N-nitrosoamides. These results may lead toward novel nitrogen oxides storing materials.     

Asymmetric induction in the reactions of 3-aryl-1,2,4-triazin-5(4H)-ones with C-nucleophiles

3-Aryl-1,2,4-triazin-5(4H)-ones, in the presence of N-protected amino acids, react with C-nucleophiles to form 1-acyl-6-Nu-3-aryl-1,6-dihydro-1,2,4-triazin-5(4H)-ones in high diastereomeric excess. This is the first case of the use of amino acids as chiral auxiliaries in nucleophilic additions to triazinones.