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排序方式: 共有390条查询结果,搜索用时 15 毫秒
1.
Seema Prasad 《Molecular Crystals and Liquid Crystals》2018,665(1):52-63
Molecular structure and vibrational spectroscopic studies of higher homologous series nematogenic p-n-alkylbenzoic acids (nBAC) that have 6 (6BAC) and 7 (7BAC) carbon atoms in the alkyl chain have been investigated using the Density Functional Becke3-Lee-Yang-Parr (B3LYP) level with the basis set 6-31++G (d.p) and Hartree Fock (HF) with the same basis set. The observed vibrational spectra has been resolved and assigned in detail for comparision with both the molecules. These results indicate that DFT and HF values are slightly different at both the levels. A comparision of chemical reactivity such as HOMO (EH), LUMO (EL) energies, energy gap (Eg), ionization energy (I), electron affinity (A), electro negativity (χ), chemical hardness (η), electronic chemical potential (μ), electrophilicity index (ω), and softness (S) has been made. It has been observed that the decrement has occurred in the energy band gap value of isolated molecule with increment in alkyl chain length. This provides valuable information regarding enhancing the stability of liquid crystal materials by maintaining the conductivity. 相似文献
2.
Doshi DA Shah PB Singh S Branson ED Malanoski AP Watkins EB Majewski J van Swol F Brinker CJ 《Langmuir : the ACS journal of surfaces and colloids》2005,21(17):7805-7811
Neutron reflectivity (NR) is used to probe the solid, liquid, vapor interface of a porous superhydrophobic (SH) surface submerged in water. A low-temperature, low-pressure technique was used to prepare a rough, highly porous organosilica aerogel-like film. UV/ozone treatments were used to control the surface coverage of hydrophobic organic ligands on the silica framework, allowing the contact angle with water to be continuously varied over the range of 160 degrees (superhydrophobic) to <10 degrees (hydrophilic). NR shows that the superhydrophobic nature of the surface prevents infiltration of water into the porous film. Atomic force microscopy and density functional theory simulations are used in combination to interpret the NR results and help establish the location, width, and nature of the SH film-water interface. 相似文献
3.
A new tetradentate dihydrogen perchlorate macrocyclic ligand (2,4,9,11-tetraphenyl-1,5,8,12-tetraazacyclotetradeca-1,4,8,11-tetraene dihydrogen perchlorate) was prepared and characterised. The macrocycle behaves as a selective chelating ion-exchanger for some metal ions. The polystyrene-based membrane electrode is found to exhibit quite promising selectivity for Cr3+ ions. It can be used to estimate chromium concentrations in the range 3.16x 10(-6)-1.00x10(-1) M with a near-Nernstian slope of 17.5 mV per decade of concentration between pH 3.0 to 6.5. The electrode is found to possess a fast response time of 15 s and was used over a period of three months with good reproducibility (s = +/- 0.3 mV). The selectivity coefficient values for mono-, di- and trivalent cations indicate excellent selectivity for Cr3+ ions over a large number of other cations. Anions such as Cl- and SO4(2-) do not interfere and the electrode also works satisfactorily in a mixed organic-water solution. The sensor has been used as an indicator electrode for the potentiometric titration of Cr3+ with EDTA. The practical utility of the membrane sensor has also been demonstrated in solutions contaminated with detergents (CTAB and SDS). Above all, the membrane sensor has been very successfully used to determine Cr3+ in some foods. 相似文献
4.
C. D. Kalkar S. V. Doshi Seema Teli 《Journal of Radioanalytical and Nuclear Chemistry》1989,136(4):283-290
The oxidation of iron/II/ ions has been studied by dissolving -irradiated NaCl crystals in aqueous Fricke solution. The yield of iron/III/ ions was determined as a function of the amount of NaCl added, storage time, dose, concentration of iron/II/ ions and pH of the Fricke solution. The energy transfer parameter, , which is the ratio of G/Fe3+/ obtained by the addition of irradiated NaCl to that by direct radiolysis was evaluated. 相似文献
5.
Bhavesh Khatri Puja Majumder Jayashree Nagesh Aravind Penmatsa Jayanta Chatterjee 《Chemical science》2020,11(35):9480
Abundant n → π* interactions between adjacent backbone carbonyl groups, identified by statistical analysis of protein structures, are predicted to play an important role in dictating the structure of proteins. However, experimentally testing the prediction in proteins has been challenging due to the weak nature of this interaction. By amplifying the strength of the n → π* interaction via amino acid substitution and thioamide incorporation at a solvent exposed β-turn within the GB1 proteins and Pin 1 WW domain, we demonstrate that an n → π* interaction increases the structural stability of proteins by restricting the ϕ torsion angle. Our results also suggest that amino acid side-chain identity and its rotameric conformation play an important and decisive role in dictating the strength of an n → π* interaction.Amino acid residues adopt a right-handed α-helical conformation with increasing strength of the n → π* interaction. We also demonstrate a direct consequence of n → π* interactions on enhancing the structural stability of proteins. 相似文献
6.
Appu Aravind 《Tetrahedron letters》2005,46(17):2965-2968
A highly regioselective oxidative cleavage of 1,3:4,6-di-O-benzylidene-d-mannitol was carried out using NBS and the resultant product was readily converted to the C2-symmetric chiral ligand, (R,R)-3,4-dihydroxy-1,5-hexadiene. On the other hand, reductive cleavage of 1,3:4,6-di-O-benzylidene-d-mannitol was achieved in a highly regioselective manner using BF3·OEt2 and Et3SiH to give a highly functionalized benzyl ether, which was converted to a synthetically useful C2-symmetric bis-amino alcohol derivative. 相似文献
7.
Microwave-assisted acyl chloride-isonitrile condensation and CaCO3-mediated hydrolysis constitute a one-pot, 2-minute process to prepare α-ketoamides. 相似文献
8.
9.
Summary Reactions of bis(1-oxopyridine-2-thione) NiII or CuII with 2,2-bipyridine (bipy) or 1,10-phenanthroline (phen) yield complexes of stoichiometry: Ni(C5H4NOS)2L {L = bipy, two isomers: (1) and (2), L = phen, one isomer (3)} and Cu(C5H4NOS)2(phen)·0.75CHCl3
(4). The spectroscopy (i.r., u.v.-vis., e.s.r.) and magnetism studies of the above complexes are described. On the basis of conductivity, the CuII-phen complex has been formulated as [Cu(C5H4NOS)(phen)2][Cu(C5H4NOS)3]·1.5CHCl3
(4). The vis. absorption spectra support similar octahedral structures for the minor bipy isomer (2) and for the NiII-phen complex [(3)], whereas the major isomer [(1)] has a different structure. The e.s.r. spectrum of the CuII-phen complex (4) is commensurate with an elongated octahedral structure. New methods for the preparation and spectroscopy of M(C5H4NOS)2 (M = Mn, Ni, Cu or Zn) compounds have been investigated. 相似文献
10.