Search results for "crystal and molecular structure"
showing 5 items of 5 documents
New crystal structures of fluorinated α-aminophosphonic acid analogues of phenylglycine
2020
The four novel phosphonic acid analogues of phenylglycine with various substituents in phenyl ring (mostly fluorine atoms) have been synthesized by using procedure of amidoalkylation of phosphorus trichloride with aromatic aldehydes and acetamide. The NMR, ESI-MS spectroscopy, and single-crystal X-Ray diffraction methods were used to characterize unusual structures: the amino-(4-trifluoromethylbenzyl)-(1), amino-(3,4-difluorobenzyl)-(2), amino-(2,4,6-trifluorobenzyl)-(3), and amino-(2-fluoro-4-hydroxybenzyl)-(4) phosphonic acids. Since the α-aminophosphonates have a potential for biological activity and could be used as building blocks in medicinal chemistry, it is important to know their d…
Synthesis and structure of tetrakis(tetramethylammonium) octacosachlorooctaantimonate(III) [(CH3)4N]4Sb8Cl28
2000
Abstract The reaction between antimony trichloride and tetramethylammonium chloride in nitromethane gives transparent, irregular crystals of tetrakis(tetramethylammonium) octacosachlorooctaantimonate(III) [(CH 3 ) 4 N] 4 Sb 8 Cl 28 . Crystals are triclinic, space group P-1, a =11.846(2), b =12.217(2), c=14.120(3) A , α =95.71(3), β =101.39(3), γ =118.59(3)°, V=1713.7(5) A 3 , Z =1, d c =2.193, d m =2.17(2) Mg m −3 . The structure contains a structurally novel Sb 8 Cl 28 4- anion. It is composed of eight deformed octahedra, connected with each other by faces. In cavities formed by inorganic sublattice are located two crystallographically nonequivalent tetramethylammonium cations. One of them…
Conformational investigation of α,β-dehydropeptides. X. Molecular and crystal structure of Ac-ΔAla-NMe2 compared with those of Ac-L-Ala-NMe2, Ac-DL-A…
2002
A series of three homologous dimethyldiamides Ac-DeltaAla-NMe2, Ac-L-Ala-NMe2 and Ac-DL-Ala-NMe2 has been synthesized and the structures of these amides determined from single-crystal X-ray diffraction data. To learn more about the conformational preferences of compounds studied, the fully relaxed (phi-psi) conformational energy maps in vacuo (AM1) of Ac-DeltaAla-NMe2 and Ac-L-Ala-NMe2 were obtained, and the calculated minima reoptimized with the DFT/B3LYP/6-31G** method. The crystal-state results have been compared with the literature data. Ac-DeltaAla-NMe2 and other alpha,beta-dehydroamino acid dimethyldiamides, Ac-DeltaXaa-NMe2 adopt the conservative conformation of the torsion angles ph…
Proton tautomerism in 2-nitramino-C-nitropyridine derivatives - Experimental and quantum chemical study
2019
Abstract The structures of 2-nitramino-3-nitropyridine and 2-nitramino-5-nitropyridine have been characterized by X-ray diffraction and Density Functional Theory (DFT) studies. In the crystals, both compounds exist as the imino forms. The DFT calculations were performed in order to explore the amino-imino tautomerism of the studied compounds in the gas phase and the influence of solvent polarity on the tautomeric equilibrium. The Harmonic Oscillator Model of Aromaticity index (HOMA) and Nucleus Independent Chemical Shift (NICS) calculated for the pyridine rings of the studied systems, demonstrated a noticeable decrease in aromaticity of the imino forms. This study showed also that the highe…
High temperature ferro-paraelectric phase transition in tris(trimethylammonium) nonachlorodiantimonate(III) (TMACA) studied by X-ray diffraction meth…
2000
Abstract The structure of [NH(CH3)3]3Sb2Cl9, tris(trimethylammonium) nonachlorodiantimonate(III) (TMACA) has been determined at 295 K and 373 K, below and above the high temperature ferro-paraelectric phase transition. In both phases the anionic sublattice of TMACA is built of characteristic two-dimensional (Sb2Cl93−)n polyanionic layers lying in the bc plane. In room temperature, ferroelectric phase (monoclinic, Pc space group) there are three crystallographically non-equivalent trimethylammonium [NH(CH3)3]+ cations. Two of them are located between polyanionic layers and the third one, disordered, inside the cavity formed by six SbCl63− octahedra. In the high temperature paraelectric phase…