Search results for "BOND"
showing 10 items of 3527 documents
(1Z,3Z)-1,4-Di(pyridin-2-yl)buta-1,3-diene-2,3-diol: The Planar Highly Conjugated Symmetrical Enediol with Multiple Intramolecular Hydrogen Bonds
2002
1H, (13)C, and (15)N NMR spectral data show that in chloroform solution (1Z,3Z)-1,4-di(pyridin-2-yl)buta-1,3-diene-2,3-diol, OO, is in ca. 9:1 equilibrium with (3Z)-3-hydroxy-1,4-di(pyridin-2-yl)but-3-en-2-one, OK, while no 1,4-di(pyridin-2-yl)-2,3-butanedione, KK, was detected. The species present in the tautomeric mixture were identified by comparing their experimental chemical shifts with those known for similar compounds as well as with the theoretically calculated (GIAO-HF/DFT) values. Ab initio calculations show that OK and especially the highly conjugated OO forms are preferred in the tautomeric mixtures both in vacuo and in chloroform solution. Comparison of experimental (Arrhenius)…
Spin-Transition in [Fe(II)(2,6-Bis-(Benzimidazol-2′-yl)pyridine)2] (CIO4)2: Hysteresis Effect Dependent on the Matrix
1999
Abstract Far-Infrared spectroscopical investigation of the spin-crossover in [Fe(II)(2,6-bis-(benzimidazol-2′-yl)-pyridine)2] (CIO4)2 exhibits a hysteresis in both CsI and polyethylene matrices within temperature cycles between 100K and 520K. The hysteresis broadening is dependent on the matrix and bigger in CsI. This can be explained due to polarity and hydrogen bonding. Two low spin vibrations, LS1 at 437 cm−1 and LS2 at 424cm−1, are observed. On heating from 100K to 520K: during LS1 decreases, the LS2 raises temporarily, until both LS1 and LS2 disappear; for the HS only one raising species was observed. This gives raise to assume two different sub-lattices.
Synthesis and characterization of a new spirooxindole grafted pyrrolidino/piperidine moiety
2021
In this text, we synthesized and characterized a new spirooxindole grafted pyrrolidino/piperidine moieties. The new hit obtained via one-pot reaction of the chalcone based cyclohexanone with the isatin and (R)-piperidine-2-carboxylic acid in MeOH under reflux for 48 h. The compound exclusively obtained in regio-selective and diastereo-selective manner. The chemical feature of the target compound is confirmed by 1H NMR and 13C NMR spectroscopy. In addition, we reported for the first time the X-ray single crystal structure of isatin. Its molecular packing depends mainly on strong O…H hydrogen bonds and π-π stacking interactions as well as weak H…H and H…C contacts. Using DFT calculations, is…
1-Chloro-1,1-difluoro-N-(4-methoxyphenyl)-3-(pyrrolidin-2-ylidene)propan-2-imine
2000
In the title compound, C(14)H(15)ClF(2)N(2)O, the Z configuration has been confirmed. The molecular structure shows an intramolecular N-H.N hydrogen bond [H.N 2.04 (6), N.N 2.709 (6) A and N-H.N 124 (5) degrees ]. This interaction could be responsible for the Z configuration.
Substituent and temperature controlled tautomerism of 2-phenacylpyridine: the hydrogen bond as a configurational lock of (Z )-2-(2-hydroxy-2-phenylvi…
2000
2-Phenacylpyridines substituted in the benzene ring are in equilibrium with (Z)-2-(2-hydroxy-2-phenylvinyl)pyridines when dissolved in chloroform. The substituent affects significantly the tautomeric equilibrium [the amount of the enolimine form stabilized by the intramolecular hydrogen bond is 1 and 92% for R = p-N(CH2)4 and p-NO2, respectively]. The negative logarithm of the tautomeric equilibrium constant, KT, is linearly dependent on the Hammett σ substituent constants. The dependence of KTvs. temperature is exponential in character: the more electron-withdrawing is the substituent, the more distinct is the influence of temperature. Unexpectedly, the tautomer present in the crystalline …
Effect of structural parameters on the polarizabilities of methanol clusters: a hirshfeld study
2008
The polarizabilities of fifty methanol clusters (CH3OH)n, n = 1 to 12, were calculated at the B3LYP/6-311++G** level of theory and partitioned into molecular contributions using the Hirshfeld-I method. The resulting molecular polarizabilities were found to be determined by the polarizabilities of the two parts of the molecule, the hydrophilic hydroxyl group and the hydrophobic methyl group, each exhibiting a different dependency upon the local environment. The polarizability of the hydroxyl group was found to be dependent on the number, type, and strength of the hydrogen bonds a methanol molecule makes, whereas the polarizability of the methyl groups is mostly influenced by sterical hindran…
Diethylammonium hydrogen oxalate
2006
The structure of the title compound, C4H12N+·C2HO4−, consists of discrete oxalate monoanions and diethylammonium cations. The N atom lies on a crystallographic twofold rotation axis and the oxalate ion is centrosymmetric. The oxalate monoanions are present as hydrogen-bonded linear chains. Conformationally extended diethylammonium cations link the linear chains through three–centre N–H⋯O hydrogen bonds.
Chemical transformations of a crystalline coordination polymer: a multi-stage solid–vapour reaction manifold
2013
In its crystal structure the one-dimensional coordination polymer [Ag4(O2C(CF2)2CF3)4(TMP)3]n (1) (TMP = 2,3,5,6-tetramethylpyrazine) adopts a zig-zag arrangement in which pairs of silver(I) centres bridged by two fluorocarboxylate ligands are linked alternately via one or two neutral TMP ligands. This material can reversibly absorb/desorb small alcohols (ROH) in single-crystal-to-single-crystal transformations, despite the lack of porosity in the crystals, to yield a related material of formula [Ag4(O2C(CF2)2CF3)4(TMP)3(ROH)2]n (1-ROH). The absorption process includes coordination of the alcohol to silver(I) centres and, in the process, insertion of the alcohol into one-quarter of the Ag–O…
Bonding Trends in Lewis Acid Adducts of S4N4 — X-Ray Structure of TeCl4×S4N4.
2006
Tetrasulfur tetranitride and tellurium tetrachloride react in dichloromethane to form a 1:1 adduct TeCl4·S4N4 (1). The crystal structure of 1 shows that TeCl4 is bonded to the S4N4 ring through a Te–N linkage. As a consequence, the transannular S···S bonds in S4N4 are broken and the molecule assumes an open, monocyclic conformation. The Te–N bond of 2.16(1) A is slightly longer than the single bond. The S–N bonds span a range of 1.55(1)–1.67(1) A. The adduct 1 was also characterized by mass spectrometry and Raman spectroscopy. The bonding and spectroscopic properties of 1 are compared by DFT calculations at the B3PW91/(RLC ECP) level of theory with those of BF3·S4N4 (2), SO3·S4N4 (3), AsF5·…
G2(MP2) study of the substituent effects in the H3BXHnMe3−n (X=N, P; n=0–3) donor–acceptor complexes
1998
Abstract The complexation energies of H 3 BXH n Me 3− n (X=N, P; n =0–3) donor–acceptor complexes have been investigated at the G2(MP2) level of theory. MP2(Full)/6-31G(d) optimized geometries and G2(MP2) calculated complexation energies are in good agreement with experiment. Increasing methyl substitutions on `X' donor atom augments both the basicity of XH n Me 3− n Lewis bases and the stability of complex. The NBO partitioning scheme suggests that there is no correlation between the charge transfer and the complexation energies.