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51.
Thierry Paris Jean-Pierre Vigneron Jean-Marie Lehn Michele Cesario Jean Guilhem Claudine Pascard 《Journal of inclusion phenomena and macrocyclic chemistry》1999,33(2):191-202
Molecular recognition of flat substrates requires the design of receptor molecules containing complementary flat units. If two such units are incorporated into a macrocyclic framework, a face to face inclusion of a planar substrate may take place, leading to an intercalative supramolecular structure. The water-soluble macrocyclic bis-intercaland receptor 1.4H+, containing two naphthalene subunits, linked by two positively charged oxy-bis- ethylamine binding sites, is able to bind strongly flat organic anions. The crystal structures of the terephthalate 2 and isophthalate 3 inclusion complexes are reported here. Complex 2, triclinic, P-1(N°), a = 7.717(3), b = 10.625(6), c = 16.238(9) Å, = 99.00(7), = 99.70(6), = 109.46(4)°, Z = 1. Complex 3, triclinic, P1 (N°1), a = 7.513(10), b = 10.640(9), c = 16.164(10) Å, = 98.81(5), = 99.77(10), = 109.36(12)°, Z = 1. Comparison of the environment (water molecules, anions and macrocycle) in the two X-ray structures highlights the formation of a similar organized assembly with the two different substrates. 相似文献
52.
T. E. Kokina L. A. Glinskaya E. A. Sankova R. F. Klevtsova S. V. Larionov 《Journal of Structural Chemistry》2005,46(6):1031-1038
The interaction of the Co(iso-Bu2PS2)2 chelate with 4-NH2Py afforded a paramagnetic complex [Co(4-NH2Py)(iso-Bu2PS2)2] (μeff = 4.53 BM). Single crystals of [Ni(4-NH2Py)2(iso-Bu2PS2)2] (I) and [Co(4-NH2Py)(iso-Bu2PS2)2] (II) were grown and used for X-ray diffraction investigation (X8 APEX diffractometer, MoK
α radiation). Crystals I are monoclinic with unit cell parameters a = 12.5336(5) Å, b = 9.4356(4) Å, c = 16.4095(6) Å; β = 111.351(1)°; V = 1807.4(1) Å3; Z = 2, ρ = 1.223 g/cm3, space group P21/n. Crystals II are triclinic with unit cell parameters a = 8.7572(4) Å, b = 9.6934(6) Å, c = 18.665(1) Å; α = 79.374(2)°, β = 87.049(2)°, γ = 75.640(2)°; V = 1508.6(1) Å3; Z = 2, ρ = 1.259 g/cm3; space group
. The structures of I and II are formed by isolated mononuclear molecules. The coordination unit is NiN2S4 (octahedron) in I and CoNS4 (tetragonal pyramid) in II. The 4-NH2Py molecule is coordinated through the N atom of the heterocycle. Electronic spectroscopy data for II agree with the symmetry of the NS4 polyhedron found by X-ray diffraction (XRD) analysis. The noncoordinated amine groups link the complex molecules via N-H...S
hydrogen bonds.
__________
Translated from Zhurnal Strukturnoi Khimii, Vol. 46, No. 6, pp.1072–1080, November–December, 2005.
Original Russian Text Copyright ? 2005 by T. E. Kokina, L. A. Glinskaya, E. A. Sankova, R. F. Klevtsova, and S. V. Larionov 相似文献
53.
Crystalline HCl and CF3SO3H hydrates serve as excellent model systems for protonated water and perfluorosulphonic acid membranes, respectively. They contain characteristic H3O+, H5О+2, H7О+3 and H3O+(H2O)3 (the Eigen cation) structures. The properties of these cations in the crystalline hydrates of strong monobasic acids are studied by solid-state density function theory (DFT). Simultaneous consideration of the HCl and CF3SO3H hydrates reveals the impact of the size of a counter ion and the crystalline environment on the structure and infrared active bands of the simplest proton hydrates. The H7O+3 structure is very sensitive to the size of the counter ion and symmetry of the local environment. This makes it virtually impossible to identify the specific features of H7O+3 in molecular crystals. The H3O+ ion can be treated as the Eigen-like cation in the crystalline state. Structural, infrared and electron-density features of H5О+2 and the Eigen cation are virtually insensitive to the size of the counter ion and the symmetry of the local crystalline environment. These cations can be considered as the simplest stable proton hydrates in the condensed phase. Finally, the influence of the Grimme correction on the structure and harmonic frequencies of the molecular crystals with short (strong) intermolecular O–H···O bonds is discussed. 相似文献
54.
Danuta Dobrzyńska Lucjan B. JerzykiewiczMarek Duczmal Agnieszka Wojciechowska 《Polyhedron》2011,30(16):2684-2689
The new complex of chromium (III) with quinoline-2-carboxylate ion, [Cr(quin-2-c)2ClMeOH]·MeOH (1), has been synthesized and its structure has been established by single crystal X-ray diffraction studies. The spectroscopic (IR, UV-Vis) and magnetic study have been undertaken. The chromium ion is coordinated by ClN2O3 donor set of pseudoctahedral geometry. The structure of 1 consists of hydrogen-bonded dimers which are further connected by weaker C-H?O bonds and C-H?Cl interactions into the layers. The layers are held together by the aromatic π?π contacts. The electronic experimental energies of d-d transitions are comparable with values calculated for crystal field parameters Dq = 1669, Ds = 705, and B = 684 cm−1. The splitting of the d-d bands was observed by applying the filtration process. Magnetization measurements revealed the occurrence of weak antiferromagnetic interactions together with zero field splitting effects. The appearance of magnetic exchange between distant Cr(III) ions (Cr?Cr separation >6 Å) was ascribed to hydrogen bond extension of carboxylate ligands. 相似文献
55.
A representative acetate-(5-methylimidazole)-methanol system has been employed as a model of catalytic triad in serine protease
to validate the formation processes of low-barrier H-bonds (LBHB) at the B3LYP/6-311++G** level of theory, and variable H-bonding
characters from conventional ones to LBHBs have been represented along with the proceedings of proton transfer. Solvent effect
is an important factor in modulation of the existence of an LBHB, where an LBHB (or a conventional H-bond) in the gas phase
can be changed into a non-LBHB (an LBHB) upon solvation. The origin of the additional stabilization energy arising from the
LBHB may be attributed to the H-bonding energy difference before and after proton transfer because the shared proton can freely
move between the proton donor and proton acceptor. Most importantly, the order of magnitude of the stabilization energy depends
on the studied systems. Furthermore, the nonexistence of LBHBs in the catalytic triad of serine proteases has been verified
in a more sophisticated model treated using the ONIOM method. As a result, only the single proton transfer mechanism in the
catalytic triad has been confirmed and the origin of the powerful catalytic efficiency of serine proteases should be attributed
to other factors rather than the LBHB.
Supported by the National Natural Science Foundation of China (Grant Nos. 20633060 & 20573063), the Natural Science Foundation
of Shandong Province (Grant No. Y2007B23), the Scientific Research Foundation of Qufu Normal University (Grant Nos. Bsqd2007003
and Bsqd2007008), and the State Key Laboratory of Physical Chemistry of Solid Surfaces (Xiamen University) 相似文献