Construction of coordination polymers of cadmium(II) with mixed hexamethylenetetramine and terephthalate or thiocyanate ligands
TL;DR: In this paper, three new polymeric complexes [Cd(hmt)(SCN)(2)(H2O)(2)](n) (1), [cd-3(mu(2)-hmt(2)(scN)(6)(H 2O)(6) (n) n) (2), and [ cd-2(Hmt)(2)tP)(2), [hmt = hexamethylenetetetramine, tp = terephthalate] have been synthesized and characterized by single crystal
About: This article is published in Polyhedron.The article was published on 2003-09-15. It has received 48 citations till now. The article focuses on the topics: Thiocyanate & Denticity.
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TL;DR: In this paper, the main structural and topological types of coordination polymers bearing hexamethylenetetramine (hmt) are summarized, showing that a diversity of metal-organic networks can be generated by facile self-assembly routes in aqueous medium and using rather simple chemicals.
153 citations
TL;DR: In this article, two new cadmium-II-terephthalate complexes were synthesized by a conventional solution method, which are composed of 1-D polymeric zig-zag chains with distorted pentagonal-bipyramidal Cadmium centers.
53 citations
TL;DR: In this paper, three μ1,5-dicyanamide bridged Mn(II) and Co(II)-complexes have been synthesized and characterized by single crystal X-ray diffraction study, low temperature (300-2,K) magnetic measurement and thermal behavior.
44 citations
TL;DR: The luminescent properties of the title complex in the solid state were investigated and a novel Cd(II) coordination polymer with hexagonal metallocyclic rings was synthesized and characterized.
42 citations
TL;DR: In this paper, four new cadmium(II) complexes with hexamine (hmt) and monocarboxylate ions, benzoate (bz), phenylacetate (pa), or acetate (ac), were synthesized and characterized structurally.
Abstract: Four new cadmium(II) complexes [Cd2(bz)4(H2O)4(μ2-hmt)]·Hbz·H2O (1), [Cd3(bz)6(H2O)6(μ2-hmt)2]·6H2O (2), [Cd(pa)2(H2O)(μ2-hmt)]n (3), and {[Cd3(ac)6(H2O)3(μ3-hmt)2]·6H2O}n (4) with hexamine (hmt) and monocarboxylate ions, benzoate (bz), phenylacetate (pa), or acetate (ac) have been synthesized and characterized structurally. Structure determinations reveal that 1 is dinuclear, 2 is trinuclear, 3 is a one-dimensional (1D) infinite chain, and 4 is a two-dimensional (2D) polymer with fused hexagonal rings consisting of CdII and hmt. All the CdII atoms in the four complexes (except one CdII in 2) possess seven-coordinate pentagonal bipyramidal geometry with the various chelating bidentate carboxylate groups in equatorial sites. One of the CdII ions in 2, a complex that contains two monodentate carboxylates is in a distorted octahedral environment. The bridging mode of hmt is μ2- in complexes 1−3 but is μ3- in complex 4. In all complexes, there are significant numbers of H-bonds, C−H/π, and π−π interactions wh...
41 citations
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TL;DR: In this article, a phase annealing method, related to the simulated-annealing approach in other optimization problems, is proposed and it is shown that it can result in an improvement of up to an order of magnitude in the chances of solving large structures at atomic resolution.
Abstract: A number of extensions to the multisolution approach to the crystallographic phase problem are discussed in which the negative quartet relations play an important role. A phase annealing method, related to the simulated annealing approach in other optimization problems, is proposed and it is shown that it can result in an improvement of up to an order of magnitude in the chances of solving large structures at atomic resolution. The ideas presented here are incorporated in the program system SHELX-90; the philosophical and mathematical background to the direct-methods part (SHELXS) of this system is described.
14,787 citations
TL;DR: In this article, a Fourier series in the polar angles of the incident and diffracted beam paths is used to model an absorption surface for the difference between the observed and calculated structure factors.
Abstract: Absorption effects usually present the most serious source of systematic error in the determination of structure factors from single-crystal X-ray diffraction measurements if the crystal is not ground to a sphere or cylinder. A novel method is proposed for the correction of these effects for data collected on a diffractometer. The method works from the premise that the manifestation of systematic errors due to absorption, unlike most other sources of systematic error, will not be evenly distributed through reciprocal space, but will be localized. A Fourier series in the polar angles of the incident and diffracted beam paths is used to model an absorption surface for the difference between the observed and calculated structure factors. Knowledge of crystal dimensions or linear absorption coefficient is not required, and the method does not necessitate the measurement of azimuthal scans or any extra data beyond the unique set. Moreover, application of the correction is not dependent upon the Laue symmetry of the crystal or the geometry of the diffractometer. The method is compared with other commonly used corrections and results are presented which demonstrate its potential.
4,930 citations
TL;DR: In this paper, a Fortran program is developed for the reduction of single-crystal diffraction data from a sequence of adjacent rotation pictures recorded at a fixed X-ray wavelength by an electronic area detector.
Abstract: A Fortran program has been developed for the reduction of single-crystal diffraction data from a sequence of adjacent rotation pictures recorded at a fixed X-ray wavelength by an electronic area detector. The electronic pictures (data frames) covering the first 5° of crystal rotation are used to locate strong diffraction spots and to estimate the background. The orientation of the crystal is derived automatically from the list of observed spots and all parameters describing the diffraction pattern are refined. The only input required from the user is the specification of the space group, approximate cell dimensions and detector setting. When the initialization step is finished the program goes back to the first picture and evaluates all data frames in the order they arrive from the measurement. Each element of an electronic picture (pixel) is labelled by the indices of the nearest reflection using the current refined parameters describing the diffraction geometry. If the pixels close to its nearest reflection the counts contribute to the three-dimensional profile; otherwise the counts are used to update the background. Each profile is represented as if the reflection had followed the shortest path through the Ewald sphere and had been recorded on the surface of the sphere. Reflections close to the Ewald sphere are kept in a hash table to allow rapid access for updating the profiles. Reflections which have completely passed through the Ewald sphere are removed from the table and saved for further processing. Intensities are estimated by fitting their profiles to an average shape learned from strong neighbouring reflections. Smoothly varying scaling factors are applied to the Lp-corrected intensities which minimize discrepancies between symmetry-related reflections and fit to a reference data set if available.
1,519 citations
TL;DR: In this article, the reaction of M(II) acetate hydrate (M = Co, Ni, and Zn) with 1,3,5-benzenetricarboxylic acid yields a material formulated as M3(BTC)2·12H2O.
Abstract: The reaction of M(II) acetate hydrate (M = Co, Ni, and Zn) with 1,3,5-benzenetricarboxylic (BTC) acid yields a material formulated as M3(BTC)2·12H2O. These compounds are isostructural as revealed by their XRPD patterns and a single crystal structure analysis performed on the cobalt containing solid [monoclinic, space group C2, a = 17.482 (6) A, b = 12.963 (5) A, c = 6.559 (2) A, β = 112.04°, V = 1377.8 (8) A, Z = 4]. This solid is composed of zigzag chains of tetra-aqua cobalt(II) benzenetricarboxylate that are hydrogen-bonded to yield a tightly held 3-D network. Upon liberating 11 water ligands per formula unit a porous solid results, M3(BTC)2·H2O, which was found to reversibly and repeatedly bind water without destruction of the framework. The proposed 1-D channels of the monohydrate have a pore diameter of 4 × 5 A, which is typical of those observed in zeolites and molecular sieves. The successful inclusion of ammonia into the porous solid was demonstrated. Larger molecules and others without a reactiv...
759 citations
544 citations