Structure validation in chemical crystallography

Spek, Anthony L.

doi:10.1107/s090744490804362x

Cited by 15,327 publications

(12,918 citation statements)

References 27 publications

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“…Whereas, amino hydrogen and water hydrogen atoms were found in the difference Fourier map, positionally fixed and their thermal parameters set to 1.2 times the equivalent U iso in the case of amino groups and 1.5 times for the O\H bonds. In the particular case of C5 the solvent contribution to the scattering was removed with the SQUEEZE routine in PLATON [24] due to the extent of solvent disorder, the formula mass and density informed for this complex don't account for the solvent present. The electron count in cell void volume ran with squeeze gives a total of 66 electrons equivalent to 6.5 water molecules per unit cell.…”

Section: Crystal Structure Determinationmentioning

confidence: 99%

Synthesis, structural characterization and cytotoxic activity of ternary copper(II)–dipeptide–phenanthroline complexes. A step towards the development of new copper compounds for the treatment of cancer

Iglesias¹,

Álvarez²,

Torre³

et al. 2014

Journal of Inorganic Biochemistry

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Section: Crystal Structure Determinationmentioning

confidence: 99%

Synthesis, structural characterization and cytotoxic activity of ternary copper(II)–dipeptide–phenanthroline complexes. A step towards the development of new copper compounds for the treatment of cancer

Iglesias¹,

Álvarez²,

Torre³

et al. 2014

Journal of Inorganic Biochemistry

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“…The final structural models were analyzed using PLATON. 19 Molecular graphics were prepared in Mercury, 20 ORTEP-3, 21 and POV-Ray. 22 Patterns used for qualitative X-ray powder diffraction (PXRD) analysis of the samples were collected on a Philips PW 3710 diffractometer, CuKα radiation, flat plate sample on a zero background in Bragg-Brentano geometry, tension 40 kV, current 40 mA.…”

Section: X-ray Crystallographic Studymentioning

confidence: 99%

Crystal structures and magnetic properties of a set of dihalo-bridged oxalamidato copper(ii) dimers

et al. 2014

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A set of four copper(II) complexes, L 1 -X and L 2 -X (X = Cl, Br; L 1 = N-(L-leucine methyl ester)-N'-((2-pyridin-2-yl)methyl)oxalamide and L 2 = N-benzyl-N'-((2-pyridin-2-yl)methyl)oxalamide) have been synthesized and characterized by X-ray structural analysis, electron paramagnetic resonance (EPR) spectroscopy on single crystal and by SQUID magnetization measurements. X-ray diffraction studies show one-dimensional hydrogen bonded networks of dimeric copper(II)-complexes bridged by two halide ions and with the two metal centers 3.44-3.69Å apart. The geometry at each copper(II) atom is ideal or near ideal square pyramidal. EPR and SQUID studies indicate that all complexes exhibit weak antiferromagnetic interactions between the Cu(II) paramagnetic centers, with exchange parameter |J| ∼1 cm −1 . Magneto-structural comparisons among similar dihalo-bridged Cu(II) dinuclear complexes are also provided, and a possible correlation has been established.

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“…The product was obtained as a green solid (0.23 g, 53%). 1 38,H 5.60,N 5.66. Found: C 50.36,H 5.46,N 5.93. Crystal Structure Determinations.…”

Section: Synthesis Of 2amentioning

confidence: 99%

Probing Intermetallic Coupling in Dinuclear N-Heterocyclic Carbene Ruthenium(II) Complexes

et al. 2011

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N-heterocyclic carbenes (NHCs) have had and continue to have an enormous influence on the development of new and highly powerful catalysts based on transition metals. 1,2 The success of NHCs as ligands has been largely associated with their unique donor properties paired with the strong bond they typically form with transition metals. 3 Despite the rapid evolution of these ligands from niche compounds to some of the most relevant scaffolds for transition metal chemistry, the application of NHC ligands in domains other than catalysis has remained scarce. 4 Perhaps most impressive achievements in noncatalytic domains encompass the exploitation of anticarcinogenic 5 and antimicrobial activities 6 of some NHC metal complexes. Applications in other domains such as molecular electronics have been very limited thus far. This seems remarkable, especially when considering the potential of the metal-NHC synthon in such areas, imparted in particular by the significant π character of the MÀC bond established for various metal NHC complexes. 7,8 This bonding situation is expected to enhance the electronic coupling between a redox-active metal center and the ligand, 9 for example, for catalyst (de)activation, 10 and constitutes a pivotal prerequisite for the construction of transition metal-based molecular diodes. 11 Specifically, electronic communication between metal and ligand provides access to metalÀmetal interactions in bimetallic systems, which is essential for generating mixed-valent species, 12 and which offers advantages for the fabrication of electronically active devices such as switches or junctions in molecular wires. 13 The most successful linkers used today are bi-and terpyridines, 14 and (poly)acetylides. 15 Because of their synthetic flexibility and the covalent MÀC bond, NHCs have great potential for combining the benefits of both types of linkers.Only recently ditopic NHC ligands have emerged as potentially conjugated spacers for interlinking two metal centers. 16 The dicarbene spacer A (Figure 1), pioneered by Bielawski and coworkers, 17 provides a versatile platform for the formation of bimetallic complexes. Despite the apparent conjugation between the two carbene sites, only very weak intermetallic interactions were observed with different metals (Fe, Ru, Ir). 18 Such weak coupling has been attributed tentatively to a small orbital overlap between the NCN amidylidene fragment and the central benzene ring, resulting in an insulating effect of this spacer unit. 18a With heavy transition metals such as iridium, an energy mismatch between the metal 5d orbitals and the carbene 2p orbitals constitutes an additional barrier to electronic metalÀmetal coupling. 18b,19 Consistent with these considerations, related ditopic ligands such as the dicarbene B are less efficient spacers. 20 In contrast, interconnection of the two ligating carbene sites via the nitrogen atom as in C and D may alleviate the insulating effects encountered with spacer A and may thus stimulate metalÀmetal interactions. Because of the i...

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Structure validation in chemical crystallography

Cited by 15,327 publications

References 27 publications

Synthesis, structural characterization and cytotoxic activity of ternary copper(II)–dipeptide–phenanthroline complexes. A step towards the development of new copper compounds for the treatment of cancer

Synthesis, structural characterization and cytotoxic activity of ternary copper(II)–dipeptide–phenanthroline complexes. A step towards the development of new copper compounds for the treatment of cancer

Crystal structures and magnetic properties of a set of dihalo-bridged oxalamidato copper(ii) dimers

Probing Intermetallic Coupling in Dinuclear N-Heterocyclic Carbene Ruthenium(II) Complexes

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