An empirical method for correcting diffractometer data for absorption effects

Walker, Nigel; Stuart, D.I.

doi:10.1107/s0108767383000252

Cited by 6,124 publications

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“…Refraction data were corrected for both Lorentz and polarization effects, and empirical absorption corrections were applied by using the DIFABS program. 20 The experiments for complexes 1 was carried out on a Rigaku Mercury CCD system with graphite monochromated Mo Kα radiation (λ = 0.71070 Å). The crystal was mounted on a glass fiber.…”

Section: X-ray Structure Determinationsmentioning

confidence: 99%

π–π Stacking assisted binding of aromatic amino acids by copper(ii)–aromatic diimine complexes. Effects of ring substituents on ternary complex stability

et al. 2007

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Ternary Cu(II) complexes containing an aromatic diimine (DA = di(2-pyridylmethyl)amine (dpa), 4,4'-disubstituted 2,2'-bipyridine (Y 2 bpy; Y = H (bpy), Me, Cl, N(Et) 2 , CONH 2 , or COOEt), or 2,2'-bipyrimidine) and an aromatic amino acid (AA = p-substituted L-phenylalanine (Xphe; X = H (phe), NH 2 , NO 2 , F, Cl, or Br), L-tyrosine, L-tryptophan (trp), or L-alanine) were studied by X-ray diffraction, spectroscopic, and potentiometric measurements.The structures IntroductionNoncovalent or weak interactions involving aromatic rings attract much attention for their importance in molecular recognition, stabilization of protein structures, and supramolecular architecture in chemistry and biology. [1][2][3][4] Studies on benzene and porphyrin dimers showed that the edge-to-face and offset face-to-face interactions between the aromatic molecules are more effective than the face-to-face interactions, 5,6 and a survey of protein structures revealed that the former type of interactions are most common for phenylalanine residues. 3 Cozzi and Siegel reported that the intensities of face-to-face interactions are influenced by ring substituents;electron-withdrawing groups strengthen the interactions while electron-donating groups weaken them. 7 On the other hand, cation-π interactions have been revealed for various systems including proteins, where the cationic groups of amino acid side chains such as guanidinium and ammonium groups were found to be located close to the aromatic rings of aromatic amino acid residues. 8Both gas-phase experiments and theoretical calculations indicated that alkali metal ions bind strongly to aromatic rings in the gas phase. 8,9 Metalation of porphyrin is known to enhance the π-π interaction between two porphyrin molecules due to intramolecular polarization of the metal ion and the porphyrin. 5,10 We have been studying aromatic ring stacking interactions in ternary Cu(II) and Pd(II) complexes, [M(DA)(AA)] (M = Cu(II) or Pd(II); DA = aromatic diimines such as 1,10-phenanthroline (phen); AA = aromatic amino acids such as L-tyrosine (tyr)); we found that metal-coordinated DA effectively stacks with the side chain aromatic ring of coordinated AA 11 and that the ring substituent in the interacting ring of AA has influence on the stacking. 11,12 While 2N1O-donor tripod-like ligands containing one pyridine and one phenol ring and a pendent indole ring were found to undergo only weak intramolecular indole-pyridine interactions in CH 3 CN, their Pd(II) complexes exhibited much stronger interactions as evidenced by the 1 H NMR upfield shifts due to the ring current effect and the methylene proton signals showing a fixed side chain conformation. 13 The adduct formation between planar Pt(II) complexes, Pt(DA)(L') (L' = 4 ethylenediamine or amino acids), and mononucleotides was revealed to be enthalpically driven mainly through stacking interactions by the relevant thermodynamic parameters 14 and decrease the electron density of the Pt(II) center as seen from and the downfield shift of the 195 Pt NMR s...

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Section: X-ray Structure Determinationsmentioning

confidence: 99%

π–π Stacking assisted binding of aromatic amino acids by copper(ii)–aromatic diimine complexes. Effects of ring substituents on ternary complex stability

et al. 2007

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“…The other nonhydrogen atoms were found by standard difference Fourier techniques. After isotropic block-diagonal least-squares refinement an empirical absorption correction (DIFABS [38]) was applied (crystal dimensions 0.01 X 0.1 X 0.4 mm; ~(Mo-K,) = 41.2 cm-'). Hydrogen atoms were placed in calculated positions.…”

Section: Synthesis Of Bis[8-(dimethylamino)-l-naphthyl]tin Dibromide mentioning

confidence: 99%

Oxidative-addition reactions of molecular diiodine and dibromine to divalent organotin compounds. Crystal structures of bis[8-(dimethylamino)-1-naphthyl]tin(IV) dibromide and {2,6-[bis(dimethylamino)methyl]phenyl}- (4-tolyl)tin(IV) diodide

Jastrzebski

Schaaf

Boersma

et al. 1991

Journal of Organometallic Chemistry

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“…159.5(3) 160.6(5) Ta(1)-C(13)-C (14) 97.9(3) 98.6(5) Ta(1)-C(15)-C (14) 98.6(3) 96.2(4) C(13)-C(14)-C (15) 96.5(4) 97.7(5) C(13)-Ta(1)-C (15) 60.63 (19) 61.0(3) values for C R and C fall in the range 20-50 ppm, and the 1 J(C,H) values of approximately 125 Hz indicate that the carbon atoms of the metallacycle have more aliphatic (sp 3 ) than olefinic (sp 2 ) character. In each complex the absolute differences in chemical shift between the C R and C atoms, i.e.…”

Section: Resultsmentioning

confidence: 99%

“…1 In both 2 and 3 coordination of the inner N(Me) nitrogen donor of CNN makes this nitrogen donor a stereogenic center; Figure 1 shows the S configuration, but both enantiomers are present in the unit cell. Furthermore, the metallacycle Ta-C(13)-C(14)-C(15) in 2 and 3 has an organyl substituent (Me and Ph, respectively) on the -carbon (C (14)) of the ring. Accordingly this CH(R) carbon atom is a stable chiral center and each complex can exist in two diastereoisomeric forms.…”

Section: Resultsmentioning

confidence: 99%

Tantalacyclobutane Complexes Containing the Potentially C,N,N‘-Coordinating Ligand [C₆H₄(CH₂N(Me)CH₂CH₂NMe₂)-2]^- (CNN) and Their Reactivity with Carbon Monoxide and tert-Butyl Isocyanide. X-ray Molecular Structures of [Ta{CH₂CH(Me)CH₂-1,3}(CNN)(O-t-Bu)₂], [Ta{CH₂CH(Ph)CH₂-1,3}(CNN)(O-t-Bu)₂], [Ta{C(O)((CH₂)₃-1,3)}(CN

et al. 1997

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From the reactions of the unsubstituted tantalacyclobutane complex [Ta{(CH 2 ) 3 -1,3}(CNN)-(O-t-Bu) 2 ] (CNN ) [C 6 H 4 (CH 2 N(Me)CH 2 CH 2 NMe 2 )-2] -) (1) with propene and styrene have been isolated in good yields the substituted tantalacyclobutane complexes [Ta{CH 2 CH(Me)-CH 2 -1,3}(CNN)(O-t-Bu) 2 ] (2) and [Ta{CH 2 CH(Ph)CH 2 -1,3}(CNN)(O-t-Bu) 2 ] (3), respectively. The X-ray molecular structures of 2 and 3 show them to be seven-coordinate pentagonal bipyramidal species in which the meridional ligation comprises C,N,N′-bonding of the aryldiamine ligand CNN and σ-bonding of two carbons of the metallacycle; the two alkoxide groups occupy the apical positions. The organyl substituent of the metallacycle is positioned on the -carbon. Complexes 2 and 3 can both be converted back into 1 by reacting them in Et 2 O with ethene. The reaction of 1 with carbon monoxide yields the oxytantalacyclopropane complex [Ta{C(O)((CH 2 ) 3 -1,3)}(CNN)(O-t-Bu) 2 ] (4), which has been isolated as an air-stable white solid in 59% yield. The X-ray molecular structure of 4 reveals that the carbon and oxygen atoms of the CdO function are ligated in the meridional plane with further η 3 -C,N,N′-ligation of CNN and the two alkoxides as found in 2 and 3. Reaction of the tantalacyclobutane complexes 2-4 with 1 equiv of t-BuNC affords the 1:1 insertion products [Ta{C(dN-t-Bu)-CH 2 CH(R)CH 2 -1,4}(CNN)(O-t-Bu) 2 ] (R ) H (5), Me (6), and Ph (7), respectively). Complexes 5 and 7 have been isolated as yellow solids (yields: 5, 62%; 7, 50%), while 6 has been prepared and characterized in situ. 1 H and 13 C NMR spectroscopy of 6 and 7 indicate for each complex the presence of two isomers in solution. The X-ray molecular structure of 7 shows η 2 -C,Nbonding of the CNN ligand through the aryl C ipso atom and the N(Me) donor atom and, most importantly, the presence of two tantalacyclic rings of different sizes that have a common Ta-C bond. The smaller three-membered ring comprises the metal center with the nitrogen and the R-carbon atom of the η 2 -bonded iminoacyl fragment, while the larger five-membered ring is a metallacylopentane system comprising the metal center and four carbon atoms.

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An empirical method for correcting diffractometer data for absorption effects

Cited by 6,124 publications

References 1 publication

π–π Stacking assisted binding of aromatic amino acids by copper(ii)–aromatic diimine complexes. Effects of ring substituents on ternary complex stability

π–π Stacking assisted binding of aromatic amino acids by copper(ii)–aromatic diimine complexes. Effects of ring substituents on ternary complex stability

Oxidative-addition reactions of molecular diiodine and dibromine to divalent organotin compounds. Crystal structures of bis[8-(dimethylamino)-1-naphthyl]tin(IV) dibromide and {2,6-[bis(dimethylamino)methyl]phenyl}- (4-tolyl)tin(IV) diodide

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