Analysing Friedel averages and differences

Parsons, Simon; Pattison, Philippa; Flack, H. D.

doi:10.1107/s0108767312034885

Cited by 31 publications

(35 citation statements)

References 16 publications

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“…The complete absolute configuration of 1 was determined by an X-ray crystallographic study of single crystals of 2-(−)-R-MPA-derivative (5). The crystal structure is shown in Figure 3, and the result is consistent with the absolute configuration (3S, 4R), confirming the previous results obtained by Horeau's and Mosher's methods.…”

supporting

confidence: 83%

Absolute Configuration of Clemateol

Pedroso¹,

Gehn²,

Stivanin³

et al. 2017

J. Braz. Chem. Soc.

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The present study reports the determination of absolute stereochemistry of clemateol, an irregular monoterpene containing an epoxy group, which was isolated as the main component from the essential oil of Calea clematidea (Asteraceae). Its absolute stereochemistry was unambiguously established on the basis of detailed nuclear magnetic resonance (NMR) spectroscopic evidence ( 3 J H-H analysis, derivatization as Mosher's esters and nuclear Overhauser effect (NOESY) spectrum) and also by resonance scattering effects in the single crystal X-ray diffraction (XRD) resolution of its (R)-mandelic acid ester derivative.

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supporting

confidence: 83%

Absolute Configuration of Clemateol

Pedroso¹,

Gehn²,

Stivanin³

et al. 2017

J. Braz. Chem. Soc.

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“…Observed and modelled data were then separated in centric and acentric reflexions. [68][69][70][71][72][73][74][75][76][77] The slopes given by the plots of Dobs (difference for paired observed Friedel reflections) vs. Dsingle (difference for paired Friedel reflections calculated from a single domain model) were in perfect agreement with the Flack parameter issued from the least-square refinement including the racemic twin law, evidencing that those compounds are indeed racemic twins. One must note that crystals observed under polarized light did not evidence macroscopic domains of opposite handedness.…”

Section: Results and Discussion Synthesis And Characterization Of Chimentioning

confidence: 60%

“…We calculated then for each point group Rmerge for |Fobs| 2 , A and D (A and D being the average and the difference of Friedel opposites respectively). [68][69][70][71][72][73][74] There was a clear preference for non-centrosymmetric point groups 3 and 32. Systematic extinctions led to potential R3 and R32 space groups respectively.…”

Section: Results and Discussion Synthesis And Characterization Of Chimentioning

confidence: 99%

Design and Study of Structural Linear and Nonlinear Optical Properties of Chiral [Fe(phen)₃]²⁺Complexes

et al. 2018

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The dependence of nonlinear optical properties upon the spin state in molecular switches is still an unexplored area. Chiral [Fe( phen)] complexes are excellent candidates for those studies because they are expected to show nonlinear optical properties of interest and at the same time show photoconversion to a short-lived metastable high-Spin state by ultrafast optical pumping. Herein, we present the synthesis, crystallographic, and spectroscopic comparison of chiral [Fe( phen)] complexes obtained with chiral anions, a new lipophilic derivative of the D-symmetric (As(tartrate)), and D-symmetric tris(catechol)phosphate(V) (TRISCAT), tris(catechol)arsenate(V) (TRISCAS), and 3,4,5,6-tetrachlorocatechol phosphate(V) (TRISPHAT). Complexes [Fe( phen)]( rac-TRISCAT) (2) and [Fe( phen)](X-TRISCAS) (X = rac (3), Δ (4), Λ (5)) were found to be isomorphous in the R32 Sohncke space group with twinning by inversion correlated with the starting chiral anion optical purity. The structures show the [Fe( phen)] complex interacting strongly along its 3-fold axis with two anions. Only the structure of a [Fe( phen)]( rac-TRISPHAT) solvate (6) could be obtained, which showed no particular anion/cation interaction contrary to what was observed previously in solution. The [Fe( phen)](X-As(tartrate)) (X = Δ (7), Λ (8), and racemic mixture (9)) crystallizes in enantiomorphic space groups P321/ P321 with the same solid-state packing. Dichroic electronic absorption studies evidenced racemization for all chiral complexes in solution due to ion pair dissociation, whereas the asymmetric induction is conserved in the solid state in KBr pellets. We evidenced on chiral complexes 4 and 5 strong nonlinear second harmonic generation, the intensity of which could be correlated with the complex electronic absorption.

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“…The Flack parameter converged to a value of 0.1 (2), so it was not possible to distinguish whether the sample was a pure enantiomorph of whatever chirality or whether it was an inversion twin (Flack & Bernardinelli, 2000). This is in agreement with a low value of Friedif stat = 25 (Flack & Bernardinelli, 2008;Parsons et al, 2012). The corresponding assessed standard uncertainty of the Flack parameter (Flack et al, 2006) was 0.29, which is in fair agreement with the refined value.…”

Section: Refinementmentioning

confidence: 69%

A study of the planarity of the pyrrolone fragment in 2-isopropyl-2,3-dihydro-1H-isoindol-1-one

et al. 2016

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Orthophthalaldehyde (o-phthalaldehyde, OPA) is an aromatic dialdehyde bearing two electron-withdrawing carbonyl groups. The reactions of OPA with primary amines are broadly applied for the synthesis of important heterocyclic compounds with biological relevance. A number of such reactions have been investigated recently and several structures of condensation products have been reported, however, the complex reaction mechanism is still not fully understood and comprises concurrent as well as consecutive reactions. The reaction products depend on the primary amine which reacts with OPA, the reaction environment (solvent) and the proportion of the reactants. The title molecule, C11H13NO, the product of the reaction of OPA with isopropylamine, contains a five-membered pyrrole C4N ring with a carbonyl substituent, which forms part of the isoindolinone unit. Though this pyrrole ring contains one C atom in the sp(3)-hybridized state, it is fairly planar. The title molecule has been compared with similar structures retrieved from the Cambridge Structural Database in order to study this phenomenon. The planarity of this fragment has been explained by the presence of partially delocalized C-C, C-N and C-O bonds, and by an inner angle in the planar pentagonal ring (∼108°), which is close to the ideal tetrahedral value for the sp(3)-hybridized state of the constituent C atom. Due to this propitious angle, this C atom can be present in states intermediate between sp(3)- and sp(2)-hybridized in different structures, while still maintaining the planarity of the ring. There are only weak intermolecular C-H...O hydrogen bonds and C-H...π-electron ring interactions in the structure. In particular, it is the pyrrole ring which is involved in these interactions.

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Analysing Friedel averages and differences

Cited by 31 publications

References 16 publications

Absolute Configuration of Clemateol

Absolute Configuration of Clemateol

Design and Study of Structural Linear and Nonlinear Optical Properties of Chiral [Fe(phen)₃]²⁺Complexes

A study of the planarity of the pyrrolone fragment in 2-isopropyl-2,3-dihydro-1H-isoindol-1-one

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Analysing Friedel averages and differences

Cited by 31 publications

References 16 publications

Absolute Configuration of Clemateol

Absolute Configuration of Clemateol

Design and Study of Structural Linear and Nonlinear Optical Properties of Chiral [Fe(phen)3]2+Complexes

A study of the planarity of the pyrrolone fragment in 2-isopropyl-2,3-dihydro-1H-isoindol-1-one

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Design and Study of Structural Linear and Nonlinear Optical Properties of Chiral [Fe(phen)₃]²⁺Complexes