scholarly journals The meso Helix: Symmetry and Symmetry-Breaking in Dynamic Oligourea Foldamers with Reversible Hydrogen-Bond Polarity

2016 ◽  
Vol 128 (33) ◽  
pp. 9809-9813 ◽  
Author(s):  
Romina Wechsel ◽  
James Raftery ◽  
Dominique Cavagnat ◽  
Gilles Guichard ◽  
Jonathan Clayden
Keyword(s):  
Hydrogen Bond ◽  
Symmetry Breaking ◽  
Bond Polarity

scholarly journals The meso Helix: Symmetry and Symmetry-Breaking in Dynamic Oligourea Foldamers with Reversible Hydrogen-Bond Polarity

2016 ◽  
Vol 55 (33) ◽  
pp. 9657-9661 ◽  
Author(s):  
Romina Wechsel ◽  
James Raftery ◽  
Dominique Cavagnat ◽  
Gilles Guichard ◽  
Jonathan Clayden
Keyword(s):  
Hydrogen Bond ◽  
Symmetry Breaking ◽  
Bond Polarity

Symmetry breaking in the axial symmetrical configurations of enolic propanedial, propanedithial, and propanediselenal: pseudo Jahn–Teller effect versus the resonance-assisted hydrogen bond theory

2015 ◽  
Vol 93 (6) ◽  
pp. 673-684 ◽  
Author(s):  
Elahe Jalali ◽  
Davood Nori-Shargh
Keyword(s):  
Density Functional Theory ◽  
Hydrogen Bond ◽  
Symmetry Breaking ◽  
Density Functional ◽  
Teller Effect ◽  
Electron Delocalization ◽  
Functional Theory ◽  
Jahn Teller ◽  
Jahn Teller Effect ◽  
Resonance Assisted Hydrogen Bond

The origin of the symmetry breaking in the axial symmetrical configurations of enolic propanedial (1), propanedithial (2), and propanediselenal (3) have been investigated by means of time-dependence density functional theory and natural bond orbital interpretations. The results obtained at the quantum chemistry composite (G2MP2, CBS-QB3), ab initio molecular orbital (MP2/6-311++G**), and hybrid density functional theory (B3LYP/6-311++G**) levels of theory showed that the hydrogen-centered synchronous axial symmetrical (C2v) configurations of compounds 1–3 possessing the maximum π-electron delocalization within the M1=C2–C3=C4–M5–H6 keto-enol groups are less stable than their corresponding plane symmetrical (Cs) forms. Importantly, the symmetry breaking in the C2v configurations of the enol forms of compounds 1–3 to their corresponding plane symmetrical Cs configurations is due to the pseudo Jahn–Teller effect (PJTE) by mixing the ground A1 and excited B2 electronic states resulting in a PJT (A1 + B2) ⊗ b2 problem. We may expect that by the decrease of the energy gaps between reference states in the C2v forms that are involved in the PJTE decrease from compound 1 to compound 3, the PJT stabilization energy (PJTSE) may increase but the results obtained showed that the corresponding PJTSEs decrease. This fact can be justified by the increase of the electron delocalizations from the nonbonding orbitals of the C=M moieties to the antibonding orbitals of the H–M bonds, which leads to an increase of the π-electron delocalization within the M1=C2–C3=C4–M5–H6 keto-enol groups. In confrontation between the impacts of the resonance-assisted hydrogen bond and PJTE in the structural and configurational properties of compounds 1–3, PJTE has an overwhelming contribution and causes the symmetry breaking of the C2v configurations to their corresponding Cs forms. The correlations between the structural parameters, synchronicity indices, natural charges, PJTSEs, electron delocalizations, and the hardness of compounds 1–3 have been investigated.

Hybrid αγ Polypeptides: Structural Characterization of a C12/C10Helix with Alternating Hydrogen-Bond Polarity

2008 ◽  
Vol 47 (34) ◽  
pp. 6430-6432 ◽  
Author(s):  
Prema G. Vasudev ◽  
Sunanda Chatterjee ◽  
Kuppanna Ananda ◽  
Narayanaswamy Shamala ◽  
Padmanabhan Balaram
Keyword(s):  
Hydrogen Bond ◽  
Structural Characterization ◽  
Bond Polarity

Hydrogen bond induced chiral symmetry breaking in the crystallization of nickel(II) complexes

2014 ◽  
Vol 39 (4) ◽  
pp. 393-398 ◽  
Author(s):  
Guang-Chuan Ou ◽  
Zhi-Zhang Li ◽  
Lin Yuan ◽  
Xian-You Yuan
Keyword(s):  
Hydrogen Bond ◽  
Symmetry Breaking ◽  
Chiral Symmetry ◽  
Chiral Symmetry Breaking

scholarly journals Hydrogen-Bond-Assisted Symmetry Breaking in a Network of Chiral Metal–Organic Assemblies

2019 ◽  
Vol 141 (4) ◽  
pp. 1707-1715 ◽  
Author(s):  
Felix J. Rizzuto ◽  
Patrick Pröhm ◽  
Alex J. Plajer ◽  
Jake L. Greenfield ◽  
Jonathan R. Nitschke
Keyword(s):  
Hydrogen Bond ◽  
Symmetry Breaking ◽  
Metal Organic ◽  
Organic Assemblies

Hybrid αγ Polypeptides: Structural Characterization of a C12/C10Helix with Alternating Hydrogen-Bond Polarity

2008 ◽  
Vol 120 (34) ◽  
pp. 6530-6532 ◽  
Author(s):  
Prema G. Vasudev ◽  
Sunanda Chatterjee ◽  
Kuppanna Ananda ◽  
Narayanaswamy Shamala ◽  
Padmanabhan Balaram
Keyword(s):  
Hydrogen Bond ◽  
Structural Characterization ◽  
Bond Polarity

Symmetry breaking in convergent-beam diffraction

1989 ◽  
Vol 47 ◽  
pp. 480-481
Author(s):  
D.J. Eaglesham
Keyword(s):  
Symmetry Breaking ◽  
Point Group ◽  
X Ray Diffraction ◽  
Multiple Diffraction ◽  
Space Groups ◽  
Atomic Displacements ◽  
Small Probe ◽  
Phase Sensitive ◽  
Convergent Beam

Convergent Beam Electron Diffraction is now almost routinely used in the determination of the point- and space-groups of crystalline samples. In addition to its small-probe capability, CBED is also postulated to be more sensitive than X-ray diffraction in determining crystal symmetries. Multiple diffraction is phase-sensitive, so that the distinction between centro- and non-centro-symmetric space groups should be trivial in CBED: in addition, the stronger scattering of electrons may give a general increase in sensitivity to small atomic displacements. However, the sensitivity of CBED symmetry to the crystal point group has rarely been quantified, and CBED is also subject to symmetry-breaking due to local strains and inhomogeneities. The purpose of this paper is to classify the various types of symmetry-breaking, present calculations of the sensitivity, and illustrate symmetry-breaking by surface strains.CBED symmetry determinations usually proceed by determining the diffraction group along various zone axes, and hence finding the point group. The diffraction group can be found using either the intensity distribution in the discs

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