Steric effects on the dialkyl substituted X2C2Si silylenes: A theoretical study

2006 ◽  
Vol 17 (7) ◽  
pp. 619-633 ◽  
Author(s):  
M. Z. Kassaee ◽  
S. M. Musavi ◽  
S. Soleimani-Amiri ◽  
M. Ghambarian
Keyword(s):  
Theoretical Study ◽  
Steric Effects

scholarly journals Theoretical Study of N-Heterocyclic-Carbene–ZnX2 (X = H, Me, Et) Complexes

Materials ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 6147
Author(s):  
Mirosław Jabłoński
Keyword(s):  
Theoretical Study ◽  
Twist Angle ◽  
Steric Effects ◽  
Torsional Angle ◽  
Steric Repulsion ◽  
Hydrogen Atoms ◽  
Wide Range ◽  
The Relationship ◽  
Tetrel Bonds ◽  
Negligible Influence

This article discusses the properties of as many as 30 carbene–ZnX2 (X = H, Me, Et) complexes featuring a zinc bond C⋯Zn. The group of carbenes is represented by imidazol-2-ylidene and its nine derivatives (labeled as IR), in which both hydrogen atoms of N-H bonds have been substituted by R groups with various spatial hindrances, from the smallest Me, iPr, tBu through Ph, Tol, and Xyl to the bulkiest Mes, Dipp, and Ad. The main goal is to study the relationship between type and size of R and X and both the strength of C⋯Zn and the torsional angle of the ZnX2 plane with respect to the plane of the imidazol-2-ylidene ring. Despite the considerable diversity of R and X, the range of dC⋯Zn is quite narrow: 2.12–2.20 Å. On the contrary, D0 is characterized by a fairly wide range of 18.5–27.4 kcal/mol. For the smallest carbenes, the ZnX2 molecule is either in the plane of the carbene or is only slightly twisted with respect to it. The twist angle becomes larger and more varied with the bulkier R. However, the value of this angle is not easy to predict because it results not only from the presence of steric effects but also from the possible presence of various interatomic interactions, such as dihydrogen bonds, tetrel bonds, agostic bonds, and hydrogen bonds. It has been shown that at least some of these interactions may have a non-negligible influence on the structure of the IR–ZnX2 complex. This fact should be taken into account in addition to the commonly discussed R⋯X steric repulsion.

Theoretical Study on Steric Effects of DNA Phosphorothioation: B-Helical Destabilization in Rp-Phosphorothioated DNA

2012 ◽  
Vol 116 (35) ◽  
pp. 10639-10648 ◽  
Author(s):  
Yi-Chao Zhang ◽  
Juan Liang ◽  
Peng Lian ◽  
Yiwen Han ◽  
Yifan Chen ◽  
...  
Keyword(s):  
Theoretical Study ◽  
Steric Effects

The Structure of Two 1-(Nitrophenyl)-Δ2-pyrazolines: a Crystallographic and Theoretical Study

2004 ◽  
Vol 57 (11) ◽  
pp. 1103 ◽  
Author(s):  
Glenn P. A. Yap ◽  
Ibon Alkorta ◽  
Nadine Jagerovic ◽  
José Elguero
Keyword(s):  
Density Functional Theory ◽  
Solid State ◽  
Gas Phase ◽  
Density Functional ◽  
Theoretical Study ◽  
Chemical Shifts ◽  
Molecular Structures ◽  
Steric Effects ◽  
Functional Theory ◽  
Crystal And Molecular Structures

The crystal and molecular structures of two nitrophenylpyrazolines have been determined. The geometries have been used as starting geometries for density functional theory (DFT) calculations. The differences in conformation between both molecules and between the solid state and gas phase are explained in terms of steric effects. An attractive intramolecular N···N interaction between the nitro group and the pyrazoline N2 nitrogens has been found. Absolute shieldings have been calculated (GIAO) and compared with experimental 1H and 13C chemical shifts.

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