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Molecular geometry
About: Molecular geometry is a research topic. Over the lifetime, 8246 publications have been published within this topic receiving 170635 citations. The topic is also known as: molecular structure.
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TL;DR: The crystal structure of human glutathione reductase has been established at 1.54 A resolution using a restrained least-squares refinement method and shows clearly that there are no buried cations compensating the charge of the pyrophosphate moiety of FAD.
474 citations
TL;DR: The reaction of 2,2,3,3-tetrabromo-1,1,4, 4,4-tetrakis[bis(trimethylsilyl)methyl]-1, 4-diisopropyltetrasilane with four equivalents of potassium graphite (KC8) in tetrahydrofuran produces 1,1-4,4-, which shows half the magnitude of the bond shortening of alkynes compared with that
Abstract: The reaction of 2,2,3,3-tetrabromo-1,1,4,4-tetrakis[bis(trimethylsilyl)methyl]-1,4-diisopropyltetrasilane with four equivalents of potassium graphite (KC 8 ) in tetrahydrofuran produces 1,1,4,4-tetrakis[bis(trimethylsilyl)methyl]-1,4-diisopropyl-2-tetrasilyne, a stable compound with a silicon-silicon triple bond, which can be isolated as emerald green crystals stable up to 100°C in the absence of air. The SiSi triple-bond length (and its estimated standard deviation) is 2.0622(9) angstroms, which shows half the magnitude of the bond shortening of alkynes compared with that of alkenes. Unlike alkynes, the substituents at the SiSi group are not arranged in a linear fashion, but are trans-bent with a bond angle of 137.44(4)°.
467 citations
TL;DR: In this paper, the authors discuss the calculation approaches to determine molecular structure and energy by force-field methods, including the ab initio method, the force field method, mechanical model, and energy minimization schemes.
Abstract: Publisher Summary This chapter discusses the calculation approaches to determine molecular structure and energy by force-field methods. These include the ab initio method, the force-field method, mechanical model, and energy minimization schemes. Methods for determining the internal energy of an organic molecule traditionally depend on heats of combustion. Because calculations of the force-field variety have become so accurate and efficient, many studies using such calculations to attack problems in molecular structure have been and are currently being carried out. These studies give, as a minimum, the bond lengths, bond angles, and torsional angles of the molecules examined, in addition to information concerning energy. The force-field method offers a rapid, convenient and reliable method for the determination of molecular structures and energies. While there are limitations to the method, as there are with each of the experimental methods, the usefulness of this technique is generally appreciated.
441 citations
TL;DR: In this article, the structure optimization and vibrational wavenumber calculations based on the density functional theory (DFT) using the standard B3LYP/6-31G* basis set were performed for the 2,6-bis cyclohexanone.
Abstract: NIR-FT Raman and FT-IR spectra of the crystallized 2,6-bis (p-N,N-dimethyl benzylidene)cyclohexanone (C24H28N2O) have been recorded in the region 3200–500 and 4000–400 cm−1, respectively. The spectral interpretation has been done following full structure optimization and vibrational wavenumber calculations based on the density functional theory (DFT) using the standard B3LYP/6-31G* basis set. The predicted vibrational spectra are in excellent agreement with the experiment, permitting an unambiguous assignment for the unusual downshifting of νCO caused by expanded conjugation effects in the dienone system. The optimized geometry clearly demonstrates the ‘half-chair’ conformation of the central nonheterocyclic ring. The ring CH stretching vibrational modes involving aromatic hydrogen atoms participating in steric interaction have been observed with low intensities. There are valid structural and spectral bases for the enhancement of its bioactivity due to full charge transfer reaction by the substitution of the electron-donating 4-dimethylamino group into the aryl rings. The existence of intramolecular, CH…O, improper, blue-shifted hydrogen bond was investigated by means of the natural bonding orbitals (NBO) analysis. There are also slight dissimilarities in the bond lengths and endocyclic bond angles of both phenyl rings due to the effect of the heavy substitution. The characteristic ring modes have also been assigned in detail. Copyright © 2006 John Wiley & Sons, Ltd.
438 citations
TL;DR: In this article, it was shown that rate constants can be expressed as a product of a nuclear, an electronic, and a frequency factor, and good agreement with measured rate constants is obtained in the normal free-energy region.
Abstract: The crux of the problem is the fact that the equilibrium configuration of a species changes when it loses an electron. Configuration changes of organometallic metal complexes involve the metal-ligand and intra-ligand bond lengths and angles as well as changes in vibrations and rotation of surrounding solvent dipoles. Discussion indicates that rate constants can be expressed as a product of a nuclear, an electronic, and a frequency factor. Good agreement with measured rate constants is obtained in the normal free-energy region. Understanding of electron transfer rates in highly exothermic regions remains uncertain. 75 references, 2 figures, 2 tables.
420 citations