structure of molecules
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Author(s):  
Patrick Wikus ◽  
Wolfgang Frantz ◽  
Rainer Kümmerle ◽  
Patrik Vonlanthen

Abstract Nuclear Magnetic Resonance (NMR) spectroscopy is a wide-spread analytical technique which is used in a large range of different fields, such as quality control, food analysis, material science and structural biology. In the widest sense, NMR is an analytical technique to determine the structure of molecules. At the time of writing this manuscript, commercial NMR spectrometers with a proton resonance frequency ≥ 900 MHz are only available from Bruker. In 2019, Bruker installed the first 1.1 GHz (25.8 T) NMR spectrometer at the St. Jude Children Research Hospital in Memphis, Tennessee, followed by the installation of the first 1.2 GHz (28.2 T) NMR spectrometer at the University of Florence in Italy in 2020. These were the first commercial NMR spectrometers operating at magnetic fields in excess of what can be achieved with conventional low temperature superconductors, and which depend on high temperature superconductors to generate the required magnetic field. In this paper, the requirements on commercial NMR magnets are discussed and the history of high-field NMR magnets is reviewed. Bruker’s R&D program for 1.1 and 1.2 GHz NMR magnets and spectrometers will be described, and some of the key properties of these first commercial NMR magnets with high-temperature superconductors are reported.


2022 ◽  
Vol 9 ◽  
Author(s):  
Marta Chołuj ◽  
Josep M. Luis ◽  
Wojciech Bartkowiak ◽  
Robert Zaleśny

Infrared (IR) spectroscopy is commonly used in chemical laboratories to study the geometrical structure of molecules and molecular complexes. The analysis of experimental IR spectra can nowadays be reliably supported by the results of quantum-chemical computations as vibrational frequencies and corresponding vibrational transition intensities are routinely calculated using harmonic approximation by virtually all quantum chemistry packages. In the present study we combine the methodology of computing vibrational spectra using high-level electron correlation treatments with an analytical potential-based approach to take into account spatial confinement effects. Using this approach, we perform a pioneering analysis of the impact of the spatial confinement caused by a cylindrical harmonic oscillator potential on the harmonic vibrational transition intensities and frequencies of two hydrogen-bonded complexes: HCN…HCN and HCN…HNC. The emphasis is put on the largest-intensity bands, which correspond to the stretching vibrations. The obtained results demonstrate that embedding the molecular complexes in an external confining potential causes significant changes of transition intensities and vibrational frequencies.


2021 ◽  
Vol 2015 (1) ◽  
pp. 012036
Author(s):  
N V Doroshina ◽  
A A Ushkov ◽  
N A Brazhe ◽  
D A Gorin ◽  
M D Mokrousov ◽  
...  

Abstract Surface-enhanced Raman spectroscopy (SERS) is a potent and highly selective tool to chemically identify and determine the structure of molecules and materials. However, the large biomolecules and living cells are still difficult to study using modern SERS-substrates. Here we present a new approach to the geometry of the surface of plasmon nanostructures (cellular surfaces), which makes it possible to efficiently work with volumetric objects as cells or organelles. We use the scanning Raman microscope to map the SERS from the specially prepared microcapsules formed with a Layer-by-Layer deposition method and with built-in Raman tags (Indocyanine green). It demonstrated the possibility to detect SERS signal from Indocyanine green in microcapsules located in cavities, while the signal from the Raman dye in microcapsules located on a flat surface is not detected. The obtained results can be useful in biosensors applications.


2021 ◽  
Vol 30 (5) ◽  
pp. 470-476
Author(s):  
Girija Shankar Singh ◽  

The role of molecular models in teaching chemistry is well-known. It is widely used in explaining the shape of molecules. Several authors have reported the difficulty in teaching stereochemistry/chirality. Some researchers have pleaded that the students face difficulty in solving stereochemistry problems because of poor visualization of three-dimensional structure of molecules. The present paper describes herewith the use of simple and inexpensive ball-stick molecular models in teaching stereoisomerism (conformation, configuration, and chirality in allenes) of organic molecules at undergraduate introductory organic chemistry course. It specially describes the use of simplified molecular models in determining the configuration (R or S) of the molecule.


Materials ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 6098
Author(s):  
Kamila Gryko ◽  
Monika Kalinowska ◽  
Piotr Ofman ◽  
Renata Choińska ◽  
Grzegorz Świderski ◽  
...  

Cinnamic acid (CA), p-coumaric acid (4-hydroxycinnamic acid, 4-HCA), caffeic acid (3,4vdihydroxycinnamic acid, 3,4-dHCA), and 3,4,5-trihydroxycinnamic acid (3,4,5-tHCA) were studied for their structural, anti-/pro-oxidant properties and biodegradability. The FT-IR, FT-Raman, UV/Vis, 1H and 13C NMR, and quantum chemical calculations in B3LYP/6-311++G** were performed to study the effect on number and position of hydroxyl group in the ring on the molecular structure of molecules. The antioxidant properties of the derivatives were examined using DPPH● and HO● radicals scavenging assays, ferric ion reducing antioxidant power (FRAP), cupric reducing antioxidant capacity (CUPRAC), inhibition of linoleic acid oxidation, as well as the biological antioxidant assay with Saccharomyces cerevisiae. Moreover, the pro-oxidant activity of compounds in Trolox oxidation assay was estimated. The effect of the derivatives on environment on the basis of increasing the carbon and nitrogen compounds transformation processes occurring in biological wastewater treatment was studied.


Author(s):  
Алексей Викторович Котомкин ◽  
Наталья Петровна Русакова ◽  
Владимир Владимирович Туровцев ◽  
Юрий Димитриевич Орлов

Найдена равновесная структура молекул ряда тетрафторалканов вида CF-CFH-(CH) -CH, где 0 ≤ n ≤ 7; в рамках QTAIM вычислены электронные параметры групп, рассмотрены внутримолекулярные взаимодействия, построена шкала электроотрицательностей групп. Within the «quantum theory of atoms in molecules» (QTAIM) the electron structure of molecules of the tetrafluorinealkane series CF-CFH-(CH)-CH, where 1 ≤ n ≤ 7, was studied. Intramolecular interactions were considered. Series of electronegativity of the functional groups has been made.


2021 ◽  
pp. 159-180
Author(s):  
Teru Miyake ◽  
George E. Smith

Although the realism debate has focused on the work of Jean Perrin on Brownian motion, this chapter claims that the best place to look for a resolution of this debate is the period after the late 1920s, when stable theory-mediated measurement of molecular parameters first became possible through the application of quantum mechanics to spectroscopy. The chapter first examines how stable measurement of the molecular parameters of diatomic molecules was achieved in spectroscopy and then gauges what evidence there is that this stable measurement is giving spectroscopists access to the real properties and structure of molecules. It argues that an evaluation of the latter question requires a distinction to be made between physically meaningful representations and those that are not, and a full answer requires the deployment of that distinction in the analysis of scientific research on atoms and molecules in the period after 1950.


2021 ◽  
Vol 2021 ◽  
pp. 1-22
Author(s):  
Akbar Jahanbani ◽  
Rana Khoeilar ◽  
Hajar Shooshtari

Irregularity indices are usually used for quantitative characterization of the topological structure of nonregular graphs. In numerous applications and problems in material engineering and chemistry, it is useful to be aware that how irregular a molecular structure is? In this paper, we are interested in formulating closed forms of irregularity measures of some of the crystallographic structures of Cu 2 O p , q , r and crystallographic structure of titanium difluoride of T i F 2 p , q , r . These theoretical conclusions provide practical guiding significance for pharmaceutical engineering and complex network and quantify the degree of folding of long organic molecules.


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