نتایج جستجو برای: nmr shielding tensor

تعداد نتایج: 110240  

Journal: :Frontiers in Chemistry 2023

In this study, long-lived nuclear singlet order methods are combined with diffusion tensor imaging the purpose of characterizing full molecules diffusing freely in large pores up to a millimeter size. Such sizes out reach conventional because limitations imposed by relaxation decay constant longitudinal magnetization. A singlet-assisted methodology able circumvent such is discussed, and new pos...

Hooriye Yahyaei Neda Hasanzadeh

In this research, Quantum-mechanical calculations were performed at the HF method with the 6-31+G*basis set and at the B3LYP method with the 6-31+G* basis set in the gas phase and five solvents such as water, DMSO, methanol, ethanol and dichloromethane at six temperatures. According to these theoretical results of IR, we extracted thermo chemical parameters such as enthalpy (∆H Kcal/mol), Gibbs...

Journal: :Review of Scientific Instruments 2021

Recently, in situ studies using nuclear magnetic resonance (NMR) have shown the possibility to monitor local transport phenomena of gas-phase reactions inside opaque structures. Their application heterogeneously catalyzed remains challenging due inherent temperature and pressure constraints. In this work, an NMR-compatible reactor was designed, manufactured, tested, which can endure high temper...

2017
Robert Laskowski Khoong Hong Khoo Frank Haarmann Peter Blaha

We present first-principles calculations of the isotropic NMR Ga shielding in metallic MGa2 with M = Ca, Sr, Ba and MGa4 with M = Na, Ca, Sr and Ba. We show that the experimentally observed trend of Ga NMR shifts is as expected driven mainly by the spin part of the response, but the orbital contribution must not be neglected. For all analyzed compounds the spin contact term constitute the major...

2012
Tomasz Pawlak Marek J. Potrzebowski Jiří Czernek

Hooriye Yahyaei Neda Hasanzadeh

In this research, Quantum-mechanical calculations were performed at the HF method with the 6-31+G*basis set and at the B3LYP method with the 6-31+G* basis set in the gas phase and five solvents such as water, DMSO, methanol, ethanol and dichloromethane at six temperatures. According to these theoretical results of IR, we extracted thermo chemical parameters such as enthalpy (∆H Kcal/mol), Gibbs...

2017
Stefan Grimme Christoph Bannwarth Sebastian Dohm Andreas Hansen Jana Pisarek Philipp Pracht Jakob Seibert Frank Neese

We present a composite procedure for the quantum-chemical computation of spin-spin-coupled 1 H NMR spectra for general, flexible molecules in solution that is based on four main steps, namely conformer/rotamer ensemble (CRE) generation by the fast tight-binding method GFN-xTB and a newly developed search algorithm, computation of the relative free energies and NMR parameters, and solving the sp...

2012
Abedien Zabardasti

The aromatic character of porphyrins can also be seen by NMR spectroscopy. Studies performed in the last decades demonstrated that 1H NMR spectra are very informative and adequately reflect the structural features of porphyrins.[1] The presence of the extended delocalized -electron system of the porphyrin macrocycle gives rise to a strong ring current in the molecules placed in the magnetic fi...

2012
K. R. Koch

Although some of the platinum(II/IV) and rhodium(III) chemistry is considered ‘old’ and wellknown, the application of modern multinuclear NMR spectroscopic methods to this chemistry in solution reveals new details about their rich and relevant solution chemistry. In this paper we will briefly illustrate that the highly-sensitive 195 Pt NMR shielding is an excellent probe to explore aspects such...

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