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Vanadium-51 Nuclear Magnetic Resonance
Vanadium-51 nuclear magnetic resonance (51V NMR spectroscopy) is a method for the characterization of vanadium-containing compounds and materials. 51V comprises 99.75% of naturally occurring element. The nucleus is quadrupolar with I = 7/2, which is not favorable for NMR spectroscopy. The quadrupole moment is small, thus the linewidths are small. The magnetogyric ratio is relatively high (+7.0492 rad T−1s−1), such that 51V has 38% receptivity vs 1H. Its resonance frequency is close to that of 13C (gyromagnetic ratio = 6.728284 rad T−1s−1). The chemical shift dispersion is great as illustrated by this series: 0 for VOCl3 (chemical shift standard), −309 for VOCl2(O-i-Pr), −506 VOCl(O-i-Pr)2, and −629 VO(O-i-Pr)3. For vanadates, the parent orthovanadate In chemistry, a vanadate is an anionic coordination complex of vanadium. Often vanadate refers to oxoanions of vanadium, most of which exist in its highest oxidation state of +5. The complexes and are referred t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nuclear Magnetic Resonance Spectroscopy
Nuclear magnetic resonance spectroscopy, most commonly known as NMR spectroscopy or magnetic resonance spectroscopy (MRS), is a spectroscopic technique to observe local magnetic fields around atomic nuclei. The sample is placed in a magnetic field and the NMR signal is produced by excitation of the nuclei sample with radio waves into nuclear magnetic resonance, which is detected with sensitive radio receivers. The intramolecular magnetic field around an atom in a molecule changes the resonance frequency, thus giving access to details of the electronic structure of a molecule and its individual functional groups. As the fields are unique or highly characteristic to individual compounds, in modern organic chemistry practice, NMR spectroscopy is the definitive method to identify monomolecular organic compounds. The principle of NMR usually involves three sequential steps: # The alignment (polarization) of the magnetic nuclear spins in an applied, constant magnetic field B0. # The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Magnetogyric Ratio
In physics, the gyromagnetic ratio (also sometimes known as the magnetogyric ratio in other disciplines) of a particle or system is the ratio of its magnetic moment to its angular momentum, and it is often denoted by the symbol Gamma, , gamma. Its SI unit is the radian per second per tesla (unit), tesla (rad⋅s−1⋅T−1) or, equivalently, the coulomb per kilogram (C⋅kg−1). The term "gyromagnetic ratio" is often used as a synonym for a ''different'' but closely related quantity, the g-factor (physics), -factor. The -factor only differs from the gyromagnetic ratio in being dimensionless. For a classical rotating body Consider a Electrical resistivity and conductivity, nonconductive Electric charge, charged body rotating about an axis of symmetry. According to the laws of classical physics, it has both a magnetic dipole moment due to the movement of charge and an angular momentum due to the movement of mass arising from its rotation. It can be shown that as long as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orthovanadate
In chemistry, a vanadate is an anionic coordination complex of vanadium. Often vanadate refers to oxoanions of vanadium, most of which exist in its highest oxidation state of +5. The complexes and are referred to as hexacyanovanadate(III) and nonachlorodivanadate(III), respectively. A simple vanadate ion is the tetrahedral orthovanadate anion, (which is also called vanadate(V)), which is present in e.g. sodium orthovanadate and in solutions of in strong base ( pH > 13). Conventionally this ion is represented with a single double bond, however this is a resonance form as the ion is a regular tetrahedron with four equivalent oxygen atoms. Additionally a range of polyoxovanadate ions exist which include discrete ions and "infinite" polymeric ions. There are also vanadates, such as rhodium vanadate, , which has a statistical rutile structure where the and ions randomly occupy the positions in the rutile lattice, that do not contain a lattice of cations and balancing ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Decavanadate
Sodium decavanadate describes any member of the family of inorganic compounds with the formula Na6 10O28H2O)n. These are sodium salts of the orange-colored decavanadate anion 10O28sup>6−. Numerous other decavanadate salts have been isolated and studied since 1956 when it was first characterized. Preparation The preparation of decavanadate is achieved by acidifying an aqueous solution of ortho-vanadate: :10 Na3 O4 + 24 HOAc → Na6 10O28 + 12 H2O + 24 NaOAc The formation of decavanadate is optimized by maintaining a pH range of 4–7. Typical side products include metavanadate, O3sup>−, and hexavanadate, 6O16sup>2−, ions. Structure The decavanadate ion consists of 10 fused VO6 octahedra and has D2h symmetry. The structure of Na6 10O28�18H2O has been confirmed with X-ray crystallography. The decavanadate anions contains three sets of equivalent V atoms (see fig. 1). These include two central VO6 octahedra (Vc) and four each peripheral tetragonal-pyramidal VO5 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nuclear Magnetic Resonance
Nuclear magnetic resonance (NMR) is a physical phenomenon in which nuclei in a strong constant magnetic field are perturbed by a weak oscillating magnetic field (in the near field) and respond by producing an electromagnetic signal with a frequency characteristic of the magnetic field at the nucleus. This process occurs near resonance, when the oscillation frequency matches the intrinsic frequency of the nuclei, which depends on the strength of the static magnetic field, the chemical environment, and the magnetic properties of the isotope involved; in practical applications with static magnetic fields up to ca. 20 tesla, the frequency is similar to VHF and UHF television broadcasts (60–1000 MHz). NMR results from specific magnetic properties of certain atomic nuclei. Nuclear magnetic resonance spectroscopy is widely used to determine the structure of organic molecules in solution and study molecular physics and crystals as well as non-crystalline materials. NM ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
