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2 results on '"2,2' bipyridine derivative"'

1. Manifestation of diamagnetic chemical shifts of proton NMR signals by an anisotropic shielding effect of nitrate anions

Author

Md. Hedayetullah Mir, S. Mahalakshmi, Dillip Kumar Chand, Himansu Sekhar Sahoo, and R. Raghunathan

Subjects
2,2' bipyridine, Inorganic chemistry, Ethylenediamine, anisotropy, proton nuclear magnetic resonance, Biochemistry, chemistry.chemical_compound, Nitrate, nitrate, complex formation, Drug Discovery, Shielding effect, Molecule, palladium(2,2 bipyridine)dinitrate, Chemical shift, Organic Chemistry, anion, Nuclear magnetic resonance spectroscopy, 2,2' bipyridine derivative, palladium, unclassified drug, Crystallography, chemistry, magnetism, Proton NMR, Diamagnetism, molecular model
Abstract

A remarkable upfield shift of the py? protons of complexed 2,2?-bipyridine in [cis-Pd(bpy)(NO3)2] is observed which is considered to originate from the anisotropic influence of suitably positioned coordinated nitrate anions around the Pd(II) centre of the molecule. A typical complexation-induced downfield shift is observed for the NH2 protons in [cis-Pd(en)(NO3)2] where 'en' stands for ethylenediamine. � 2006 Elsevier Ltd. All rights reserved.

Published
2007

2. A New Class of Ferromagnetically-Coupled Mixed Valence Vanadium(IV/V) Polyoxometalates

Author

Manos, Manolis J., Tasiopoulos, Anastasios J., Tolis, Evangelos I., Lalioti, N., Woollins, J. D., Slawin, A. M. Z., Sigalas, Michael P., Kabanos, Themistoklis A., Tasiopoulos, Anastasios J. [0000-0002-4804-3822], and Kabanos, Themistoklis A. [0000-0001-6944-5153]

Subjects
chemical reaction, 2,2' bipyridine, Denticity, Ab initio, Crystal structure, X ray analysis, ligand, Catalysis, law.invention, Magnetic susceptibility, Paramagnetism, phenanthroline derivative, Computational chemistry, law, Intermolecular interaction, Antiferromagnetism, Electron paramagnetic resonance, Reaction kinetics, Paramagnetic resonance, methanol, ab initio calculation, Valence (chemistry), Chemistry, Polyoxometalates, electron spin resonance, Organic Chemistry, article, ferromagnetic material, temperature, Vanadium, General Chemistry, vanadium derivative, 1,10 phenanthroline, 2,2' bipyridine derivative, structure analysis, triethylamine, Vanadium compounds, Crystallography, UHF calculations, Synthesis (chemical), magnetism, metal derivative, molecular interaction, Coupling constants, Ferromagnetism, Ferromagnetic materials
Abstract

Reaction of [V(VI)OCl(2)(thf)(2)] with a bidentate nitrogen-donor ligand (L: phen=1,10-phenanthroline, 5-mephen=5-methyl-1,10-phenanthroline, bipy=2,2'-bipyridine, 5,5'-me(2)bipy=5,5'-dimethyl-2,2'-bipy) in methyl alcohol, in the presence of triethylamine, leads to the formation of hexameric [V(2) (IV)V(4) (V)] oxo-alkoxo-vanadates of the general formula [V(6)O(12)(mu(2)-OCH(3))(4)(L)(4)].x H(2)O [L=phen (1.4 H(2)O), 5-mephen (2.6 H(2)O), bipy (3.4 H(2)O), 5,5'-me(2)bipy (4.H(2)O)]. X-ray structure analysis of 1.2 H(2)O and 4.8 CH(3)OH revealed a pair of V(3)O(13)N(4) trimeric units sharing two corners, with a centrosymmetric planar V(6)-core. In addition, a fully oxidized V(V) species [V(V) (4)O(8)(OCH(3))(2)(mu(3)-OCH(3))(2)(5,5'-me(2)bipy)(2)].3 CH(3)OH (5.3 CH(3)OH) was isolated from the reaction mixture used for the synthesis of 4.H(2)O. The crystal structure of 5.3 CH(3)OH revealed a dicubane-like framework with two missing vertices. Electron paramagnetic resonance (EPR) and variable temperature magnetic susceptibility studies for the hexamers 1.4 H(2)O and 3.4 H(2)O showed the complete localization of the single 3d electrons on the V(IV) ions and unusual ferromagnetic interaction between the two paramagnetic vanadium(IV) ions separated by a distance of about 5.1 A. Furthermore, intermolecular antiferromagnetic interactions through pi-contacts of phenyl rings were observed for these species below 8 K. The ferromagnetic exchange coupling observed in the hexanuclear compounds 1.4 H(2)O and 3.4 H(2)O is also discussed using ab initio UHF calculations on a model compound. The value of the exchange coupling constant (3.7 cm(-1)) for this model compound, calculated using the broken symmetry approach, is in good agreement, both in sign and magnitude, with the experimental J values (6.00 cm(-1) for 1.4 H(2)O and 8.54 cm(-1) for 3.4 H(2)O).

Published
2003

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