Tetrahedral molecular geometry

About: Tetrahedral molecular geometry is a research topic. Over the lifetime, 1795 publications have been published within this topic receiving 30706 citations.

Spectroscopic and Electronic Structural Studies of Blue Copper Model Complexes. 1. Perturbation of the Thiolate−Cu Bond

Abstract: A tris(pyrazolyl)hydroborate triphenylmethylthiolate Cu(II) model complex (1) that reproduces structural and spectroscopic features of active sites of blue Cu proteins is characterized using low-temperature absorption, magnetic circular dichroism (MCD), X-ray absorption (XAS), and resonance Raman (rR) spectroscopies combined with DFT calculations to define its electronic structure. The electronic structure of 1 is further related to the oxidized Cu site in plastocyanin. The key spectral differences relative to plastocyanin include an increase in the intensity of the S pπ → Cu CT band and a decrease in the absorption intensity at ∼450 nm. The energies of d → d transitions in 1 decrease relative to plastocyanin, which reflects the more tetrahedral geometry of 1. S K-edge XAS measurements demonstrate a more covalent thiolate interaction in the HOMO of 1 (52% S p) than in plastocyanin (38% S p). The effects of the high thiolate covalency on the absorption and Raman spectral features for 1 are evaluated. Addit...

Torsional ground state splitting for tetrahedral molecules

Abstract: With improved neutron scattering and nuclear magnetic resonance techniques it has been possible to observe the splitting of the torsional ground state—commonly referred to as tunnel splitting—of a number of high symmetry molecules in various crystal fields. The tunnel splitting depends nearly exponentially on the strength of the potential experienced by a molecule as it rotates in the crystal. Tunneling spectroscopy may thus be developed into a sensitive probe for measuring rotational potentials once the relation between the potentials and the tunnel splitting is known. We have used the pocket state formalism to calculate the splitting for tetrahedral molecules in tetrahedral fields. With increasing potentials the wave function becomes smaller in the overlap region making an accurate prediction of the tunnel splittings more difficult. Our calculation provides reliable results for splittings from 200 μeV down to about 1 μeV. Detailed predictions are made for the isotope effect in solid methane and for the ...

Synthesis, Structure, and DNA Cleavage Activity of New Trinuclear Zn3 and Zn2Cu Complexes of a Chiral Macrocycle: Structural Correlation with the Active Center of P1 Nuclease

Abstract: New homo trinuclear Zn(II) complexes [Zn3L1(μ-OAc)](ClO4)2·3CHCl3·H2O, 1, and [Zn3L1(μ-OAc)]·ClO4·PF6·5CH3OH·H2O, 2, and hetero trinuclear complex [Zn2CuL1(μ-OAc)](ClO4)2·3CHCl3·H2O, 3, of optically active hexaaza triphenolic macrocycle H3L1 were synthesized and crystallographically characterized. The cation [Zn3L1(μ-OAc)]+ structure of 1 and 2 closely resembles the trinuclear Zn(II) active site of P1 nuclease. The distorted tetrahedral geometry of Zn3 was successfully reproduced at Cu1 in complex 3. The complexes 2 and 3 cleave CT DNA at 37 and 50 °C.

Metal ions directing the geometry and nuclearity of azido-metal(II) complexes derived from bis(2-(3,5-dimethyl-1H-pyrazol-1-yl)ethyl)amine

Abstract: The reaction of a methanolic solution containing M(ClO4)2·nH2O (M = Cu, Ni, Zn or Cd) or CoCl2·6H2O with bis(2-(3,5-dimethyl-1H-pyrazol-1-yl)ethyl)amine (bedmpza) in the presence of NaN3 afforded the complexes [Cu(bedmpza)(μ1,1-N3)]2(ClO4)2 (1), [Ni(bedmpza)(N3)(μ1,1-N3)]2·1.5H2O (2), [Co(bedmpza)(N3)2] (3), [Zn(bedmpza)(N3)]ClO4 (4) and [Cd(bedmpza)(N3)(μ1,1-N3)]2·1.5H2O (5). The five complexes were characterized by spectroscopic techniques and their molecular structures were determined by single crystal X-ray crystallography. The two mononuclear complexes 3 and 4 display distorted TBP and tetrahedral geometry, respectively with the azide ions acting as monodentate ligands. Doubly bridged end-on-azido dinuclear complexes were obtained in the remaining compounds. Compounds 2 and 5 are isomorphic with distorted octahedral geometry, whereas distorted square pyramidal geometry was determined in the Cu(II) complex 1. The magnetic properties for complexes 1 and 2 were investigated by measuring the magnetic susceptibilities at variable temperatures (300–2 K). The Ni(II) complex exhibits moderate ferromagnetic coupling, whereas [Cu(bedmpza)(μ1,1-N3)]2(ClO4)2 (1) which contains two crystallographic independent dinuclear subunits in the unit cell, with different Cu–N(N3)–Cu bond angles, reveals different signs in the magnetic coupling. The complex represents the first example in the literature that has simultaneously two moieties with ferro- (J = 15.4 cm−1) and antiferromagnetic (J = −18.9 cm−1) interactions.

Liquid-liquid phase transitions of phosphorus via constant-pressure first-principles molecular dynamics simulations.

Abstract: Pressure-induced phase transitions in liquid phosphorus have been studied by constant-pressure first-principles molecular dynamics simulations. By compressing a low-pressure liquid which consists of the tetrahedral P4 molecules, a structural phase transition from the molecular to polymeric liquid (a high-pressure phase) observed in the recent experiment by Katayama et al. [Nature (London) 403, 170 (2000)] was successfully realized. It is found that this transition is caused by a breakup of the tetrahedral molecules with large volume contraction. The same transition is also realized by heating. This indicates that only the polymeric liquid can stably exist at high temperature.