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.

Characterization of the inhibitor complexes of cobalt carboxypeptidase A by electron paramagnetic resonance spectroscopy.

Abstract: The metal coordination sphere of cobalt-substituted carboxypeptidase A and its complexes with inhibitors has been characterized by X-band electron paramagnetic resonance (EPR) spectroscopy. The temperature dependence of the EPR spectrum of cobalt carboxypeptidase and the g anisotropy are consistent with a distorted tetrahedral geometry for the cobalt ion. Complexes with L-phenylalanine, a competitive inhibitor of peptide hydrolysis, as well as other hydrophobic L-amino acids all exhibit very similar EPR spectra described by three g values that differ only slightly from that of the cobalt enzyme alone. In contrast, the EPR spectra observed for the cobalt enzyme complexes with 2-(mercaptoacetyl)-D-Phe, L-benzylsuccinate, and L-beta-phenyllactate all indicate an approximately axial symmetry of the cobalt atom in a moderately distorted tetrahedral metal environment. Phenylacetate, beta-phenylpropionate, and indole-3-acetate, which exhibit mixed modes of inhibition, yield EPR spectra indicative of multiple binding modes. The EPR spectrum of the putative 2:1 inhibitor to enzyme complex is more perturbed than that of the 1:1 complex. For beta-phenylpropionate, partially resolved hyperfine coupling (122 x 10(-4) cm-1) is observed on the g = 5.99 resonance, possibly indicating a stronger metal interaction for this binding mode. The structural basis for the observed EPR spectral perturbations is discussed with reference to the existing crystallographic kinetic and electronic absorption, nuclear magnetic resonance, and magnetic circular dichroic data.

The Nature of the Metal—Silicon Bond in [M(SiR3)H3(PPh3)3] (M = Ru, Os) And the Crystal Structure of [Os{Si(N-pyrrolyl)3}H3(PPh3)3]

Abstract: The compounds [M(SiR3)H3(PPh3)3] (1: M = Ru, R = 1 - NC4H4 = pyr; 2a-c: M = Os, R = pyr, Et, Ph) are prepared through reaction of either [RuH2(PPh3)4] or [OsH4(PPh3)3] with the appropriate silane HSiR3 (3a-c: R = pyr, Et, Ph). The X-ray structure analysis of compound 2 a and ab initio calculations on the model compounds [Os(SiR3)H3(PH3)3] (4a-c: R = H, NH2, pyr) reveal a trigonal distortion along the Os-Si axis from an idealised tetrahedral geometry for the central OsSiP3 heavy-atom skeleton. The structure can be described as two face-shared octahedra, one based on osmium (OsH3P3) and the other based on silicon (SiH3N3). Studies of the bonding situation in 2 a reveal that the N-pyrrolyl substituents have a marked shortening effect on the osmium-silicon distance (229.3(3) pm) and that each of the three hydride ligands participates in partial three-centre bonding involving osmium, silicon and hydrogen. 1H, 13C, 29Si and 31P NMR spectra were used to determine the solution structures of complexes 1 and 2 a.

On the rotational partition function for tetrahedral molecules

Abstract: A rigorous calculation of the quantum-mechanical rotational partition function for tetrahedral XY4 molecules yields Qr = ( 1 12 )(2IY + 1)4π 1 2 α- 3 2 exp(α/4), where IY is the spin of the Y nucleus, and α ≡ Bhc/kT. This result is accurate to 1 per cent or better for all values of B and T such that α 1 5 .

"Two-in-one" organic-inorganic hybrid MnII complexes exhibiting dual-emissive phosphorescence.

Abstract: Unprecedented organic–inorganic hybrid complexes, [Mn(L)3]MnHal4, containing both four- and hexacoordinated Mn2+ ions were synthesized by reacting MnCl2 or MnBr2 with bis(phosphine oxide) ligands (L) such as dppmO2, dppeO2, and 2,3-bis(diphenylphosphinyl)-1,3-butadiene (dppbO2). In the [Mn(L)3]2+ cation of the complexes, the Mn2+ ion features a [MnO6] octahedral coordination environment (Oh), and the [MnHal4]2− anion adopts a tetrahedral geometry (Td). These “two-in-one” complexes exhibit strong long-lived luminescence (τav = 12–15 ms at 300 K) having interesting thermochromic behavior attributed to the thermal equilibrium between two emission bands. So, in an emission spectrum of the typical complex [Mn(dppbO2)3]MnBr4, the intense “red” (ca. 620 nm) and weak “green” (ca. 520 nm) bands, originating from Mn2+ ions in Oh and Td environments, respectively, are observed. Cooling from 300 to 77 K simultaneously leads to (i) redshift of both bands by ca. 20 nm, (ii) increasing their intensities, and (iii) causing a substantial change of their integral intensity ratio from about 4 : 1 to 2 : 1. As a result, the colour of the emission changes from orange (CIE 0.56, 0.45) at 300 K to deep red (CIE 0.62, 0.39) at 77 K. This behavior was rationalized using steady-state and time-resolved fluorescent spectroscopy at various temperatures. The high photoluminescence quantum yields (up to 61% at 300 K) and fascinating dual-emissive phosphorescence coupled with high thermal stability and solubility suggest a high potential of this novel class of emissive Mn2+ complexes as promising emitters for OLED devices and potential stimuli-responsive materials.