Electric Dipole Moments of Several Molecules from the Stark Effect
TL;DR: The following molecular electric dipole moments, in Debye units, have been obtained from the Stark effect of pure rotational spectra observed in the microwave region: 0.234±0.004 for NF3, 1.03±0,0.01 for PF3; 1.77± 0.06 for CH3CN; 3.83± 0.,3.00±0.,0.02 for HCN, 3.92± 0,2.
Abstract: The following molecular electric dipole moments, in Debye units, have been obtained from the Stark effect of pure rotational spectra observed in the microwave region: 0.234±0.004 for NF3; 1.03±0.01 for PF3; 1.77±0.02 for POF3; 3.00±0.02 for HCN; 3.92±0.06 for CH3CN; 3.83±0.06 for CH3NC; 1.79±0.02 for CH3F; 0.75±0.01 for CH3CCH; 1.26±0.01 for SiF3H. All values apply to the ground vibrational state.
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TL;DR: In this paper, a small effect of the Coriolis interaction between the ν1 and ν3 vibrations was observed on the λ3 spectrum, the analysis of which gave | ζ13(x) | = 0.37 ± 0.04 and the l-type doubling constant q3 was determined to be 42.325 MHz.
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TL;DR: In this paper, the infrared absorption intensities of the fundamental bands of CH3CCH, CD-CCH and CH3CCD were measured in the gas phase by the pressure broadening technique.
Abstract: The infrared absorption intensities of the fundamental bands of CH3CCH, CD3CCH and CH3CCD were measured in the gas phase by the pressure broadening technique. Out of 32 possible sign combinations of (∂p/∂Qi) for each of a1 and e species, only one combination was selected for both species, utilizing the isotopic data, Coriolis information, and the CNDO calculation. Thus, the polar tensor and the effective charges were obtained, as well as the dipole moment derivatives with respect to primitive coordinates. Comparison of these parameter values with those of other molecules suggests that the methyl hydrogens in methyl acetylene resemble those in methyl halides rather than those in saturated hydrocarbons, while the acetylenic hydrogen seems to retain the property in acetylene molecule itself. On the other hand, the CNDO method was not found very successful in this molecule as in propane, cyclopropane, or benzene. In particular, its capability to predict intensity parameter values concerned with the acetylenic...
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TL;DR: The semi-empirical SCF-MO-CNDO theory was used to calculate nuclear quadrupole coupling constants, considering only contributions to the electric field gradient from valence-shell p Orbitals of the same atom as the nucleus of interest, as suggested originally by Townes and Dailey as discussed by the authors.
Abstract: The semi-empirical SCF-MO-CNDO theory is used to calculate nuclear quadrupole coupling constants, considering only contributions to the electric field gradient from valence-shell p Orbitals of the same atom as the nucleus of interest, as suggested originally by Townes and Dailey. For halogen nuclei, fairly accurate results are obtained, but for nitrogen nuclei the results are much poorer.
43 citations
TL;DR: A review of the biological activity of isocyanide-containing molecules can be found in this article, which supports the idea of using the functional group as an unconventional pharmacophore especially useful as a metal coordinating warhead.
Abstract: In eons of evolution, isocyanides carved out a niche in the ecological systems probably thanks to their metal coordinating properties. In 1859 the first isocyanide was synthesized by humans and in 1950 the first natural isocyanide was discovered. Now, at the beginning of XXI century, hundreds of isocyanides have been isolated both in prokaryotes and eukaryotes and thousands have been synthesized in the laboratory. For some of them their ecological role is known, and their potent biological activity as antibacterial, antifungal, antimalarial, antifouling, and antitumoral compounds has been described. Notwithstanding, the isocyanides have not gained a good reputation among medicinal chemists who have erroneously considered them either too reactive or metabolically unstable, and this has restricted their main use to technical applications as ligands in coordination chemistry. The aim of this review is therefore to show the richness in biological activity of the isocyanide-containing molecules, to support the idea of using the isocyanide functional group as an unconventional pharmacophore especially useful as a metal coordinating warhead. The unhidden hope is to convince the skeptical medicinal chemists of the isocyanide potential in many areas of drug discovery and considering them in the design of future drugs.
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TL;DR: In this paper, microwave spectral measurements of the group V-trihalides are assembled and interpreted in terms of s-p hybridization, partial ionic, and partial multiple bond character.
Abstract: By means of microwave spectral measurements the following molecular parameters have been determined: 1. The dipole moment of NF3 is 0.235±0.007 Debye. 2. The nuclear quadrupole coupling of arsenic in AsCl3 is —173±20 Mc. 3. The internuclear distance Sb–Cl and the bond angle Cl–Sb–Cl are 2.325±0.005A and 99.5±1.5°, respectively, in SbCl3.The measured molecular parameters of the group V‐trihalides are assembled and interpreted in terms of s—p hybridization, partial ionic, and partial multiple bond character. In particular, certain regularities in the dipole moments are pointed out which indicate that apparent anomalies in the dipole moments of these molecules can be understood in terms of s—p hybridization.From the evidence of nuclear hyperfine structure, it appears that NF3 and AsH3, as was previously suggested for NH3, have an s—p hybridization which is not simply related to the bond angles. The quadrupole coupling per p‐electron of N14, previously reported to have been established by the measurements on ...
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TL;DR: A microwave spectrograph is described in which the absorption of the gas being studied is modulated by the application of a periodic Stark‐effect field so that the output of the crystal detector contains a radiofrequency component which can be amplified with a narrow‐band amplifier.
Abstract: A microwave spectrograph is described in which the absorption of the gas being studied is modulated by the application of a periodic Stark‐effect field so that the output of the crystal detector contains a radiofrequency component which can be amplified with a narrow‐band amplifier. By using a very narrow band‐width, achieved by employing phase‐sensitive detection, high sensitivity is obtained. The klystron is swept mechanically over the frequency range. Details of the components are given.
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