Abstract-The chemical shifts of aromatic nitriles of the general structure pnru-Y-C&-X-CN with X = 0, S, Se and N(CH3) have been investigated by the 13C NMR technique. For cyanates (X = 0) the 14N shifts and for Y = F the 19F shifts were likewise measured. The chemical shifts and the corresponding 13C shift increments A, have been found to correlate with the appropriate substituent constants uRo, oDo and oI, as well as with the n-electron densities calculated in the PPP approximation.Zusarnmenfassung-An aromatischen Ni trilverbindungen der allgemeinen Struktur pura-Y-C6H,-X-CN mit X = 0, S, Se und N(CH,) wurden die 13C-NMR-sowie fur X = 0 die 14N-NMRund fur Y = F die lSF-NMR-chemischenVerschiebungen bestimmt. Die Merjergebnisse wurden in Zusammenhang mit der elektronischen Struktur der Molekule (Substituentenkonstanten, TElektronendichten in PPP-Naherung) diskutiert.
A specific force field of Consistent Valence Force Field type was developed with the aim to simulate the structures of catalysts of vanadium phosphorus oxide type and the reversible adsorption of organic compounds on specific crystallographic planes of such catalysts by molecular modeling. The appropriate parameters were derived for the bonded (stretching, bending, and torsional deformations) and nonbonded (attractive and repulsive van der Waals and Coulomb forces) atomic interactions for VϪO and PϪO bonds in typical fragments of these catalysts with the vanadium atom in the oxidation state IV. The parameters for bonded interactions were computed from Hessian matrices, supplied by the program DMol for performing Density Functional Theory, by means of a program for non-linear regression. The DMol program was applied to energy minimize structures of known vanadium phosphorus oxides, which were compared with Inhaltsübersicht. Es wurde eine Erweiterung des bekannten Kraftfeldes vom Typ CVFF für Molecular Modeling mit Festkörperstrukturen von Katalysatoren vom Vanadiumphosphoroxid-Typ mit Vanadium im Oxidationszustand IV und für die Simulation der Adsorption von organischen Molekülen an ausgewählten Kristallflächen erarbeitet. Die notwendigen Parameter für die sog. bonded (stretching-, bending-und Torsions-Deformationen) und für die sog. nonbonded Wechselwirkungen (van der Waals-und Coulomb-Wechselwirkungen) in VϪO-, PϪO-und OϪH-Gruppen in typischen Fragmenten solcher Katalysatoren wurden abgeleitet. Hesse-Matrizen wurden mittels der Dichtefunktionalmethode erstellt.
The coordination of Cu" ions in Anderson and Keggin type heteropolyanion compounds in their polycrystalline and corresponding magnetically diluted forms {(NH,),[Zn(OH),Mo601 8] . nH,O/CuZ+ ; ((CH3),N),[Zn04W, 2036] * nH20/Cu2+} have been investigated by means of chemical, spectroscopic (EPR, IR), diffraction (X-ray) and quantum-mechanical methods. Simple model compounds with known Cu-0 coordination have been used for comparison. In both the Anderson ion [ C U ( O H ) ~M O ~O , ~] ~-and the Keggin ion [Si O,Wl 03,C~0,(OH,)]6-the copper coordination polyhedra consist of six oxygen atoms, forming a distorted octahedron. As expected, the magnetically diluted Anderson compound exhibits a pronounced dynamic Jahn-Teller effect.No arguments for the existence of a Keggin species with Cull ions on the central tetrahedral site [CuO,W, 20,,]6could be derived from the experimental and theoretical investigations. The Cu2+ ions incorporated into the products resulting from different attempts to synthesize the Keggin structure with a central copper heteroatom appear to be [cU(oH2)6]2' units. Therefore, the calculations of selected molecular subunits for the assumed Keggin compounds did not yield the experimental EPR parameters. The g tensor calculations in the CND0/2 approximation are consistent with the EPR spectra of the Cu Anderson compound.
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