Search results for "Theoretical calculations"
showing 10 items of 12 documents
Computational investigations of 18-electron triatomic sulfur–nitrogen anions
2018
MRCI-SD/def2-QZVP and PBE0/def2-QZVP calculations have been employed for the analysis of geometries, stabilities, and bonding of isomers of the 18-electron anions N2S2−, NS2−, and NSO−. Isomers of the isoelectronic neutral molecules SO2, S2O, S3, and O3 are included for comparison. The sulfur-centered acyclic NSN2−, NSS−, and NSO− anions are the most stable isomers of their respective molecular compositions. However, the nitrogen-centered isomers SNS− and SNO− lie close enough in energy to their more stable counterparts to allow their occurrence. The experimental structural information, where available, is in good agreement with the optimized bond parameters. The bonding in all investigate…
Supramolecular Assembly of Metal Complexes by (Aryl)I⋯dz2[PtII] Halogen Bond
2020
The theoretical data for the half‐lantern complexes [Pt(C^N)(μ‐S^N)] 2 ( 1 – 3 ; С^N is cyclometalated 2‐Ph‐benzothiazole; S^N is 2‐SH‐pyridine 1 , 2‐SH‐benzoxazole 2 , 2‐SH‐tetrafluorobenzothiazole 3 ) indicate that the Pt···Pt orbital interaction leads to an increment of the nucleophilicity of the outer d z 2 ‐orbitals to provide assembly with electrophilic species. 1 – 3 were co‐crystallized with bifunctional halogen bond (XB) donors to give adducts ( 1 – 3 ) 2 ∙(1,4‐diiodotetrafluorobenzene) and infinite polymeric [ 1 ·1,1’‐diiodoperfluorodiphenyl] n . X‐ray crystallography revealed that the supramolecular assembly is achieved via (Aryl)I∙∙∙ d z 2 [Pt II ] XB between iodine σ‐holes and …
Pt(II) nitrile complexes: New insights on old complexes from a combined experimental and theoretical study
2017
Abstract The spectroscopic characterization of cis - and trans -[PtCl 2 (NCR) 2 ] (R = CH 3 , Ph, CH 2 Ph) was reported in solid state and solution phase. Moreover, the X-ray structures of cis -[PtCl 2 (NCCH 3 ) 2 ], cis - and trans -[PtCl 2 (NCPh) 2 ] were redetermined at low temperature. FT-IR and NMR showed a blue-shift and a slight shielding of the νCN and δ ( 13 C CN ) values, respectively, in a counterintuitive way with respect to the well known improved reactivity towards nucleophiles of nitriles ligands coordinated to platinum(II), when compared to their free forms. These spectroscopic behaviors were also confirmed by theoretical experiments at DFT level. Moreover, DFT approach show…
Interactions of zinc octacarboxyphthalocyanine with selected amino acids and with albumin
2015
Effect of selected amino acids (glycine, l-histidine, l-cysteine, l-serine, l-tryptophan) and albumin on the spectroscopic properties and photostability of zinc octacarboxyphthalocyanine (ZnPcOC) was explored in the phosphate buffer at a pH of 7.0. The photodegradation of ZnPcOC alone and in the presence of amino acids or albumin has been investigated in aqueous phase using UV-366 nm and daylight irradiation. Kinetic analysis showed that the interaction with amino acids or albumin enhances the photostability of ZnPcOC. To answer the question of how zinc phthalocyanine interacts with amino acids extensive DFT calculations were performed. Analysis of the optimized geometry features of ZnPcOC:…
Structural and Molecular Characterization of meso-Substituted Zinc Porphyrins: A DFT Supported Study
2011
Structural parameters of a range of over 100 meso-substituted zinc porphyrins were reviewed and compared to show how far the nature of the functional group may affect the interatomic distances and bond angles within the porphyrin core. It was proved that even despite evident deformations of the molecular structure, involving twisting of the porphyrin's central plane, the coupled π-bonding system remains flexible and stable. DFT calculations were applied to a number of selected porphyrins representative for the reviewed compounds to emphasize the relevance of theoretical methods in structural investigations of complex macrocyclic molecular systems. Experimental and DFT-simulated IR spectral …
A combined experimental and theoretical study of the thermal [3+2] cycloaddition of carbonyl ylides with activated alkenes
2018
International audience; 4-Benzoyl-3,5-diaryltetrahydrofuran-2,2-dicarbonitriles were first synthesized from 2,2-dicyano-3-aryloxiranes and chalcones at toluene reflux; the 4,5-cis products proved to be predominantly formed and were isolated. Whereas shortened reaction times were observed by using microwave irradiation or catalytic cuprous chloride, no significant stereoselectivity change was in general noticed. Reacting 2,2-dicyano-3-aryloxiranes with 2-cyclopentenone next afforded 3-aryl-4-oxohexahydro-1H-cyclopenta[c]furan-1,1-dicarbonitriles, and the endo stereoisomers were isolated. That no stereoselectivity change was noticed in the presence of cuprous chloride rather suggests an impac…
The characterization of molecular alkaly metal azides
2006
Matrix isolation infrared (IR) studies have been carried out on the vaporisation of the alkali-metal azides MN(3) (M = Na, K, Rb and Cs). The results show that under high vacuum conditions, molecular KN(3), RbN(3) and CsN(3) are present as stable high-temperature vapour species, together with variable amounts of nitrogen gas and the corresponding metal atoms. The characterisation of these molecular azides is supported by ab initio molecular orbital calculations and density functional theory (DFT) calculations, and for CsN(3) in particular, by the detection of the isotopomers CS((14)N(15)N(14)N) and Cs((15)N(14)N(14)N). The IR spectra are assigned to a "side-on" (C(2v)) structure by comparis…
Structural study of α-Bi2O3 under pressure
2013
An experimental and theoretical study of the structural properties of monoclinic bismuth oxide (alpha-(BiO3)-O-2) under high pressures is here reported. Both synthetic and mineral bismite powder samples have been compressed up to 45 GPa and their equations of state have been determined with angle-dispersive x-ray diffraction measurements. Experimental results have been also compared with theoretical calculations which suggest the possibility of several phase transitions below 10 GPa. However, experiments reveal only a pressure-induced amorphization between 15 and 25 GPa, depending on sample quality and deviatoric stresses. The amorphous phase has been followed up to 45 GPa and its nature di…
Characterization of gas phase aggregates of bis(2-ethylhexyl)sulfosuccinate (AOT) and divalent metal ions. Elimination of radical species in the deco…
2012
Structure and properties of even-electron anionic species formed by bis(2-ethylhexyl)sulfosuccinate (AOT) and divalent metal ions (MII) with stoichiometry [AOTMIICl2]– have been investigated by using electrospray ionization and different mass spectrometry techniques, such as high resolution, accurate mass measurements, collision-induced dissociation (CID) multiple-stage mass spectrometry. Owing to CID, eliminations of neutrals, mainly consisting in hydrochloric acid, 2-ethyl-1-hexene and 2-ethylhexanol, and an unexpected loss of an alkyl radical have been observed. The radical anions [C4HO6SMIICl]–• so produced have been characterized by MS3 experiments. Density functional theory calculatio…
Conformational properties of N′,N′-dimethylamides of N-acetyldehydroalanine and N-acetyl-(Z)-dehydrophenylalanine
2001
Conformational preferences of Ac-deltaAla-NMe2 and Ac-(Z)-deltaPhe-NMe2 were studied and compared with those of their monomethyl counterparts as well as with those of their saturated analogues. X-Ray data and energy calculations revealed a highly conservative conformation of the dehydro dimethylamides, which is located in a high-energy region of the Ramachandran map.