Search results

Search:
in the keywords: isomerism

Sort By:

Limit search:

A theoretical investigation on the isomerism and the NMR properties of thiosemicarbazones

100%

Nuwan De Silva N., Albu T.

Open Chemistry

2007

vol. 5

issue 2

396-419

Hybrid density functional theory calculations at the mPW1PW91/6-31+G(d,p) level of theory have been used to investigate the optimized structures and other molecular properties of five different series of thiosemicarbazones. The investigated compounds were obtained from acenaphthenequinone, isatin and its derivatives, and alloxan. The focus of the study is the isomerism and the NMR characterization of these thiosemicarbazones. It was found that only one isomer is expected for thiosemicarbazones and methylthiosemicarbazones, while for dimethylthiosemicarbazones, two isomers are possible. All investigated thiosemicarbazones exhibit a hydrazinic proton that is highly deshielded and resonates far downfield in the proton NMR spectra. This proton is a part of a characteristic sixmembered ring, and its NMR properties are a result of its strong, intermolecular hydrogen bond. The relationships between the calculated 1H and 13C NMR chemical shifts and various geometric parameters are reported. [...]

Crystallographic and structural characterization of heterometallic platinum clusters. Part IX. Heterooligonuclear Pt clusters

88%

Melník M., Mikuš P., Holloway C. E.

Open Chemistry

2015

vol. 13

issue 1

This review classifies and analyzes over thirty heterooligonuclear platinum clusters with a wide variety of metal frameworks, from twelve to forty-four. There are thirteen heterometals (Ge, Sn, Hg, W, Mo, Ru, Rh, Pd, Os, Ni, Cu, Ag, Au) which are the partners of platinum. The clusters mostly crystallize in monoclinic (36,4%) and triclinic (30,3%) crystal classes. Their structures are complex, with platinum most commonly preferring interstitial sites, such as the centroids of icosahedrons. There are examples of distortion isomerism. The most common ligands are CO and PPh3, and it is interesting that the mean Pt-CO and M-CO bond distances are identical at 1.84 Å. In contrast, the mean Pt-μCO and M-μCO are of values of 2.02 and 1.97 Å, respectively, while the Pt-PPh3 and M-PPh3 bond distances are 2.30 and 2.28 Å, respectively. The shortest Pt-Pt, Pt-M (non-transition) and Pt-M (transition) bond distances are 2.559(2) Å, 2.412(2) Å (M = Ge) and 2.510(2) Å (M = Ni).

Refine search results

2 Open Chemistry

1 2015

1 2007

1 Albu T.

1 Holloway C. E.

1 Melník M.

1 Mikuš P.

1 Nuwan De Silva N.

Search results

A theoretical investigation on the isomerism and the NMR properties of thiosemicarbazones

Crystallographic and structural characterization of heterometallic platinum clusters. Part IX. Heterooligonuclear Pt clusters