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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. [...]

Hybrid density functional theory investigation of a series of alloxan-based thiosemicarbazones and semicarbazones

81%

Nuwan De Silva N., Lisic E., Albu T.

Open Chemistry

2006

vol. 4

issue 4

646-665

Recently, the synthesis and the NMR characterization of a series of eight alloxan-based thiosemicarbazones and semicarbazones were reported. These compounds exhibit a strongly hydrogenbonded hydrazinic proton that is a part of a characteristic six-membered ring. This proton is highly deshielded and resonates far downfield in the proton NMR spectra. In this report, mPW1PW91/6-31+G(d,p) calculations have been used to investigate the structure and other molecular properties of this series of eight compounds. The relationship between the 1H and 13C NMR chemical shifts and various geometric parameters was investigated, and linear relationships for proton peaks that are involved in hydrogen-bond interactions were found.

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2 Open Chemistry

1 2007

1 2006

2 Albu T.

2 Nuwan De Silva N.

1 Lisic E.

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

Hybrid density functional theory investigation of a series of alloxan-based thiosemicarbazones and semicarbazones