The quality of theoretical NMR shieldings calculated at the quantum-chemical level depends on various theoretical aspects, of which the basis set type and size are among the most important factors. Nevertheless, not much information is available on the basis set effect on theoretical shieldings of the NMR-active nuclei of the third row. Here, we report on the importance of proper basis set selection to obtain accurate and reliable NMR shielding parameters for nuclei from the third row of the periodic table. All calculations were performed on a set of eleven compounds containing the elements Na, Mg, Al, Si, P, S, or Cl. NMR shielding tensors were calculated using the SCF-HF, DFT-B3LYP, and CCSD(T) methods, combined with the Dunning valence aug-cc-pVXZ, core-valence aug-cc-pCVXZ, Jensen polarized-convergent aug-pcSseg-n and Karlsruhe x2c-Def2 basis set families. We also estimated the complete basis set limit (CBS) values of the NMR parameters. Widely scattered nuclear shieldings were observed for the Dunning polarized-valence basis set, which provides irregular convergence. We show that the use of Dunning core-valence or Jensen basis sets effectively reduces the scatter of theoretical NMR results and leads to their exponential-like convergence to CBS. We also assessed the effect of vibrational, temperature, and relativistic corrections on the predicted shieldings. For systems with single bonds, all corrections are relatively small, amounting to less than 4% of the CCSD(T)/CBS value. Vibrational and temperature corrections were less reliable for H3PO and HSiCH due to the high anharmonicity of the molecules. An abnormally high relativistic correction was observed for phosphorus in PN, reaching ~20% of the CCSD(T)/CBS value, while the correction was less than 7% for other tested molecules.

• Keywords
• NMR shieldings, basis set dependence, third-row elements,
• MeSH
• Electrons * MeSH
• Phosphorus chemistry   MeSH
• Quantum Theory * MeSH
• Humans MeSH
• Magnetic Resonance Spectroscopy MeSH
• Vibration MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Phosphorus MeSH

Force-field parameters of the first row transition metals together with a few additional common elements such as those from the second (Rh, Ru) and third (Hg, Pt) rows of elements in ligated forms were determined based on the density functional theory calculations. Bonding characteristics were determined by averaging metal-ligand force constants in optimal geometries from several chosen complexes of each metal in the most common oxidation numbers and structural arrangements. Parameters of Lennard-Jones potential were determined based on a supermolecular model. Our determined molecular mechanical parameters are compared with presently available parameters published by other groups. We performed two different kinds of testing in order to demonstrate the reliability of these parameters in the case of ligated metallo complexes. First, the nonbonding potential was constructed for an additional set of 19 larger systems containing common complexes with organic molecules. The second test compares the Pt-O and Pt-H radial distribution functions for cisplatin in a box of TIP3P water with lately published studies.

• Publication type
• Journal Article MeSH

This paper presents a systematic study of multicenter and classical bonding on a broad series of experimentally known heteroboranes covering closo, nido, arachno and hypho types of cages with incorporated tetrel, pnictogen or chalcogen heterovertices up to the third-row elements. The nature of bonding is studied using a novel quantum-chemical tool, the intrinsic atomic/bond orbital (IAO/IBO) approach, which provides a direct connection between quantum chemistry and chemical concepts. We also discuss how the computed IBO properties are related to molecular observables such as interatomic distances, molecular electrostatic potential surfaces and dipole moments.

• Publication type
• Journal Article MeSH

A new species of Taeniacanthidae (Copepoda, Cyclopoida), Taeniacanthus kiemae sp. n., is described based on adult female and male specimens collected from the branchial cavity wall of Marilyna meraukensis (de Beaufort) and M. darwinii (Castelnau) (Teleostei, Tetraodontidae) caught in Australian waters. The new species differs from its congeners by having the following combination of characters in the adult female: (1) maxilla armed with a stout terminal process and two small elements; (2) multiple rows of spinules on the large pectinate process of the antenna; (3) an extremely long and thin maxilliped claw; (4) second exopodal segment of leg 1 with eight setae; (5) third exopodal segment of leg 3 with three spines and four setae; (6) third exopodal segment of leg 4 with three spines and two setae; and (7) each spine on the free exopodal segment of leg 5 with a subterminal flagellum. Taeniacanthus kiemae is the second copepod species reported from M. meraukensis and M. darwinii and the first taeniacanthid species reported from pufferfishes in Australia.

• MeSH
• Copepoda classification   MeSH
• Fish Diseases epidemiology   parasitology   MeSH
• Parasitic Diseases, Animal epidemiology   parasitology   MeSH
• Tetraodontiformes * MeSH
• Animals MeSH
• Check Tag
• Male MeSH
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Geographicals
• Australia epidemiology   MeSH