Biomedical subjects

Frank Blockhuys

Publications and source records attributed to Frank Blockhuys.

8 recordsLinked to original sources

PubMed2006

5,6,7,8-Tetrafluoro-3lambda4delta2,1,2,4-benzothiaselenadiazine, 5,6,7,8-tetrafluoro-1,3lambda4delta2,2,4-benzodithiadiazine, and their hydrocarbon analogues: molecular and crystal structures.

5,6,7,8-Tetrafluoro-3lambda4delta2,1,2,4-benzothiaselenadiazine (1) is prepared by the intramolecular nucleophilic cyclization of C6F5SeN=S=NSiMe3 (2) mediated by CsF. According to an X-ray diffraction analysis, the heterocycle of 1 is bent along the Se(1)...N4 line by 6.0(2) degrees in the crystal. Despite the obvious similarities between 1 and its 1,3-dithia analogue (7) with respect to molecular composition and shape, the crystal packing of 1 is substantially different from that of 7. An interesting consequence of this is the inclusion of atmospheric N2 in the crystal lattice of the selenium derivative 1. The molecular structure and bonding of 1 have been investigated using quantum-chemical calculations at the DFT/B3LYP/6-311+G level of theory, and the results have been compared to those of 5,6,7,8-tetrafluoro-1,3lambda4delta2,2,4-benzodithiadiazine (7) and their hydrocarbon analogues (5 and 8).

Journal Article↗

PubMed2006

E2(CN)2 (E = S, Se) and related compounds.

A synthetic, spectroscopic, and theoretical study of Ex(CN)2 (E = S, Se; x = 1-3) is described. The X-ray structures of Se2(CN)2 and Se3(CN)2 have been determined. Se2(CN)2 crystallizes in a chiral space group with the CN groups approximately gauche.

Journal Article↗

PubMed2005

Does a stabilising interaction favouring the Z,Z configuration of -S-N=S=N-S- systems exist?

The existence of the orbital interaction presented in the literature as being the cause for the stabilisation of the Z,Z configuration of Ph-S-N=S=N-S-Ph (1) and its derivatives in the crystal phase, has been investigated. The results of theoretical calculations at the DFT/B3LYP/6-311+G* level of theory suggest that such a stabilising interaction might not exist or be extremely weak and that packing forces must be the main cause of the observed Z,Z configuration in the solid. To reach this conclusion structural and energetic parameters were combined to study the bonding in these -S-N=S=N-S- systems. For the analogous Ph-Se-N=S=N-Se-Ph (2) in particular the isomeric equilibrium in solution found in the variable-temperature 77Se NMR spectrum indicates that, in the gas phase or in solution, the observed Z,Z configuration is not stabilised to a greater extent than the Z,E configuration.

Journal Article↗

PubMed2005

Multidimensional description of the aromaticity in planar five-membered NSNS ring systems.

The effect of the ring-closing fragment on the aromaticity of planar five-membered rings containing an NSNS fragment is investigated systematically. The influence of changing the group or period number of the ring-closing atom is studied as well as the effect of a substituent on this ring-closing element. Two sets of four five-membered ring systems were investigated. To reach a multidimensional description of the aromaticity, a robust set of geometrical, magnetic and energetic aromaticity criteria were combined. pi-Electron populations based on the stockholder scheme were calculated and lead to a quantity that correlates to the other aromaticity criteria. A third set of molecules was introduced to verify the conclusions.

Journal Article↗

PubMed2005

(E,E)-2,5-Dipropoxy-1,4-bis[2-(2,4,6-trimethoxyphenyl)ethenyl]benzene.

The title compound, C30H34O8, crystallizes in the space group P-1 with one-half of a molecule in the asymmetric unit. A three-dimensional network is generated by OCH3...pi and CH...pi interactions. The conformation of the C-C bond exocyclic to the central benzene ring is different from that of every other known derivative. A comparison of the geometry of the title molecule and of its solid-state structure with other 2,4,6-trimethoxy-substituted PPV [i.e. poly(p-phenylenevinylene)] oligomers, in particular the isopropoxy-substituted compound, is provided.

Journal Article↗

PubMed2004

(E,E)-2,5-Dimethoxy-1,4-bis[2-(3,4,5-trimethoxyphenyl)ethenyl]benzene.

In the title compound, C30H34O8, molecular symmetry is coincident with crystallographic inversion symmetry. A three-dimensional network is generated containing both C-H...pi and C-H...n(O) interactions. A comparison of the geometry of this molecule and the structure of a number of 2,4,6-trimethoxy-substituted analogues is provided.

Journal Article↗

PubMed2003

Molecular and crystal properties of E-1,2-bis(3-methoxy-2-thienyl)ethene: static disorder in the crystal.

The crystal structure of E-1,2-bis(3-methoxy-2-thienyl)ethene (C12H12O2S2) has been determined at five different temperatures, i.e. room temperature (293), 223, 173, 123 and 93 K. The solid-state work is complemented by the results of theoretical calculations of energies, geometries, difference electron densities and atomic charges of the free molecule. Analysis revealed static disorder caused by a higher energy conformer of the title compound, probably contaminating the crystal during its growth. The results support the contention that the electrical properties are mainly governed by the carbon backbone.

Journal Article↗

PubMed2003

The vibrational spectra of E-1,2-bis(3-methoxy-2-thienyl)ethene in the crystalline phase.

Density functional theoretical (DFT) calculations using the 6-311+G* basis set were carried out to study the vibrational spectrum of E-1,2-bis(3-methoxy-2-thienyl)ethene in the solid state. Based on the calculated frequencies, infrared intensities and potential energy distributions (PED), the experimental IR and Raman spectra of the solid phase were assigned.

Chemistry Techniques, Analytical↗