TY - GEN

T1 - Planar 1,3 ?4d2, 2,4.benzodithiazine and its non-planar 5,6,7,8-tetrafluoro derivative: gas phase structures studied by electron diffraction and ab initio calculations

AU - Blockhuys, F

AU - Hindley, SL

AU - Makarov, AYu

AU - Gatilov, YV

AU - Zibarev, AV

AU - Woollins, John Derek

AU - Rankin, DW

N1 - Chemistry, Eur J

PY - 2001/8/17

Y1 - 2001/8/17

N2 - The gas-phase molecular structures of 1,3 lambda (4)delta (2),2,4-benzodithiadiazine and 5,6,7,8-tetrafluoro-1,3 lambda (4)delta (2),2,4-benzodithiadiazine have been investigated by ab initio calculations and electron diffraction using the SARACEN method of structural analysis. Important structural parameters (r(hl) structure) for the parent compound were found to be: < r(S=N) > 1.546(3), r(S-N) 1.697(5), r(C-S) 1.784(5), and r(C-N) 1.393(6) Angstrom. For the tetrafluoro derivative, these are (rh(1) structure): < r(S=N) > 1.552(3), r(S-N) 1.723(8), r(C-S) 1.812(9), and r(C-N) 1.396(7) Angstrom. Furthermore, the GED experiment (Gas Electron Diffraction) quite convincingly demonstrates the nonplanarity of the former and the planarity of the latter in agreement with DFT calculations; but the results contradict calculations at the MP2 level. The effect of the fluorine atoms on the conformations of the molecules is discussed.

AB - The gas-phase molecular structures of 1,3 lambda (4)delta (2),2,4-benzodithiadiazine and 5,6,7,8-tetrafluoro-1,3 lambda (4)delta (2),2,4-benzodithiadiazine have been investigated by ab initio calculations and electron diffraction using the SARACEN method of structural analysis. Important structural parameters (r(hl) structure) for the parent compound were found to be: < r(S=N) > 1.546(3), r(S-N) 1.697(5), r(C-S) 1.784(5), and r(C-N) 1.393(6) Angstrom. For the tetrafluoro derivative, these are (rh(1) structure): < r(S=N) > 1.552(3), r(S-N) 1.723(8), r(C-S) 1.812(9), and r(C-N) 1.396(7) Angstrom. Furthermore, the GED experiment (Gas Electron Diffraction) quite convincingly demonstrates the nonplanarity of the former and the planarity of the latter in agreement with DFT calculations; but the results contradict calculations at the MP2 level. The effect of the fluorine atoms on the conformations of the molecules is discussed.

KW - ab initio calculations

KW - electron diffraction

KW - heterocycles

KW - MOLECULAR-ORBITAL METHODS

KW - VALENCE BASIS-SETS

KW - CRYSTAL-STRUCTURE

KW - HETEROCYCLES

KW - ELEMENTS

KW - SYSTEM

M3 - Other contribution

VL - 7

ER -