Wei Fan

Publications (3)14.36 Total impact

• Article: Synthesis and Structures of Dimethyldihydropyrene Iron Carbonyl Complexes

  Rui Zhang, Wei Fan, Brendan Twamley, David J. Berg, Reginald H. Mitchell
  [show abstract] [hide abstract]
  ABSTRACT: Reaction of the Diels−Alder adduct 10 (derived from the aryne 11 of dimethyldihydropyrene (DHP) and furan)7 with Fe2(CO)9 at room temperature gave the deoxygenated benzannelated DHP 9 and iron tetracarbonyl complex 6. However, the same reaction at elevated temperature produced 9 as well as the mono-iron tricarbonyl complex 7, the bis-iron tricarbonyl complex 8 (12%), and a very small amount of 6. On heating, complex 6 converts to DHP 9 and complex 7, but does not form 8. Likewise DHP 9 does not form from either complex 7 or 8, and so the latter is formed directly from 10. The structures of 7 and 8 were determined by X-ray crystallography. The main feature of these molecules is the bending of the DHP rings upon coordination of the iron tricarbonyl groups. These molecules are crowded, with strong interactions found between the carbonyl groups and the internal methyl groups and the tert-butyl groups. The π-electron delocalization in the normally aromatic DHP ring has been greatly reduced by the complexation.
  03/2007;
• Article: Measuring antiaromaticity by an analysis of ring current and coupling constant changes in a cyclopentadienone-fused dihydropyrene.

  Reginald H Mitchell, Rui Zhang, Wei Fan, David J Berg
  [show abstract] [hide abstract]
  ABSTRACT: The synthesis of the chloro- and parent cyclopentadienone-fused dihydropyrenes 10 and 7 are reported. Analysis of coupling constants, and chemical shift changes between these and the nonconjugated dihydro derivatives 11 and 8, and between the benzannulene 4 and the parent annulene 12, indicates without doubt that cyclopentadienone is behaving as an antiaromatic 4n-pi system and that in its effect on the ring current of 12, cyclopentanedienone has about 80% of the effect of benzene. This is the first time that a suitable probe has been used to estimate the relative ability of a 4n-pi system to bond localize the probe in comparison to the (4n + 2)-pi system benzene.
  Journal of the American Chemical Society 12/2005; 127(46):16251-4. · 9.91 Impact Factor
• Article: An annulene-fused cyclopentadienide. A photochromic cyclopentadienodimethyldihydropyrene where the fused cyclopentadienide group resembles benzene in its effect on the dihydropyrene-metacyclophanediene valence isomerization.

  Reginald H Mitchell, Wei Fan, Danny Y K Lau, David J Berg
  [show abstract] [hide abstract]
  ABSTRACT: The synthesis of the green cyclopentadiene-fused dimethyldihydropyrene 12 was achieved in 36% yield in 7 steps from the parent dihydropyrene 3. Reaction of 12 with KH or LiCH(2)SiMe(3) gave the [14]annulene-fused cyclopentadienide anion quantitatively. In the (1)H NMR spectra, the internal methyl protons of 12 at delta -3.9, change dramatically on formation of anion 5, becoming deshielded to delta -1.82. This is caused by the reduction in diatropicity of the [14]annulene ring on fusion to the 6pi-cyclopentadienide ring. The anion is also a photochromic switch. Irradiation of the closed form 5 with visible light opens it to the open form 5', which reverts to the closed form 5 either with UV light or thermally. The switching behavior is between that of the parent 3/3' and the benzannelated system 4/4' and suggests that in its effect on the photoswitching, cyclopentadienide is behaving chemically similar to benzene.
  The Journal of Organic Chemistry 02/2004; 69(2):549-54. · 4.45 Impact Factor