Abstract
The naphthalogous mono-bridged tetraarylethylenes 9,9′-di-(1-naphthylmethylene)-9H-fluorene (5) and 9,9′-di-(1-naphthylmethylene)-9H-xanthene (6), analogs of bifluorenylidene (1) and bixanthenylidene (2), have been synthesized and their molecular and crystal structures have been determined. Ene 5 has been prepared by two alternative synthetic routes. The molecular structures of 5 and 6 show that each of these enes has very small twist around the central double bond, but the two naphthalene rings in both 5 and 6 are highly twisted. According to the NMR study, 5 and 6 in solution adopt conformations which are similar to those found by X-ray crystal structure analysis. The notable upfield shifts of H1 and H8 (6.11 and 6.83 ppm, respectively) and H2 and H7 (6.70 and 6.44 ppm, respectively) in 5 and 6 are due to the shielding caused by the nearly orthogonally twisted naphthalene rings. The B3LYP/6-31G(d) calculations of 5, 6, and their 2-naphthyl and phenyl analogs have been performed. In the 1-naphthyl series, the more efficient conjugation between the naphthyl substituents and the central C=C and the overcrowding due to the peri-hydrogen atoms lead to higher twists of the naphthyl groups and to lower twists of the central C=C. In the 2-naphthyl series, the opposite effects are noted.
Original language | English |
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Pages (from-to) | 541-556 |
Number of pages | 16 |
Journal | Structural Chemistry |
Volume | 20 |
Issue number | 4 |
DOIs | |
State | Published - 13 May 2009 |
Externally published | Yes |
Keywords
- Crystal structures
- DFT
- Diazo-thione coupling
- Mono-bridged tetraarylethylenes
- NMR
ASJC Scopus subject areas
- Condensed Matter Physics
- Physical and Theoretical Chemistry