Overcrowded naphthologs of mono-bridged tetraarylethylenes: analogs of bistricyclic aromatic enes

Abstract

The naphthalogous mono-bridged tetraarylethylenes 9,9 0 -di-(1-naphthylmethylene)-9H-fluorene (5) and 9,9 0 -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 H 1 and H 8 (6.11 and 6.83 ppm, respectively) and H 2 and H 7 (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.

Variations of bistricyclic aromatic enes: mono-bridged tetraarylethene naphthologs

“…The syntheses of the BAE-1s 9-(di-1-naphthalenylmethylene)-9H-fluorene (11) and 9-(di-1-naphthalenylmethylene)-9H-xanthene (12) were described [20]. The starting compounds for the syntheses of 11-15 were 1,1 0 -(diazomethylene)bisnaphthylene (26) and 9H-chalcogenoxanthene-9-thiones (27) [42].…”

“…The degree of the overcrowding in BAEs may be reduced by removing the bridges X and/or Y [20]. The following two variations leading to open BAEs exist: (i) removal of one bridge (X or Y) of the BAE to give BAE-1, i.e., mono-bridged tetraarylethene e.g., 9-diphenylmethylen-9H-fluorene (7) [21] and-9-diphenylmethylen-9H-xanthene (8) [22]; and (ii) removal of the two bridges of BAE to give BAE-2, i.e., tetraarylethene, e.g., tetraphenylethene (9) [23] and tetrakis (2-naphthalenyl)ethene (10) [24,25].…”

“…The following BAE-1s with 1-naphthalenyl and 2-naphthalenyl substituents at the x position of the 9-methylene-fluorenylidene and chalcogenoxanthene were targeted: (Fig. 2): 9-(di-1-naphthalenylmethylene)-9H-fluorene (11), 9-(di-1-naphthalenylmethylene)-9H-xanthene (12), 9-(di-1-naphthalenylmethylene)-9H-thioxanthene (13), 9-(di-1-naphthalenyl methylene)-9H-selenoxanthene (14), 9-(di-1-naphthalenylmethylene)-9H-telluroxanthene (15), 9-(di-2-naphthalenylmethylene)-9H-fluorene (16), 9-(di-2-naphthalenylme thylene)-9H-xanthene (17), 9-(di-2-naphthalenylmethylene)-9H-thioxanthene (18), 9-(di-2-naphthalenylmethylene)-9H-selenoxanthene (19), 9-(di-2-naphthalenylmethyl ene)-9H-telluroxanthene (20), 9-(di-1,2 0 -naphthalenylmethylene)-9H-fluorene (21), 9-(di-1,2 0 -naphthalenylmethylene)-9H-xanthene (22), 9-(di-1,2 0 -naphthalenylmethyle ne)-)-9H-thioxanthene (23), 9-(di-1,2 0 -naphthalenylmethyl ene)-9H-selenoxanthene (24), and 9-(di-1,2 0 -naphthalenylmethylene)-9H-telluroxanthene (25).…”

“…The emphasis in the present study is on BAE-1s of the dinaphthalenylmethylene chalcogenoxanthene series. The BAE-1s naphthologs 11 and 12 have previously been described [20].…”

Polycyclic Aromatic Ketones – A Crystallographic and Theoretical Study of Acetyl Anthracenes

“…The B3LYP hybrid functional was successfully employed to treat overcrowded BAEs [Biedermann et al, 2001, Pogodin et al, 2006 and overcrowded naphthologues of BAEs-1, i.e. mono-bridged tetraarylethylenes [Assadi et al, 2009]. The monoacetylanthracenes and diacetylanthracenes under study were subjected to a systematic computational DFT study of their conformational spaces and of their relative stabilities.…”