“…260 Reaction of tetrachlorocyclopropene with cyanamide in the presence of Et 3 N gave a zwitterionic cyclopropenimine (eq 160). 261,262 Cyclopropenimines were synthesized by [2 + 1] cycloaddition between isocyanides and acetylene derivatives (eq 161). 219 Diimine 270 was obtained by the reaction of 1,4-diisocyanobenzene with an ynediamine 269 (eq 162).…”
Section: Nitrogen and Phosphorus Analoguesmentioning
confidence: 99%
“…Reaction of tetrachlorocyclopropene with cyanamide in the presence of Et 3 N gave a zwitterionic cyclopropenimine (eq 160). , …”
Section: Nitrogen and Phosphorus Analoguesmentioning
“…260 Reaction of tetrachlorocyclopropene with cyanamide in the presence of Et 3 N gave a zwitterionic cyclopropenimine (eq 160). 261,262 Cyclopropenimines were synthesized by [2 + 1] cycloaddition between isocyanides and acetylene derivatives (eq 161). 219 Diimine 270 was obtained by the reaction of 1,4-diisocyanobenzene with an ynediamine 269 (eq 162).…”
Section: Nitrogen and Phosphorus Analoguesmentioning
confidence: 99%
“…Reaction of tetrachlorocyclopropene with cyanamide in the presence of Et 3 N gave a zwitterionic cyclopropenimine (eq 160). , …”
Section: Nitrogen and Phosphorus Analoguesmentioning
“…While dianion 4 2À has not yet been prepared, [3]radialene dianion derivatives with exocyclic electron-withdrawing group, 5 2À , 6 and heteroatom analogues, 3 2À 7 and 6 2À , 8 have been realized. 9 Their characteristics are similar to those of 2 2À . Among deltate dianion analogues, only [Ph 3 MeP + ] 2 Á3 2À has an X-ray structure.…”
Reduction of a 4,5,6-triphospha[3]radialene gave the corresponding isolable dianionic species. Despite having two deltate dianion-like π-electrons delocalized over the central framework, its small NICS(0)(πzz) value (only -2.2 ppm) indicates only limited aromaticity.
A selection of dimeric tetraethynylethenes (TEEs) and perethynylated expanded radialenes, containing different donor/acceptor substitution patterns, have been prepared and fully characterized. The first X-ray crystal structure of an expanded [6]radialene, with twelve peripheral 3,5-di(tert-butyl)phenyl substituents, is presented. This macrocycle, the all-carbon core of which is isomeric with fullerene C60, adopts a non-planar, "chair-like" conformation. Also a TEE dimer, carrying N,N-dimethylaniline donor substituents, has been subjected to an X-ray crystallographic analysis. The electronic properties were studied by UV/Vis spectroscopy and electrochemistry, providing fundamental insight into mechanisms of pi-electron delocalization in the acyclic and macrocyclic chromophores. Donor or donor-acceptor-substituted dimeric TEE derivatives show very strong absorptions extending over the entire UV/Vis region; their longest wavelength absorption bands have high charge-transfer character. Macrocyclic cross-conjugation in the expanded radialenes becomes increasingly efficient with increasing donor-acceptor polarization. A dual, strongly solvent-polarity-dependent fluorescence was observed for a tetrakis(N,N-dimethylaniline)-substituted dimeric TEE; this interesting emission behavior is explained by the twisted intramolecular charge-transfer (TICT) state model. Donor-substituted expanded radialenes display huge resonance-enhanced third-order nonlinear optical coefficients.
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