The synthesis of lactone-bridged 1,3,5-triphenylbenzene derivatives as pi-expanded coumarin triskelions

Abstract

Two triply lactone-bridged 1,3,5-triphenylbenzene derivatives with solubilizing moieties have been synthesized in five and six steps from commercially available starting materials. Compounds containing the 1,3,5-triphenylbenzene core with two atom bridges are relatively unknown. This new class of pi-expanded coumarins contain triskelion architectures and X-ray crystallographic studies of one of the triskelions indicates that the 1,3,5-triphenylbenzene core adopts a near-planar geometry. This is the only known example of a two atom-bridged 1,3,5-triphenylbenzene derivative to adopt a planar structure.

Triskelion‐Shaped π‐Luminophores Bearing Coumarin: Syntheses, Structures, and Luminescence Properties

“…Among them, the molecules incorporating the functional chromophores are of great interested in the molecular photo‐ and functional chemistry. A series of lactone‐bridged derivatives, which was reported by Dahl et al., showed a bathochromic shift of absorption and maximum wavelength emission by controlling the dihedral angle between the biphenyl moiety . Furthermore, these derivatives showed pH responsivity arising from partial protonation at the carbonyl moiety in the presence of trifluoroacetic acid and an increase in its fluorescent quantum yield.…”

“…The residue was purified by column chromatography on silica gel using CHCl 3 as a eluent to afford a (737 mg, 0.81 mmol) as a white platelet crystal in % yield. Mp = 220-222°C, H NMR (600 MHz, CDCl 3 ) δ 7.69 (dd, J = 1.2, 7.8 Hz, 3H), 7.50 (dd, J = 1.2, 7.8 Hz, 3H), 7.44-7.41 (m, 3H), 7.24-7.21 (m, 3H), 13 tris(2-bromo-5-methoxyphenyl)2,4,6-tribromobenzene-1,3,5-tricarbo-xylate (7 b): Prepared according to the synthesis procedure of 7 a in 1.00 g scale and the target compound was isolated by column chromatography on silica gel using CHCl 3 /hexane (2 : 1, v/v) as the eluent to afford a white platelet crystal of 7 b (1.77 g, 1.77 mmol) in 87 % yield. Mp = 179-181°C, 1 H NMR (600 MHz, CDCl 3 ) δ 7.56 (d, J = 9.0 Hz, 3H), 7.03 (d, J = 3.0 Hz, 3H), 6.79 (dd, J = 9.0, 3.0 Hz, 3H), 3.84 (s, 9H), 13 Preparation of nanoaggregates of 1: Stock THF solutions of the 1 a and 1 b with a concentration of 10 À 3 M were prepared.…”

“…A series of lactone-bridged derivatives, which was reported by Dahl et al, showed a bathochromic shift of absorption and maximum wavelength emission by controlling the dihedral angle between the biphenyl moiety. [13] Furthermore, these derivatives showed pH responsivity arising from partial protonation at the carbonyl moiety in the presence of trifluoroacetic acid and an increase in its fluorescent quantum yield. However, lactone bridge-flipped structural isomers (1, Figure 2) have not been synthesized.…”

Strongly emitting, centrosymmetric, ladder-type bis-coumarins with crankshaft architecture

“…6 In contrast to the relatively large number and diversity of π-expanded coumarins, only a few examples of the conjugated bis-coumarins have been reported. 7–9 Among them, a series of dilactone-bridged π-expanded bis-coumarins, synthesized by Dahl and co-workers, showed limited solubility due to strong intermolecular π-stacking interactions. 8 These dyes displayed blue emission with low fluorescence quantum yields and were used as pH-driven molecular sensors that increased emission intensity in the presence of trifluoroacetic acid (TFA).…”

Janus-Type AIE Fluorophores: Synthesis and Properties of π-Extended Coumarin-Bearing Triskelions

“…Their photophysical properties are promising for laser dyes [ 9 , 10 , 11 ], molecular sensors [ 12 , 13 , 14 ], and solar cells [ 15 ]. Furthermore, numerous extended coumarin dyes have been synthesized, and the photophysical properties based on their rigid and planar structures have been described [ 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 ]. Conversely, unusual coumarin dyes with helical geometries have also been reported; these compounds represented a platform for the development of molecular chiral dopants [ 25 , 26 , 27 ].…”