Bis-, Tris-, and Tetrakis(squaraines) Linked by Stilbenoid Scaffolds

Abstract

Keywords: Conjugation / Donor-acceptor systems / Squaraines / UV/Vis spectroscopy The oligosquaraines 1−5, with stilbenoid scaffolds, were prepared by multistep syntheses in which the final steps consisted of condensation reactions between the semisquaric acid 21 and multiple resorcinols 12b−15b and 17b. The target compounds exhibit intense (ε Ͼ 250000 L·mol −1 ·cm −1 ) and sharp absorption bands with maxima between 687 to 778 nm, Results and DiscussionScheme 1 provides an overview of the two-, three-, and fourfold squaraines 1Ϫ5 described here, together with the model compound 6. The bis(squaraines) 1 and 2 have linear [a] 2757 depending on the conjugation in the stilbenoid scaffold. Comparison with the monosquaraine 6 as a model compound reveals intramolecular interactions between different donor−acceptor−donor moieties, which give rise to increased absorption intensities.

Phenolic Bis-styrylbenzenes as β-Amyloid Binding Ligands and Free Radical Scavengers

“…The preparation of 6 was an improvement on the previously published procedure in which a low-yielding (20%) double-Heck coupling was used. The overall yields of 8 (69%) and 10 (42%) were better than those (49% and 28%) previously reported , for these compounds. 1,3- and 1,2-Bis(diethylphosphonylmethyl)benzenes 19b (96%) and 19c (93%) were synthesized using the Arbuzov reaction with o - and m -xylylene dibromide.…”

“…Step 2. As described above for 4 , 10a (0.084 g, 0.16 mmol) was deprotected using 12.0 M HCl (0.214 mL, 2.57 mmol) to yield 10 (0.049 g, 88%) mp 290−305 °C (lit . mp >300 °C).…”

“…33 (E,E)-1,4-Bis(3,5-dihydroxystyryl)benzene (10). 21 Step 1. As described above for 4a, 20d (0.173 g, 0.765 mmol) and 19a (0.145 g, 0.382 mmol) yielded 10a (0.096 g, 48%): mp 101-106 °C.…”

Phenolic Bis-styrylbenzenes as β-Amyloid Binding Ligands and Free Radical Scavengers

“…The preparation of 6 was an improvement on the previously published procedure in which a low-yielding (20%) double-Heck coupling was used. The overall yields of 8 (69%) and 10 (42%) were better than those (49% and 28%) previously reported , for these compounds. 1,3- and 1,2-Bis(diethylphosphonylmethyl)benzenes 19b (96%) and 19c (93%) were synthesized using the Arbuzov reaction with o - and m -xylylene dibromide.…”

“…Step 2. As described above for 4 , 10a (0.084 g, 0.16 mmol) was deprotected using 12.0 M HCl (0.214 mL, 2.57 mmol) to yield 10 (0.049 g, 88%) mp 290−305 °C (lit . mp >300 °C).…”

“…33 (E,E)-1,4-Bis(3,5-dihydroxystyryl)benzene (10). 21 Step 1. As described above for 4a, 20d (0.173 g, 0.765 mmol) and 19a (0.145 g, 0.382 mmol) yielded 10a (0.096 g, 48%): mp 101-106 °C.…”

Synthesis of Rigid π‐Conjugated Mono‐, Bis‐, Tris‐, and Tetrakis(terpyridine)s: Influence of the Degree and Pattern of Substitution on the Photophysical Properties

“…In general, the rise in the extinction coefficients is partially attributable to the increasing numbers of chromophores per molecule. However, the growth in intensity ( S 16) of the absorption bands appears to be more than proportionate (Table 4). The largest step is found between 3 and 4 , once more emphasizing the electronic communication through the entire molecule.…”

Synthesis of Tetrastilbenylmethanes by Wittig−Horner Reactions

“…In the context of the generation of a tetrakis(squaraine), we recently prepared the fourfold phosphonate 1, [2] which proved to be suitable for the synthesis of the tetrastilbenylmethanes 3aϪe (Scheme 1). The WittigϪHorner reactions of 1 and the aldehydes 2aϪe give the target compounds in good yields and with very high trans stereoselectivities.…”

Phenolic Bis-styrylbenzenes as β-Amyloid Binding Ligands and Free Radical Scavengers

“…The preparation of 6 was an improvement on the previously published procedure in which a low-yielding (20%) double-Heck coupling was used. The overall yields of 8 (69%) and 10 (42%) were better than those (49% and 28%) previously reported , for these compounds. 1,3- and 1,2-Bis(diethylphosphonylmethyl)benzenes 19b (96%) and 19c (93%) were synthesized using the Arbuzov reaction with o - and m -xylylene dibromide.…”

“…Step 2. As described above for 4 , 10a (0.084 g, 0.16 mmol) was deprotected using 12.0 M HCl (0.214 mL, 2.57 mmol) to yield 10 (0.049 g, 88%) mp 290−305 °C (lit . mp >300 °C).…”

“…33 (E,E)-1,4-Bis(3,5-dihydroxystyryl)benzene (10). 21 Step 1. As described above for 4a, 20d (0.173 g, 0.765 mmol) and 19a (0.145 g, 0.382 mmol) yielded 10a (0.096 g, 48%): mp 101-106 °C.…”

Synthesis of Rigid π‐Conjugated Mono‐, Bis‐, Tris‐, and Tetrakis(terpyridine)s: Influence of the Degree and Pattern of Substitution on the Photophysical Properties

“…In general, the rise in the extinction coefficients is partially attributable to the increasing numbers of chromophores per molecule. However, the growth in intensity ( S 16) of the absorption bands appears to be more than proportionate (Table 4). The largest step is found between 3 and 4 , once more emphasizing the electronic communication through the entire molecule.…”

Synthesis of Tetrastilbenylmethanes by Wittig−Horner Reactions

“…In the context of the generation of a tetrakis(squaraine), we recently prepared the fourfold phosphonate 1, [2] which proved to be suitable for the synthesis of the tetrastilbenylmethanes 3aϪe (Scheme 1). The WittigϪHorner reactions of 1 and the aldehydes 2aϪe give the target compounds in good yields and with very high trans stereoselectivities.…”

Phenolic Bis-styrylbenzenes as β-Amyloid Binding Ligands and Free Radical Scavengers

“…The preparation of 6 was an improvement on the previously published procedure in which a low-yielding (20%) double-Heck coupling was used. The overall yields of 8 (69%) and 10 (42%) were better than those (49% and 28%) previously reported , for these compounds. 1,3- and 1,2-Bis(diethylphosphonylmethyl)benzenes 19b (96%) and 19c (93%) were synthesized using the Arbuzov reaction with o - and m -xylylene dibromide.…”

“…Step 2. As described above for 4 , 10a (0.084 g, 0.16 mmol) was deprotected using 12.0 M HCl (0.214 mL, 2.57 mmol) to yield 10 (0.049 g, 88%) mp 290−305 °C (lit . mp >300 °C).…”

“…33 (E,E)-1,4-Bis(3,5-dihydroxystyryl)benzene (10). 21 Step 1. As described above for 4a, 20d (0.173 g, 0.765 mmol) and 19a (0.145 g, 0.382 mmol) yielded 10a (0.096 g, 48%): mp 101-106 °C.…”

Synthesis of Rigid π‐Conjugated Mono‐, Bis‐, Tris‐, and Tetrakis(terpyridine)s: Influence of the Degree and Pattern of Substitution on the Photophysical Properties

“…In general, the rise in the extinction coefficients is partially attributable to the increasing numbers of chromophores per molecule. However, the growth in intensity ( S 16) of the absorption bands appears to be more than proportionate (Table 4). The largest step is found between 3 and 4 , once more emphasizing the electronic communication through the entire molecule.…”

Synthesis of Tetrastilbenylmethanes by Wittig−Horner Reactions

“…In the context of the generation of a tetrakis(squaraine), we recently prepared the fourfold phosphonate 1, [2] which proved to be suitable for the synthesis of the tetrastilbenylmethanes 3aϪe (Scheme 1). The WittigϪHorner reactions of 1 and the aldehydes 2aϪe give the target compounds in good yields and with very high trans stereoselectivities.…”