Synthesis of a New Amino-Furopyridine-Based Compound as a Novel Fluorescent pH Sensor in Aqueous Solution

Abstract

Development of new fluorescent molecules, especially pH-sensitive fluorescent dyes, is always in high demand due to their wide applications in various fields and the limited number of common chromophores. In this work, a family of 3-amino-N-phenylfuro­[2,3-b]­pyridine-2-carboxamides (AFP) was synthesized as novel fluorescent compounds. Besides fluorescence in an organic solvent, AFP 1 and AFP 2 exhibit good fluorescence properties in both acidic and basic aqueous solution, which could be explained by protonation or different conformations formed in solution. Density functional theory (DFT) calculations on the highest occupied molecular orbital–lowest unoccupied molecular orbital (HOMO-LUMO) of various conformations were performed for further support.

Investigation of Solvent Effect and H-Bonding on Spectroscopic Properties of 1-(3-Amino-6-(2,5-dichlorothiophen-3-yl)-4-phenylfuro[2,3-b]Pyridin-2-yl) Ethenone: Experimental and Computational Study

“…The characteristic absorption bands in the region 250 to 390 nm, are attributed to 𝜋 → 𝜋 * and 𝑛 → 𝜋 * transitions within the furo-pyridine portion, which are in a good agreement with the reported literature on similar fragments (Fig. 2) [9,[14][15]. The position of the absorption bands does not show any clear relation to solvent polarity, except with water, where dramatic changes are observed.…”

“…3, with 𝑝𝐾 𝑎 taken equal to the pH value at the inflection point of the sigmoidal curve of the absorbance at λ= 350 nm against pH values. Results reveal that 𝑝𝐾 𝑎 = 4.7 ± 0.2 (R 2 = 0.95), which can be assigned to the pyridine nitrogen of the furo-pyridine fragment of FP1 [9].…”

“…Furo [2,3-b]pyridine ring moiety is a combination of π-electron rich furan ring and a π-electron deficient pyridine ring [7], therefore, its derivatives are expected to show photo-illumination activities. However, only few fluorescence and phosphorescence articles based on furo [2,3-b]pyridine derivatives are reported [8][9].…”

Synthesis of gem-Dimethylcyclopentane-Fused Arenes with Various Topologies via TBD-Mediated Dehydro-Diels–Alder Reaction

“…Following Condition C, aryl-alkyne (3a) (80 mg, 0.21 mmol) afforded arene (4a) (46.2 mg, 83%) as a white solid: mp 82 °C; 1 H NMR (400 MHz, CDCl 3 ) δ 8.02 (t, J = 1.20 Hz, 2H), 7.36 (s, 2H), 2.89 (d, J = 1.20 Hz, 4H), 1.18 (s, 6H) ppm; 13 C{ 1 H} NMR (100 MHz, CDCl 3 ) δ 145. 6, 130.6, 125.0, 119.9, 47.6, 40.9, 28.4 ppm;IR 2955IR , 2941IR , 2922IR , 2862IR , 2833IR , 1589IR , 1464IR , 1455IR , 1440IR , 1424IR , 1383IR , 1362IR , 1315IR , 1264IR , 1246IR , 1190IR , 1175 2,2,7,7,12,3,6,7,8,11,12,h,n]triphenylene (6a). Following Condition B, arene (4a) (50 mg, 0.19 mmol) and enyne (1) (131.3 mg, 0.57 mmol) gave aryl-alkyne (5a) (119.5 mg, 73%) as a yellow oil after purification by flash column chromatography (eluent mixture: EtOAc/petroleum ether = 1:99).…”

“…Another strategy is to add protecting substituents, although such modifications impact π-stacking and charge mobilities . Molecular engineering by introducing substituent groups has been playing an important role in controlling the electrical and photophysical performances of PAHs, via affecting the electronegativity, size, shape, symmetry, and crystal packing of the material. A third strategy is to introduce heterocyclic aromatic hydrocarbons such as thiophene into the conjugative system, which could further improve the antioxidant capacity and electron transport capacity of the molecules …”