Acridine-based macrocyclic fluorescent sensors: self-assembly behavior characterized by crystal structures and a tunable bathochromic-shift in emission induced by H2PO4−via adjusting the ring size and rigidity

Abstract

In this paper, a series of novel acridine derived bisbenzimidazolium macrocyclic fluorescent sensors were designed and synthesized. X-ray crystal structures demonstrated the self-assembly behavior of these cyclophanes in the solid state driven by hydrogen bond and π-π interactions. Anion binding studies of these sensors revealed a significant effect of the macrocyclic size and rigidity for H2PO4(-) sensing via the obvious turn-on as well as bathochromic-shift in fluorescence emission. Different cavity size or rigidity of the sensors showed different bathochromic-shifts (from 36 to 126 nm) in fluorescence emission induced by H2PO4(-), which resulted in significant color changes of fluorescence from blue to orange red, orange, green and blue-green respectively. The unique fluorescence response toward H2PO4(-) may be attributed to H2PO4(-)-induced assembly of sensors forming the excimer between two acridine rings to a different extent.

An acridine derivative, [4,5-bis{(N-carboxy methyl imidazolium)methyl}acridine] dibromide, shows anti-TDP-43 aggregation effect in ALS disease models

“…Although, the backbone structure is same in the AIM2, AIM3 & AIM5 compounds, they differ in the counter ions. The PF 6 − counter ion in AIM2, BF 4 − counter ion in AIM3 & the Br − counter ion in AIM5, can play an important role in tuning the acidity of the imidazole C-H proton, which is responsible for the N(N)C-H····X, hydrogen bonding strength373839. The observed difference in the TDP-43 2C inhibition ability of AIM2 compared to AIM3 & AIM5, may possibly be due to their differential interaction capabilities with the protein molecule due to altered hydrogen bonding abilities.…”

“…Imidazolium derivatives of acridine ([4,5-bis{(N-ethoxycarbonyl methyl imidazolium)methyl}, acridine] dibromide (AIM1); [4,5-bis{(N-isopropylimidazolium) methyl} acridine] hexafluorophosphate (AIM2); [4,5-bis{(N-isopropylimidazolium)methyl}acridine] tetrafluoroborate (AIM3); [4,5-bis{(N-carboxy methyl imidazolium) methyl}acridine] dibromide (AIM4)) and [4,5-bis{(N-isopropylimidazolium)methyl}acridine] dibromide (AIM5) were synthesized as reported37. Acr-E [4,5-bis(hydroxymethyl)acridine] was synthesized as previous described54 AIM [4,5-bis(imidazole methyl)acridine] was synthesized as previously reported39. Organic solvents were purified according to standard procedures and freshly distilled under argon atmosphere prior to use55.…”

Novel benzimidazolium–urea-based macrocyclic fluorescent sensors: synthesis, ratiometric sensing of H2PO4− and improvement of the anion binding performance via a synergistic binding strategy

“…The stock solutions of anions were prepared from TBAX (where X = F -, Cl -, Br -, I -, AcO -, SCN - . 1 H NMR and 13 C NMR spectra were recorded in (CD 3 ) 2 SO at 293 K on a Bruker Avance DRX 500 FT NMR spectrometer, operating at 500 MHz and 125 MHz for 1 H NMR spectra and 13 C NMR spectra respectively. Fluorescence spectra were carried out in a Hitachi F-4500 fluorescence spectrometer.…”

“…Collect the organic phase and evaporate the CHCl 3 under vacuum to achieve the white compound 1, 3-bis-(3-chloropropyl)-urea 6 in 34% yield (2.15 g). 1 H NMR (400 MHz, CDCl 3 ) δ 1.96 (t, J = 5.8, 4H), 3.31 (d, J = 5.2, 4H), 3.60 (t, J = 5.2, 4H), 5.17 (s, 2H).…”

Synthesis and catalytic activities of bimetallic Ru (II) arene complexes bearing bis-benzimidazoles

“…For example, they are alkylated with alkyl halides so as to give 1-alkylbenzimidazoles. Bis-benzimidazoles can also be synthesized when 1,4and / or 1,6-dialkyl halides are used as linker groups (5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15). Reduction of carbonyl bonds by catalytic transfer hydrogenation using Ru (II) catalyst is of interest due to its simplicity and safety (16)(17)(18)(19).…”