3‐Pyrrolyl BODIPY Based Schiff Base Fluorophores: A Selective Chemodosimetric and Optical Sensor for Diethyl Chlorophosphate

Abstract

Diethyl chlorophosphate (DCP), an organophosphate, is utilized as a pesticide, herbicide, and for various other applications. Despite many uses of organophosphates, the organophosphates are noxious and harmful substances, and their selective detection is a critical concern in the context of the environment, physiology, and social security. In a methodological quest, here we have synthesized two Schiff base compounds 1 and 2 by introducing the hydroxyl group at the α-position of 3-pyrrolyl BODIPY either directly as hydroxylamine 1 or at the ortho position of aryl ring as 2-aminophenol 2. Both compounds 1 and 2 exhibited high selectivity and high sensitivity for DCP over other pesticides in the aqueous-alcoholic medium at physiological pH. This occurs via nucleophilic phosphorylation of the hydroxyl group, which resulted in both compounds exhibiting two different optical signals following the structurefunction correlation of the pyrrolyl BODIPY systems. Upon binding DCP, compound 1 showed a quenching in the optical spectrum because of phosphorylation of hydroxyl group whereas compound 2 exhibited enhancements in both absorption and fluorescence spectra because of hydroxyl phosphorylation followed by intramolecular cyclization. Furthermore, the fluorescent microscopy experiments also indicated that the compound could be used as a fluorescent compound for sensing DCP in plant tissues.

A white light emitting single halochromic hydrazine bridged bis(3-pyrrolyl BODIPY) fluorophore

“…However, the LUMO and LUMO+1 orbitals for both 10 and 10·2H + showed a similar electron distribution on both a-pyrrolyl BODIPY units and the hydrazine linker along with some distribution on meso -tolyl groups as well. However, similar to other reported BODIPYs, 24–27 the meso -aryl group and BF 2 unit did not contribute to the frontier molecular orbitals in 10 and 10·2H + . In addition, the electron distribution of the LUMO of 10 has a large contribution on the hydrazine linker with good orbital overlap between imine N and C, supporting the electron transfer process from the hydrazine moiety to α -pyrrolyl BODIPY.…”

“…Furthermore, the appended pyrrole of 3-pyrrolyl BODIPY is highly susceptible to functionalization at the α-position and the α-functionalized 3-pyrrolyl BODIPYs are very useful synthons to synthesize several interesting fluorescent 3-pyrrolyl BODIPY based conjugates. In due course of time, we 22–28 and others 29–31 have developed a simple method for the synthesis of 3-pyrrolyl meso -aryl BODIPY based derivatives and they have been used in fluorescence sensing, photodynamic therapy, biotechnology, bioimaging, light-harvesting systems, etc. We also developed a method 32 to remove BF 2 units from BODIPYs and the resulting ligands have been used in coordination chemistry.…”

Synthesis, Structure, Spectral, Electrochemical, and Theoretical Studies of Ru(II) Complexes of 3-Pyrrolyl BODIPY-Based Ligands

“…Compound 3 was also treated with 2aminophenol in ethanol at reflux for 4 h followed by recrystallization to afford 3-pyrrolyl BODIPY-Schiff base compound 9 by our recent publication. 34 However, when 3 was reacted with o-phenylenediamine in ethanol at reflux for 4 h, it afforded α-benzimidazolyl 3-pyrrolyl BODIPY 10 in good yields. Compound 9 was reacted with [Ru(p-cymene)Cl 2 ] 2 in toluene at reflux followed by recrystallization to yield BODIPY-Ru(II) complex 7.…”

“…To prepare Ru­(II)-α-formyl 3-pyrrolyl BODIPY complex 6 , we first prepared the required ligand, α-formyl 3-pyrrolyl BODIPY 3 , by treating 3-pyrrolyl BODIPY 2 with POCl 3 in DMF/DCE under Vilsmeier-Haack reaction conditions. , Compound 3 was then treated with [Ru­( p -cymene)­Cl 2 ] 2 in toluene in the presence of a base at reflux for 3 h followed by recrystallization to afford Ru­(II)-α-formyl 3-pyrrolyl BODIPY 6 in 40% yield (Scheme ). Compound 3 was also treated with 2-aminophenol in ethanol at reflux for 4 h followed by recrystallization to afford 3-pyrrolyl BODIPY-Schiff base compound 9 by our recent publication . However, when 3 was reacted with o -phenylenediamine in ethanol at reflux for 4 h, it afforded α-benzimidazolyl 3-pyrrolyl BODIPY 10 in good yields.…”

Synthesis and studies of covalently linked (BODIPY)2-3-pyrrolyl BODIPY triads

“…and these functionalized 3-pyrrolyl BODIPYs can be further derivatized to prepare several interesting fluorescent compounds for various applications. 6–10 Others 11–14 and we 3–10 have developed a simple route for synthesizing 3-pyrrolyl BODIPYs. We also showed that the BF 2 unit of 3-pyrrolyl BODIPYs could also be demasked by treating 3-pyrrolyl BODIPYs with Lewis acids such as AlCl 3 and ZrCl 4 to afford tripyrrolyl ligands that can be used to prepare interesting coordination complexes such as 3 .…”