Synthesis and Verification of Fluorescent pH Probes Based on 2-Quinolone Platform

Lee, Seok Beom; Lee, Nam-Geol; Jung, Ye Rim; Kim, Darong; Hong, Ki Bum; Choi, Sungwook

doi:10.1246/cl.171073

Cited by 9 publications

(9 citation statements)

References 33 publications

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“…fluorescence, for a number of systems, including a 7-nitrobenz-2-oxa-1,3-diazole system used to detect cysteine and homocysteine via restriction of C = N bond isomerization, 25 6-propionyl-2-(dimethyamino)naphthalene derivatives in which the inability to form intramolecular hydrogen bonds substantially reduces quantum yields, 26,27 fluorinated pyrazoline analogues where C−H•••F interactions impede molecular motion, 28 and 2-quinolones that form rigid complexation in acidic solutions. 29 However, dipyrrinone derivatives 6−14 are unique from previously described systems in that restricted isomerization serves as a mode of fluorescence in both protonated and deprotonated states of the molecule. The efficiency of fluorescence does seem to depend on the imidazole/pyrazole substitution pattern of the dipyrrinone analog system as compounds 6, 9, and 12 have considerably larger quantum yields in comparison to 7, 8, 10, 11, 13, and 14.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…Dipyrrinone derivatives 6 – 14 , on the other hand, can form intramolecular hydrogen bonds in both the protonated ( 6a – 12a ) and deprotonated ( 6b – 12b ) states, due to tautomerization and/or rotation of the imidazole/pyrazole ring systems; therefore, both the protonated and deprotonated states result in observed fluorescence. Similar restriction of E/Z isomerization, via intramolecular hydrogen bonding, has been described for acyl hydrazones for nonfluorescent compounds, , and intramolecular hydrogen bonds, which produce constrained rotations, have been reported to enhance intensity of fluorescence, for a number of systems, including a 7-nitrobenz-2-oxa-1,3-diazole system used to detect cysteine and homocysteine via restriction of C = N bond isomerization, 6-propionyl-2-(dimethyamino)naphthalene derivatives in which the inability to form intramolecular hydrogen bonds substantially reduces quantum yields, , fluorinated pyrazoline analogues where C–H···F interactions impede molecular motion, and 2-quinolones that form rigid complexation in acidic solutions . However, dipyrrinone derivatives 6 – 14 are unique from previously described systems in that restricted isomerization serves as a mode of fluorescence in both protonated and deprotonated states of the molecule.…”

Section: Results and Discussionmentioning

confidence: 99%

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Pyrazole, Imidazole, and Isoindolone Dipyrrinone Analogues: pH-Dependent Fluorophores That Red-Shift Emission Frequencies in a Basic Solution

et al. 2019

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Dipyrrinones are nonfluorescent yellow-pigmented constituents of bilirubin that undergo Z to E isomerization when excited with UV/blue light. Mechanical restriction of the E/Z isomerization process results in highly fluorescent compounds such as N,N-methylene-bridged dipyrrinones and xanthoglows. This manuscript describes the first examples of dipyrrinone analogues, which exhibit fluorescence without covalently linking the pyrole− pyrrolidine nitrogen atoms. Instead these analogues restrict E/Z isomerization through intramolecular hydrogen bonding, resulting in mild to moderately fluorescent compounds (Φ F = 0.01−0.30). Further, in basic solutions (pH > 12), the dipyrrinone analogues readily deprotonate and absorption/emission profiles of the fluorophores red-shifts by 10−49 nm. Directly from commercial materials, 10 analogues were prepared in 41−96% yields in one step. To estimate the capacity of which intramolecular hydrogen bonding has upon restricting the E/Z isomerization process, conformational energies of all analogues, in both the protonated and deprotonated species, were explored by using quantum-mechanical density functional theory (DFT) and time-dependent DFT calculations. The computed strengths of the intramolecular hydrogen bonds are related to the barriers of rotation about the 5−6 bond and both correlate with the experimentally measured fluorescence quantum yields.

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Section: ■ Results and Discussionmentioning

confidence: 99%

Section: Results and Discussionmentioning

confidence: 99%

Pyrazole, Imidazole, and Isoindolone Dipyrrinone Analogues: pH-Dependent Fluorophores That Red-Shift Emission Frequencies in a Basic Solution

et al. 2019

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“…While a number of naturally occurring derivatives have been released, early reports revealed hybrid compounds that are derived from an isoprene unit and quinolones, namely hemiterpenoids [ 35 , 38 , 39 , 40 , 41 , 42 , 43 ]. Selected recent examples are presented in Figure 1 C. Besides biological applications, 2-quinoline scaffolds are found in functional organic materials ( Figure 1 D) [ 44 , 45 , 46 , 47 , 48 , 49 ]. Due to the intrinsic photoactive physical properties of the conjugated system and N , O -based ligating ability, 2-quinolones could be utilized as cationic metal–sensors [ 45 , 46 , 47 ], luminescent materials [ 44 ], and fluorescent small molecule pH probes [ 45 ].…”

Section: Introductionmentioning

confidence: 99%

“…Selected recent examples are presented in Figure 1 C. Besides biological applications, 2-quinoline scaffolds are found in functional organic materials ( Figure 1 D) [ 44 , 45 , 46 , 47 , 48 , 49 ]. Due to the intrinsic photoactive physical properties of the conjugated system and N , O -based ligating ability, 2-quinolones could be utilized as cationic metal–sensors [ 45 , 46 , 47 ], luminescent materials [ 44 ], and fluorescent small molecule pH probes [ 45 ]. Moreover, they show great potential as π-electron acceptors in dye-sensitized solar cells, after the construction of a relevant electron reservoir at the 3-position of 2-quinolones [ 49 ].…”

Section: Introductionmentioning

confidence: 99%

“…Selected recent examples are presented in Figure 1C. Besides biological applications, 2-quinoline scaffolds are found in functional organic materials (Figure 1D) [44][45][46][47][48][49]. Due to the intrinsic photoactive physical properties of the conjugated system and N,O-based ligating ability, 2-quinolones could be utilized as cationic metal-sensors [45][46][47], luminescent materials [44], and fluorescent small molecule pH probes [45].…”

Section: Introductionmentioning

confidence: 99%

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Recent Advances in One-Pot Modular Synthesis of 2-Quinolones

2020

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It is known that 2-quinolones are broadly applicable chemical structures in medicinal and agrochemical research as well as various functional materials. A number of current publications about their synthesis and their applications emphasize the importance of these small molecules. The early synthetic chemistry originated from the same principle of the classical Friedländer and Knorr procedures for the preparation of quinolines. The analogous processes were developed by applying new synthetic tools such as novel catalysts, the microwave irradiation method, etc., whereas recent innovations in new bond forming reactions have allowed for novel strategies to construct the core structures of 2-quinolones beyond the bond disconnections based on two classical reactions. Over the last few decades, some reviews on structure-based, catalyst-based, and bioactivity-based studies have been released. In this focused review, we extensively surveyed recent examples of one-pot reactions, particularly in view of modular approaches. Thus, the contents are categorized as three major sections (two-, three-, and four-component reactions) according to the number of reagents that ultimately compose atoms of the core structures of 2-quinolones. The collected synthetic methods are discussed from the perspectives of strategy, efficiency, selectivity, and reaction mechanism.

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