Nitroanilines as Quenchers of Pyrene Fluorescence

Abstract

The quenching of pyrene and 1-methylpyrene fluorescence by nitroanilines (NAs), such as 2-, 3-, and 4-nitroaniline (2-NA, 3-NA, and 4-NA, respectively), 4-methyl-3-nitroaniline (4-M-3-NA), 2-methyl-4-nitroaniline (2-M-4-NA), and 4-methyl-3,5-dinitroaniline (4-M-3,5-DNA), are studied in toluene and 1,4-dioxane. Steady-state fluorescence data show the higher efficiency of the 4-NAs as quenchers and fit with a sphere-of-action model. This suggests a 4-NA tendency of being in close proximity to the fluorophore, which could be connected with their high polarity/hyperpolarizability. In addition, emission and excitation spectra evidence the formation of emissive pyrene-NA ground-state complexes in the case of the 4-NAs and, in a minor degree, in the 2-NA. Moreover, time-resolved fluorescence experiments show that increasing amounts of NA decrease the pyrene fluorescence lifetime to a degree that depends on the NA nature and is larger in the less viscous solvent (toluene). Although the NA absorption and the pyrene (Py) emission overlap, we found no evidence of dipole-dipole energy transfer from the pyrene singlet excited state ((1)Py) to the NAs; this could be due to the low NA concentration used in these experiments. Transient absorption spectra show that the formation of the pyrene triplet excited state ((3)Py) is barely affected by the presence of the NAs in spite of their efficiency in (1)Py quenching, suggesting the involvement of (1)Py-NA exciplexes which--after intersystem crossing--decay efficiently into (3)Py.

Trace level detection of nitroanilines using a solution processable fluorescent porous organic polymer

“…8,16 In contrast, the static quenching constant and radius of quenching sphere for PA were 2.8 x 10 3 M -1 and 10.4 nm respectively, much lower than those for PNA. 4,20,26 Weak interactions between nitroanilines and the π conjugated framework are likely to be more facile compared to nitrophenols (two N−H···π over single O−H···π per molecule), leading to superior quenching. 16,18,24,25 Among nitroanilines, the static quenching constants follow the order PNA > DCPNA > DNA > ONA > MNA.…”

“…The superior efficiency of nitroanilines over the other nitroaromatics and the above quenching trend can be attributed to various reasons. 20,27 Efficient charge delocalization in nitroanilines as well as weak interactions with the porous polymer leading to better preassociation are likely to govern the quenching efficiency. 4,20,26 Weak interactions between nitroanilines and the π conjugated framework are likely to be more facile compared to nitrophenols (two N−H···π over single O−H···π per molecule), leading to superior quenching.…”

“…14,15 Highly cross-linked conjugated framework in POPs allows 3D exciton migration and provides a scaffold for better interactions between analytes and polymer leading to enhanced sensitivity. 4,20 Extensive steady-state and timeresolved spectroscopic studies along with electron paramagnetic resonance (EPR) spectroscopy and computational investigations provide a viable model of nitroaniline quenching in POPs. 2,17 Static quenching by Perrin's sphere of action model has also been reported in few cases including POPs.…”

Genotoxicity of 1‐methylpyrene and 1‐hydroxymethylpyrene in chinese hamster V79‐derived cells expressing both human CYP2E1 and SULT1A1

“…It is produced from various human sources including cigarette smoke, automobile exhausts, industrial emissions, and pyrolysis of hydrocarbons. It has also been used as a fluorescent probe in laboratories [Mouffouk et al, 2011;Agudelo-Morales et al, 2012]. 1-MP is carcinogenic to rodents, exerting its greatest effects in the liver [Rice et al, 1987].…”

Pyrene‐Capped CdSe@ZnS Nanoparticles as Sensitive Flexible Oxygen Sensors in Non‐Aqueous Media

“…480 nm), can be obtained using amazingly small pyrene concentrations by attaching pyrene units to CdSe core nanoparticles via a long flexible chain ending in a thiolate group, which exhibits high affinity for the nanoparticle surface . However, the emission of the core in this nanohybrid was almost totally quenched due to the anchored thiolate and, consequently, this system exhibited a dual‐fluorescence derived from both pyrene species.…”