Fluorescence Quenching of Dipyrenylalkanes by an Electron/Charge Acceptor

Abstract

Compounds possessing two fluorophoric moieties may exhibit dual fluorescence, one characterizing the monomeric fluorophore unit and the other characterizing the intramolecular aggregate. Fluorescence quenching of two dipyrenylalkanes, 1,3-bis(1-pyrenyl)propane [1Py(3)1Py] and 1,10-bis(1-pyrenyl)decane [1Py(10)1Py] having different alkyl chains separating the two termini pyrenyl groups that are capable of forming an intramolecular excimer, by an electron/charge-accepting quencher, nitromethane, is investigated in four different solventsnonpolar (cyclohexane (CH)), polar-aprotic (acetonitrile (ACN)), polarprotic (ethanol (EtOH)), and chlorinated (dichloromethane (DCM))under ambient conditions. For a given probe in a solvent, fluorescence from the monomer and the intramolecular excimer are quenched with similar efficiencies; the efficiency of quenching is higher for the probe with the longer alkyl chain separating the two fluorophores. Quenching efficiency is significantly higher in chlorinated solvent DCM. The bimolecular quenching rate constants for intramolecular excimer, however, are either comparable or lower for the longer alkyl chain compound. It is suggested that, while the donor electronic excited-state energetics is more favorable for the long alkyl chain compound, the approach of the quencher to the intramolecular excimer appears to be hindered by the presence of a longer alkyl chain.

Highly Efficient Intramolecular Excimer Formation in a Disulfide-Linked Dipyrenyl Compound: Proton Recognition and Fluidity Assessment

“…18,34−36 Similarly, another prototypical dipyrenyl probe of the alkane backbone family 1,3bis(1-pyrenyl)propane [1Py(3)1Py] shows I E /I M values of 0.64, 0.74, and 0.67 corresponding to ACN, DCM, and EtOH, respectively. 36 These values exhibit a magnitude at least 10-fold lower than those observed for DTP.…”

“…While several short- and long-chain compounds with varying chain functionalities having both termini appended with pyrenyl groups have demonstrated the formation of an intramolecular excimer, ,,, DTP exhibits comparatively high efficiency of excimer formation. For example, the intramolecular excimer formation efficiency in 1,10- bis (1-pyrenyl)­decane [1Py(10)­1Py], a compound with a similar chain length albeit with only an alkyl functionality on the backbone, is comparably much less ( I E / I M being as low as 0.56, 0.42, 0.79, and 0.08 in ACN, DCM, EtOH, and [emim]­[Tf 2 N], respectively). ,− Similarly, another prototypical dipyrenyl probe of the alkane backbone family 1,3- bis (1-pyrenyl)­propane [1Py­(3)­1Py] shows I E / I M values of 0.64, 0.74, and 0.67 corresponding to ACN, DCM, and EtOH, respectively . These values exhibit a magnitude at least 10-fold lower than those observed for DTP.…”

“…Intramolecular excimer formation in such bifluorophoric scaffolds has been utilized in fluidity assessment of the cybotactic region as it depends on folding or cyclization of the backbone. − In this context, several compounds incorporating two strategically positioned pyrene functionalities on their scaffolds have been synthesized, and their aggregation efficiency, along with the dynamics of dimerization (i.e., association and dissociation rates), has been reported in the past. − ,,, One such dipyrenyl scaffold has been utilized to gain insight into the ring closing metathesis (RCM) in organic solvents, supercritical CO 2 , ionic liquids, and ionic liquid-poly­(ethylene glycol) mixtures. , The potential for pyrene units to associate intramolecularly has also been exploited in pyrene end-tagged polymers to investigate long-range dynamics within polymer chains. , The intramolecular excimer formation exhibited by bis pyrenyl alkanes such as 1,3- bis (1-pyrenyl)­propane and 1,3- bis (1-pyrenyl)­decane has been extensively investigated in various organic solvents and ionic liquids (ILs) by multiple research groups. − These studies have contributed significantly to our understanding of excimer formation dynamics in different solvents, offering crucial insights into the dependence of excimer formation on solvent properties, including composition, chain length, chain structure, fluorophore chemistry, tether length, and position at which the fluorophore is attached to the hydrocarbon chain. Moreover, these investigations have explored the influence of the temperature and pressure on the excimer formation process.…”

Unveiling Energy Transfer Mechanisms in Nanographene-Incorporated Metal–Organic Frameworks

“…The reduced η FRET at higher HBC concentrations implies the formation of HBC*•••HBC excimer, which not only hinders energy transfer but also quenches HBC emission. 28,77,78 In contrast, UMOF-2-X crystals exhibited a remarkable difference in the trend in η FRET (Figure 3e and Table S4). UMOF-2-X (X = 7, 14, 18, and 39) showcased η FRET values of 21%, 45%, 46%, and 47%, respectively.…”

“…The most significant decrease in HPB lifetime was observed for the HPB:HBC = 1:0.1 solution upon photoexcitation at 310 nm, which exhibited the highest η FRET of 69% (Figure S23 and Table S3). The reduced η FRET at higher HBC concentrations implies the formation of HBC*···HBC excimer, which not only hinders energy transfer but also quenches HBC emission. ,, In contrast, UMOF-2- X crystals exhibited a remarkable difference in the trend in η FRET (Figure e and Table S4). UMOF-2- X ( X = 7, 14, 18, and 39) showcased η FRET values of 21%, 45%, 46%, and 47%, respectively.…”