Excited-state Proton Transfer Process Research Articles

Structural dynamics around a hydrogen bond: Investigating the effect of hydrogen bond strengths on the excited state dynamics of carboxylic acid dimers.

The photochemical dynamics of the acetic acid and trifluoro-acetic acid dimers in hexane are studied using time-resolved infrared absorption spectroscopy and abinitio electronic structure calculations. The different hydrogen bond strengths of the two systems lead to changes in the character of the accessed excited states and in the timescales of the initial structural rearrangement that define the early time dynamics following UV excitation. The much stronger hydrogen bonding in the acetic acid dimer stabilizes the system against dissociation. Ground state recovery is mediated by a structural buckling around the hydrogen bond itself with no evidence for excited state proton transfer processes that are usually considered to drive ultrafast relaxation processes in hydrogen bonded systems. The buckling of the ring leads to relaxation through two conical intersections and the eventual reformation of the electronic and vibrational ground states on a few picosecond timescale. In trifluoro-acetic acid, the weaker hydrogen bonding interaction means that the dimer dissociates under similar irradiation conditions. The surrounding solvent cage restricts the full separation of the monomer components, meaning that the dimer is reformed and returns to the ground state structure via a similar buckled structure but over a much longer, ∼100ps, timescale.

Light-Triggered Reversible Change in the Electronic Structure of MoO3 Nanosheets via an Excited-State Proton Transfer Mechanism.

Light is an attractive source of energy for regulating stimulus-responsive chemical systems. Here, we use light as a gating source to control the redox state, the localized surface plasmonic resonance (LSPR) peak, and the structure of molybdenum oxide (MoO3) nanosheets, which are important for various applications. However, the light excitation is not that of the MoO3 nanosheets but rather that of pyranine (HPTS) photoacids, which in turn undergo an excited-state proton transfer (ESPT) process. We show that the ESPT process from HPTS to the nanosheets and the intercalation of protons within the MoO3 nanosheets trigger the reduction of the nanosheets and the broadening of the LSPR peak, a process that is reversible, meaning that in the absence of light, the LSPR peak diminishes and the nanosheets return to their oxidized form. We further show that this reversible process is accompanied by a change in the nanosheet size and morphology.

Multi-analyte fluorescence sensing based on a post-synthetically functionalized two-dimensional Zn-MOF nanosheets featuring excited-state proton transfer process

Covalent post-synthetic modification of metal–organic frameworks (MOFs) represents an underexplored but promising avenue for allowing the addition of specific fluorescent recognition elements to produce the novel MOF-based sensory materials with multiple-analyte detection capability. Here, an excited-state proton transfer (ESPT) active sensor 2D-Zn-NS-P was designed and constructed by covalent post-synthetic incorporation of the excited-state tautomeric 2-hydroxypyridine moiety into the ultrasonically exfoliated amino-tagged 2D Zn-MOF nanosheets (2D-Zn-NS). The water-mediated ESPT process facilitates the highly accessible active sites incorporated on the surface of 2D-Zn-NS-P to specifically respond to the presence of water in common organic solvents via fluorescence turn-on behavior, and accurate quantification of trace amount of water in acetonitrile, acetone and ethanol was established using the as-synthesized nanosheet sensor with the detection sensitivity (<0.01% v/v) superior to the conventional Karl Fischer titration. Upon exposure to Fe3+ or Cr2O72−, the intense blue emission of the aqueous colloidal dispersion of 2D-Zn-NS-P was selectively quenched even in the coexistence of common inorganic interferents. The prohibition of the water-mediated ESPT process and local emission, induced by the coordination of ESPT fluorophore with Fe3+ or by Cr2O72− competitively absorbs the excitation energy, was proposed to responsible for the fluorescence turn-off sensing of the respective analytes. The present study offers the attractive prospect to develop the ESPT-based fluorescent MOF nanosheets by covalent post-synthetic modification strategy as multi-functional sensors for detection of target analytes.

A new zero-dimensional (0D) hybrid bismuth (III) halide: Synthesis, crystal structure, thermal analysis, photophysical properties and DFT calculations

Low-dimensional organic-inorganic hybrid Bi(III) halides, with organic N, O-heterocycles, are promising solid-state photoluminescent materials, but are underexplored. In this work, we present the synthesis and characterization of a novel bismuth (III) hybrid salt, namely (C8H12NO)4[Bi2Cl10] (referred as (1)). (1) was synthesized using a solvent-evaporation method and extensively characterized using various techniques. The crystal structure of (1) was determined to be zero-dimensional (0D). In this structure, the individual bioctahedral [Bi2Cl10]4− dimers, which share edges, are completely isolated from each other. These dimers are separated by large 4-methoxybenzylammonium cations (C8H12NO)+. The latter are crucial for the crystal structural stability by balancing [Bi2Cl10]4-dimer charges and maintaining overall integrity. Solid-state diffuse reflectance UV–Vis spectrum demonstrates that (1) is a semiconductor with a band gap of 3.32 eV. Its photoluminescence spectrum exhibits intense blue emission when exposed to UV light, with CIE chromaticity coordinates of (0.22, 0.21). Theoretical calculations suggest that the emission with multiple centers originates both from a charge transition between (C8H12NO)+ and Bi2Cl104− ions and from excited-state proton transfer (ESPT) processes related to fluorescence properties. These ESPT processes occur through C–H…π and C–H…O intermolecular hydrogen bonding between the organic cations.

Excited state proton transfer mechanism of a thiazolo [5,4-d] thiazole derivative in different solvents

In this paper, the excited state proton transfer mechanism of a thiazolo [5,4-d] thiazole derivative, 4-tert-butyl-2-(5-(5-tert-butyl-2-methoxyphenyl) thiazolo [5,4-d] thiazol-2-yl) phenol (MTTH), has been investigated in different polar solvents by using DFT and TDDFT methods. The hydrogen bond lengths, bond angles, and corresponding infrared vibrational frequencies of MTTH in three different polar solvents were compared, and the analytical results showed that the intramolecular hydrogen bonding of MTTH was enhanced in all S1 states. In addition, the simulated absorption and emission spectra values of MTTH are in good agreement with the experimental data, which further proves the rationality of the calculation method. Meanwhile, the electron density rearrangement between the proton acceptor and donor was found by analyzing the frontline molecular orbitals of the MTTH, which is favorable for the excited state proton transfer process. Finally, the potential energy curves of MTTH in three different solvents were calculated, and the results indicated that the weakly polar solvents were more favorable for the excited state intramolecular proton transfer of MTTH.

Manipulating the ESPT process and photophysical properties of HQCT by water-based hydrogen bond bridge

The 8-hydroxyquinoline-2-carboxaldehyde thiosemicarbazone (HQCT) is sensitive to water molecules in dimethyl sulfoxide according to the experimental phenomenon description, with a sensory performance that is dependent on the water-based hydrogen bond bridge as mediator. Here the excited state intramolecular (ESAPT) and intermolecular (ESEPT) proton transfer mechanism involved by water solvent and the optical properties associated with them are clarified in details. Along the minimum energy pathways in the scanned potential energy surfaces (PESs), we find that the ESEPT reaction induced by water molecule is a synergistic double-proton transfer process. And the results indicate that trace water molecules can promote the reaction effectively. In addition, we also investigate the photophysical properties involved with the excited state proton transfer (ESPT) reaction with the increase of water fraction in the solvent. The results show that the fluorescent oscillator strength (f) and radiative rates (kr) decrease with the increase of water fraction, which are consistent with the experimental phenomenon. We attribute the phenomenon of fluorescence quenching to the increasing transition dipole moment (μ) which accelerates the intramolecular charge transfer (ICT) process. Our work not only explain the water-detection mechanism in the organic solvent before water-sensitive reactions essentially, but also provide a theoretical basis for the synthesis of new Schiff base fluorescent chromophores for the water detection in organic solvents.

Excited-State Proton Transfer in a Photoacid-Based Crystalline Coordination Compound: Reversible Photochromism, Near-Infrared Photothermal Conversion, and Conductivity.

By harnessing the power of coordination self-assembly, crystalline materials can act as carriers for photoacids. Unlike their solution-based counterparts, these photoacids are capable of altering the properties of the crystalline material under light and can even generate proton transfer in a solid-state environment. Due to the photoinduced proton transfer and charge transfer processes within this functional material, this crystal exhibits powerful absorption spanning the visible to near-infrared spectrum upon light irradiation. This feature enables reproducible, significant chromatic variation, near-infrared photothermal conversion, and photocontrollable conductivity for this photoresponsive material. The findings suggest that the synthesis of pyranine photoacid-based crystalline materials via coordination self-assembly can not only enhance light-harvesting efficiency but also enable excited-state proton transfer processes within solid crystalline materials, thereby maintaining and even improving the properties of photoacids.

Excited-State Proton Transfer in Luminescent Dyes: From Theoretical Insight to Experimental Evidence.

The effective utilization of luminescent dyes often relies on a comprehensive understanding of their excitation and relaxation pathways. One such pathway, Excited-State Proton Transfer (ESPT), involves the tautomerization of the dye in its excited state, resulting in a new structure that exhibits distinct emission properties, such as a very large Stokes' shift or dual-emission. Although the ESPT phenomenon is well-explained theoretically, its experimental demonstration can be challenging due to the presence of numerous other phenomena that can yield similar experimental observations. In this review, we propose that an all-encompassing methodology, integrating experimental findings, computational analyses, and a thorough evaluation of diverse mechanisms, is essential for verifying the occurrence of ESPT in luminescent dyes. Investigations have offered significant understanding of the elements impacting the ESPT process and the array of approaches that can be used to validate the existence of ESPT. These discoveries hold crucial ramifications for the advancement of molecular probes, sensors, and other applications that depend on ESPT as a detection mechanism.

Theoretical insights into ultrafast excited state proton transfer coupled with twisted intramolecular charge transfer mechanism in 7-(2ʹ-pyridyl)indole: Effect of hydrogen bonding

The ultrafast proton transfer (PT) process in the excited state of 7-(2′-pyridyl)indole (abbreviated as 7PyIn) has been elucidated by on-the-fly dynamics simulations using the algebraic-diagrammatic construction scheme of second order (ADC(2)) method under the resolution of identity (RI) approximation. The tautomers of 7PyIn alone and associated with an acetonitrile molecule in the 7PyIn-CH3CN complex are most likely found after the excited state intramolecular proton transfer (ESIntraPT) within an ultrafast time scale between 40 and 60 fs. While a methanol molecule in the complex of 7PyIn-CH3OH could establish both ESIntraPT and excited-state intermolecular proton transfer (ESInterPT). ESInterPT of 7PyIn-CH3OH possibly occurs through a concerted process via the intermolecular hydrogen bonding bridge of the methanol molecule almost twice faster than that of ESIntraPT. This slower circumstance of the ESIntraPT process found in 7PyIn-CH3OH may be caused by the competition between formations of the intramolecular and intermolecular hydrogen bonds between 7PyIn and methanol. In addition, after the accomplishment of excited state proton transfer (ESPT), the initiation of conical intersection could be taking place by the structural twist of 7PyIn. The geometries, energies, proton probabilities, and provided mechanisms via the dynamics simulations of 7PyIn and its solvent clusters exhibiting ESIntraPT and ESInterPT are explored to provide the dynamic pictures of the ESPT processes at the molecular level.

Photocurrent Generation and Polarity Switching in Electrochemical Cells through Light‐induced Excited State Proton Transfer of Photoacids and Photobases**

AbstractLight is a common source of energy in sustainable technologies for photocurrent generation. To date, in such light‐harvesting applications, the excited electrons generate the photocurrent. Here, we introduce a new mechanism for photocurrent generation that is based on excited state proton transfer (ESPT) of photoacids and photobases that can donate or accept a proton, respectively, but only after excitation. We show that the formed ions following ESPT can either serve as electron donors or acceptors with the electrodes, or modify the kinetics of mass transport across the diffuse layer, both resulting in photocurrent generation. We further show that control of the current polarity is obtained by switching the irradiation between the photoacid and the photobase. Our study represents a new approach in photoelectrochemistry by introducing ESPT processes, which can be further utilized in light‐responsive energy production or energy storage.

Photocurrent Generation and Polarity Switching in Electrochemical Cells through Light-induced Excited State Proton Transfer of Photoacids and Photobases.

Light is a common source of energy in sustainable technologies for photocurrent generation. To date, in such light-harvesting applications, the excited electrons generate the photocurrent. Here, we introduce a new mechanism for photocurrent generation that is based on excited state proton transfer (ESPT) of photoacids and photobases that can donate or accept a proton, respectively, but only after excitation. We show that the formed ions following ESPT can either serve as electron donors or acceptors with the electrodes, or modify the kinetics of mass transport across the diffuse layer, both resulting in photocurrent generation. We further show that control of the current polarity is obtained by switching the irradiation between the photoacid and the photobase. Our study represents a new approach in photoelectrochemistry by introducing ESPT processes, which can be further utilized in light-responsive energy production or energy storage.

Effects of solvents on excited‐state proton transfer behaviors and photophysical properties of 3NTF

AbstractIn this work, we systematically investigate the effects of solvent on the mechanism of excited‐state proton transfer and photophysical properties of 3NTF using density functional and time‐dependent density functional. The geometry of 3NTF (normal structure and isomer structure) was optimized. Based on the optimized geometry, the parameters related to hydrogen bond indicate that the hydrogen bond is strengthened in the S1 state. Further, reduced density gradient functions provide a more intuitive proof of the excited hydrogen bond strengthening mechanism. The analysis of frontier molecular orbitals shows that the charge density of the S0 and S1 states has changed significantly, which is the driving force for proton transfer in the excited state. The infrared vibrational spectra show that the hydrogen bond strength decreases with the increase of solvent polarity. The absorption and fluorescence spectra of the molecules are very sensitive to the solvent polarity. Through the analysis of the potential energy curves, it is concluded that the decrease of solvent polarity will promote the occurrence of the excited state proton transfer process.

Exploring the excited state proton transfer mechanisms of flavonoid probe in three representative solvents

The role of intermolecular hydrogen bond is often ignored in the study of the solvent effect on the excited state proton transfer (ESPT) processes. The ESPT mechanisms of 2-(4-(dimethylamino)phenyl)-3‑hydroxy-6,7-dimethoxy-4H-chromen-4-one (HOF) in three representative solvents, which were toluene, dimethyl sulfoxide (DMSO) and ethanol (EtOH), were investigated through time-dependent density functional theory (TD-DFT) method, and the effect of intermolecular hydrogen bond on the ESPT was fully considered in this paper. The results show that the enhancement of intra- and inter-molecular hydrogen bonds is the key factor of proton transfer process. The change of electron density distribution is also more conducive to the ESPT processes. Due to the existence of intermolecular hydrogen bond in HOF-DMSO complex, the energy barrier of ESPT in DMSO is higher than that in toluene. In EtOH solvent, the excited state double proton transfer (ESDPT) reaction can occur between HOF and EtOH along two different reaction channels with the assistance of dual intermolecular hydrogen bonds. Although the ESPT modes in DMSO and EtOH solvents are different, the energy barriers are basically the same. The energy barriers of ESPT processes in two polar solvents increase obviously due to intermolecular hydrogen bond. Moreover, in polar solvents, a relatively large red-shift was observed in the fluorescence spectra.

Nonlinear optical properties and transient absorption in Hibiscus Sabdariffa dye solution probed with femtosecond pulses

Highly conjugated organic molecules are attractive chromophores for nonlinear optics due to their significant third-order nonlinear response near the absorption bands located in the broad spectral range from 200 to 900 nm. In this work, we report on the wavelength-dependence of one- and two-photon absorption processes in Hibiscus sabdariffa organic dye excited by femtosecond (fs) laser pulses centered at 1030 nm and 515 nm. Z-scan and transient absorption (TA) techniques have been employed to investigate the absorption and relaxation processes in the target dye. The dye is found to have a significant negative nonlinear absorption coefficient (β) of value ∼ −2.7 × 10−11 cm/W at 515 nm probing laser pulses, while it has a positive value equal to +2.1 × 10−13 cm/W when 1030 nm laser pulses were employed. The TA decay measurements using 40 fs laser pulses, centered at 515 nm wavelength, reveal that the dye exhibits a short relaxation time of ∼3 ps attributed to the involvement of the excited state proton transfer (ESPT) process in the Hibiscus dye solution. Moreover, our time-integrated fluorescence measurements revealed that no fluorescence emission could be detected. The application of ultrashort pulses of ∼40 fs duration enabled the tracking of ESPT in the Hibiscus dye, which was not detected in previous studies that employed laser pulses of picoseconds and nanoseconds duration.

Selectively probing ferric ions in aqueous environments using protonated and neutral forms of 7-azaindole as a multiparametric chemosensor.

7-azaindole (7AI) dimer is a model molecule for DNA study and understanding the mutagenic behavior based on the excited-state proton transfer process in hydrogen-bonded networks. The neutral and protonated forms of 7AI monomer with significant fluorescence (FL) intensity fit the fluorescent sensor strategy to recognize selective metal ions. Out of several metal ions (Fe3+, Al3+, Fe2+, Pb2+, Ba2+, Ni2+, Zn2+, Mg2+, Ca2+, Cu2+, Hg2+ and Cd2+), the absorption, fluorescence and fluorescence lifetime of 7AI in the aqueous medium are selectively sensitive to the ferric (Fe3+) ions. The absolute value of absorption intensity increases linearly with concentration of a particular metal ions. FL intensity of both the forms of 7AI decreases gradually with Fe3+ ions and trails the linear Stern-Volmer relation. The formation of non-fluorescent complexes was confirmed with Benesi-Hildebrand and Job plots, along with FL and FL decays. The FL lifetime of the protonated form of 7AI, which is 0.83 ± 0.01ns, is nearly constant with Fe3+ ions concentrations, confirming the static quenching mechanism. The limit of detection (LoD) of Fe3+ ions over the long range of 16-363µM for the neutral and protonated forms of 7AI is 0.46 ± 0.02 and 0.49 ± 0.02µM, respectively, estimated using FL spectra. Additionally, the linear plot of absorbance with Fe3+ ions of both the forms of 7AI can also act as a calibration curve with very close LoDs, as obtained by FL spectra. Thus, the multi-parameters-based probe for detecting the Fe3+ ions over long-range in real aqueous environments with operational, high sensitivity, fast response (< 5s), and good selectivity (over 12 metal ions) is undoubtedly a superior approach over other methods.

Different competition mechanism between ESPT and TICT process regulated by protic and aprotic solvent in DHP

In this study, we adopt density functional theory and time-dependent density functional theory (DFT/TDDFT) methods to compare and analyze the disparate competing mechanisms of excited state proton transfer (ESPT) and twisted intramolecular charge transfer (TICT) process of 2-(4′-diethylamino-2′-hydroxyphenyl)-1H-imidazo-[4,5-b] pyridine (DHP) in protic and aprotic solvent. The results show that the DHP molecule undergoes excited state intramolecular proton transfer (ESIPT) in aprotic solvent ether. Differently, ESIPT is effectively inhibited in protic solvent methanol, whereas the coupling process of excited state double proton transfer (ESDPT) and TICT occurs. Combined with the analysis of potential energy surfaces, we clarify that DHP molecule in ether is more inclined to the channel of TICT → ESIPT → reverse TICT process to implement the ESIPT process. In DHP-MeOH complex, we confirm that the significant redshift phenomenon of fluorescence spectra observed in the experiment is attributed to the ESDPT induced TICT process. Our work offers a new avenue for switching ESPT and TICT competing mechanisms through protic and aprotic solvent, and considerably help the synthesis and development of highly efficient molecular photoswitch.

Indirubin: Nature finding efficient light-activated protective molecular mechanisms

Indirubin (INR), a red structural isomer of the blue indigo (IND) shows, for an organic dye, a high stability towards light. The nature of this photostability is unknown and is here proposed to be linked to efficient dark processes dominating the excited state deactivation. As with IND, an excited state proton transfer (ESPT) process, together with the possibility of rotation around the central carbon-carbon bond (with formation of a syn-rotamer) are, solvent dependent, active molecular mechanisms of the decay pathways in INR. To equate this behaviour, INR, together with N-methyl-(MINR) and N,N′-dimethyl-indirubin (DMINR) have been synthetized and fully investigated from a combination of steady-state, fast-transient absorption and fluorescence techniques together with TDDFT electronic calculations. To rationalize the behaviour of INR in water, the water-soluble sulfonated indirubin (5SINR) and the tri-sulfonated indigo (3SIND) were further investigated. For INR in viscous solvents (e.g. glycerol) ESPT is present. With the studied indirubin derivatives (exception made to DMINR), an additional pathway, to ESPT, exists involving rotation between the two indole-like moieties, with a syn-conformer, leading to a more efficient radiationless deactivation pathway, when compared to indigo. The mechanism of syn-conformer formation is found to involve a longer lifetime in the viscous solvent. This new deactivation process is not present in IND. ESPT, found to be enhanced in water via intermolecular water assisted proton transfer, with a kinetic isotopic effect (KIE = kH/kD), equal to 2 for 3SIND, is also found present for 5SINR with a KIE = 1.5. The common structural origin of the N–H⋯OC bonds in the DNA nucleotides and the indigoid dyes (INR and IND), introduces a new perspective for the study of the molecular protective mechanisms in these molecules.

TDDFT study on the simultaneous sensing mechanism for peroxynitrite and glutathione by a bifunctional fluorescent probe

Using time-dependent density functional theory (TDDFT) method, the response mechanism of a reported bifunctional fluorescent probe for simultaneous recognition of peroxynitrite and glutathione (Chem. Commun. 2018, 54, 11336) was theoretically studied. Calculated vertical excitation energies based on the ground-state and excited-state geometries were consistent with the corresponding experimental ultraviolet–visible and fluorescence spectra. In the ground state, electron delocalization in the probe was limited because its geometry was restrained by steric hindrance. Frontier molecular orbital analysis has shown that the probe should undergo photoinduced electron transfer (PET) from the benzothiazole moiety to the maleimide moiety after excitation. The nonplanar structure together with PET led to fluorescence quenching of the probe. The probe could be dealkylated by peroxynitrite anion. The resulting intramolecular hydrogen bond increasesd the planarity of the molecule, while also gave rise to an excited-state proton-transfer process. Moreover, the addition reaction between the probe and glutathione inhibited the PET process. These two analytes together contributed to the fluorescence enhancement of the final product. This theoretical sensing mechanism for peroxynitrite and glutathione may potentially be important for the design and enhancement of novel probes.

Effect of salt addition on a triblock copolymer-zwitterionic surfactant assembly: insight from excited-state proton transfer.

Copolymer-surfactant assemblies are frequently utilized across various fields, from medicine to nanotechnology. Understanding the organization of the mixed assemblies in a saline environment will further expand their application horizons, especially under physiological conditions. Excited-state proton transfer (ESPT) can provide insight into the hydration nature and organization of the non-toxic assembly of a triblock copolymer F127 (poly-(ethylene oxide)101 (PEO101)-poly(propylene oxide)56 (PPO56)-PEO101)) and a zwitterionic sulfobetaine surfactant N-dodecyl-N,N-dimethyl-3-ammoniopropane sulfonate (SB12). Here, we present a comprehensive investigation of the compactness and hydration nature of the F127-SB12 mixed assemblies at different salt concentrations using the ESPT of 8-hydroxy pyrene-1,3,6-trisulfonate (HPTS). In the absence of salts, gradual SB12 addition to a premicellar (0.4 mM) or a post-micellar (4 mM) F127 solution leads to an anomalous modulation of the protonated and deprotonated emission bands. The emission intensity ratio (protonated/deprotonated) first increases to a maximum at a particular SB12 concentration (6 mM and 35 mM for the premicellar and post-micellar F127 assemblies, respectively), and then the ratio decreases with a further increase in the surfactant concentration. Since the intensity ratio is an indicator of the retardation of the ESPT process, the mixed micellar configuration displaying a maximum intensity ratio represents the most compact and least hydrated state. Salt addition to this configuration lowers the intensity ratio, signifying an enhanced ESPT process. Dynamic light scattering (DLS) results indicate that the size of the mixed assembly remains almost unaltered with the addition of salts. Thus, salinity enhances the ESPT process inside the F127-SB12 mixed assemblies without significantly altering the hydrodynamic radius.

Exploring cationic polyelectrolyte-micelle interaction via excited-state proton transfer. Signatures of probe transfer.

Excited-state proton transfer (ESPT) is a sensitive tool for the delicate monitoring of structural reorganization, hydration level, and confinement within surfactant and polymer assemblies. Here, we investigate the interaction of a cationic polyelectrolyte, poly(diallyl dimethylammonium chloride) (PDADMAC), with micelles of differently charged surfactants using 8-hydroxypyrene-1,3,6-trisulfonic acid (HPTS) as an ESPT probe. We used three surfactants: anionic sodium dodecyl sulfate (SDS), cationic dodecyl trimethylammonium bromide (DTAB), and zwitterionic N-dodecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (SB12), possessing the same alkyl (dodecyl) chain but varying headgroup charges. The fluorescence of HPTS residing initially within the micellar medium modulates differently in the presence of PDADMAC. For the anionic SDS and cationic DTAB micelles, the emission spectrum of HPTS does not alter significantly; however, for SB12 micelles, the emission spectrum undergoes a strong modulation upon adding the polyelectrolyte. The emission intensities quench strongly at a low concentration of PDADMAC but recover at a higher concentration. The emission intensity ratio of the two emission bands also changes significantly, implying strong modulation of the ESPT process with varying PDADMAC concentrations. The time-resolved area normalized emission spectra (TRANES) disclose single isoemissive points in the SB12 micelle at low and high concentrations of PDADMAC but two different isoemissive points (one characteristic of the SB12 micelle at 500 nm and another characteristic of the PDADMAC interface at 480 nm) in the mixed assembly at an intermediate concentration. Detailed analysis suggests that the polyelectrolyte can enforce the transfer of the anionic probe HPTS from the zwitterionic micelle to the PDADMAC assembly above a specific PDADMAC concentration. The transfer of the molecular probe between two assemblies resembles a drug sequestration event, and the study reveals necessary emission signatures.