Excited-state Proton Transfer Dynamics Research Articles

Revisiting the Excited State Proton Transfer Dynamics in N-Oxide-Based Fluorophore: A Keto-Enol/Enolate Interplay to Detect Trace Water in Organic Solvents

This work highlights the unique proton transfer ability observed in cyanoquinoxaline N-oxide-based fluorophores. A fluorophore HCQ was synthesized for this purpose, and a detailed study of its photophysical characteristics was...

Excited-State Dynamics of a Photoacid: A Potential Probe for Recognizing Transition from Lamellar to Nonlamellar Inverted Structures of Liposome based Nanocarriers.

Liposomes of a cationic lipid dioctadecyldimethylammonium bromide (DODAB) are efficient nanocarriers of nucleic acids. Incorporation of a neutral lipid monoolein (MO) in excess (xMO >0.5) changes the lamellar organization of DODAB liposomes into non-lamellar inverted structures of DODAB/MO liposomes facilitating nucleic acid delivery to cells. Photoexcitation of 8-hydroxypyrene-1,3,6-trisulfonic acid (HPTS), a photoacid, initiates an excited state proton transfer (ESPT) reaction in its protonated form (ROH*) generating the deprotonated anionic form (RO- *). The fluorescence intensity ratio (IROH* /IRO-* ) of these two forms is governed by the ESPT dynamics, and increases with increasing MO content (xMO ) in the cationic liposomes of DODAB. Transition from lamellar organization of DODAB liposomes into non-lamellar inverted structures of DODAB/MO liposomes, due to incorporation of MO (xMO ~0.7), is manifested by a significant increase of ESPT time (τPT ) and the time constant of wobbling motion (τW ) of HPTS. Thus, the lamellar organizations of DODAB or DODAB-rich (xMO 0.2) liposomes and the non-lamellar organizations of MO-rich (xMO ~0.7) liposomes are recognized by significantly different excited state dynamics of the photoacid.

Alcoholic Solvent-Mediated Excited-State Proton Transfer Dynamics of a Novel Dihydroxynaphthalene Dye.

The excited-state proton transfer (ESPT) reaction is an important primary photochemical process because it is closely related to photophysical properties. Although ESPT research in aqueous solutions is predominant, alcoholic solvent-mediated ESPT studies are also significant in terms of photoacid-based reactions. Especially, the research for dihydroxynaphthalenes (DHNs) has been largely neglected due to the challenging data interpretation of two hydroxyl groups. A novel fluorescent dye, resveratrone, synthesized by light irradiation of resveratrol, which is famous for its antioxidant properties, can be regarded as a type of DHN, and it has distinctive optical properties, including high quantum yield, a large two-photon absorption coefficient, a large Stokes shift, and very high biocompatibility. In this study, we investigate the overall kinetics of the optical properties of resveratrone and find evidence for alcoholic solvent-mediated ESPT involvement in the radiative properties of resveratrone with a large Stokes shift. Our investigation provides an opportunity to revisit the overlooked photophysical properties of intriguing photoacid behavior and the large Stokes shift of the dihydroxynaphthalene dye.

Suppression of Charge Recombination by Auxiliary Atoms in Photoinduced Charge Separation Dynamics with Mn Oxides: A Theoretical Study.

Charge separation is one of the most crucial processes in photochemical dynamics of energy conversion, widely observed ranging from water splitting in photosystem II (PSII) of plants to photoinduced oxidation reduction processes. Several basic principles, with respect to charge separation, are known, each of which suffers inherent charge recombination channels that suppress the separation efficiency. We found a charge separation mechanism in the photoinduced excited-state proton transfer dynamics from Mn oxides to organic acceptors. This mechanism is referred to as coupled proton and electron wave-packet transfer (CPEWT), which is essentially a synchronous transfer of electron wave-packets and protons through mutually different spatial channels to separated destinations passing through nonadiabatic regions, such as conical intersections, and avoided crossings. CPEWT also applies to collision-induced ground-state water splitting dynamics catalyzed by Mn4CaO5 cluster. For the present photoinduced charge separation dynamics by Mn oxides, we identified a dynamical mechanism of charge recombination. It takes place by passing across nonadiabatic regions, which are different from those for charge separations and lead to the excited states of the initial state before photoabsorption. This article is an overview of our work on photoinduced charge separation and associated charge recombination with an additional study. After reviewing the basic mechanisms of charge separation and recombination, we herein studied substituent effects on the suppression of such charge recombination by doping auxiliary atoms. Our illustrative systems are X–Mn(OH)2 tied to N-methylformamidine, with X=OH, Be(OH)3, Mg(OH)3, Ca(OH)3, Sr(OH)3 along with Al(OH)4 and Zn(OH)3. We found that the competence of suppression of charge recombination depends significantly on the substituents. The present study should serve as a useful guiding principle in designing the relevant photocatalysts.

Comparison of interaction patterns of a triblock copolymer micelle with zwitterionic vs. cationic surfactant: An excited-state proton transfer dynamics investigation

This investigation explored the interaction between a triblock copolymer F127 (poly-(ethylene oxide)101 (PEO101)–poly(propylene oxide)56 (PPO56)–PEO101)) micelle and a zwitterionic sulfobetaine surfactant N-dodecyl-N, N-dimethyl-3-ammoniopropane sulfonate (SB3–12 or SB12), primarily utilizing the excited-state proton transfer (ESPT) dynamics of a photoacid, 8-hydroxy pyrene-1,3,6-trisulfonate (HPTS). We compared the obtained interaction pattern to that of the cationic surfactant, dodecyl trimethylammonium bromide (DTAB or C12TAB), with the same alkyl chains. The two surfactants, irrespective of charge differences, grossly follow the same pattern as manifested by the change in the intensity ratio of the protonated and deprotonated emission bands. For both cases, the ratio first increases above a specific surfactant concentration, attaining a maximum at a particular concentration. The ratio decreases at a high concentration and finally levels off at a very high concentration. Interestingly, the ratio attains maximum for a post-micellar (30–35 mM) concentration (~ 10 times higher than critical micellar concentration or CMC) for SB12 whereas, the maximum occurs at a sub-micellar (6–8 mM) concentration (significantly lower than its CMC) for DTAB. Detailed analysis of the time-dependent emission intensity ratio reveals that ESPT dynamics is slower in the optimum F127-SB12 assembly than in the case of the cationic surfactant. The fluorescence anisotropy decay of 8-methoxypyrene-1,3,6-trisulfonate (MPTS), a methoxy analog of HPTS, also corroborates well with the anomalous pattern; the rotational dynamics become more retarded inside the F127-SB12 assembly than in the case of the cationic surfactant. Thus, although SB12 requires a higher surfactant concentration to acquire the optimum state, it results in a more organized and less hydrated state than the cationic surfactant.

Excited-State Proton Transfer Dynamics in LSSmOrange Studied by Time-Resolved Impulsive Stimulated Raman Spectroscopy.

LSSmOrange is a fluorescent protein that exhibits a large energy gap between absorption and emission, which makes it a useful tool for multicolor bioimaging. This characteristic of LSSmOrange originates from excited-state proton transfer (ESPT): The neutral chromophore is predominantly present in the ground state while the bright fluorescence is emitted from the anionic excited state after ESPT. Interestingly, it was reported that this ESPT process follows bimodal dynamics, but its origin has not clearly been understood. We investigate ESPT of LSSmOrange using time-resolved impulsive stimulated Raman spectroscopy (TR-ISRS) that provides femtosecond time-resolved Raman spectra. The results indicate that the bimodal ESPT dynamics originates from the structural heterogeneity of the chromophore. Species-associated Raman spectra obtained by spectral analysis based on singular value decomposition (SVD) suggest that cis and trans chromophores coexist in the ground state. It is considered that these two forms are photoexcited and undergo ESPT in parallel, resulting in the bimodal dynamics of ESPT in LSSmOrange.

Excited State Proton Transfer of Quinone Cyanine 9: Implications on the Origin of Super‐Photoacidity

AbstractQuinone cyanine 9 (QCy9) is one of the strongest photoacids known to date. The origin of “super”‐photoacidity was investigated via time‐resolved fluorescence (TF) with high time resolution to accurately resolve the ultrafast dynamics of the excited‐state proton transfer (ESPT) to solvent. The ESPT of QCy9 in water is found to proceed fully by two ultrafast time constants of 40 fs (65 %) and 200 fs (35 %). More importantly, the initially created base form of QCy9 in the excited state undergoes a significant dynamic red shift of over 2700 cm−1 by solvation. We suggest that the entirely ultrafast reaction rate and the massive solvation of the conjugate base could make QCy9 a particularly strong photoacid. Quantum chemical calculations show that structural diversity leads to the nonexponential behavior of the ESPT dynamics.

Enabling Control over Mechanical Conformity and Luminescence in Molecular Crystals: Interaction Engineering in Action

Molecular crystals of π-conjugated molecules are of great interest as the highly ordered dense packing offers superior charge and exciton transport compared with its amorphous counterparts. However, integration into optoelectronic devices remains a major challenge owing to its inherently brittle nature. Herein, control over the mechanical conformity in single crystals of pyridine-appended thiazolothiazole derivatives is reported by modulating the molecular packing through interaction engineering. Two polymorphs were prepared by achieving control over the thermodynamic/kinetic factors of crystallization; one of the polymorphs exhibits elastic bending whereas the other is brittle. The control over the bending ability was achieved by forming co-crystals with hydrogen/halogen bond donors. A seamless extended crisscross pattern with respect to the bend plane through a ditopic hydrogen-bonding motif showed the highest compliance towards mechanical bending, whereas the co-crystals with a layered crisscross arrangement with segregated layers of co-formers exhibit slightly lower bending conformity. These results update the rationale behind the plastic/elastic bending in molecular crystals. The co-crystals of ditopic halogen bond co-assemblies are particularly appealing for waveguiding applications as the co-crystals blend high mechanical flexibility and luminescence properties. The hydrogen bonded co-crystals are non-emissive in nature owing to excited state proton transfer dynamics. The rationale behind the fluorescence properties of these materials was also established from DFT calculations in a quantum mechanics/molecular mechanics (QM/MM) framework.

Ultrafast excited-state proton transfer dynamics in dihalogenated non-fluorescent and fluorescent GFP chromophores.

Green fluorescent protein (GFP) has enabled a myriad of bioimaging advances due to its photophysical and photochemical properties. To deepen the mechanistic understanding of such light-induced processes, novel derivatives of GFP chromophore p-HBDI were engineered by fluorination or bromination of the phenolic moiety into superphotoacids, which efficiently undergo excited-state proton transfer (ESPT) in aqueous solution within the short lifetime of the excited state, as opposed to p-HBDI where efficient ESPT is not observed. In addition, we tuned the excited-state lifetime from picoseconds to nanoseconds by conformational locking of the p-HBDI backbone, essentially transforming the nonfluorescent chromophores into highly fluorescent ones. The unlocked superphotoacids undergo a barrierless ESPT without much solvent activity, whereas the locked counterparts exhibit two distinct solvent-involved ESPT pathways. Comparative analysis of femtosecond transient absorption spectra of these unlocked and locked superphotoacids reveals that the ESPT rates adopt an "inverted" kinetic behavior as the thermodynamic driving force increases upon locking the backbone. Further experimental and theoretical investigations are expected to shed more light on the interplay between the modified electronic structure (mainly by dihalogenation) and nuclear motions (by conformational locking) of the functionalized GFP derivatives (e.g., fluorescence on and off).

Anomalous Variation of Excited-State Proton Transfer Dynamics inside a Triblock Copolymer-Cationic Surfactant Mixed Micelle.

Mixed micelles formed by triblock copolymers [poly(ethylene oxide)m (EOm)-poly(propylene oxide)n (POn)-EOm] with various surfactants have widespread applications. Molecular-level understanding of the composition, interfacial organization, and hydration of the copolymer-surfactant mixed micelle is greatly necessary from application perspectives. Here, we applied 8-hydroxypyrene-1,3,6-trisulfonate (HPTS) to probe the mixed micelle of a triblock copolymer F127 (EO101-PO56-EO101) and a cationic surfactant dodecyltrimethylammonium bromide (DTAB) at various compositions. The emission spectrum of HPTS modulates anomalously with the variation of DTAB concentration, displaying at least four regimes. The ratio of the emission intensities of the two bands (protonated/deprotonated) (1) first increases steeply in the low-concentration range (0.1-6 mM), (2) remains almost steady at the intermediate concentration (8-20 mM), (3) decreases at high concentration (20-80 mM), and (4) finally, remains almost constant at a very high concentration (100-400 mM) of DTAB. Time-resolved measurements confirm that excited-state proton transfer dynamics varies unusually with the concentration of DTAB in the mixed micelle; substantial retardation is observed up to ∼12 mM, but after that, the dynamics becomes somewhat faster upon further addition. The rotational dynamics of a methoxy analogue of HPTS, 8-methoxypyrene-1,3,6-trisulfonate, becomes slower up to ∼12 mM DTAB and after that becomes faster at higher concentration. Moreover, dynamic light scattering measurements showed that the size of the mixed micelle decreases sharply in the low-concentration region (<20 mM DTAB) but decreases moderately at high concentration. Thus, the nature of the mixed micelle is very different at low and high concentrations of DTAB. At low concentration, the incorporation of DTAB results in a more compact and less hydrated mixed micelle, whereas a more hydrated and less organized assembly is formed at high concentration of DTAB.

Following Bimolecular Excited-State Proton Transfer between Hydroxycoumarin and Imidazole Derivatives.

The ultrafast dynamics of a bimolecular excited-state proton transfer (ESPT) reaction between the photoacid 7-hydroxy-4-(trifluoromethyl)-1-coumarin (CouOH) and 1-methylimidazole (MI) base in aprotic chloroform- d1 solution were investigated using ultrafast transient infrared (TRIR) and transient absorption (TA) spectroscopies. The excited-state lifetime of the photoacid in solution is relatively short (52 ps), which at the millimolar photoacid and base concentrations used in our study precludes any diffusion-controlled bimolecular ESPT reactions. This allows the prompt ESPT reaction between hydrogen-bonded CouOH and MI molecules to be studied in isolation and the "contact" ESPT dynamics to be unambiguously determined. Our time-resolved studies reveal that ultrafast ESPT from the CouOH moiety to hydrogen-bonded MI molecules occurs within ∼1 ps, tracked by unequivocal spectroscopic signatures of CouO-* photoproducts that are formed in tandem with HMI+. Some of the ESPT photoproducts subsequently π-stack to form exciplexes on a ∼35 ps time scale, minimizing the attractive Coulombic forces between the oppositely charged aromatic molecules. For the concentrations of CouOH and MI used in our study (up to 8 mM), we saw no evidence for excited-state tautomerization of coumarin anions.

Modulation of Excited-State Proton-Transfer Dynamics inside the Nanocavity of Microheterogeneous Systems: Microenvironment-Sensitive Förster Energy Transfer to Riboflavin.

The excited-state proton-transfer efficiency of a tetraarylpyrene derivative, 1,3,6,8-tetrakis(4-hydroxy-2,6-dimethylphenyl)pyrene (TDMPP), was investigated thoroughly in the presence of various surfactant assemblies, such as micelles and vesicles. The confined microheterogeneous environments can significantly retard the extent of the excited-state proton-transfer process, resulting in a distinguishable optical signal compared to that in the bulk medium. Physical characteristics of the surfactant assemblies, such as order, interfacial hydration, and surface charge, influence the proton transfer process and allow multiparametric sensing. A higher degree of interfacial hydration facilitates the proton-transfer process, while the positively charged head groups of the surfactants specifically stabilize the anionic form of the probe (TDMPP-O*). Furthermore, Forster energy transfer from the probe to riboflavin was studied in a phospholipid membrane, wherein the relative ratio of the neutral versus anionic forms (TDMPP-OH/TDMPP-O*) was found to influence the extent of energy transfer. Overall, we demonstrate how an ultrafast photophysical process, that is, the excited-state proton transfer, can be influenced by the microenvironment.

Analysis of excited state proton transfer dynamics of HPTS in methanol-water mixtures from time-resolved area-normalised emission spectrum (TRANES)

Although excited state proton transfer (ESPT) dynamics has been extensively investigated in several aqueous-organic mixtures in the literature, but those are based on analysis of single wavelength transient representing either of the protonated or the deprotonated emission. Single wavelength decay, in principle, contains all necessary dynamic information but usually susceptible to potential error, if overlap of different excited species are not properly considered. Moreover, analysis of these decays are less intuitive and more challenging, since various dynamic parameters operate together. Recently, we proposed a simple and intuitive analysis to extract ESPT dynamics of 8-hydroxypyrene-1,3,6-trisulphonic acid (HPTS) from time-resolved area-normalised emission spectrum (TRANES). Here, we further refined the analysis by inducting contact ion-pair into the ESPT scheme and applied to elucidate ESPT dynamics of HPTS in methanol-water mixtures at different mole fractions of methanol. The time constants were extracted from the decay and rise of the overlap-corrected protonated or deprotonated intensities (or areas of individual emission bands) of TRANES by either a global fit or from the ratio of their intensities (or areas). We found an exponential correlation between the deprotonation times and the mole fraction of methanol, which leads to the conclusion that the activation energy of ESPT in the mixture increases linearly with increase of the mole fraction of methanol.

Modulation of Excited-State Proton Transfer Dynamics in a Model Lactim–Lactam Tautomeric System by Anisotropic Gold Nanoparticles

The past few decades have witnessed significant advances in the development of functionalized gold nanoparticles (GNPs) for diverse applications in various fields such as chemistry, biology, pharmacy, and physics. However, a recent in vivo toxicity study of GNPs in Drosophila melanogaster demonstrated that GNPs are capable of inducing mutagenesis. Considering mutagenicity and tautomerism (lactim–lactam and amine–imine) of DNA base pairs are correlated with each other, a recent theoretical study reveal the modification of double-proton-transfer process of guanine–cytosine DNA base pairs upon interaction with the gold surface (Au(111)). However, there is a dearth of experimental data about the proton-transfer (PT) process in isolated base pairs on gold nanosurface. In this particular work, we have chosen a model lactim–lactam tautomeric system, namely, 1-(2-hydroxy-5-chloro-phenyl)-3,5-dioxo-1H-imidazo-[3,4-b] isoindole (ADCL), and carried out for the first time a comprehensive study of the modification of excited-state PT dynamics in the presence of synthesized isotropic (spherical) and anisotropic (trianglular, rod, and trigonal bipyramidal) GNPs by means of steady-state and time-resolved fluorescence spectroscopy. The PT process operative in ADCL was experimentally found to be accelerated on the anisotropic gold nanosurface, whereas spherical-shaped GNPs showed little impact on the dynamics of the above-mentioned photophysical phenomenon. Therefore, our experimental results regarding the modification of lactim–lactam tautomerism of a model compound on the gold nanosurface are an indirect evidence of mutation caused by GNPs.

A Ratio-Analysis Method for the Dynamics of Excited State Proton Transfer: Pyranine in Water and Micelles.

The emission spectrum of a fluorophore undergoing excited state proton transfer (ESPT) often exhibits two distinct bands each representing emissions from protonated and deprotonated forms. The relative contribution of the two bands, best represented by an emission intensity ratio ( R) (intensity maximum of the protonated band/intensity maximum of the deprotonated band), is an important parameter which usually denotes feasibility or promptness of the ESPT process. However, the use of a ratio is only limited to the interpretation of steady-state fluorescence spectra. Here, for the first time, we exploit the time dependence of the ratio ( R( t)), calculated from time-resolved emission spectra (TRES) at different times, to analyze ESPT dynamics. TRES at different times were fitted with a sum of two log-normal functions representing each peak, and then, the peak intensity ratio, R( t), was calculated and further fitted with an analytical function. Recently, a time-resolved area-normalized emission spectra (TRANES)-based analysis was presented where the decay of protonated emission or the rise of deprotonated emission intensity conveniently accounts for the ESPT dynamics. We show that these two methods are equivalent but the new method provides more insights on the nature of the ESPT process.

Solvent Relaxation Accompanied Ultrafast Excited State Proton Transfer Dynamics Revealed in a Salicylideneaniline Derivative

AbstractIn this study, we have investigated the excited state intramolecular proton transfer (ESIPT) and subsequent dielectric relaxation of a newly synthesized Schiff base molecule in cyclohexane, methanol and SDS micelle through femtosecond fluorescence up‐conversion and broadband transient absorption spectroscopy. We found that the molecule showed ultrafast proton transfer with a timescale about 0.2 ps followed by solvent relaxation of the keto tautomer in methanol and SDS medium. In non‐polar cyclohexane, the solvation part was completely absent as expected. Computational study suggested the existence of a transition state in the proton transfer surface. Quantification of the system was done with two step model assigning the first rate constant to the relaxation of the excited state enol form and the second to the barrier crossing from the enol to the keto form.

Improved Complete Active Space Configuration Interaction Energies with a Simple Correction from Density Functional Theory.

Recent algorithmic advances have extended the applicability of complete active space configuration interaction (CASCI) methods to molecular systems with hundreds of atoms. While this enables simulation of photochemical dynamics in the condensed phase, the underlying CASCI method has some well-known problems resulting from a severe neglect of dynamic electron correlation. Vertical excitation energies, vibrational frequencies, and reaction barriers are systematically overestimated; these errors limit the applicability of CASCI. We develop a correction for the CASCI energy using density functional theory (DFT). The DFT correction incorporates the effect of dynamic electron correlation among the core electrons into the CASCI Hamiltonian. We show that the resulting DFT-corrected CASCI approach is applicable in situations where the usual single-reference DFT methods fail, such as the description of systems with biradicaloid electronic structure and conical intersections between ground and excited electronic states. Finally, we apply this DFT-corrected CASCI approach to ultrafast excited-state proton transfer dynamics. Without the DFT correction, CASCI predicts spurious reaction barriers to these processes, and, as a result, a qualitatively correct description of the dynamics is not possible. With the DFT-corrected CASCI method, we demonstrate qualitative and quantitative agreement with both theory and experiment for two model systems for excited-state intramolecular proton transfer. Finally, we apply the DFT-corrected CASCI method to excited-state proton transfer dynamics in a system with more than 150 atoms.

Effect of Cosurfactants on the Interfacial Hydration of CTAB Quaternary Reverse Micelle Probed Using Excited State Proton Transfer.

It has been proven previously that the negatively charged photoacid 8-hydroxypyrene-1,3,6-trisulfonic acid trisodium salt (HPTS) resides at the interface of the cationic reverse micelle (RM) cetyltrimethylammonium bromide (CTAB)/octanol/water/cyclohexane and is a potential reporter of hydration through the excited state proton transfer (ESPT) process. However, the ESPT dynamics monitored by the pump-probe study was limited to the ultrafast timescale and hence did not report any discernible ESPT signature. Herein, we reinvestigate the ESPT behavior using fluorescence spectroscopy in the nanosecond timescale and at different values of w0 (=[water]/[surfactant]). We clearly observed distinct w0-dependent ESPT signatures analogous to conventional ternary cationic RMs implying considerable interfacial hydration. The results agree with a recent molecular simulation study, where significant penetration of water molecules into the interface was predicted for the CTAB quaternary RM. Moreover, we also found that the ESPT dynamics and the fluorescence anisotropy decay of HPTS depend differentially on the octanol/CTAB ratio (p0). The ESPT process was found to be disfavored, whereas the anisotropy decay accelerates upon the increase in p0 values. Our analysis indicates that with the increase in the octanol concentration, dehydrated regions enrich gradually at the interface. However, the increase in octanol concentration may reduce the effective electrostatic potential experienced by the probe and thus may result in faster rotational relaxation.

Role of Coherent Low-Frequency Motion in Excited-State Proton Transfer of Green Fluorescent Protein Studied by Time-Resolved Impulsive Stimulated Raman Spectroscopy.

Green fluorescent protein (GFP) from jellyfish Aequorea victoria, an essential bioimaging tool, luminesces via excited-state proton transfer (ESPT) in which the phenolic proton of the p-hydroxybenzylideneimidazolinone chromophore is transferred to Glu222 through a hydrogen-bond network. In this process, the ESPT mediated by the low-frequency motion of the chromophore has been proposed. We address this issue using femtosecond time-resolved impulsive stimulated Raman spectroscopy. After coherently exciting low-frequency modes (<300 cm(-1)) in the excited state of GFP, we examined the excited-state structural evolution and the ESPT dynamics within the dephasing time of the low-frequency vibration. A clear anharmonic vibrational coupling is found between one high-frequency mode of the chromophore (phenolic CH bend) and a low-frequency mode at ∼104 cm(-1). However, the data show that this low-frequency motion does not substantially affect the ESPT dynamics.

Topological Influence of Lyotropic Liquid Crystalline Systems on Excited-State Proton Transfer Dynamics.

In the present work, we have investigated the excited-state proton transfer (ESPT) dynamics inside lipid-based reverse hexagonal (HII), gyroid Ia3d, and diamond Pn3m LLC phases. Polarized light microscopy (PLM) and small-angle X-ray scattering (SAXS) techniques have been employed for the characterization of LLC systems. Time-resolved fluorescence results reveal the retarded ESPT dynamics inside liquid crystalline systems compared to bulk water, and it follows the order HII < Ia3d < Pn3m < H2O. The slower solvation, hampered "Grotthuss" proton transfer process, and most importantly, topological influence, of the LLC systems are believed to be mainly responsible for the slower and different extent of ESPT dynamics. Interestingly, recombination dynamics is found to be faster with respect to bulk water and it follows the order H2O < Pn3m < Ia3d < HII. Faster recombination dynamics arises due to lower dielectric constant and different channel diameters of these LLC systems. However, the dissociation dynamics is found to be slower than bulk water and it follows the order HII < Ia3d < Pn3m < H2O. Differences in critical packing parameter of LLC systems are believed to be the governing factors for the slower dissociation dynamics in these liquid crystalline systems.