Decay Of Excited State Research Articles

Mechanochemistry toward Organic "Salt" via Integer-Charge-Transfer Cocrystal Strategy for Rapid, Efficient, and Scalable Near-Infrared Photothermal Conversion.

Inspired by the concept of ionic charge-transfer complexes for the Mott insulator, integer-charge-transfer (integer-CT) cocrystals are designed for NIR photo-thermal conversion (PTC). With amino-styryl-pyridinium dyes and F4TCNQ (7,7',8,8'-Tetracyano-2,3,5,6-tetrafluoroquinodimethane) serving as donor/acceptor (D/A) units, integer-CT cocrystals, including amorphous stacking "salt" and segregated stacking "ionic crystal", are synthesized by mechanochemistry and solution method, respectively. Surprisingly, the integer-CT cocrystals are self-assembled only through multiple D-A hydrogen bonds (C-H⋅⋅⋅X (X=N, F)). Strong charge-transfer interactions in cocrystals contribute to the strong light-harvesting ability at 200-1500 nm. Under 808 nm laser illumination, both the "salt" and "ionic crystal" display excellent PTC efficiency beneficial from ultrafast (∼2 ps) nonradiative decay of excited states. Thus integer-CT cocrystals are potential candidates for rapid, efficient, and scalable PTC platforms. Especially amorphous "salt" with good photo/thermal stability is highly desirable in practical large-scale solar-harvesting/conversion applications in water environment. This work verifies the validity of the integer-CT cocrystal strategy, and charts a promising path to synthesize amorphous PTC materials by mechanochemical method in one-step.

Improvement in Radiative Efficiency Via Intramolecular Charge Transfer in ortho-Carboranyl Luminophores Modified with Functionalized Biphenyls.

In this study, we found that the electronic effects of the functional groups on aromatic units attached to o-carboranyl species can enhance the efficiency of intramolecular charge transfer (ICT)-based radiative decay processes. Six o-carboranyl-based luminophores having attached functionalized biphenyl groups with CF3, F, H, CH3, C(CH3)3, and OCH3 substituents were prepared and fully characterized by multinuclear magnetic resonance spectroscopy. In addition, their molecular structures were determined by single-crystal X-ray diffractometry, which revealed that the distortion of the biphenyl rings and the geometries around the o-carborane cages were similar. All compounds exhibited ICT-based emissions in the rigid state (solution at 77 K and film). Intriguingly, the quantum efficiencies (Φem) of five compounds (that of the group with CF3 could not be measured because of its extremely weak emissions) in the film state increased gradually as the electron-donating power of the terminal functional group modifying the biphenyl moiety increased. Furthermore, the nonradiative decay constants (knr) for the group with OCH3 were estimated to be one-tenth of those for the group with F, whereas the radiative decay constants (kr) for the five compounds were similar. The dipole moments (μ) calculated for the optimized first excited state (S1) structures gradually increased, from that of the group with CF3 to that of the group with OCH3, implying that the inhomogeneity of the molecular charge distribution was enhanced by electron donation. The electron-rich environment formed as a result of electron donation led to efficient charge transfer to the excited state. Both experimental and theoretical findings revealed that the electronic environment of the aromatic moiety in o-carboranyl luminophores can be controlled to accelerate or interrupt the ICT process in the radiative decay of excited states.

First Observation of the β3αp Decay of ^{13}O via β-Delayed Charged-Particle Spectroscopy.

The β-delayed proton decay of ^{13}O has previously been studied, but the direct observation of β-delayed 3αp decay has not been reported. Rare 3αp events from the decay of excited states in ^{13}N^{⋆} provide a sensitive probe of cluster configurations in ^{13}N. To measure the low-energy products following β-delayed 3αp decay, the Texas Active Target (TexAT) time projection chamber was employed using the one-at-a-time β-delayed charged-particle spectroscopy technique at the Cyclotron Institute, Texas A&M University. A total of 1.9×10^{5} ^{13}O implantations were made inside the TexAT time projection chamber. A total of 149 3αp events were observed, yielding a β-delayed 3αp branching ratio of 0.078(6)%. Four previously unknown α-decaying excited states were observed in ^{13}N at 11.3, 12.4, 13.1, and 13.7MeV decaying via the 3α+p channel.

Heptamethine Cyanine Dyes with Ultra‐Efficient Excited‐State Nonradiative Decay for Synergistic Photothermal Immunotherapy

AbstractOrganic dyes in the excited singlet state (S1) decay via intersystem crossing (ISC) to the triplet state, radiative dissipation as fluorescence, or nonradiative decay for thermal deactivation. Although many studies are conducted to improve ISC and fluorescence efficiency, few have optimized S1 decay via thermal deactivation, which is crucial for designing photothermal agents. A strategy for inhibiting radiative decay and ISC by introducing electron withdraw groups (EWGs) into the meso position of heptamethine cyanines (Cy7) is reported here, which allows S1 energy decay via nonradiative relaxation. The decrease in the electron density of Cy7 caused by EWGs improved the photostability, which is important for biological applications because conventional cyanine dyes are easily photobleached. The EWG substitutes acted as efficient rotation groups with low‐energy barriers, narrowing the energy gap between S1 and the ground state and considerably improving the photothermal conversion efficiency (PCE). The PCE of CF3cy with the strongest EWG is increased up to 83%. Liposome is used as a carrier to improve the biocompatibility and tumor retention of CF3cy, which is combined with the toll‐like receptor agonist resiquimod (R848) for synergistic photothermal immunotherapy against both primary and distant tumors and elicits a long‐lasting immunological memory effect.

Femtosecond Spectroscopy on a Dibenzophenazine-Cored Macrocycle Exhibiting Thermally Activated Delayed Fluorescence.

The photophysics of a thermally activated delayed fluorescence (TADF) emitting macrocycle consisting of two dibenzo[a,j]phenazine acceptor moieties bridged by two N,N,N',N'-tetraphenylene-1,4-diamine donor units was scrutinized in solution by steady-state and time-resolved spectroscopy. The fluorescence lifetime of the compound proved to be strongly solvent-dependent. It ranges from 6.3 ns in cyclohexane to 34 ps in dimethyl sulfoxide. In polar solvents the fluorescence decay is predominantly due to internal conversion. In non-polar ones radiative decay and intersystem crossing contribute. Contrary to the behaviour in polymer matrices (S. Izumi et al., J. Am. Chem. Soc. 2020, 142, 1482) the excited state decay is not predominantly due to prompt and delayed fluorescence. The solvent-dependent behaviour is analyzed with the aid of quantum chemical computations.

Long-lived NIR emission in sulfur-doped zeolites due to the presence of [S3]2- clusters

The exploration of novel long-lived near-infrared (NIR) luminescent materials has attracted significant attention due to their applications in optical communications, anticounterfeiting, and bioimaging. However, these materials usually present low photoluminescence quantum yields and low photo- and chemical stability. Novel emitters that overcome these limitations are in demand. In this study, NIR emission was achieved using widely available, sustainable, and non-toxic materials through the synthesis of sulfur-doped zeolites, with different S/Cl ratios. With a combination of computational calculations (TD-DFT) and spectroscopic data, this emission was assigned to the radiative decay of excited triplet states of [S3]2- clusters, which resulted in a remarkably high Stokes shift (1.97 eV, 440 nm) and an average decay time of 0.54 ms. These new materials present high stability, external quantum efficiency of up to 17%, and a long-lived NIR emission, placing these compounds in a unique position to be used in applications demanding NIR emitters.

Tunable resonance Raman scattering of quantum dots in a nonlinear excitation regime.

Controllable tuning of electron-phonon coupling strength and excited state dynamics is important for the understanding of resonance Raman scattering in low-dimensional semiconductors. Here, we report a significant and reversible field-induced modulation in absolute resonance Raman intensity of quantum dots using ionic liquid gating. Meanwhile, a potential-dependent nonlinear relationship is present between Raman intensity and excitation power density. By exploring the parameter space within a time domain model, we find that the Raman intensity variation is mainly determined by the homogeneous linewidth. We further propose that the Fermi level positions and exciton species play key roles in the excited state decay rates.

Ultrafast Charge Injection in Silver-Modified Graphitic Carbon Nitride.

Graphitic carbon nitride (gCN) is a promising organic platform for driving light-activated charge-transfer reactions in a number of valuable photocatalytic cycles. A primary limitation of gCN as a photocatalyst is its short excited-state lifetime, which is mediated by a high density of trap and defect sites that result in rapid excited-state decay and low photocatalytic efficiency. To enhance the catalytic activity, gCN is often functionalized with a metal co-catalyst; however, the mechanism by which metal co-catalysts enhance the reactivity has not been clearly established. In this work, the excited-state dynamics of gCN and silver-modified gCN are compared using ultrafast transient absorption and time-resolved photoluminescence spectroscopies. In silver-modified gCN, an ultrafast spectral shift in the silver plasmon resonance provides direct spectral evidence of electron transfer from gCN to the silver nanoparticles. The electron-transfer rate is competitive with other non-radiative relaxation pathways, with electron-transfer yields approaching 50%, thus providing an effective strategy for mitigating losses associated with defects and trap sites.

Effect of the π-bridge structure on the intramolecular charge transfer of push–pull 2-phenylthiophene and 2-(furan-2-yl)pyridine derivatives

Effect of the bridge structure on the photophysical properties of D-π-A of structurally similar 2,5-diphenylthiophene (cpd. I) and 2-(5-phenylfuran-2-yl)pyridine (cpd. 2) derivatives having the same electron donating and electron withdrawing groups were studied in different solvents. Solvent effect on the absorption and fluorescence emission spectra as well as their excited state decay were studied in detail. Introduction of 2,5-diphenylthiophene and 2-(5-phenylfuran-2-yl)pyridine between methoxy and carbonitrile groups lead to a shift of about 20 nm in both the absorption and fluorescence emission maxima of the former. Stokes shift of about 90 nm was observed for both compounds in protic solvents and polar aprotic solvents and decreases as the solvent polarity decreases. The solvatochromism in the fluorescence emission spectra was higher than the observed in absorption spectra, indicating higher dipole moment in the excited state than in the ground state for both compounds. DFT and TD-DFT optimized geometry calculations show that (I) is planar in the excited state while (II) is planar in both the ground and excited states reflecting the importance of the bridge structure on the geometry in the ground and excited states. Theoretical calculations of the dipole moment change from the ground to the excited states were consistent with the values obtained from Lippert-Mataga relationship and higher than values obtained from Reichardt-Ravi relationship. It has been found that the fluorescence lifetime of both compounds was found to decrease as the emission energy increases and being higher for (II) than for (I), and also was found to increase as the solvent’s dielectric constant increases. All photophysical properties were found to correlate well with Reichardt’s solvent polarity parameter, ETN. We have employed Kamlet-Taft, Catalán and Laurence et al. multi-parametric relationships to assign the contribution of the specific and non-specific solute–solvent interactions. Non-specific interactions were found to be mostly dominating in all cases.

Multiple Photoisomerization Pathways of the Green Fluorescent Protein Chromophore in a Reversibly Photoswitchable Fluorescent Protein: Insights from Quantum Mechanics/Molecular Mechanics Simulations

Herein, we have employed a combined CASPT2//CASSCF approach within the quantum mechanics/molecular mechanics (QM/MM) framework to explore the early time photoisomerization of rsEGFP2 starting from its two OFF trans states, i.e., Trans1 and Trans2. The results show similar vertical excitation energies to the S1 state in their Franck-Condon regions. Considering the clockwise and counterclockwise rotations of the C11-C9 bond, four pairs of the S1 excited-state minima and low-lying S1/S0 conical intersections were optimized, based on which we determined four S1 photoisomerization paths that are essentially barrierless to the relevant S1/S0 conical intersections leading to efficient excited-state deactivation to the S0 state. Most importantly, our work first identified multiple photoisomerization and excited-state decay paths, which must be seriously considered in the future. This work not only sheds significant light on the primary trans-cis photoisomerization of rsEGFP2 but also aids in the understanding of the microscopic mechanism of GFP-like RSFPs and the design of novel GFP-like fluorescent proteins.

Merging thermally activated delayed fluorescence and two-photon ionization mechanisms for highly efficient and ultralong-lived organic afterglow

It is challenging to simultaneously achieve high afterglow efficiency and long afterglow duration in organic systems. Here we report dopant-matrix materials with afterglow efficiency of 92.4 ± 10.7 % and afterglow duration up to 1 h under ambient conditions. The materials exhibit thermally activated delayed fluorescence (TADF) mechanism at room temperature to harvest triplet energies and possess afterglow efficiency close to unity. At high excitation dose where two-photon ionization mechanism is switched on, the materials follow a power law decay of excited states due to retarded charge recombination and display hour-long afterglow duration. The TADF mechanism and two-photon ionization are respectively responsible for the high efficiency and hour-long duration. This two-mechanism strategy provides a new pathway to address efficiency-to-duration conflict in afterglow systems. Moreover, the present afterglow materials can serve as efficient donors of Förster resonance energy transfer, exhibit excellent processability, and function as background-free bioimaging agents.

Reaction Dynamics in the Chrimson Channelrhodopsin: Observation of Product-State Evolution and Slow Diffusive Protein Motions.

Chrimson is a red-light absorbing channelrhodopsin useful for deep-tissue optogenetics applications. Here, we present the Chrimson reaction dynamics from femtoseconds to seconds, analyzed with target analysis methods to disentangle spectrally and temporally overlapping excited- and product-state dynamics. We found multiple phases ranging from ≈100 fs to ≈20 ps in the excited-state decay, where spectral features overlapping with stimulated emission components were assigned to early dynamics of K-like species on a 10 ps time scale. Selective excitation at the maximum or the blue edge of the absorption spectrum resulted in spectrally distinct but kinetically similar excited-state and product-state species, which gradually became indistinguishable on the μs to 100 μs time scales. Hence, by removing specific protein conformations within an inhomogeneously broadened ensemble, we resolved slow protein backbone and amino acid side-chain motions in the dark that underlie inhomogeneous broadening, demonstrating that the latter represents a dynamic interconversion between protein substates.

π-Conjugated In-Plane Heterostructure Enables Long-Lived Shallow Trapping in Graphitic Carbon Nitride for Increased Photocatalytic Hydrogen Generation.

The relatively short-lived excited states, such as the nascent electron-hole pairs (excitons) and the shallow trapping states, in semiconductor-based photocatalysts produce an exceptionally high charge carrier recombination rate, dominating a low solar-to-fuel performance. Here, a π-conjugated in-plane heterostructure between graphitic carbon nitride (g-CN) and carbon rings (Crings ) (labeling g-CN/Crings ) is effectively synthesized from the thermolysis of melamine-citric acid aggregates via a microwave-assisted heating process. The g-CN/Crings in-plane heterostructure shows remarkably suppressed excited-state decay and increased charge carrier population in photocatalysis. Kinetics analysis from the femtosecond time-resolved transient absorption spectroscopy illustrates that the g-CN/Crings π-conjugated heterostructure produces slower exciton annihilation (τ1 = 7.9ps) and longer shallow electron trapping (τ2 = 407.1ps) than pristine g-CN (τ1 = 3.6ps, τ2 = 264.1ps) owing to Crings incorporation, both of which enable more photoinduced electrons to participate in the photocatalytic reactions, thereby realizing photoactivity enhancement. As a result, the photocatalytic activity exhibits an eightfold enhancement in visible-light-driven H2 generation. This work provides a viable route of constructing π-conjugated in-plane heterostructures to suppress the excited-state decay and improve the photocatalytic performance.

Variation in nonadiabaticity and dual fluorescence causality by extension with aromatic rings in tropolone

Photophysical aspects of tropolone upon extension with aromatic rings are studied theoretically. Tropolone possesses three energetically close lying singlet excited states (S 1 (1 π π ∗ ), S 2 (2 π π ∗ ) and S 3 (1 n π ∗ )), resulting in a rapid internal conversion among these states upon photoexcitation. The excited-state energetics and decay dynamics of benzotropolone are similar to the tropolone molecule. On the other hand, upon extending the tropolone with naphthalene moiety (naphthatropolone), the molecule exhibits relatively well-separated electronic states, thus displaying significantly slower photorelaxation compared to the tropolone molecule. Both benzotropolone and naphthatropolone exhibit the dual emission feature, which is absent in the parent tropolone due to the symmetrical double-well potential of S 1 . • Loss of near-degeneracy upon ring extension in tropolone. • Competing nonadiabatic relaxation and ESIPT. • O-H vibrations facilitates rapid internal conversion. • Dual emission features in extended tropolones.

Cyclic Carbaporphyrin Arrays

Two cyclic carbaporphyrin arrays (trimer 6 and tetramer 7) were synthesized from a dibrominated carbaporphyrin precursor (5) via a one-pot Yamamoto-type coupling. Single-crystal X-ray diffraction analyses revealed that 6 and 7 contain three and four covalently linked carbaporphyrin (formally dicarbacorrole) units, respectively. Trimer 6 adopts a roughly planar conformation and tetramer 7 adopts an up-and-down zig-zag conformation. Both 6 and 7 contain a [n]cyclo-meta-phenylene ([n]CMP) core, namely, [6]- and [8]CMP for 6 and 7, respectively. Transient absorption (TA) anisotropy and pump-power-dependent excited-state decay studies provided evidence for excitation energy transfer (EET) within both trimer 6 and tetramer 7. The exciton energy hopping (EEH) times were estimated to be 18 and 35 ps for 6 and 7, respectively, as inferred from pump-power-dependent TA measurements. Since the center-to-center distances between adjacent carbaporphyrin units are similar in 6 and 7, the different EEH times are attributed to differences in the orientation of the transition dipoles in these two congeneric arrays. The orientation factor κ2, the key parameter defining the Förster resonance energy transfer efficiency, was calculated to be 2.15 and 1.03 for 6 and 7, respectively, a finding that supports the shorter excitation energy hopping time seen in the case of trimer 6. To our knowledge, this is the first time that covalently linked cyclic carbaporphyrin arrays were synthesized using a single carbaporphyrin as the starting point and that EET between carbaporphyrin subunits constrained within a well-defined polycyclic framework has been correlated with structural differences.

Fluorescence Modulation by Amines: Mechanistic Insights into Twisted Intramolecular Charge Transfer (TICT) and Beyond

Amine groups are common constituents of organic dyes and play important roles in tuning fluorescence properties. In particular, intensive research works have demonstrated the tendency and capabilities of amines in influencing chromophore brightness. Such properties have been explained by multiple mechanisms spanning from twisted intramolecular charge transfer (TICT) to the energy gap law and beyond, which introduce additional nonradiative energy dissipation pathways. In this review, we aim to provide a focused overview of the mechanistic insights mainly for the TICT mechanism, accompanied by a few other less common or influential fluorescence quenching mechanisms in the amine-containing fluorescent molecules. Various aspects of current scientific findings including the rational design and synthesis of organic chromophores, theoretical calculations, steady-state and time-resolved electronic and vibrational spectroscopies are reviewed. These in-depth understandings of how the amine groups with diverse chemical structures at various atomic sites affect excited-state nonradiative decay pathways will facilitate the strategic and targeted development of fluorophores with desired emission properties as versatile chemosensors for broad applications.

Prototropically Controlled Dynamics of Cytosine Photodecay

The effect of the existence of several prototropic tautomers of cytosine on its UV/vis spectra and the excited state decay dynamics is studied by spectral and nonadiabatic molecular dynamics (NAMD) simulations in connection with the mixed-reference spin-flip time-dependent density functional theory (MRSF-TDDFT) method. Simulated UV/vis spectra provide a strong indication that the H3N keto-amino cytosine tautomer (the least anticipated species) may be present under experimental conditions. The NAMD simulations yield a wide range of excited state decay constants for various tautomers of cytosine, ranging from ∼1.3 ps for the biologically relevant H1N keto-amino tautomer to ∼0.1 ps for the keto-imino tautomer. The slowness of the H1N decay dynamics follows from the presence of a barrier on the excited state energy surface separating the Franck-Condon structure from the major decay funnel, the conical intersection seam. It is suggested that the experimentally observed photodecay dynamics may result from a combination of the decay processes of various tautomers (H3N in particular) present simultaneously under the experimental conditions.

From a one-mode to a multi-mode understanding of conical intersection mediated ultrafast organic photochemical reactions.

Over the last few decades, conical intersections (CoIns) have grown from theoretical curiosities into common mechanistic features of photochemical reactions, whose function is to funnel electronically excited molecules back to their ground state in regions where the potential energy surfaces (PESs) of two electronic states become degenerate. Analogous to transition states in thermal chemistry, CoIns appear as transient structures providing a kinetic bottleneck along a reaction coordinate. However, such a bottleneck is not associated with the probability of crossing an energy barrier but rather with an excited state decay probability along a full "line" of transient structures connected by non-reactive modes, the intersection space (IS). This article will review our understanding of the factors controlling CoIn mediated ultrafast photochemical reactions, taking a physical organic chemist approach by discussing a number of case studies for small organic molecules and photoactive proteins. Such discussion will be carried out by first introducing the "standard" one-mode model based on Landau-Zener (LZ) theory to describe a reactive excited state decay event intercepting, locally, a single CoIn along a single direction, and then by providing a modern perspective based on the effects of the phase matching of multiple modes on the same local event, thus redefining and expanding the description of the excited state reaction coordinate. The direct proportionality between the slope (or velocity) along one mode and decay probability at a single CoIn is a widely applied fundamental principle that follows from the LZ model, yet it fails to provide a complete understanding of photochemical reactions whose local reaction coordinate changes along the IS. We show that in these situations, in particular by focussing on rhodopsin double bond photoisomerization, it is mandatory to consider additional molecular modes and their phase relationship approaching the IS, hence providing a key mechanistic principle of ultrafast photochemistry based on the phase matching of those modes. We anticipate that this qualitative mechanistic principle should be considered in the rational design of any ultrafast excited state process, impacting various fields of research ranging from photobiology to light-driven molecular devices.

Quantum mechanics/molecular mechanics studies on the excited-state decay mechanisms of cytidine aza-analogues: 5-azacytidine and 2'-deoxy-5-azacytidine in aqueous solution.

The excited state properties and deactivation pathways of two DNA methylation inhibitors, i.e., 5-azacytidine (5ACyd) and 2'-deoxy-5-azacytidine (5AdCyd) in aqueous solution, are comprehensively explored with the QM(CASPT2//CASSCF)/MM protocol. We systematically map the feasible decay mechanisms based on the obtained excited-state decay paths involving all the identified minimum-energy structures, conical intersections, and crossing points driving the different internal conversion (IC) and intersystem crossing (ISC) routes in and between the 1ππ*, 1nπ*, 3ππ*, 3nπ*, and S0 states. Unlike the 1nπ* state below the 1ππ* state in 5ACyd, deoxyribose group substitution at the N1 position leads to the 1ππ* state becoming the S1 state in 5AdCyd. In 5ACyd and 5AdCyd, the initially populated 1ππ* state mainly deactivates to the S0 state through the direct 1ππ* → S0 IC or mediated by the 1nπ* state. The former nearly barrierless IC channel of 1ππ* → S0 occurs ultrafast via the nearby low-lying 1ππ*/S0 conical intersection. In the latter IC channel of 1ππ* → 1nπ* → S0, the initially photoexcited 1ππ* state first approaches the nearby S2/S1 conical section 1ππ*/1nπ* and then undergoes efficient IC to the 1nπ* state, followed by the further IC to the initial S0 state via the S1/S0 conical intersection 1nπ*/S0. The 1nπ*/S0 conical intersection is estimated to be located 6.0 and 4.9 kcal mol-1 above the 1nπ* state minimum in 5ACyd and 5AdCyd, respectively, at the QM(CASPT2)/MM level. In addition to the efficient singlet-mediated IC channels, the minor ISC routes would populate 1ππ* to T1(ππ*) through 1ππ* → T1 or 1ππ* → 1nπ* → T1. Relatively, the 1ππ* → 1nπ* → T1 route benefits from the spin-orbit coupling (SOC) of 1nπ*/3ππ* of 8.7 cm-1 in 5ACyd and 10.2 cm-1 in 5AdCyd, respectively. Subsequently, the T1 system will approach the nearby T1/S0 crossing point 3ππ*/S0 driving it back to the S0 state. Given the 3ππ*/S0 crossing point located above the T1 minimum and the small T1/S0 SOC, i.e., 8.4 kcal mol-1 and 2.1 cm-1 in 5ACyd and 6.8 kcal mol-1 and 1.9 cm-1 in 5AdCyd, respectively, the slow T1 → S0 would trap the system in the T1 state for a while. The present work could contribute to understanding the mechanistic photophysics and photochemistry of similar aza-nucleosides and their derivatives.

Intramolecular dimer formation reveals anomalous solvation within fluorous solvent perfluorodecalin.

Due to the unusual properties of fluorine, a fluorous solvent obtained by replacing hydrogen atoms with fluorine atoms in a hydrocarbon solvent may afford unusual solute solvation and aggregation. A fluorescent dipyrenyl probe, 1,3-bis(1-pyrenyl)propane (BPP), was utilized to explore intramolecular aggregation within perfluorodecalin (PFD), a prototypical fluorous solvent. Steady-state fluorescence emission and excitation along with excited-state emission intensity decay of BPP were acquired in the temperature range of 293.15 to 333.15 K in fluorous solvent PFD and n-hexane-added PFD. The probe BPP is known to form an intramolecular excimer in common hydrocarbon solvents, which is characterized by a broad structureless low-energy emission band; the formation of intramolecular excimers exclusively in the excited state was confirmed via excitation scans along with the intensity decay of the monomer and excimer, respectively. While intramolecular dimerization of BPP does occur in PFD, emission wavelength-dependent excitation spectra and fits of the intensity decay data reveal that intramolecular aggregation takes place in the ground state as well. This ground-state heterogeneity is reduced as the temperature is increased. In the presence of as small as 0.1 mole fraction of n-hexane, the ground-state aggregation vanishes, and intramolecular dimerization again takes place exclusively in the excited state. The data hint at the poor solvation of BPP in PFD to be responsible for intramolecular ground-state aggregation. In PFD-rich (PFD + n-hexane) mixtures, probe pyrene (Py) was found to be preferentially solvated by n-hexane, further corroborating the above-mentioned proposition. Clear differences in solute solvation within a fluorous solvent as compared to hydrocarbon solvents leading to unexpected solubilization and aggregation in fluorous media are amply demonstrated.