Red-shifted Emission Research Articles

Photophysical Properties of Tandem Quantum Defects in Carbon Nanotubes.

Single-walled carbon nanotubes (SWCNTs) are versatile near-infrared (NIR) fluorophores that can be chemically functionalized to create biosensors. Numerous noncovalent approaches were developed to detect analytes, but these design concepts can be susceptible to nonspecific binding and reduced stability. In contrast, covalent modification of SWCNTs with quantum defects can be utilized to tune their fluorescence properties and enable new molecular recognition concepts. Here, we present and assess four different synthetic pathways/sequences to modify SWCNTs covalently with both sp3 quantum defects and DNA-based guanine defects. We find that it is possible to create two defect types without disrupting the optical properties or chemical stability. Interestingly, the emission peak associated with sp3 defects (E11*) shifts around 3 nm when combined with guanine defects, indicating a coupling between the two defect types. However, it is far lower than the red-shift in bandgap-related emission (E11) by guanine quantum defects (40 nm). We furthermore demonstrate that combinations of defects can be used for (bio)sensing. In summary, the combination of multiple quantum defect types in SWCNTs provides a platform for multifunctional biosensors and a new design space that can be explored.

Nonalternant Extension of Multiple Resonance Emitter via Palladium-Catalyzed [5+2]-Annulation

Despite the proliferation of multiple resonance (MR) emitters with rigid 1,4-borazine-based skeletons, the straightforward and efficient incorporation of nonhexagonal rings, especially for heptagons, to avoid notorious aggregation-induced quenching effect remains elusive. Here, a green-yellow emitter consisting of two azepines was designed and synthesized via a palladium-catalyzed one-pot twofold [5+2]-annulation reaction with high selectivity and efficiency. The tetrabenzene-fused benzo[1,2-b:5,4-b']bis(azepine) (TBBBA) core induced a highly twisted and dynamically helical rim for the novel MR-skeleton, which reduced Π-Π stacking in the solid state. Moreover, the nonalternant topology facilitated the delocalization of frontier molecular orbitals (FMO) within the twisted geometry, thus achieving red-shifted narrow emission. Our work provides a new synthetic strategy towards nonalternant extension of MR-emitters and gives insights into the electronic effects of multiple azepination on FMO distribution.

Abnormal Blueshift of Mn d-d Emission Unlocked by Decreasing Phonon Coupling under High Pressure.

Mn d-d emissionhas been a star transition-metal activated phosphors that were extensivelyused in optoelectronic devices. However, due to the complex and elusive luminescence mechanism, the full potential of this material remains largely untapped. Here, we designed a core-shell structure of MnS@CdS quantum dots to investigate the effect of the internal strain on the Mn emission. Upon pressure processing, an unexpected blueshift of Mn emission was achieved. When the pressure reached a pressure of 2.1 GPa, the conventional redshift of Mn emission reappeared. Remarkable color transition from red to orange and then back to red was observed during pressure treatment. Further analysis revealed that the application of external pressure facilitated the diffusion of Mn atoms into the CdS shell, strengthened host-dopant coupling and mitigated the lattice mismatch rate within the MnS@CdS QDs. These factors resulted in a reduction in phonon coupling strength and an increase in energy transfer efficiency from the exciton of the CdS host lattice to the Mn dopants, thus ultimately accounting for the abnormal blueshift of Mn d-d emission. Our findings represent a significant breakthrough in the quest for precise control and regulation of Mn-related emission, offeringinsights into the underlyingluminescence mechanism of Mn emission.

Abnormal Blueshift of Mn d–d Emission Unlocked by Decreasing Phonon Coupling under High Pressure

Mn d–d emission has been a star transition‐metal activated phosphors that were extensively used in optoelectronic devices. However, due to the complex and elusive luminescence mechanism, the full potential of this material remains largely untapped. Here, we designed a core‐shell structure of MnS@CdS quantum dots to investigate the effect of the internal strain on the Mn emission. Upon pressure processing, an unexpected blueshift of Mn emission was achieved. When the pressure reached a pressure of 2.1 GPa, the conventional redshift of Mn emission reappeared. Remarkable color transition from red to orange and then back to red was observed during pressure treatment. Further analysis revealed that the application of external pressure facilitated the diffusion of Mn atoms into the CdS shell, strengthened host‐dopant coupling and mitigated the lattice mismatch rate within the MnS@CdS QDs. These factors resulted in a reduction in phonon coupling strength and an increase in energy transfer efficiency from the exciton of the CdS host lattice to the Mn dopants, thus ultimately accounting for the abnormal blueshift of Mn d–d emission. Our findings represent a significant breakthrough in the quest for precise control and regulation of Mn‐related emission, offering insights into the underlying luminescence mechanism of Mn emission.

Antagonistic Effects of Distance and Overlap toward Anomalous Pressure-Induced Blueshift of π-π Excimer Fluorescence in 9-(2,2-Diphenylvinyl)anthracene Crystals.

Piezochromic materials usually exhibit a gradual redshift of emission as pressure increases due to the formation of a low-energy "dark" state, e.g., excimer. However, our study presents an anomalous excimer-based pressure-induced emission blueshift. A crystal was investigated here with a discrete π-π anthracene dimer stacking and excimer emission, and the dimer is characterized by an overshifted off-center stacking pattern. Intriguingly, under isotropic hydrostatic pressure, this crystal exhibits negative linear compressibility almost along the c-axis of the unit cell. Furthermore, an antagonistic effect between overlap ratio (Sπ-π) and interplanar distance (Dπ-π) within the dimer on emission was identified: reduced Dπ-π typically dominates the emission redshift, while decreasing Sπ-π can cause emission blueshift. When the pressure reaches around 5.00 GPa, the π-π excimer fluorescence exhibits an unexpected blueshift, indicating the reign of decreasing Sπ-π. This study not only sheds light on the modulation of fluorescence properties by noncovalent interactions but also introduces an innovative approach to anomalous piezochromism.

Rational design of AIEgens through π-bridge engineering for dual-modal photodynamic and photothermal therapy.

A series of aggregation-induced emission luminogens (AIEgens) with donor-π-acceptor (D-π-A) architecture were rationally designed and synthesized through π-bridge engineering for dual-modal photodynamic and photothermal therapy. The AIEgens (TPT, TFT, and TTT) were constructed using methoxy-substituted tetraphenylene as the electron donor and tricyanofuran as the electron acceptor, connected via different π-bridges (phenyl, furan, or thiophene). These compounds exhibited red-shifted absorption (460-545nm) and emission (712-720nm) with remarkable aggregation-induced emission characteristics. Among them, TTT demonstrated superior photophysical properties and was successfully encapsulated into amphiphilic calixarene-based nanoparticles (T@Q NPs) with uniform morphology. The T@Q NPs showed efficient reactive oxygen species generation and photothermal conversion (η=6.98%), enabling effective tumor cell ablation through combined photodynamic and photothermal therapy. In vivo studies revealed that T@Q NPs achieved 70% tumor growth inhibition in 4T1 tumor-bearing mice without obvious systemic toxicity. This work presents an effective strategy for designing AIEgens-based phototherapeutic agents through π-bridge engineering, offering promising candidates for clinical translation in tumor phototherapy.

Novel AIE-Active Polyarylethersulfone Polymers Incorporating Tetraphenylethene for Enhanced Fluorescence.

Aggregation-induced emission (AIE) materials have gained significant attention for their unique fluorescence enhancement in the aggregated state. However, combining rigid polymers with AIE molecules to enhance luminescent properties remains to be investigated. In this work, two novel AIE-active polyarylethersulfone (PAES) derivatives are synthesized by incorporating tetraphenylethene (TPE) into either the side chain or main chain of PAES, resulting in side-chain polyarylethersulfone-tetraphenylethene (PAES-TPE) and main-chain polyarylethersulfone-tetraphenylethene (m-PAES-TPE), respectively. These derivatives are designed to investigate the influence of the rigid polymer backbone on the AIE properties of TPE. The incorporation of TPE into PAES resulted in a notable redshift in fluorescence emission compared to pure TPE. Notably, m-PAES-TPE50%, a polymer with 50% molar content of TPE, exhibited a fluorescence quantum yield to 57.43%, more than twice that of TPE powder. Thermal analysis showed that both PAES-TPE and m-PAES-TPE have excellent thermal stability and temperature-dependent fluorescence. Additionally, these materials are processed into hydrophobic nanoparticles, and in vitro experiments demonstrated good fluorescence properties and biocompatibility for cancer cell bioimaging. This work highlights the potential of rigid AIE-active PAES derivatives for advanced bioimaging applications.

Red-Shifted and Enhanced Photoluminescence Emissions from Hydrogen-Bonded Multicomponent Nontraditional Luminogens.

Nontraditional luminogens (NTLs) without large π-conjugated aromatic structures have attracted a great deal of attention in recent years. Developing NTLs with red-shifted and enhanced emissions remains a great challenge. In this work, we developed a NTL composed of three components, i.e., polymaleic acid (PMA), arginine (Arg), and polyacrylamide (PAM), and investigated its photoluminescent behavior and mechanism. Compared with the single components and binary components, the PMA/Arg/PAM solid exhibited two red-shifted emission peaks at 510 and 562 nm and higher quantum yields. Structural characterizations demonstrated that hydrogen bonds formed between the nonconventional chromophores in PMA and Arg lead to more extended through-space conjugation and rigidified conformations, which is the fundamental reason for the red-shifted emission and higher quantum yield of the PMA/Arg/PAM solid. In addition, theoretical calculations proved that excited-state proton transfer occurs between the carboxyl groups of PMA and amino groups of Arg via photoexcitation, resulting in dual emissions in the PMA/Arg/PAM solid. This work provides a deeper understanding of the photoluminescence mechanism of NTLs based on multiple hydrogen bonds and is helpful in guiding the design of NTLs with red-shifted and enhanced emissions.

Strategic Modulation of Polarity and Viscosity Sensitivity of Bimane Molecular Rotor-Based Fluorophores for Imaging α-Synuclein.

Molecular rotor-based fluorophores (RBFs) that are target-selective and sensitive to both polarity and viscosity are valuable for diverse biological applications. Here, we have designed next-generation RBFs based on the underexplored bimane fluorophore through either changing in aryl substitution or varying π-linkages between the rotatable electron donors and acceptors to produce red-shifted fluorescence emissions with large Stokes shifts. RBFs exhibit a twisted intramolecular charge transfer mechanism that enables control of polarity and viscosity sensitivity, as well as target selectivity. These features enable their application in: (1) turn-on fluorescent detection of α-synuclein (αS) fibrils, a hallmark of Parkinson's disease (PD), including amplified fibrils from patient samples; (2) monitoring early misfolding and oligomer formation during αS aggregation; and (3) selective imaging of αS condensates formed by liquid-liquid phase separation (LLPS). In all three cases, we show that our probes have high levels of selectivity for αS versus other aggregating proteins. These properties enable one to study the interplay of αS and tau in amyloid aggregation and the mechanisms underlying neurodegenerative disorders.

High-performance TADF-OLEDs utilizing copper(i) halide complexes containing unsymmetrically substituted thiophenyl triphosphine ligands

The introduction of trimethylsilyl groups results in red-shifted emission, shorter decay times and higher PLQYs of the complexes.

Unveiling emissive H-aggregates of benzocoronenediimide, their photophysics and ultrafast exciton dynamics.

H- and J-aggregates of many molecules can be considered ordered mesoscopic structures that behave like a single entity. This is due to coherent electronic coupling between electronic excitations of aggregated molecules, resulting in distinct electronic properties compared to the monomer. H-aggregates are generally non-emissive and, due to this property, they are considered unfit for optoelectronics applications, but they have found applications in organic light-emitting transistors. Herein, we designed t-butyl-substituted benzocoronenediimide (t-But-BCDI) forming rare emissive H-aggregates. The tertiary butyl groups are placed to inhibit the formation of strong aggregates. Photophysical studies showed that t-But-BCDI forms H-aggregates in a concentrated solution in a THF/CHCl3 mixture. A blue shift in absorption along with a decrease in the A0-0/A0-1 ratio and red-shifted weaker emission are observed for the aggregate compared to the monomer. Ultrafast transient absorption studies revealed biphasic relaxation with lifetimes of 150 (±10) fs and 13 (±2) ps, which are attributed to a higher-to-lower state transition and vibrational cooling, respectively. The transient spectral signature suggests the Frenkel-type (localized to a monomer) character of the exciton. Faster evolution at the tens of picosecond timescale suggests relaxation of the exciton state within the H-type exciton band. An extraordinarily long emission lifetime from the H-aggregated state is observed.

Mechanisms and applications of bacterial luciferase and its auxiliary enzymes.

Bacterial luciferase (LuxAB) catalyzes the conversion of reduced flavin mononucleotide (FMNH⁻), oxygen, and a long-chain aldehyde to oxidized FMN, the corresponding acid and water with concomitant light emission. This bioluminescence reaction requires the reaction of a flavin reductase such as LuxG (in vivo partner of LuxAB) to supply FMNH⁻ for the LuxAB reaction. LuxAB is a well-known self-sufficient luciferase system because both aldehyde and FMNH⁻ substrates can be produced by the associated enzymes encoded by the genes in the lux operon, allowing the system to be auto-luminous. This makes it useful for in vivo applications. Structural and functional studies have long been performed in efforts to gain a better understanding of the LuxAB reaction. Recently, continued exploration of the LuxAB reaction have elucidated the mechanisms of C4a-hydroperoxyflavin formation and identified key catalytic residues such as His44 that facilitates the generation of flavin intermediates important for light generation. Advancements in protein engineering and synthetic biology have improved the bioluminescence properties of LuxAB. Various applications of LuxAB for bioimaging, bioreporters, biosensing in metabolic engineering and real-time monitoring of aldehyde metabolites in biofuel production pathways have been developed during the last decade. Challenging issues such as achieving red-shifted emissions, optimizing the signal intensity and identifying mechanisms related to the generation of light-emitting species remain to be explored. Nevertheless, LuxAB continues to be a promising tool for diverse biotechnological and biomedical applications.

A Cd-based crystalline network material: catalytic properties and post-synthetic metal-ion metathesis with enhanced stability and gas sorption behaviour.

This study presents the synthesis of a Cd(II) based hydrophobic three dimensional crystalline network material (CNM), [Cd3(L)2(LH)2(bpe)2], {L = {4,4'-(hexafluroisopropylidine)bis(benzoate)} and 1,2-di(4-pyridyl) ethylene (bpe)}, 1(Cd), by employing the slow-diffusion method. The three-dimensional structure of 1(Cd) was determined by single crystal X-ray diffraction and characterized by powder X-ray diffraction (PXRD), FT-IR spectroscopy and thermogravimetric analysis (TGA). Subsequently, post-synthetic modification of 1(Cd) with Cu(II) at room temperature led to the formation of isostructural 1(Cu) with partial substitution. This transformation, unattainable through de novo synthesis, was monitored using energy dispersive X-ray analysis (EDX), PXRD, FT-IR spectroscopy, and through visual observation confirming a single crystal to single crystal metal exchange. The modified material, 1(Cu), exhibited red-shifted emission with enhanced thermal stability and a tenfold increase in N2 uptake. Furthermore, the catalytic potential of 1(Cd) in aza-Michael addition reactions of α,β-unsaturated olefins to nucleophilic aromatic/aliphatic amines was demonstrated successfully under ambient conditions. This approach employed a heterogeneous and acid-base free methodology, showcasing the versatility and effectiveness of 1(Cd) as a catalyst.

Tuning Fluorescence Properties of BIM Probes via Clay Integration: Targeting Rifampicin with improved selectivity.

The incorporation of photoactive organic dyes into layered inorganic materials enhances their optical and chemical properties, making them ideal for sensing applications. In this study, Bisindolyl methane (BIM)-based neutral probes were integrated with bentonite clay to explore their sensing capabilities. Probe 1 (unoxidized BIM) and Probe 2 (oxidized BIM) generally exhibited quenched luminescence in solution due to intramolecular rotations. Embedding Probe 1 within bentonite interlayers or adsorbing it onto the clay surface immobilized its conformation, restricting intramolecular rotations through planarization and significantly enhancing fluorescence emission. Conversely, rigid Probe 2, adsorbed predominantly on the clay surface, showed fluorescence quenching. Photophysical studies confirmed that the intercalation of Probe 1 into the clay induced unique planarization compared to its behavior in solution. The 1.clay composite exhibited selective fluorescence quenching and a red-shifted emission band upon interaction with rifampicin. This suggests that rifampicin displaced the probe from the clay interlayers into solution via strong hydrogen bonding with the clay's hydroxyl groups. Additionally, Probe 1 demonstrated higher selectivity for rifampicin over other tuberculosis drugs. These findings underscore the potential of the 1.clay composite as a highly selective, efficient sensing platform for rifampicin detection in clinical diagnostics and therapeutic drug monitoring.

Fe-Doped 4-Aminophenylacetylene-Derived Red Emissive Polymer Carbon Dots: Synthesis and Anti-Counterfeiting Applications.

Phenylacetylene derivatives serve as typical monomers for polyaddition reactions. In this study, we present a straightforward one-step protocol for synthesizing polyacetylene P0 (undoped), P0.09 (doped with 0.09 mg/mL Fe3+), and carbonized polymer dots CPDs-Fe (doped with 0.13 mg/mL Fe3+) using 4-aminophenylacetylene and varying concentrations of Fe3+ via solvothermal addition and carbonization (EtOH, 200 °C, 6 h, high-pressure reactor). The resulting P0, P0.09, and CPDs-Fe exhibit green, light red, and red luminescence with maxima at 514 nm (quantum yield, QY = 20.08%), 623 nm (QY = 8.17%), and 645 nm (QY = 9.03%), respectively. Structural and morphological analyses indicate that altering the doping concentration of Fe3+ and the reaction temperature results in a transformation from the amorphous, short-conjugated structure of P0 to the low-crystallinity, fibrous, and longer-conjugated structure of P0.09, and finally to the highly crystalline, elliptical, and largest-conjugated structure of CPDs-Fe, respectively. These structural and morphological changes lead to a shift in emission from green in P0 to red in CPDs-Fe. Density functional theory (DFT) calculations on the CPDs-Fe substructures reveal that coordination with Fe3+/Fe2+ and the elongation of the alkene chain enhances conjugation interactions, reduces the band gap, and consequently induces a red shift in emission. CPDs-Fe can be incorporated into poly(vinyl alcohol) (PVA) to form a CPDs-Fe@PVA composite film, which exhibits dual-mode fluorescence and room-temperature phosphorescence with tunable lifetimes, making it suitable for anti-counterfeiting applications based on phosphorescence. This study provides a strategy for converting 4-aminophenylacetylene into tunable CPDs with tailored structural and photonic properties, offering potential applications in fluorescence and phosphorescence-based technologies.

Manipulation and Theoretical Modeling of the Luminescence Performance of Silver Clusters in LTA Zeolites by Adjusting Extra-framework Cations.

Luminescent silver clusters that are confined inside porous zeolites have attracted great research interest due to the combined advantages of high quantum yield, tunable emission, excellent chemical stability, and desirable adoption ability of this micronano-composite. In this research, a series of Ag-exchanged R-LTA/Ag (R = Li, Na, K) zeolites were synthesized, in which the silver clusters showed blue-shifted excitation in the UV region, red-shifted emission in the visible region, and decreased emission intensity when taking Li+, Na+, and K+ as the extra-framework cations, respectively. The [Ag4(H2O)xR4-sod]6- (x = 2, 4; R = Li, Na, K) structures were constructed, and the TD-DFT method was further carried out to study the influence of extra-framework cations on the luminescence performance of [Ag4]2+ clusters, in which the substitution of Al for Si and the reasonable hydrate levels were both taken into consideration. It is estimated that the S1 and S3 levels for the [Ag4(H2O)4Li4-sod]6- cluster, the S4 level for the [Ag4(H2O)4Na4-sod]6- cluster, and the S5 level for the [Ag4(H2O)2K4-sod]6- cluster can be effectively populated through direct excitation, and the S1 → S0 transition is assumed to be responsible for the radiative emission in the visible region for the [Ag4]2+ pseudo-tetrahedrons. This calculated energy level diagram and simulated absorption spectra of [Ag4(H2O)xR4-sod]6- (x = 2, 4; R = Li, Na, K) clusters explained the modified luminescence property of silver clusters in R-LTA/Ag (R = Li, Na, K) zeolites studied in this research and reported literature.

Pseudohalide Anions Driven Structural Modulation in Distorted Tetrahedral Manganese(II) Hybrids Toward Tunable Green‐Red Emissions

AbstractMn(II)‐based halides have recently garnered significant interest as emerging luminescence materials for diverse photonic applications. Generally, Mn(II) hybrids with tetrahedral coordination show green emission, however, ones with octahedral coordination give red emission. Herein, we design the synthesis of tetrahedral Mn(II) pseudohalide hybrids, (RPh3P)2MnBrxNCS4−x (R=phenyl, pentyl or methyl; Ph3P=triphenylphosphine; x=1–3), achieved by gradually substituting bromides with pseudohalides (NCS−). Compared to the green‐emitting A2MnBr4 (512 nm), the mixed hybrids exhibit significantly distorted [MnBrxNCS4−X] tetrahedra with high dipole moment, thus leading to the distinct Stokes shift energies and noticeable red shift emission in the range of 549–613 nm. Furthermore, the photoluminescence quantum yield (PLQY) of these hybrids correlates strongly with the pair correlation function of Mn(II) ions, specifically the Mn⋅⋅⋅Mn distance. These findings highlight the critical role of dipole moments in determining the emission properties and expand the luminescent family of Mn(II) pseudohalide hybrids.

Pseudohalide Anions Driven Structural Modulation in Distorted Tetrahedral Manganese(II) Hybrids toward Tunable Green-Red Emissions.

Mn(II)-based halides have recently garnered significant interest as emerging luminescence materials for diverse photonic applications. Generally, Mn(II) hybrids with tetrahedral coordination show green emission, however, ones with octahedral coordination give red emission. Herein, we design the synthesis of tetrahedral Mn(II) pseudohalide hybrids, (RPh3P)2MnBrxNCS4-x (R= phenyl, pentyl or methyl; Ph3P = triphenylphosphine; x = 1 - 3), achieved by gradually substituting bromides with pseudohalides (NCS-). Compared to the green-emitting A2MnBr4 (512 nm), the mixed hybrids exhibit significantly distorted [MnBrxNCS4-X] tetrahedra with high dipole moment, thus leading to the distinct Stokes shift energies and noticeable red shift emission in the range of 549 ~ 613 nm. Furthermore, the photoluminescence quantum yield (PLQY) of these hybrids correlates strongly with the pair correlation function of Mn(II) ions, specifically the Mn···Mn distance. These findings highlight the critical role of dipole moments in determining the emission properties and expand the luminescent family of Mn(II) pseudohalide hybrids.

Exploring photophysical behavior and fullerene-induced quenching in difluoroboron flavanone [formula omitted]-diketonates for application in organic electronic devices: Experimental and theoretical analysis

The photophysical properties of two difluoroboron flavanone β-diketonates (DK1 and DK2) and their interaction with fullerene (C60) in toluene solution and spin-coated films were investigated using time-correlated single-photon counting, absorption spectroscopy, and steady-state fluorescence spectroscopy. In molecular crystal, the complexes exhibited red-shifted absorption and emission relative to their spectra in solution. Additionally, both complexes displayed bi-exponential decay behavior in time-resolved fluorescence measurements, indicating their capability to form both H and J types of aggregates in the solid state. The introduction of C60 resulted in significant fluorescence quenching and reduced excited-state lifetimes for both complexes. This quenching, observed in both solution and spin-coated films, was primarily driven by photo-induced electron transfer (PET) processes, underscoring the potential of these complexes as donors in fullerene-based heterojunction organic solar cells. To elucidate the process of aggregate formation and the impacts of different dimerization types within the crystalline structure of the complexes, first-principles calculations using Density Functional Theory (DFT) and time-dependent density functional theory (TD-DFT) were performed. We also employed DFT to explore various DK configurations on the fullerene surface, evaluating intermolecular distances and formation energies. These calculations highlighted the energetically favourable gap between the low-lying LUMO levels of the complexes and C60, confirming their suitability for such applications.

Strong Correlation Between A‐Site Cation Order and Self‐Trapped Exciton Emission in 0D Hybrid Perovskites

Metal halide perovskites and their derived materials have garnered significant attention as promising materials for solar cell and light‐emitting applications. Among them, 0D perovskites, characterized by unique crystallographic/electronic structures with isolated metal halide octahedra, exhibit tremendous potential as light emitters with self‐trapped exciton (STE). However, the modulation of STE emission characteristics in 0D perovskites primarily focuses on regulating B‐ or X‐site elements. In this work, a lead‐free compound, Sb3+‐doped ((C2H5)2NH2)3InCl6 single crystal, which exhibits a high photoluminescence quantum yield, is synthesized, and with increasing temperature, the A‐site organic cations undergo a transition from an ordered configuration to a disordered one, accompanied by a redshift in the STE emission. Furthermore, Hirshfeld surface calculations reveal that high temperatures enhance the thermal vibrations of SbCl63− clusters and the octahedra distortion, which are responsible for the redshift. Since this thermally triggered transition of A‐site order is reversible, it can be exploited for temperature‐sensing applications. Overall, in this work, valuable insights are provided into the role of A‐site cations in modulating STE emission and the design of efficient light emitters.