Bimolecular Process Research Articles

Evaluating theoretical rate constants for bimolecular antioxidant processes involving ionic species under physiological conditions

The rate constant for the reaction of CO3∙- with anionic species could be influenced by Columbic forces and ionic strength of the cellular environment. We investigated the reaction of CO3∙- with urate, ascorbate and caffeate at the M06-2X/6–311 + G(d,p) level in an aqueous environment. The thermal rate constant was adjusted using the Debye-Smoluchowski and Brønsted-Bjerrum equations. Electrostatic interactions moderately reduced the rate constant for single electron transfer from urate and caffeate to CO3∙-, but were negligible for the reaction with ascorbate. However, when we took into account the primary kinetic salt effect, the Debye-Smoluchowski rate constants were increased to values close to those predicted without inclusion of the Debye factor. Columbic repulsion and ionic strength have a modest impact on the rate constant for reactions involving an ionic radical. However, if the reactions involved ions of opposite charge, the influence of the Debye function would become more significant.

Red-to-Blue Triplet-Triplet Annihilation Upconversion for Calcium Sensing.

Triplet-triplet annihilation upconversion is a bimolecular process converting low-energy photons into high-energy photons. Here, we report a calcium-sensing system working via triplet-triplet annihilation (TTA) upconverted emission. The probe itself was obtained by covalent conjugation of a blue emitter, perylene, with a calcium-chelating moiety, and it was sensitized by the red-light-absorbing photosensitizer palladium(II) tetraphenyltetrabenzoporphyrin (PdTPTBP). Sensing was selective for Ca2+ and occurred in the micromolar domain. In deoxygenated conditions, the TTA upconverted luminescence gradually appeared upon adding an increasing concentration of calcium ions, to reach a maximum upconversion quantum yield of 0.0020.

A methodology of quantifying membrane permeability based on returning probability theory and molecular dynamics simulation.

We propose a theoretical approach to estimate the permeability coefficients of substrates (permeants) for crossing membranes from donor (D) phase to acceptor (A) phase by means of molecular dynamics (MD) simulation. A fundamental aspect of our approach involves reformulating the returning probability (RP) theory, a rigorous bimolecular reaction theory, to describe permeation phenomena. This reformulation relies on the parallelism between permeation and bimolecular reaction processes. In the present method, the permeability coefficient is represented in terms of the thermodynamic and kinetic quantities for the reactive (R) phase that exists within the inner region of a membrane. One can evaluate these quantities using multiple MD trajectories starting from phase R. We apply the RP theory to the permeation of ethanol and methylamine at different concentrations (infinitely dilute and 1 mol % conditions of permeants). Under the 1 mol% condition, the present method yields a larger permeability coefficient for ethanol (0.12 ± 0.01cms-1) than for methylamine (0.069 ± 0.006cms-1), while the values of the permeability coefficient are satisfactorily close to those obtained from the brute-force MD simulations (0.18 ± 0.03 and 0.052 ± 0.005cms-1 for ethanol and methylamine, respectively). Moreover, upon analyzing the thermodynamic and kinetic contributions to the permeability, we clarify that a higher concentration dependency of permeability for ethanol, as compared to methylamine, arises from the sensitive nature of ethanol's free-energy barrier within the inner region of the membrane against ethanol concentration.

Ab Initio Chemical Kinetics for Oxidation of CH3OH by N2O4: Elucidation of the Mechanism for Major Product Formation and Its Relevancy to Tropospheric Chemistry.

Next to CH4, CH3OH is the most abundant C1 organics in the troposphere. The redox reaction of CH3OH with N2O4 had been shown experimentally to produce CH3ONO, instead of CH3ONO2. The mechanism for the reaction remains unknown to date. We have investigated the reaction by ab initio MO calculations at the UCCSD(T)/6-311+G(3df,2p)//UB3LYP/6-311+G(3df,2p) level. The result indicates that the reaction takes place primarily by the isomerization of N2O4 to ONONO2 through a very loose transition state within the N2O4-CH3OH collision complex with a 14.3 kcal/mol barrier, followed by the rapid attack of ONONO2 at CH3OH producing CH3ONO and HNO3. The predicted mechanism for the redox reaction compares closely with the hydrolysis of N2O4. The computed rate constant, k1 = 1.43 × 10-8 T1.96 exp (-9092/T) (200-2000 K) cm3molecule-1s-1, for the formation of CH3ONO and HNO3 agrees reasonably with available low-temperature kinetic data and is found to be similar to that of the isoelectronic N2O4 + CH3NH2 reaction. We have also estimated the kinetics for the termolecular reaction, 2 NO2 + CH3OH, and compared it with the direct bimolecular process; the latter was found to be 4.4 × 105 times faster under the troposphere condition. On the basis of the known pollution levels of NO2, N2O4, and CH3OH, both processes were estimated to be of negligible importance to tropospheric chemistry, however.

Triplet-Triplet Annihilation Upconverting Liposomes: Mechanistic Insights into the Role of Membranes in Two-Dimensional TTA-UC.

Triplet-triplet annihilation upconversion (TTA-UC) implemented in nanoparticle assemblies is of emerging interest in biomedical applications, including in drug delivery and imaging. As it is a bimolecular process, ensuring sufficient mobility of the sensitizer and annihilator to facilitate effective collision in the nanoparticle is key. Liposomes can provide the benefits of two-dimensional confinement and condensed concentration of the sensitizer and annihilator along with superior fluidity compared to other nanoparticle assemblies. They are also biocompatible and widely applied across drug delivery modalities. However, there are relatively few liposomal TTA-UC systems reported to date, so systematic studies of the influence of the liposomal environment on TTA-UC are currently lacking. Here, we report the first example of a BODIPY-based sensitizer TTA-UC system within liposomes and use this system to study TTA-UC generation and compare the relative intensity of the anti-Stokes signal for this system as a function of liposome composition and membrane fluidity. We report for the first time on time-resolved spectroscopic studies of TTA-UC in membranes. Nanosecond transient absorption data reveal the BODIPY-perylene dyad sensitizer has a long triplet lifetime in liposome with contributions from three triplet excited states, whose lifetimes are reduced upon coinclusion of the annihilator due to triplet-triplet energy transfer, to a greater extent than in solution. This indicates triplet energy transfer between the sensitizer and the annihilator is enhanced in the membrane system. Molecular dynamics simulations of the sensitizer and annihilator TTA collision complex are modeled in the membrane and confirm the co-orientation of the pair within the membrane structure and that the persistence time of the bound complex exceeds the TTA kinetics. Modeling also reliably predicted the diffusion coefficient for the sensitizer which matches closely with the experimental values from fluorescence correlation spectroscopy. The relative intensity of the TTA-UC output across nine liposomal systems of different lipid compositions was explored to examine the influence of membrane viscosity on upconversion (UC). UC showed the highest relative intensity for the most fluidic membranes and the weakest intensity for highly viscous membrane compositions, including a phase separation membrane. Overall, our study reveals that the co-orientation of the UC pair within the membrane is crucial for effective TTA-UC within a biomembrane and that the intensity of the TTA-UC output can be tuned in liposomal nanoparticles by modifying the phase and fluidity of the liposome. These new insights will aid in the design of liposomal TTA-UC systems for biomedical applications.

Use of a Clay from Southern Ivory Coast (Bingerville) for the Adsorption of Methyl Orange in Aqueous Media

Increasing levels of textile dyes being discharged into the environment as industrial waste represent a serious threat to human health, life, resources and ecological systems. It is therefore necessary to treat wastewater from textile industries before discharging it into the environment. The aim of this project is to eliminate methyl orange (MO) from textile industry wastewater using clay from Bingerville (Ivory Coast). The clay used was characterized by Scanning Electron Microscopy, Brunauer-Emmett-Teller and pH of Zero Charge. MO concentration was monitored using a UV-visible spectrophometer. Characterization of the clay by SEM and BET showed that our clay is microporous. The study showed that the surface of our clay has a pH of zero. Adsorption of methyl orange on our clay reaches adsorption equilibrium in 60 minutes. The adsorption model corresponds to the pseudo-order 2 kinetic model. Two adsorption isotherm models (Langmuir and Freundlich) are applicable to the adsorption of our dye on clay. This implies that the dye adsorption process on our clay is governed by a bimolecular process involving a collision between an active site on the clay and a dye molecule. Bingerville clay can be used to effectively treat dye-contaminated wastewater, since the maximum adsorbed quantity is equal to 58.139 mg g<sup>-1</sup>. The best adsorption rate was obtained in acid medium (pH = 2.26) with an adsorption rate of 91.84%.

Dealkylation of alkylphenols in phenol oil on acid zeolites

The majority of the phenolic compounds in coal tar are alkyl-substituted phenols. To overcome the difficulty of separation, zeolites catalyzed dealkylation of alkylphenols was studied in a slurry-bed reactor. ZSM-5 displayed higher catalytic performance than other zeolites within a group of acidic zeolites with various topologies (including SAPO-34, ZSM-23, MCM-22, USY, and Mordenite). The yield of phenol gradually increased together with the zeolite acidity, but the types and yields of byproducts also increased in step with it. The pore size of the zeolites was a significant influence at similar acidity. The micropore of ZSM-5 inhibited some bimolecular processes, decreasing disproportionation/transalkylation as a result of transition state shape selection. In this study, the reaction paths of alkylphenols were investigated, based on the composition of products catalyzed by different zeolites, the distribution of products under different conditions, and the reaction process of various alkylphenols. Reaction process of alkylphenols included dealkylation, isomerization, disproportionation, transalkylation, and C-C cracking. Dealkylation took the place of isomerization as the primary reaction when the reaction temperature exceeded 350 °C. Disproportionation, transalkylation, and C-C cracking were exacerbated by excessive temperature. In addition, excessive reaction time and pressure can exacerbate side reactions, alkylphenols yields and coke deposition.

Phospha-bicyclohexene-germylenes exhibiting unexpected reactivity.

Introducing phospha-bicyclohexene (BCH)-germylenes (BCHGe's) as a novel, multifunctional compound class: the title compounds 15-18 are obtained from simple salt metathesis reactions of dipotassium germacyclopentadienediides K2[1] with phosphorusdichlorides. The BCHGe's 15-18 are stabilized by homoconjugation of the germanium(ii) centre with the remote C[double bond, length as m-dash]C double bond. Despite substantial thermodynamic stabilization, phospha-BCHGe's are reactive and undergo a reductive elimination of elemental germanium to give the corresponding phospholes. The elimination is a nucleophilic, bimolecular process and is prevented by large substituents. The reaction of phospha-BCHGe's with small electrophiles gives the corresponding phosphonium salts. Oxidation with chalcogens takes place at both the germanium and the phosphorus atom, and after elimination of germanium chalcogenides the corresponding phosphole chalcogenides were isolated. The introduced germylenes exhibit strong nucleophilic but also non-neglectable electrophilic properties.

Charge photogeneration and recombination dynamics in non-fullerene solar cells based on a polymer donor with a mono-fluorinated π-bridge.

Non-symmetric fluorine substitution is an important route for designing π-conjugated polymers for high-performance solar cells. However, excited state dynamics in a non-symmetric fluorinated polymer and solar cells are poorly understood. In this work, excited state dynamics in a neat mono-fluorinated polymer (PTzBI-dF) film and blend films (PTzBI-dF:Y6) were studied using time-resolved spectroscopy. For the neat donor film, we found the activation energy of the PTzBI-dF film transiting from radiative states to non-radiative states to be ∼58 meV. Besides, we found that both exciton diffusion coefficient and exciton diffusion length in the PTzBI-dF film are higher than those in the PTzBI-Cl film, which has no fluorinated π-bridge. The high exciton diffusion length of the PTzBI-dF film benefits from its long exciton lifetime (∼327.8 ps), which is much longer than that of the polymer donors such as P3HT and PM6. For PTzBI-dF:Y6 blend films, we found that the energy level offsets of the HOMO (0.13 eV) and LUMO (0.23 eV) are sufficient to dissociate the acceptor and donor excitons, respectively. Besides, we found that carrier recombination in PTzBI-dF:Y6 and PTzBI-Cl:Y6 blend films are dominated by bimolecular recombination processes, and thermal annealing treatment has a weak influence on the charge photogeneration and recombination process of the PTzBI-dF:Y6 film at an ultrafast time scale. Thus, this work is helpful for understanding photoelectrical conversion processes in non-symmetric fluorinated polymer-based solar cells.

Intermolecular interactions and the weakly bound precursor states of elementary physicochemical processes

This study concerns the importance of the precursor (or pre-reactive) state of elementary physicochemical processes whose basic features, as structure, stability, and trapping effect of reagents, are controlled by the balance of intermolecular forces that arise at long range and operate at intermediate and short separation distances. The detailed formulation of such forces, determining formation probability and dynamical evolution of the precursor state, is of relevance in molecular science and difficult to be treated by quantum chemistry. Such a problem has been tackled by us exploiting the phenomenological approach, which employs semi-empirical and empirical formulas to represent strength, range and angular dependence of the leading interaction components involved. In addition to the study of transport phenomena, part of the attention is addressed to chemi-ionization (or Penning ionization) reactions for which neutral reagents lead to atomic and/or molecular ions plus electrons as products. Chemi-ionizations are bimolecular processes occurring in several environments of interest, where a reagent is a species, formed in excited-metastable electronic states by collisions with energetic electrons or cosmic rays. For such reactions all crucial electronic rearrangements, affecting stability and evolution of the weakly bound precursor state, here coincident with the reaction transition state, are characterized with a high detail. The results of the present study are of interest for many other processes, whose precursor states and their relevant features are difficult to characterize, often masked by several other effects.Graphical abstract

Highly Efficient OLEDs by Using a Brominated Thermally Activated Delayed Fluorescent Host due to Balanced Carrier Transport and Enhanced Exciton Upconversion.

Thermally activated delayed fluorescent (TADF) materials are naturally bipolar and can potentially serve as hosts. However, triplet excitons in TADF materials are long-lived and prone to unfavorable bimolecular processes. Implementing an efficient reverse system intersection (RISC) process is an effective solution. Moreover, although the general TADF host is bipolar, polarity differences still cause a mobility imbalance. In this work, we designed and synthesized a novel TADF host material, 11-(3-(4-(3-bromophenyl)-6-phenyl-1,3,5-triazin-2-yl)phenyl)-12,12-dimethyl-11,12-dihydroindeno[2,1-a]carbazole (Br-DMIC-TRZ). The upconversion of the TADF host and its doped films is facilitated due to enhanced spin-orbit coupling (SOC) induced by bromine, which exhibits a higher rate of RISC. This progress facilitates the involvement of more triplet excitons in luminescence. Meanwhile, the attachment of bromine to the acceptor fragment of TADF enhances the electron mobility, where hole mobility and electron mobility are more comparable. Enhanced exciton upconversion and balanced carrier transport allow devices formed based on brominated TADF hosts to outperform other hosts. The Br-TADF-based devices with three dopants sensitized achieved improvements of 29.8, 21.4, and 24.4% compared to the DMIC-TRZ-based device. This work provides a feasible molecular design strategy for further developing efficient hosts.

SEMA3G functions as a novel prognostic biomarker associated with Wnt pathway in clear cell renal cell carcinoma

Renal cell cancer (RCC) is one of the most common cancer, and the incidence of clear cell renal cell cancer rank at the first among multiple subtypes of RCC. Tumor heterogeneity and limited therapies expedite researches and studies on prognostic biomarkers and molecular mechanism. SEMA3G mediates various bimolecular processes but few studies have assessed the influence of SEMA3G on ccRCC. The expression of SEMA3G at mRNA level in ccRCC was analyzed using 4 TCGA datasets. The expression at protein level was verified by immunohistochemistry and western blot. Biological pathway was explored by GSEA and western blot. At both mRNA and protein level, SEMA3G expressed significantly lower in ccRCC tissues compared with normal renal tissues, and the expression was highly associated with clinical stage and pathological grade. Low expression of SEMA3G indicated a poorer overall survival and disease specific survival. Transwell and wound-healing assays showed that overexpressed SEMA3G inhibited the cell motility of renal cancer cells. Upregulated SEMA3G suppressed the invasion and proliferation of both 769-P and 786-O cells. Wnt signaling pathway was tested to work in the interfering of SEMA3G on tumorigenesis and progression of ccRCC. The results provide novel insight into the role of SEMA3G in ccRCC, suggesting the prognostic value and potential suppressor role of SEMA3G.

Visible light-mediated radical perfluoroalkylation reactions using heterogeneous graphitic carbon nitride

Photocatalytic radical fluoroalkylation has become an important approach to prepare valuable organofluorine compounds under mild conditions. Compared to the homogenous photocatalytic fluoroalkylation reactions based on the precious metal complexes or organic dyes, heterogeneous photocatalysis using metal-free carbon nitride catalyst shows cost-effective, easier separation and excellent recyclability. In this work, we report the visible-light-induced photocatalytic perfluoroalkylation of alkynes with perfluoroalkyl iodides (RfI) using heterogeneous cyano-modified graphitic carbon nitride (g-NCNCNx) as the photocatalyst. The mechanism proposed by the experimental and computational studies reveals that the long-lived triplet excited states in photoinduced g-NCNCNx are involved in the initial bimolecular electron transfer process, resulting in the effective activation of RfI and the improvement of sequential photocatalytic reactions. Moreover, the stronger interaction between the substate and surface of catalyst g-NCNCNx can further improve the photocatalytic activity, comparing to the pristine carbon nitride (g-CNx). Through simple variation of the reaction conditions, the photocatalytic addition or coupling reaction can be achieved effectively and selectively. Importantly, the heterogeneous g-NCNCNx photocatalyst can not only show high performance with a wide reaction scope, but also be readily recovered and reused for at least five catalytic cycles with high photocatalytic activity. This work provides a sustainable alternative to the conventional metal-based photocatalysts for organofluorine synthesis.

Kinetic and computational investigation on the reaction of Os5C(CO)15 with (Z)-Ph2PCH=CHPPh2 (dppen): Stepwise conversion to nido Os5C(CO)13(κ2-Pa,Pb-dppen)

The reaction of the pentaosmium cluster Os5C(CO)15 (1) with the diphosphine (Z)-Ph2PCHCHPPh2 (dppen) has been studied over the temperature range 328–358 K. Diphosphine addition to Os5C(CO)15 yields the arachno cluster Os5C(CO)15(κ1-Peq-dppen) (2) as the initially observed product. Cluster 2 transforms to the arachno cluster Os5C(CO)14(κ2-Peq,Peq-dppen) (3) upon CO loss and chelation of the pendent phosphine moiety. The loss of a second CO in cluster 3 is accompanied by polyhedral contraction to give the square pyramidal nido cluster Os5C(CO)13(κ2-Pa,Pb-dppen) (4). Clusters 2–4 were characterized in solution by IR and NMR spectroscopies, and the molecular structure of each new cluster was established by X-ray crystallography. The kinetics for the formation of 2 from 1 and dppen support a bimolecular process involving dppen addition to 1 analogous to the reported ligand additions to the family of M5C(CO)15 clusters (where M = Fe, Ru). Cluster 2 is labile and serves as the precursor to 3 + CO, which undergoes conversion to 4 + CO. The kinetics for these reactions have been explored, and these data, in conjunction with DFT calculations, have provided mechanistic insight into the stepwise conversion of 1 and dppen to 4 + 2CO.

HINT, a code for understanding the interaction between biomolecules: a tribute to Donald J. Abraham.

A long-lasting goal of computational biochemists, medicinal chemists, and structural biologists has been the development of tools capable of deciphering the molecule-molecule interaction code that produces a rich variety of complex biomolecular assemblies comprised of the many different simple and biological molecules of life: water, small metabolites, cofactors, substrates, proteins, DNAs, and RNAs. Software applications that can mimic the interactions amongst all of these species, taking account of the laws of thermodynamics, would help gain information for understanding qualitatively and quantitatively key determinants contributing to the energetics of the bimolecular recognition process. This, in turn, would allow the design of novel compounds that might bind at the intermolecular interface by either preventing or reinforcing the recognition. HINT, hydropathic interaction, was a model and software code developed from a deceptively simple idea of Donald Abraham with the close collaboration with Glen Kellogg at Virginia Commonwealth University. HINT is based on a function that scores atom-atom interaction using LogP, the partition coefficient of any molecule between two phases; here, the solvents are water that mimics the cytoplasm milieu and octanol that mimics the protein internal hydropathic environment. This review summarizes the results of the extensive and successful collaboration between Abraham and Kellogg at VCU and the group at the University of Parma for testing HINT in a variety of different biomolecular interactions, from proteins with ligands to proteins with DNA.

Molecular Insights into Photochemical Hydrogen Evolution Dual Catalysis within the Shell of Polymer Micelle-Based Nanoreactors

Polymer micelles are promising candidates for facilitating efficient catalysis within their distinguished nanospaces. However, the design of polymer micelle-based nanoreactors for dual photocatalysis, where a photocatalyst and another catalyst are involved in a single catalysis, remains limited in scope due to the lack of molecular insight into the bimolecular process within polymer micelles. Here, we investigated the cooperativity of a photocatalyst and a hydrogen evolution catalyst immobilized within the shell of polymer micelle-based nanoreactors. The results of several photochemical experiments suggested the existence of two types of catalyst pairs, the fluctuated and contacted pairs of the photocatalyst and hydrogen evolution catalyst within the nanoreactors. Moreover, the reaction rates of the photochemical hydrogen evolution were strongly affected by molecular crowding within the shell. Our study paves the way for developing polymer micelle-based nanoreactors for efficient dual photocatalysis.

Probing charge carrier and triplet dynamics in TADF-based OLEDs using transient electroluminescence studies

Thermally activated delayed fluorescence (TADF) systems exhibit high emissive yield due to efficient back-conversion of nonemissive triplet states to emissive singlet states via reverse intersystem crossing (RISC). In this paper, both the charge carrier and triplet exciton dynamics are explored using transient electroluminescence (TrEL) measurements in the TADF molecule, 2,3,4,6-Tetra(9H-carbazol-9-yl)-5-fluorobenzonitrile (4CzFCN)-based devices. The analysis of the rising edge of the TrEL pulse indicates that the carriers follow multiple trapping, de-trapping, and exciton recombination dynamics. The trailing edge of the TrEL pulse provides insight into the monomolecular and bimolecular exciton dynamics. These studies along with a kinetic model reveal triplet harvesting processes in a 4CzFCN molecule via both RISC and triplet–triplet annihilation (TTA). Furthermore, at high temperatures, the analysis suggests that TADF processes are dominant with negligible contribution from TTA. The presence of bimolecular triplet processes acts as bottlenecks for accessing higher efficiencies in TADF organic light emitting diodes.

Sterical index: a novel, simple tool for the interpretation of organic reaction mechanisms

A new, simple index for the quantitative description of steric effects was proposed based on the results of DFT calculations. This effect was connected with the disturbance of synchronicity within transition states of the model Diels-Alder reaction. The obtained results offer the possibility of predicting steric effects determined by alkyl groups for a wide range of bimolecular processes.

Competing dynamics of intramolecular deactivation and bimolecular charge transfer processes in luminescent Fe(iii) N-heterocyclic carbene complexes.

Steady state and ultrafast spectroscopy on [FeIII(phtmeimb)2]PF6 (phtmeimb = phenyl(tris(3-methylimidazol-2-ylidene))borate) was performed over a broad range of temperatures. The intramolecular deactivation dynamics of the luminescent doublet ligand-to-metal charge-transfer (2LMCT) state was established based on Arrhenius analysis, indicating the direct deactivation of the 2LMCT state to the doublet ground state as a key limitation to the lifetime. In selected solvent environments photoinduced disproportionation generating short-lived Fe(iv) and Fe(ii) complex pairs that subsequently undergo bimolecular recombination was observed. The forward charge separation process is found to be temperature-independent with a rate of ∼1 ps-1. Subsequent charge recombination takes place in the inverted Marcus region with an effective barrier of 60 meV (483 cm-1). Overall, the photoinduced intermolecular charge separation efficiently outcompetes the intramolecular deactivation over a broad range of temperatures, highlighting the potential of [FeIII(phtmeimb)2]PF6 to perform photocatalytic bimolecular reactions.

Singlet fission preserves polarisation correlation of excitons.

Singlet fission (SF) holds the promise to circumvent the photovoltaic efficiency limit to reach a power-conversion efficiency above 34%. SF of TIPS-pentacene (TIPS-Pn) has been investigated but its mechanism is yet to be well elucidated. Recently, we developed a nanoparticle (NP) system, in which doping of TIPS-Pn in a host matrix yields a range of average intermolecular distances, d, to study the dependence of SF in TIPS-Pn on d. At large d values, where the bimolecular SF process should be unfavourable, a relatively high SF quantum yield (ΦSF) is still observed, which implies a deviation from a random distribution of TIPS-Pn throughout the NP. Here, using polarisation-sensitive femtosecond time-resolved spectroscopy and Monte Carlo simulations of exciton migration and SF, we quantify the level of clustering of TIPS-Pn in the host matrix, which is responsible for the higher than expected ΦSF. The experimental data indicate a preservation of polarisation correlation by SF, which is uncommon because energy transfer in amorphous materials tends to result in depolarisation. We show that the preservation of polarisation correlation is due to SF upon exciton migration. Although exciton migration decorrelates polarisation, SF acts to remove decorrelated excitons to give an overall preservation of polarisation correlation.