Robust vibrational coherence protected by a core-shell structure in silver nanoclusters.

Vibrational coherence has attracted considerable research interests because of its potential functions in light harvesting systems. Although positive signs of vibrational coherence in metal nanoclusters have been observed, the underlying mechanism remains to be verified. Here, we demonstrate that robust vibrational coherence with a lifetime of 1 ps can be clearly identified in Ag44(SR)30 core-shell nanoclusters, in which an icosahedral Ag12 core is well protected by a dodecahedral Ag20 cage. Ultrafast spectroscopy reveals that two vibrational modes at around 2.4 THz and 1.6 THz, corresponding to the breathing mode and quadrupolar-like mode of the icosahedral Ag12 core, respectively, are responsible for the generation of vibrational coherence. In addition, the vibrational coherence of Ag44 has an additional high frequency mode (2.4 THz) when compared with that of Ag29, in which there is only one low frequency vibration mode (1.6 THz), and the relatively faster dephasing in two-layer Ag29 relative to that in Ag44 further supports the fact that the robust vibrational coherence in Ag44 is ascribed to its unique matryoshka-like core-shell structure. Our findings not only present unambiguous experimental evidence for a multi-layer core-shell structure protected vibrational coherence under ambient conditions but also offers a practical strategy for the design of highly efficient quantum optoelectronic devices.

Accelerating Intersystem Crossing in Multiresonance Thermally Activated Delayed Fluorescence Emitters via Long-Range Charge Transfer.

Multiresonance thermally activated delayed fluorescence (MR-TADF) emitters are excellent candidates for high-performance organic light-emitting diodes (OLEDs) due to their narrowband emission properties. However, the inherent mechanism of regulating the rate of intersystem crossing (ISC) is ambiguous in certain MR-TADF skeletons. Herein, we propose a mechanism of accelerating ISC in B/S-based MR-TADF emitters by peripheral modifications of electron-donating groups (EDGs) without affecting the narrowband emission property. The long-range charge transfer (LRCT) stems from the introduced EDG leading to high-lying singlet and triplet excited states. The ISC process is accelerated by the enhanced spin-orbital coupling (SOC) between the singlet short-range charge transfer (SRCT) and triplet LRCT manifolds. Meanwhile, the narrowband emission derived from the MR-type SRCT state is well retained as expected in the peripherally modified MR-TADF emitters. This work reveals the regulation mechanism of photophysical properties by high-lying LRCT excited states and provides a significant theoretical basis for modulating the rate of ISC in the further design of MR-TADF materials.

Theoretical Study on the Reaction between Carcinogenic 2,5-Dichloro-1,4-benzoquinone and tert-Butyl Hydroperoxide: Self-Catalysis and Water Catalysis.

The potentially carcinogenic halobenzoquinones (HBQs) have been recently identified in drinking water as disinfection byproducts. Several radical intermediates in the reaction of 2,5-dichloro-1,4-benzoquinone (DCBQ) and t-butyl hydroperoxide (t-BuOOH), which may induce DNA damage, were detected experimentally, and metal-independent decomposition reactions of t-BuOOH by DCBQ were proposed. It has not yet been confirmed by theoretical calculations. The theoretical study in this work provides insights into the details of the reaction. An unprecedented self-catalysis mechanism of organic hydroperoxides, that is, the reactant t-BuOOH also has a catalytic effect, was uncovered at the molecular level. Moreover, as the solvent, water molecules also clearly have an efficient catalytic effect. Due to the catalysis of t-BuOOH and water, the metal-independent reaction of t-BuOOH and DCBQ can occur under moderate conditions. Our findings about the novel catalytic effect of organic hydroperoxides t-BuOOH could offer a unique perspective into the design of new catalysts and an understanding of the catalytic biological, environmental, and air pollution reactions. Furthermore, organic hydroperoxide t-BuOOH could serve as a proton shuttle, where the proton transfer process is accompanied by simultaneous charge transfer. Therefore, organic hydroperoxides may disrupt the vital proton transfer process in biological systems and may give rise to unexpected toxicity.

Triplet Excited-State Dynamics in Benzothiadiazole-Based Thermally Activated Delayed Fluorescence Compound.

The "hot exciton" thermally activated delayed fluorescence (TADF) materials have attracted considerable research interest for their utilization of high-lying triplet excitons. In this work, we reported the mechanism of photoluminescence by revealing the spectral evolution from singlet to triplet states in "hot exciton" TADF molecules by transient absorption (TA) spectra and triplet sensitization experiments. The internal conversion and intersystem crossing are much faster than reverse intersystem crossing (RISC), so that high-lying triplet states (Tn) are difficult to accumulate to be observed in the transient absorption spectra. In contrast, the emergence of delayed fluorescence in time-resolved emission spectra demonstrates the existence of a high-lying RISC process (hRISC) from Tn to S1. Triplet sensitization experiments successfully identified the spectral features of the T1 state in the TA spectra. This work sheds light on critical factors for the systematic design of these materials to achieve a high emission quantum yield.

Excimer Formation Driven by Excited-State Structural Relaxation in a Covalent Aminonaphthalimide Dimer.

Strongly coupled excimer formation from interchromophoric charge transfer driven by the ultrafast excited-state structural dynamics of a 5,5'-linked 4-amino-1,8-naphthalimide covalent homodimer was investigated by ultrafast transient spectroscopy and chemical calculations. Theoretical calculations indicate that the structural relaxation associated with the dihedral motion leads to significantly enhanced interchromophoric charge transfer (CT) coupling, which favors the formation of an excimer-like symmetry-broken CT state. The formation and relaxation dynamics of the excimer state in the dimer are identified via ultrafast transient absorption and fluorescence spectroscopy. The structural relaxation following the photoexcitation occurs in tens of picoseconds and stabilizes the dimer to the strongly coupled excimer state. The highly polar solvents further stabilize the excimer state and enhance the CT character, which enable efficient electron and excitation energy transport in covalent molecular aggregates.

Genomic structural variation is associated with hypoxia adaptation in high-altitude zokors.

Zokors, an Asiatic group of subterranean rodents, originated in lowlands and colonized high-elevational zones following the uplift of the Qinghai-Tibet plateau about 3.6 million years ago. Zokors live at high elevation in subterranean burrows and experience hypobaric hypoxia, including both hypoxia (low oxygen concentration) and hypercapnia (elevated partial pressure of CO2). Here we report a genomic analysis of six zokor species (genus Eospalax) with different elevational ranges to identify structural variants (deletions and inversions) that may have contributed to high-elevation adaptation. Based on an assembly of a chromosome-level genome of the high-elevation species, Eospalax baileyi, we identified 18 large inversions that distinguished this species from congeners native to lower elevations. Small-scale structural variants in the introns of EGLN1, HIF1A, HSF1 and SFTPD of E. baileyi were associated with the upregulated expression of those genes. A rearrangement on chromosome 1 was associated with altered chromatin accessibility, leading to modified gene expression profiles of key genes involved in the physiological response to hypoxia. Multigene families that underwent copy-number expansions in E. baileyi were enriched for autophagy, HIF1 signalling and immune response. E. baileyi show a significantly larger lung mass than those of other Eospalax species. These findings highlight the key role of structural variants underlying hypoxia adaptation of high-elevation species in Eospalax.

Exploring Solvent Polarity-Dependent Photocatalysis Mechanism of Organic Photoredox Catalysts.

Organic dyads with intramolecular charge-transfer (ICT) character are emerging as viable and more sustainable photocatalysts than metal-based complexes. Herein, a carbazole- and naphthalimide-based organic dyad (Cz-NI) was designed as an efficient organic photocatalyst for the direct C(sp3)-H carbamoylation of saturated aza-heterocycles. Aiming at understanding the effect of environment, especially the solvent polarity on photocatalysis performance, the excited-state dynamics of Cz-NI in different polar solvents were studied by femtosecond (fs) and nanosecond (ns) time-resolved transient absorption (TA) spectroscopy. Fs-TA measurements indicate that the formation of an intramolecular charge separation (ICS) state with twisted structural feature in polar solvents is driven and stabilized by solvation dynamics. Combined with chemical calculations, we found that orbital decoupling, poor conjugation between Cz and NI groups due to intramolecular torsional motion and transition moments associated with ICT emission, limits excited-state deactivation through radiation and nonradiation transition to the ground state. In addition, the orthogonal π-system of the ICS state enables the efficient spin-orbit, charge-transfer intersystem crossing to a triplet state, which is localized on the NI group. Spectroscopic and computational results reveal the formation of an ICS state at an appropriate energy that enables the population of the triplet state with high quantum yield, and the localized triplet state has long lifetime and high reduction potential for subsequent reactions. Therefore, solvent-solute interaction, especially the solvation-coupled excited-state structural relaxation, is the main factor that the photocatalysis efficiency of Cz-NI has a significant polarity correlation.

Unveiling Solvation Dynamics of Excited and Ground States via Ultrafast Pump-Dump-Probe Spectroscopy.

The conventional ultrafast pump-probe spectroscopy has primarily focused on examining the formation and decay of the excited state intermediates, but it is very difficult to detect those intermediates while the formation is slow and dissipation is much fast because of the limited concentration during the intrinsic photocycle. To address this issue, a multipulse ultrafast pump-dump-probe spectroscopy was employed to generate and probe the short-lived ground state intermediates (GSIs) in an electronic push-pull pyrene derivative (EPP). This particular derivative undergoes planarized intramolecular charge transfer (PICT) in the excited state upon initial femtosecond pulse excitation. After applying the dump pulse once the PICT was formed, the blue-shifted transient absorption GSIs with the ground state dynamics of the structure recovery was directly observed. It is found that GSIs undergo slower reorganization than the PICT formation in the excited state of EPP due to the solvation effect with different dipole moments of ground states and excited states. These findings provide a comprehensive understanding of the full photocycle dynamics of both the ground and excited states, shedding light on the presence of hidden ground state behaviors.

Intrinsic Photostability in Dithiolonaphthalimide Achieved by Disulfide Bond-Induced Excited-State Quenching.

Disulfide bridges common in proteins show excellent photostability achieved by ultrafast internal conversion and maintain the stability of the tertiary structure. When disulfide bonds exist in aromatic compounds, the rigid chemical structure may affect the cleavage and reforming dynamics of disulfide bonds. In this work, a model compound with a disulfide five-membered-ring structure, 4,5-dithiolo-N-(2,6-dimethylphenyl)-1,8-naphthalimide (DTDPNI), is selected to elaborate the effect of disulfide modification on the excited-state deactivation mechanism. Quantum chemical calculations show that the S-S stretching leads to a dramatic decrease in the energy gap between the S1 and S0 states, similar to the situation in 1,2-dithiane. Due to the efficient nonradiative process, the excited-state lifetime of DTDPNI resolved by ultrafast spectroscopy is determined to be ∼20 ps. It is found that the excellent photostability is achieved by ultrafast excited-state quenching induced by the S-S stretching, rather than the cleavage of the disulfide bond; even the disulfide bridge is in a very rigid aromatic molecular system.

Spin-orbit charge-transfer intersystem crossing in heavy-atom-free orthogonal covalent boron-dipyrromethene heterodimers.

Boron-dipyrromethene (BODIPY) derivatives are prospective organic-based triplet photosensitizers. Since the triplet generation yield of the parent BODIPY is low, heavy atoms are widely used to improve the triplet yield. However, the dimerization of BODIPYs can also significantly improve their ability to produce triplets. Through a comparative study of the triplet formation dynamics of two heavy-atom-free orthogonal covalent BODIPY heterodimers that differ in their dihedral angles, we have demonstrated that the mechanism of spin-orbit charge-transfer intersystem crossing (SOCT-ISC) promotes the triplet generation of BODIPY heterodimers in solution. Different from the general understanding of SOCT-ISC, the heterodimer with a smaller dihedral angle and low structural rigidity showed better triplet generation due to (a) the stronger inter-chromophoric interaction in the heterodimer, which promoted the formation of a solvent-stabilized charge-transfer (CT) state, (b) the more favorable energy level alignment with sizeable spin-orbit coupling strength, and (c) the balance between the stabilized singlet CT state and limited direct charge recombination to the ground state in a weakly polar solvent. The complete spectral characterization of the triplet formation dynamics clarified the SOCT-ISC mechanism and important factors affecting the triplet generation in BODIPY heterodimers.

Efficacy of acupuncture for cardiopulmonary cerebral resuscitation: A systematic review and meta-analysis.

Background: Cerebral resuscitation is one of the main therapeutic aims in the treatment of cardiac arrest (CA) patients who experience a return of spontaneous circulation (ROSC). However, the therapeutic effects of current treatments are not ideal. The purpose of this study was to evaluate the efficacy of neurological function of acupuncture combined with conventional cardiopulmonary cerebral resuscitationthe (CPCR) for patients after ROSC. Methods: Seven electronic databases and other related websites were searched to identify studies on acupuncture combined with conventional CPCR for patients after ROSC. R software was used to conduct a meta-analysis, and the outcomes that could not be pooled were analyzed using a descriptive analysis. Results: Seven RCTs involving 411 participants who had experienced ROSC were eligible for inclusion. The main acupoints were Neiguan (PC6), Shuigou (DU26), Baihui (DU20), Yongquan (KI1), and Sanyinjiao (SP6). Compared to conventional CPCR, acupuncture combined with conventional CPCR led to significantly higher Glasgow Coma Scale (GCS) scores on day 3 (mean difference (MD)=0.89, 95% CI: 0.43, 1.35, I2 = 0%), day 5 (MD = 1.21, 95% CI: 0.27, 2.15; I2 = 0%), and day 7 (MD = 1.92, 95% CI: 1.35, 2.50; I2 = 0%). Conclusion: Acupuncture-assisted conventional CPCR may have a potential role in improving neurological function in CA patients after ROSC, but the certainty of evidence is very low and more high-quality studies are required. Protocol registration: This review was registered at the International Prospective Registry of Systematic Reviews (PROSPERO): CRD42021262262.

Ultrafast Charge Separation Driven by Torsional Motion in Orthogonal Boron Dipyrromethene Dimer.

In this work, the photoinduced charge separation (CS) via symmetry breaking in an orthogonal meso-ß-linked boron dipyrromethene (BODIPY) dimer was investigated by polarized transient absorption spectroscopy. The time constant about 0.76 ps of the CS reaction determined in dimethyl sulfoxide is much faster than the solvation dynamics. The observed transient anisotropy of the BODIPY anion band implies that both hole and electron transfers occur with similar probabilities. The bidirectional charge transfer processes suggest that the locally excited state is weakly coupled to the polar solvent, and the solvation coupled excited-state structural relaxation within the BODIPY monomeric unit is rather limited. In combination with the electronic excitation analysis based on time-dependent density-functional theory calculations, we deduced that the CS in the orthogonal BODIPY dimer is enabled via the torsional motion associated with covalently connected BODIPY units, promoting the electronic coupling, and irrelevant to the dynamic solvent relaxation.

The preliminary evidence on the association of the gut microbiota with stroke risk stratification in South Chinese population.

Aims: This study aimed to investigate the association between the gut microbiota and the risk of stroke. Methods: Faecal samples from 60 participants in South China, including 45 individuals with risk factors for stroke and 15 healthy controls, were collected and subjected to 16S rRNA sequencing. A bioinformatics analysis was performed to characterise the gut microbial diversity and taxonomic compositions at different risk levels (low, moderate, and high) of stroke. Functional prediction and correlation analyses between the microbiota and laboratory markers were performed to explore the potential mechanisms. Results: A significant difference in beta diversity was observed between the participants from the stroke risk and healthy control groups. Linear discriminant effect size analysis revealed a large number of vascular beneficial bacteria enriched in the participants from the healthy control and low-risk groups, but a few vascular harmful bacteria were more abundant in the participants from the high-risk group than in those from the other groups. In addition, Anaerostipes, Clostridium_XlVb, and Flavonifractor, all of which belonged to the Firmicutes phylum, were enriched in the participants from the low-risk group, and their relative abundances gradually decreased as the stroke risk increased. Spearman's analysis revealed that these outstanding microbiota correlated with the levels of triglycerides, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, white blood cells, neutrophils, and carotid intima-media thickness. Conclusion: The preliminary evidence suggests that gut microbiota is associated with stroke risk. It potentially ameliorates atherosclerosis by targeting lipid metabolism and inflammation. This provides novel insights into the early screening of stroke risk and primary prevention.

Host diet shapes functionally differentiated gut microbiomes in sympatric speciation of blind mole rats in Upper Galilee, Israel.

The gut microbiome is important for host nutrient metabolism and ecological adaptation. However, how the gut microbiome is affected by host phylogeny, ecology and diet during sympatric speciation remain unclear. Here, we compare and contrast the gut microbiome of two sympatric blind mole rat species and correlate them with their corresponding host phylogeny, ecology soil metagenomes, and diet to determine how these factors may influence their gut microbiome. Our results indicate that within the host microbiome there is no significant difference in community composition, but the functions between the two sympatric species populations vary significantly. No significant correlations were found between the gut microbiome differentiation and their corresponding ecological soil metagenomes and host phylogeny. Functional enrichment analysis suggests that the host diets may account for the functional divergence of the gut microbiome. Our results will help us understand how the gut microbiome changes with corresponding ecological dietary factors in sympatric speciation of blind subterranean mole rats.

The role of acupuncture and moxibustion in the treatment, prevention, and rehabilitation of patients with COVID-19: A scoping review.

Introduction: This study aims to summarize the available evidence and guideline/consensus recommendations for acupuncture and moxibustion in the treatment, prevention and rehabilitation of patients with coronavirus disease 2019 (COVID-19). Methods: A scoping review was performed. Eight electronic databases and other related websites were searched. All studies related to acupuncture and moxibustion for COVID-19 were considered. Descriptive analysis was applied to analyze the all included studies and guideline recommendations. Results: We ultimately included 131 eligible studies. The main topics of the included studies were the treatment (82.4%) and prevention (38.9%) of COVID-19. The most included studies were literature reviews (65, 49.6%), protocols of systematic reviews (20, 15.3%), and guidelines and consensuses (18, 13.7%). The 18 (13.7%) COVID-19 guidelines and consensuses included 47 recommendations on acupuncture and moxibustion, which focused on the treatment (21/47, 44.7%), rehabilitation (17/47, 36.2%) and prevention (6, 12.8%) of COVID-19 patients. Zusanli (ST36), Feishu (BL13), Guanyuan (RN4) were recommended mostly for the treatment, rehabilitation and prevention respectively. Conclusion: Acupuncture and moxibustion are effective in the treatment of COVID-19 patients to some extent. However, more high-quality of clinical trials still needed to determine the feasibility of acupuncture and moxibustion in COVID-19 patients to better guide clinical practice. Study registration: Open Science Framework Registries (Registration DOI: 10.17605/OSF.IO/Z35WN; https://osf.io/z35wn).

Coherent vibrational dynamics of Au144(SR)60 nanoclusters.

The coherent vibrational dynamics of gold nanoclusters (NCs) provides important information on the coupling between vibrations and electrons as well as their mechanical properties, which is critical for understanding the evolution from a metallic state to a molecular state with diminishing size. Coherent vibrations have been widely explored in small-sized atomically precise gold NCs, while it remains a challenge to observe them in large-sized gold NCs. In this work, we report the coherent vibrational dynamics of atomically precise Au144(SR)60 NCs via temperature-dependent femtosecond transient absorption (TA) spectroscopy. The population dynamics of Au144(SR)60 consists of three relaxation processes: internal conversion, core-shell charge transfer and relaxation to the ground state. After removing the population dynamics from the TA kinetics, fast Fourier transform analysis on the residual oscillation reveals distinct vibrational modes at 1.5 THz (50 cm-1) and 2 THz (67 cm-1), which arise from the wavepacket motions along the ground-state and excited-state potential energy surfaces (PES), respectively. These results are helpful for understanding the physical properties of gold nanostructures with a threshold size that lies in between those of molecular-like NCs and metallic-state nanoparticles.

Traditional Chinese Medicine for Post-stroke Sleep Disorders: The Evidence Mapping of Clinical Studies.

Background and Purpose: Recently, there are a number of clinical studies on traditional Chinese medicine (TCM) for post-stroke sleep disorders (PSSDs). This study aimed to map the current clinical studies and identify gaps to inform future study agendas. Methods: PubMed, Embase, Cochrane Library, and Chinese databases, including SinoMed, CNKI, and Wanfang, were searched for clinical studies on PSSDs treated with TCM from their inception to September 2021. Evidence sources, number of studies, types of PSSDs, intervention categories, effectiveness, and quality assessment were graphically displayed. Results: The evidence map involved 810 clinical studies, of which the earliest report was dated back to 1993, and an advanced growth of the whole evidence was observed in 2012. Randomized controlled trials (RCTs) were the most common type of study design (78.15%), and post-stroke insomnia was the most common type of sleep disorders (65.80%). The benefits of Chinese herbal medicine (CHM) and acupuncture therapies for post-stroke insomnia have been widely reported in RCTs (81.60% and 75.38%, respectively). However, the benefits of CHM interventions were assessed using a global approach rather than being based on a specific formula, and the highest level of evidence supporting the effectiveness of acupuncture therapies was of low methodological quality. In addition, evidence from primary studies was insufficient in the areas of TCM for post-stroke sleep-related breathing disorders (SBDs) and Chinese mind-body exercises for post-stroke insomnia. Conclusions: PSSDs treated with TCM have been widely assessed in clinical studies. For better evidence translation, clinical trials on specific CHM interventions and high-quality systematic reviews on acupuncture for post-stroke insomnia should be conducted. For a better solution to clinical questions, TCM on SBDs after stroke and the benefits of Chinese mind-body exercises for post-stroke insomnia should be explored in future clinical studies.

Incipient Sympatric Speciation and Evolution of Soil Bacteria Revealed by Metagenomic and Structured Non-Coding RNAs Analysis.

Soil bacteria respond rapidly to changes in new environmental conditions. For adaptation to the new environment, they could mutate their genome, which impacts the alternation of the functional and regulatory landscape. Sometimes, these genetic and ecological changes may drive the bacterial evolution and sympatric speciation. Although sympatric speciation has been controversial since Darwin suggested it in 1859, there are several strong theoretical or empirical evidences to support it. Sympatric speciation associated with soil bacteria remains largely unexplored. Here, we provide potential evidence of sympatric speciation of soil bacteria by comparison of metagenomics from two sharply contrasting abutting divergence rock and soil types (Senonian chalk and its rendzina soil, and abutting Pleistocene basalt rock and basalt soil). We identified several bacterial species with significant genetic differences in the same species between the two soil types and ecologies. We show that the bacterial community composition has significantly diverged between the two soils; correspondingly, their functions were differentiated in order to adapt to the local ecological stresses. The ecologies, such as water availability and pH value, shaped the adaptation and speciation of soil bacteria revealed by the clear-cut genetic divergence. Furthermore, by a novel analysis scheme of riboswitches, we highlight significant differences in structured non-coding RNAs between the soil bacteria from two divergence soil types, which could be an important driver for functional adaptation. Our study provides new insight into the evolutionary divergence and incipient sympatric speciation of soil bacteria under microclimatic ecological differences.

Symmetry-breaking charge separation in a nitrogen-bridged naphthalene monoimide dimer.

The photophysical properties of 4-aminonaphthalene-1,8-imide-based derivatives, bis-ANI, consisting of two naphthalimide (NI) units linked by a butylamine bridge and its monomer ANI have been intensively investigated by steady-state and transient spectroscopy combined with quantum chemical calculations. The excited state relaxation dynamics of the two molecules are studied in three solvents of varying polarity - from hexane to tetrahydrofuran to acetone. A strong reduction in the fluorescence quantum yields and larger red shifts of the emission spectra are observed when going from the monomer ANI to dimer bis-ANI with increasing solvent polarity. It is found that the presence of the central amino linker in bis-ANI facilitates the formation of an asymmetric CS state between the ANI and NI moieties in bis-ANI, where NI˙- is the dominant radical anion unit after CS, evidenced by the femtosecond transient absorption measurements and spectroelectrochemistry in polar solvents. Femtosecond transient absorption spectra and quantum chemical calculations reveal the conformational change after the formation of the symmetry-breaking charge separation (SBCS) state upon photoexcitation, while a near-orthogonal structure in the excited state of bis-ANI retards charge recombination. In addition, it is evidenced that the rate of SBCS can be tuned by changing the different polar solvents.

Correlation between Excited-State Intramolecular Proton Transfer and Electron Population on Proton Donor/Acceptor in 2-(2'-Hydroxyphenyl)oxazole Derivatives.

Modulating the excited-state intramolecular proton transfer (ESIPT) reaction to achieve anticipant performance is always fascinating for chemists. However, feasible methods and a definite mechanism for tuning the ESIPT reaction remain insufficient. In this work, we reported the feasibility of continuously modulating the ESIPT dynamics in 2-(2'-hydroxyphenyl)oxazole (HPO) derivatives with different substitutions on the positions 5 and 5' of the core HPO through steady-state/transient spectroscopy and theoretical calculations. We found that the main factor affecting the tendency of the ESIPT reaction is the variation of electron population on proton donor and acceptor. An index Δpdif was proposed to evaluate the overall promotion effect on proton transfer caused by the variation of electron population on proton donor and acceptor, which shows high reliability in interpreting the ESIPT tendency. This method, for its capacity to quickly estimate the tendency of ESIPT, shows great potential in ESIPT molecular design with chemical substitution of electron-donating/withdrawing moieties.