Organic lasers that emit light in the deep-red and near-infrared(NIR)region are of essential importance in laser communication,night vision,bioimaging,and information-secured displays but are still challenging because...Organic lasers that emit light in the deep-red and near-infrared(NIR)region are of essential importance in laser communication,night vision,bioimaging,and information-secured displays but are still challenging because of the lack of proper gain materials.Herein,a new molecular design strategy that operates by merging two excited-state intramolecular proton transfer-active molecules into one excited-state double proton transfer(ESDPT)-active molecule was demonstrated.Based on this new strategy,three new materials were designed and synthesized with two groups of intramolecular resonance-assisted hydrogen bonds,in which the ESDPT process was proven to proceed smoothly based on theoretical calculations and experimental results of steady-state and transient spectra.Benefiting from the effective six-level system constructed by the ESDPT process,all newly designed materials showed low threshold laser emissions at approximately 720 nm when doped in PS microspheres,which in turn proved the existence of the second proton transfer process.More importantly,our well-developed NIR organic lasers showed high laser stability,which can maintain high laser intensity after 12000 pulse lasing,which is essential in practical applications.This work provides a simple and effective method for the development of NIR organic gain materials and demonstrates the ESDPT mechanism for NIR lasing.展开更多
Excited-state intramolecular proton transfer(ESIPT) molecules are broadly applied to UV absorbers, fluorescence sensing, and lighting materials. In previous work, the fluorescence colors of oxazoline-substituted hydro...Excited-state intramolecular proton transfer(ESIPT) molecules are broadly applied to UV absorbers, fluorescence sensing, and lighting materials. In previous work, the fluorescence colors of oxazoline-substituted hydroxyfluorenes and hydroxylated benzoxazole were diversified by adding the π-conjugation. There is intriguing that the mechanism of diversified fluorescence colors induced by ESIPT. Here, the density functional theory(DFT) and time-dependent DFT(TDDFT)are advised to identify the effects of π-conjugation on ESIPT and photophysical properties. The stabilized geometrical configurations, frontier molecular orbitals(FMOs) isosurfaces, and O–H stretching vibration frequency analysis demonstrate that PT processes are more active in S1state. Constructing the minimum energy pathways of ESIPT processes, we find that the calculated peak of enol and keto fluorescence of naphthoxazole(NO–OH) is distinctly bathochromic-shift relative to the oxazoline-substituted hydroxyfluorenes(Oxa–OH) configuration when adding π-conjugation-substitution, and it means that π-conjugation-substitution can diversify the fluorescence color. We hope our studies can establish new channels to devise the ESIPT-based molecules.展开更多
Intracellular pH is a key parameter related to various biological and pathological processes.In this study,a ratiometric pH fluorescent sensor ABTT was developed harnessing the amino-type excited-state intramolecular ...Intracellular pH is a key parameter related to various biological and pathological processes.In this study,a ratiometric pH fluorescent sensor ABTT was developed harnessing the amino-type excited-state intramolecular proton transfer(ESIPT) process.Relying on whether the ESIPT proceeds normally or not,ABTT exhibited the yellow fluorescence in acidic media,or cyan fluorescence in basic condition.According to the variation,ABTT behaved as a promising sensor which possessed fast and reversible response to pH change without interference from the biological substances,and exported a steady ratiometric signal(I_(478)/I_(546)).Moreover,due to the ESIPT effect,large Stokes shift and high quantum yield were also exhibited in ABTT.Furthermore,ABTT was applied for monitoring the pH changes in living cells and visualizing the pH fluctuations under oxidative stress successfully.These results elucidated great potential of ABTT in understanding pH-dependent physiological and pathological processes.展开更多
In contrast to the widely reported excited-state single proton-transfer,excited-state multiple proton transfer(ESMPT)containing two or more intra-or inter-molecular proton transfers has greatly expanded the research s...In contrast to the widely reported excited-state single proton-transfer,excited-state multiple proton transfer(ESMPT)containing two or more intra-or inter-molecular proton transfers has greatly expanded the research scope of the excited-state proton transfers.In recent decades,ESMPT-active organic molecules have attracted much attention owing to their unique photophysical properties,such as large magnitude Stokes shifts and dual emission.These photophysical properties facilitate the application of the organic molecules in organic solid-state lasers,fluorescent probes and sensors,and molecular switches.Herein,we introduce the fundamentals of the ESMPT and review the recent advances in different types of ESMPTs in organic molecules.Finally,we present our conclusions and the future development prospects of the ESMPT in organic molecules.展开更多
A neutral N-amidothiourea-based excited state intramolecular proton transfer (ESIPT) anion receptor bearing an o-hydroxynaphthamide fluorophore and a thiourea binding site, N-(3-hydroxy-2-naphthamide)-N’-phenylthiour...A neutral N-amidothiourea-based excited state intramolecular proton transfer (ESIPT) anion receptor bearing an o-hydroxynaphthamide fluorophore and a thiourea binding site, N-(3-hydroxy-2-naphthamide)-N’-phenylthiourea (1a), was designed and synthesized. Fluorescence and absorption response of 1a toward anions were assessed in acetonitrile. IR and NMR experiments indicated that the "OH…O=C" intramolecular hydrogen bond (IHB) in 1a was weak so that it only exhibited the short-wavelength normal emission other than ESIPT fluorescence. Due to the high anion binding affinity of the N-amidothiourea binding site and the formation of a hydrogen binding network in the 1a-anion c omplex, 1a underwent structural change upon anion binding that strengthens the "OH…O=C" IHB, leading to the ESIPT and the observation of the long-wavelength ESIPT emission whereas the normal fluorescence is quenched. On the basis of NMR and fluorescence titrations and control experiments with model compounds, a sensing mechanism of the anion-binding-induced ESIPT was proposed.展开更多
Based on density functional theory(DFT) and time-dependent density functional theory(TD-DFT), the effects of substituent on the excited-state intramolecular proton transfer(ESIPT) process and photophysical properties ...Based on density functional theory(DFT) and time-dependent density functional theory(TD-DFT), the effects of substituent on the excited-state intramolecular proton transfer(ESIPT) process and photophysical properties of 2-(2’-hydroxyphenyl)-4-chloromethylthiazole(HCT) are studied. The electron-donating group(CH_(3), OH) and electronwithdrawing group(CF_(3), CHO) are introduced to analyze the changes of intramolecular H-bond, the frontier molecular orbitals, the absorption/fluorescence spectra, and the energy barrier of ESIPT process. The calculation results indicate that electron-donating group strengthens the intramolecular H-bond in the S_(1) state, and leads to an easier ESIPT process. The electron-withdrawing group weakens the corresponding H-bond and makes ESIPT process a little harder. Different substituents also affect the photophysical properties of HCT. The electron-withdrawing group(CF_(3), CHO) has a little effect on electronic spectra. The electron-donating group(CH_(3), OH) red-shifts both the absorption and fluorescence emission peaks of HCT, respectively, which causes the Stokes shift to increase.展开更多
Excited-state intramolecular proton transfer(ESIPT) reactions of three ortho-hydroxylated oxazolines, 2-(4,4-dimethyl-4,5-dihydro-oxazol-2-yl)-phenol(DDOP), 4-(4,4-dimethyl-4,5-dihydro-oxazol-2-yl)-[1,1?-biphenyl]-3-o...Excited-state intramolecular proton transfer(ESIPT) reactions of three ortho-hydroxylated oxazolines, 2-(4,4-dimethyl-4,5-dihydro-oxazol-2-yl)-phenol(DDOP), 4-(4,4-dimethyl-4,5-dihydro-oxazol-2-yl)-[1,1?-biphenyl]-3-ol(DDOP-C_(6)H_(5)) and 4-(4,4-dimethyl-4,5-dihydrooxazol-2-yl)-3-hydroxy-benzonitrile(DDOP-CN), have been systematically explored by density functional theory(DFT) and time-dependent density functional theory(TDDFT) methods. Two stable configurations(enol and keto forms) are found in the ground states(S_(0)) for all the compounds while the enol form only exists in the first excited states(S_(1)) for the compound modified with electron donating group(-C_(6)H_(5)). In addition, the calculated absorption and emission spectra of the compounds are in good agreements with the experiments. Infrared vibrational spectra at the hydrogen bond groups demonstrate that the intramolecular hydrogen bond O(1)-H(2)···N(3) in DDOP-C_(6)H_(5) is strengthened in the S_(1) states, while the frontier molecular orbitals further reveal that the ESIPT reactions are more likely to occur in the S_(1) states for all the compounds. Besides, the proton transfer potential energy curves show that the enol forms can barely convert into keto forms in the S_(0) states because of the high energy barriers. Meanwhile, intramolecular proton transfer of all the compounds could occur in S_(1) states. The ESIPT reactions of the ortho-hydroxylated oxazolines are barrierless processes for unsubstituted DDOP and electron withdrawing substituted DDOP-CN, while the electron donating substituted DDOP-C_(6)H_(5) has a small barrier, so the electron donating is unfavorable to the ESIPT reactions of ortho-hydroxylated oxazolines.展开更多
Developing fluorescence porous probe for detecting and eliminating Cu^(2+) contamination in water or biosystem is an essential research project that has attracted considerable attention.However,improving the fluoresce...Developing fluorescence porous probe for detecting and eliminating Cu^(2+) contamination in water or biosystem is an essential research project that has attracted considerable attention.However,improving the fluorescence detecting efficiency while enhancing the adsorption capacity of the porous probe is of great challenge.Herein,a bifunctional two-dimensional imine-based porous covalent organic framework(TTP-COF)probe was designed and synthesized from 1,3,5-tris(4-aminophenyl)benzene(TAPB)and 2,4,6-Triformylphloroglucinol(TP)ligand.TTP-COF displayed rapid detection of Cu^(2+)(limit of detection(LOD)=10 nmol·L^(−1) while achieving a high adsorption capacity of 214 mg·g^(−1)(pH=6)at room temperature with high reusability(>5 cycles).The key roles and contributions of highπ-conjugate and delocalized electrons in TABP and functional–OH groups in TP were proved.More importantly,the fluorescence quenching mechanism of TTP-COF was studied by density functional theory theoretical calculations,revealing the crucial role of intramolecular hydrogen bonds among C=N and–OH groups and the blocking of the excited state intramolecular proton transfer process in detecting process of Cu^(2+).展开更多
Recently,a novel tetraarylimidazole derivative 2-(benzo[d]thiazol-2-yl)-4-(4,5-bis(4-methoxyphenyl)-1-phenyl-1H-imidazol-2-yl)-phenol(be called MHBT herein)was architectured by our research group showing the fascinati...Recently,a novel tetraarylimidazole derivative 2-(benzo[d]thiazol-2-yl)-4-(4,5-bis(4-methoxyphenyl)-1-phenyl-1H-imidazol-2-yl)-phenol(be called MHBT herein)was architectured by our research group showing the fascinating synergy of aggregation-induced emission(AIE)characteristic,excited-state intramolecular proton transfer(ESIPT)mechanism and intramolecular charge transfer(ICT)effect.Nevertheless,a detailed and reasonable interpretation of its mechanisms both in theory is urgently needed.Consequently,to unveil the working mechanism meticulously,herein,we tactfully applied density functional theory(DFT)and time-dependent density functional theory(TD-DFT)methods to illuminate the underlying mechanisms in different solvent conditions.After optimizing the structures,the geometric parameters of hydrogen bonds(HBs),the infrared(IR)vibrational spectrum,the reduced density gradient(RDG)isosurfaces were calculated in detail,vividly explaining how the enhancement of HBs behaved as the driving force to proceed ESIPT process.Simultaneously,the frontier molecular orbitals(FMOs)combined with the potential energy curves(PECs)were conducted to interpretate the role and character of ICT and ESIPT in molecule MHBT.Further,the PECs of MHBT for dihedral angles in different organic solvents were calculated to compare the dominant torsion degree,rationalizing the AIE phenomenon from the view of the restriction of intramolecular rotation process.This work may well underpin the understanding of the interaction between different mechanisms in fluorescent dyes and thereby provide meaningful guideline for the design and construction of ideal molecules.展开更多
t-Butyl and t-pentylcalix[4]arenes bearing two 2-naphthol-1-hydrazone groups at the lower rim were synthesized,and showed excited-state intermolecular proton transfer fluorescent signal with basic anion.They are more ...t-Butyl and t-pentylcalix[4]arenes bearing two 2-naphthol-1-hydrazone groups at the lower rim were synthesized,and showed excited-state intermolecular proton transfer fluorescent signal with basic anion.They are more sensitive to dihydrogen phosphate anion than to fluoride anion,although the latter has stronger basicity.Compared with t-butylcalix[4]arene bearing two 2-naphthol-1-hydrazone groups,t-pentylcalix[4]arenes derivative has a larger fluorescent difference between dihydrogen phosphate and fluoride anion.This finding may be used to analyze dihydrogen phosphate anion in the presence of fluoride anion and provide a new approach for designing fluorescence probes that are highly selective for H2PO4-.展开更多
Cysteine is well-known to be an important biothiol and related to many diseases. However, the in vivo detection of endogenous cysteine still suffers from lacking small-molecule fluorophores with both excitation and em...Cysteine is well-known to be an important biothiol and related to many diseases. However, the in vivo detection of endogenous cysteine still suffers from lacking small-molecule fluorophores with both excitation and emission in the near-infrared(650-900 nm)/shortwave-infrared region. Herein, we report a molecular engineering strategy for shortwave infrared(SWIR, 900-1700 nm) sensing of cysteine, which integrated an excited-state intermolecular proton transfer(ESIPT) building block into the intramolecular charge transfer(ICT) scaffold. The obtained novel fluorophore SH-OH displays a maximum absorption at the NIR region, and emission at the SWIR region. We introduce the cysteine-recognition moiety to SH-OH structure, and demonstrate sensing of endogenous cysteine in living animals, using the SWIR emission as a reliable off-on fluorescence signal. This fluorophore design strategy of cooperation of ICT and ESIPT processes expands the in vivo sensing toolbox for accurate analysis in clinical applications.展开更多
基金We are grateful for financial supports from the National Natural Science Foundation of China(Nos.52173177,21971185,22105139)Fundação Universidade de Ciência e Tecnologia de Macao(No.0006/2021/AKP)+1 种基金the Natural Science Foundation of Jiangsu Province(No.BK20221362)the Science and Technology Support Program of Jiangsu Province(No.TJ-2022-002).This project is also funded by Suzhou Key Laboratory of Functional Nano&Soft Materials,Collaborative Innovation Center of Suzhou Nano Science&Technology,the 111 Project,Joint International Research Laboratory of Carbon-Based Functional Materials and Devices,and Soochow University Tang Scholar.
文摘Organic lasers that emit light in the deep-red and near-infrared(NIR)region are of essential importance in laser communication,night vision,bioimaging,and information-secured displays but are still challenging because of the lack of proper gain materials.Herein,a new molecular design strategy that operates by merging two excited-state intramolecular proton transfer-active molecules into one excited-state double proton transfer(ESDPT)-active molecule was demonstrated.Based on this new strategy,three new materials were designed and synthesized with two groups of intramolecular resonance-assisted hydrogen bonds,in which the ESDPT process was proven to proceed smoothly based on theoretical calculations and experimental results of steady-state and transient spectra.Benefiting from the effective six-level system constructed by the ESDPT process,all newly designed materials showed low threshold laser emissions at approximately 720 nm when doped in PS microspheres,which in turn proved the existence of the second proton transfer process.More importantly,our well-developed NIR organic lasers showed high laser stability,which can maintain high laser intensity after 12000 pulse lasing,which is essential in practical applications.This work provides a simple and effective method for the development of NIR organic gain materials and demonstrates the ESDPT mechanism for NIR lasing.
基金supported by the National Natural Science Foundation of China (Grant No. 11974152)the Shenyang High level Innovative Talents Program (Grant No. RC200565)+1 种基金the Science program of Liaoning Provincial Department of Education (Grant No. LJKZ0097)the Intercollegiate cooperation project of colleges and universities of Liaoning Provincial Department of Education。
文摘Excited-state intramolecular proton transfer(ESIPT) molecules are broadly applied to UV absorbers, fluorescence sensing, and lighting materials. In previous work, the fluorescence colors of oxazoline-substituted hydroxyfluorenes and hydroxylated benzoxazole were diversified by adding the π-conjugation. There is intriguing that the mechanism of diversified fluorescence colors induced by ESIPT. Here, the density functional theory(DFT) and time-dependent DFT(TDDFT)are advised to identify the effects of π-conjugation on ESIPT and photophysical properties. The stabilized geometrical configurations, frontier molecular orbitals(FMOs) isosurfaces, and O–H stretching vibration frequency analysis demonstrate that PT processes are more active in S1state. Constructing the minimum energy pathways of ESIPT processes, we find that the calculated peak of enol and keto fluorescence of naphthoxazole(NO–OH) is distinctly bathochromic-shift relative to the oxazoline-substituted hydroxyfluorenes(Oxa–OH) configuration when adding π-conjugation-substitution, and it means that π-conjugation-substitution can diversify the fluorescence color. We hope our studies can establish new channels to devise the ESIPT-based molecules.
基金the financial supports from National Natural Science Foundation of China (Nos.81971678 and 81671756)the Innovation Fund for Postgraduate Students of Central South University (No.2019zzts1019)。
文摘Intracellular pH is a key parameter related to various biological and pathological processes.In this study,a ratiometric pH fluorescent sensor ABTT was developed harnessing the amino-type excited-state intramolecular proton transfer(ESIPT) process.Relying on whether the ESIPT proceeds normally or not,ABTT exhibited the yellow fluorescence in acidic media,or cyan fluorescence in basic condition.According to the variation,ABTT behaved as a promising sensor which possessed fast and reversible response to pH change without interference from the biological substances,and exported a steady ratiometric signal(I_(478)/I_(546)).Moreover,due to the ESIPT effect,large Stokes shift and high quantum yield were also exhibited in ABTT.Furthermore,ABTT was applied for monitoring the pH changes in living cells and visualizing the pH fluctuations under oxidative stress successfully.These results elucidated great potential of ABTT in understanding pH-dependent physiological and pathological processes.
基金financially supported by the National Natural Science Foundation of China (52173177,21971185,22105139)China Postdoctoral Science Foundation (2020M681707)+1 种基金funded by the Collaborative Innovation Center of Suzhou Nano Science and Technology (CIC-Nano)by the “111” Project of the State Administration of Foreign Experts Affairs of China
文摘In contrast to the widely reported excited-state single proton-transfer,excited-state multiple proton transfer(ESMPT)containing two or more intra-or inter-molecular proton transfers has greatly expanded the research scope of the excited-state proton transfers.In recent decades,ESMPT-active organic molecules have attracted much attention owing to their unique photophysical properties,such as large magnitude Stokes shifts and dual emission.These photophysical properties facilitate the application of the organic molecules in organic solid-state lasers,fluorescent probes and sensors,and molecular switches.Herein,we introduce the fundamentals of the ESMPT and review the recent advances in different types of ESMPTs in organic molecules.Finally,we present our conclusions and the future development prospects of the ESMPT in organic molecules.
基金Supported by the National Natural Science Foundation of China (Grant Nos. 20425518, 20675069 & 20835005)the National Fund for Fostering Talents of Basic Science (Grant No. J0630429)
文摘A neutral N-amidothiourea-based excited state intramolecular proton transfer (ESIPT) anion receptor bearing an o-hydroxynaphthamide fluorophore and a thiourea binding site, N-(3-hydroxy-2-naphthamide)-N’-phenylthiourea (1a), was designed and synthesized. Fluorescence and absorption response of 1a toward anions were assessed in acetonitrile. IR and NMR experiments indicated that the "OH…O=C" intramolecular hydrogen bond (IHB) in 1a was weak so that it only exhibited the short-wavelength normal emission other than ESIPT fluorescence. Due to the high anion binding affinity of the N-amidothiourea binding site and the formation of a hydrogen binding network in the 1a-anion c omplex, 1a underwent structural change upon anion binding that strengthens the "OH…O=C" IHB, leading to the ESIPT and the observation of the long-wavelength ESIPT emission whereas the normal fluorescence is quenched. On the basis of NMR and fluorescence titrations and control experiments with model compounds, a sensing mechanism of the anion-binding-induced ESIPT was proposed.
文摘Based on density functional theory(DFT) and time-dependent density functional theory(TD-DFT), the effects of substituent on the excited-state intramolecular proton transfer(ESIPT) process and photophysical properties of 2-(2’-hydroxyphenyl)-4-chloromethylthiazole(HCT) are studied. The electron-donating group(CH_(3), OH) and electronwithdrawing group(CF_(3), CHO) are introduced to analyze the changes of intramolecular H-bond, the frontier molecular orbitals, the absorption/fluorescence spectra, and the energy barrier of ESIPT process. The calculation results indicate that electron-donating group strengthens the intramolecular H-bond in the S_(1) state, and leads to an easier ESIPT process. The electron-withdrawing group weakens the corresponding H-bond and makes ESIPT process a little harder. Different substituents also affect the photophysical properties of HCT. The electron-withdrawing group(CF_(3), CHO) has a little effect on electronic spectra. The electron-donating group(CH_(3), OH) red-shifts both the absorption and fluorescence emission peaks of HCT, respectively, which causes the Stokes shift to increase.
基金supported by the National Natural Science Foundation of China(Nos.21963008 and 21767010)the Natural Science Foundation of Hubei Province(No.2018CFB650)the Postgraduate Research and Innovation Plan Project of Hubei Minzu University(No.MYK2020001)。
文摘Excited-state intramolecular proton transfer(ESIPT) reactions of three ortho-hydroxylated oxazolines, 2-(4,4-dimethyl-4,5-dihydro-oxazol-2-yl)-phenol(DDOP), 4-(4,4-dimethyl-4,5-dihydro-oxazol-2-yl)-[1,1?-biphenyl]-3-ol(DDOP-C_(6)H_(5)) and 4-(4,4-dimethyl-4,5-dihydrooxazol-2-yl)-3-hydroxy-benzonitrile(DDOP-CN), have been systematically explored by density functional theory(DFT) and time-dependent density functional theory(TDDFT) methods. Two stable configurations(enol and keto forms) are found in the ground states(S_(0)) for all the compounds while the enol form only exists in the first excited states(S_(1)) for the compound modified with electron donating group(-C_(6)H_(5)). In addition, the calculated absorption and emission spectra of the compounds are in good agreements with the experiments. Infrared vibrational spectra at the hydrogen bond groups demonstrate that the intramolecular hydrogen bond O(1)-H(2)···N(3) in DDOP-C_(6)H_(5) is strengthened in the S_(1) states, while the frontier molecular orbitals further reveal that the ESIPT reactions are more likely to occur in the S_(1) states for all the compounds. Besides, the proton transfer potential energy curves show that the enol forms can barely convert into keto forms in the S_(0) states because of the high energy barriers. Meanwhile, intramolecular proton transfer of all the compounds could occur in S_(1) states. The ESIPT reactions of the ortho-hydroxylated oxazolines are barrierless processes for unsubstituted DDOP and electron withdrawing substituted DDOP-CN, while the electron donating substituted DDOP-C_(6)H_(5) has a small barrier, so the electron donating is unfavorable to the ESIPT reactions of ortho-hydroxylated oxazolines.
基金This study was financially supported by the National Natural Science Foundation of China(Nos.22001156 and 22271178)the Innovation Capability Support Program of Shaanxi(No.2022KJXX-88)the Technology Innovation Leading Program of Shaanxi(No.2020QFY07-05).
文摘Developing fluorescence porous probe for detecting and eliminating Cu^(2+) contamination in water or biosystem is an essential research project that has attracted considerable attention.However,improving the fluorescence detecting efficiency while enhancing the adsorption capacity of the porous probe is of great challenge.Herein,a bifunctional two-dimensional imine-based porous covalent organic framework(TTP-COF)probe was designed and synthesized from 1,3,5-tris(4-aminophenyl)benzene(TAPB)and 2,4,6-Triformylphloroglucinol(TP)ligand.TTP-COF displayed rapid detection of Cu^(2+)(limit of detection(LOD)=10 nmol·L^(−1) while achieving a high adsorption capacity of 214 mg·g^(−1)(pH=6)at room temperature with high reusability(>5 cycles).The key roles and contributions of highπ-conjugate and delocalized electrons in TABP and functional–OH groups in TP were proved.More importantly,the fluorescence quenching mechanism of TTP-COF was studied by density functional theory theoretical calculations,revealing the crucial role of intramolecular hydrogen bonds among C=N and–OH groups and the blocking of the excited state intramolecular proton transfer process in detecting process of Cu^(2+).
基金W.Zeng sincerely thank the financial contribution from the National Natural Science Foundation of China(Nos.81971678 and 81671756)M.Liu appreciate the Natural Science Foundation of Hunan Province(No.2021JJ41008)the Key Project of Changsha Science and Technology Plan(No.kh2201059)for financial support.
文摘Recently,a novel tetraarylimidazole derivative 2-(benzo[d]thiazol-2-yl)-4-(4,5-bis(4-methoxyphenyl)-1-phenyl-1H-imidazol-2-yl)-phenol(be called MHBT herein)was architectured by our research group showing the fascinating synergy of aggregation-induced emission(AIE)characteristic,excited-state intramolecular proton transfer(ESIPT)mechanism and intramolecular charge transfer(ICT)effect.Nevertheless,a detailed and reasonable interpretation of its mechanisms both in theory is urgently needed.Consequently,to unveil the working mechanism meticulously,herein,we tactfully applied density functional theory(DFT)and time-dependent density functional theory(TD-DFT)methods to illuminate the underlying mechanisms in different solvent conditions.After optimizing the structures,the geometric parameters of hydrogen bonds(HBs),the infrared(IR)vibrational spectrum,the reduced density gradient(RDG)isosurfaces were calculated in detail,vividly explaining how the enhancement of HBs behaved as the driving force to proceed ESIPT process.Simultaneously,the frontier molecular orbitals(FMOs)combined with the potential energy curves(PECs)were conducted to interpretate the role and character of ICT and ESIPT in molecule MHBT.Further,the PECs of MHBT for dihedral angles in different organic solvents were calculated to compare the dominant torsion degree,rationalizing the AIE phenomenon from the view of the restriction of intramolecular rotation process.This work may well underpin the understanding of the interaction between different mechanisms in fluorescent dyes and thereby provide meaningful guideline for the design and construction of ideal molecules.
基金the National Natural Science Foundation of China (Grant No 20872040)the Scientific Research Projects of Education Department of Guangxi Province (2006) for financial supportthe Analytical and Testing Centre at Huazhong University of Science and Technology for measurement
文摘t-Butyl and t-pentylcalix[4]arenes bearing two 2-naphthol-1-hydrazone groups at the lower rim were synthesized,and showed excited-state intermolecular proton transfer fluorescent signal with basic anion.They are more sensitive to dihydrogen phosphate anion than to fluoride anion,although the latter has stronger basicity.Compared with t-butylcalix[4]arene bearing two 2-naphthol-1-hydrazone groups,t-pentylcalix[4]arenes derivative has a larger fluorescent difference between dihydrogen phosphate and fluoride anion.This finding may be used to analyze dihydrogen phosphate anion in the presence of fluoride anion and provide a new approach for designing fluorescence probes that are highly selective for H2PO4-.
基金supported by the National Natural Science Foundation of China (Nos.21878087,21908060)the Innovation Program of Shanghai Municipal Education Commission,Shuguang Program (No.18SG27)+1 种基金the NIH guidelines for the care and use of laboratory animals (NIH Publication No.85-23,Rev.1985)approved by the Institutional Animal Care and Use Committee of National Tissue Engineering Center (Shanghai,China)。
文摘Cysteine is well-known to be an important biothiol and related to many diseases. However, the in vivo detection of endogenous cysteine still suffers from lacking small-molecule fluorophores with both excitation and emission in the near-infrared(650-900 nm)/shortwave-infrared region. Herein, we report a molecular engineering strategy for shortwave infrared(SWIR, 900-1700 nm) sensing of cysteine, which integrated an excited-state intermolecular proton transfer(ESIPT) building block into the intramolecular charge transfer(ICT) scaffold. The obtained novel fluorophore SH-OH displays a maximum absorption at the NIR region, and emission at the SWIR region. We introduce the cysteine-recognition moiety to SH-OH structure, and demonstrate sensing of endogenous cysteine in living animals, using the SWIR emission as a reliable off-on fluorescence signal. This fluorophore design strategy of cooperation of ICT and ESIPT processes expands the in vivo sensing toolbox for accurate analysis in clinical applications.