The origin of opposite reactivity in the ring-opening polymerizations of lactide(LA)and cyclohexene oxide(CHO)catalyzed by redox-switchable bis(imino)pyridine iron complexes has been computationally elucidated.It is f...The origin of opposite reactivity in the ring-opening polymerizations of lactide(LA)and cyclohexene oxide(CHO)catalyzed by redox-switchable bis(imino)pyridine iron complexes has been computationally elucidated.It is found that larger geometrical deformation accounts for the lower activity of the oxidized form(Fe^(ox))of the iron catalyst toward LA polymerization in comparison with the reduced analogue(Fered)enabling LA insertion with a moderate energy barrier of 27.1 kcal mol^(−1).In contrast,compared with the Fered species,the higher activity of Fe^(ox)toward CHO polymerization could be ascribed to the stronger interaction between Fe^(ox)and CHO moieties,stabilizing the corresponding transition state.This originated from the higher electrophilicity of Fe^(ox),which is more sensitive to the binding of the monomer with higher nucleophilicity,such as CHO.Driven by this theoretical understanding,various Fe^(ox)analogues were computationally modelled by changing the para-substituents of the initial phenoxyls or modifying the backbone of the bis(imino)pyridine ligand to increase the Lewis acidity(electrophilicity)of such complexes.Expectedly,a lower energy barrier is observed in CHO enchainment mediated by the complexes with electron-withdrawing groups.Notably,such energy barriers positively correlate with the LUMO energies of these complexes with various substituents on the initial phenoxyl groups or on the backbone of the bis(imino)pyridine ligand.These results could provide useful information on the development of redox-switchable polymerization systems.展开更多
The polymerization mechanism of methyl methacrylate(MMA)catalyzed by rare-earth/phosphorus(RE/P)Lewis pairs has been systematically studied through density functional theory(DFT)calculations.Having achieved an agreeme...The polymerization mechanism of methyl methacrylate(MMA)catalyzed by rare-earth/phosphorus(RE/P)Lewis pairs has been systematically studied through density functional theory(DFT)calculations.Having achieved an agreement between theory and experiment,it is found that the polymerization of MMA mediated by intermolecular RE/P Lewis pairs mainly follows the bimetallic mechanism,while the monometallic pathway could not be excluded in the case of a La analogue.In comparison with phenyl phosphorus as a Lewis base,the higher activity of cyclohexyl phosphorus toward MMA polymerization could be ascribed to the electron-donation ability,rendering more electron flow in the addition reaction.Besides,a computational modelling of analogous intramolecular RE/P systems indicates that the size of the central metal and the length of the chain connecting Lewis pairs play an important role in the catalytic activity.展开更多
Although rare-earth-catalysed C-H addition to unsaturated hydrocarbons has emerged as a powerful and atom-economical strategy,the mechanistic principles governing selectivity in reactions involving conjugated dienes r...Although rare-earth-catalysed C-H addition to unsaturated hydrocarbons has emerged as a powerful and atom-economical strategy,the mechanistic principles governing selectivity in reactions involving conjugated dienes remain poorly understood.Here,density functional theory(DFT)calculations are employed to elucidate the mechanistic origins of divergent selectivity in rare-earth-catalysed pyridine C-H alkylation and aldimine annulation reactions with conjugated dienes.The results indicate that,despite producing formal 1,4-and 1,2-insertion products,respectively,both transformations proceed through a preferred 1,4-cis-insertion pathway to generate η^(3)-allyl intermediates.Comprehensive computational analyses reveal that the divergence arises from distinct post-insertion pathways:sterically favored protonation at the terminal carbon in pyridine alkylation,versus electronically and sterically driven cyclization at the internal carbon in aldimine annulation.These results demonstrate that product selectivity is dictated primarily by the site-selective evolution of the η^(3)-allyl intermediate rather than by the initial insertion event.This work establishes a unified mechanistic framework for diene-enabled rare-earth-catalysed C-H functionalization and provides theoretical insights into selectivity control through post-insertion reactivity.展开更多
Redox-switchable polymerization has drawn increasing attention,in particular for the ring-opening polymerization(ROP)of biomass-derived monomers.However,an understanding of how the switch determines the observed chang...Redox-switchable polymerization has drawn increasing attention,in particular for the ring-opening polymerization(ROP)of biomass-derived monomers.However,an understanding of how the switch determines the observed changes is still limited.In this study,DFT calculations were employed to understand the redox-switchable ROP mechanism ofε-caprolactone catalyzed by group 4 metal complexes bearing[OSSO]-type ferrocene ligands.Our results suggest that two oxidized forms show higher reactivity because of the higher Lewis acidity of their catalytic metal centers in comparison with that of the corresponding reduced states.In one case,however,a lower activity of the oxidized species was observed that is likely due to the increased stability of the substrate-catalyst intermediate leading to a high activation barrier.In addition,other analogous metal complexes were computationally modelled by changing the metal center or modifying the ancillary ligand with different bridging-heteroatoms,and the results provide useful information on the development of new redox-switchable polymerization catalysts.展开更多
Large language models(LLMs)have opened up new possibilities for intelligent agents,endowing them with human-like thinking and cognitive abilities.In this work,we delve into the potential of large language models(LLMs)...Large language models(LLMs)have opened up new possibilities for intelligent agents,endowing them with human-like thinking and cognitive abilities.In this work,we delve into the potential of large language models(LLMs)in autonomous driving(AD).We introduce DriveMLM,an LLM-based AD framework that can perform close-loop autonomous driving in realistic simulators.To this end,(1)we bridge the gap between the language decisions and the vehicle control commands by standardizing the decision states according to the off-the-shelf motion planning module.(2)We employ a multimodal LLM(MLLM)to model the behavior planning module of a module AD system,which uses driving rules,user commands,and inputs from various sensors(e.g.,camera,LiDAR)as input and makes driving decisions and provide explanations.This model can plug-and-play in existing AD systems such as Autopilot and Apollo for close-loop driving.(3)We design an effective data engine to collect a dataset that includes decision state and corresponding explanation annotation for model training and evaluation.We conduct extensive experiments and show that replacing the decision-making modules of the Autopilot and Apollo with DriveMLM resulted in significant improvements of 3.2 and 4.7 points on the CARLA Town05 Long,respectively,demonstrating the effectiveness of our model.We hope this work can serve as a baseline for autonomous driving with LLMs.展开更多
The design of efficient iron-based catalysts remains a great challenge for selective cyclohexane oxidation to cyclohexanone under mild conditions.Because of the complex distribution of iron location on the support,the...The design of efficient iron-based catalysts remains a great challenge for selective cyclohexane oxidation to cyclohexanone under mild conditions.Because of the complex distribution of iron location on the support,the selectivity is always low.Here,we report a general strategy to selectively deposit highly-dispersed FeO_(x) into the micropore of ZSM-5 by atomic layer deposition(ALD).The framework of ZSM-5 and the Bronsted acid sites are intact during ALD,and the Fe species are selectively deposited onto the defect and Lewis acid sites of ZSM-5.Besides,more Fe–O–Si bonds are formed over FeO_(x)/ZSM-5 with a low loading of Fe,while FeO_(x) nanoparticles are generated at high Fe loading.They cannot be realized by the traditional solution method.The obtained FeO_(x)/ZSM-5 catalysts perform high selectivity of cyclohexanone(92%–97%),and ALD cycle numbers of FeO_(x) control the activity.Compared with the Fe nanoparticles,the Fe–O–Si species performs higher turnover frequency and stability in the oxidation reaction.展开更多
of main observation and conclusion The mechanism of Rh-catalyzed C(sp^3)—H amination has been computationally investigated.The reaction mechanism mainly involves sequential C(sp^3)—H activation,decarboxylation,nitre...of main observation and conclusion The mechanism of Rh-catalyzed C(sp^3)—H amination has been computationally investigated.The reaction mechanism mainly involves sequential C(sp^3)—H activation,decarboxylation,nitrene migration insertion,and protonation steps.Competitive concerted metalation deprotonation(CMD)and external base assisted deprotonation(EBAD)pathways are found for the involved C(sp^3)—H activation in both Rh and Co analogous systems.This is different from the previously reported C(sp^2)—H activation,where the CMD is dominant.The key mechanistic difference between the two systems is found to be in the C(sp^3)—H activation step.In comparison with Rh species,the lower activity of Co complex toward the C(sp^3)—H activation could be ascribed to smaller atomic size of Co and thus larger steric repulsion between ancillary ligand and substrate along with the CMD pathway.In view of the EBAD pathway,however,the lower activity of Co species could be imputed to the triplet nature of Co center,which is against the electron transfer from the electron-rich carbon atom of the deprotonating C(sp^3)—H bond to the Co center.As to the subsequent decarboxylation and nitrene insertion steps,compared with the Co system,the relatively lower reactivity of Rh species is partially due to the stronger Rh—N bond,and the higher Ti(Rh—N)and n^*(Rh—N)orbital energies of the corresponding transition state structure.展开更多
基金supported by the NSFC(21674014,U1862115,and 21704011).
文摘The origin of opposite reactivity in the ring-opening polymerizations of lactide(LA)and cyclohexene oxide(CHO)catalyzed by redox-switchable bis(imino)pyridine iron complexes has been computationally elucidated.It is found that larger geometrical deformation accounts for the lower activity of the oxidized form(Fe^(ox))of the iron catalyst toward LA polymerization in comparison with the reduced analogue(Fered)enabling LA insertion with a moderate energy barrier of 27.1 kcal mol^(−1).In contrast,compared with the Fered species,the higher activity of Fe^(ox)toward CHO polymerization could be ascribed to the stronger interaction between Fe^(ox)and CHO moieties,stabilizing the corresponding transition state.This originated from the higher electrophilicity of Fe^(ox),which is more sensitive to the binding of the monomer with higher nucleophilicity,such as CHO.Driven by this theoretical understanding,various Fe^(ox)analogues were computationally modelled by changing the para-substituents of the initial phenoxyls or modifying the backbone of the bis(imino)pyridine ligand to increase the Lewis acidity(electrophilicity)of such complexes.Expectedly,a lower energy barrier is observed in CHO enchainment mediated by the complexes with electron-withdrawing groups.Notably,such energy barriers positively correlate with the LUMO energies of these complexes with various substituents on the initial phenoxyl groups or on the backbone of the bis(imino)pyridine ligand.These results could provide useful information on the development of redox-switchable polymerization systems.
基金supported by the NSFC(U1862115 and 21674014)the Innovation and Entrepreneurship Project of Overseas Returnees in Anhui Province(2020LCX006).
文摘The polymerization mechanism of methyl methacrylate(MMA)catalyzed by rare-earth/phosphorus(RE/P)Lewis pairs has been systematically studied through density functional theory(DFT)calculations.Having achieved an agreement between theory and experiment,it is found that the polymerization of MMA mediated by intermolecular RE/P Lewis pairs mainly follows the bimetallic mechanism,while the monometallic pathway could not be excluded in the case of a La analogue.In comparison with phenyl phosphorus as a Lewis base,the higher activity of cyclohexyl phosphorus toward MMA polymerization could be ascribed to the electron-donation ability,rendering more electron flow in the addition reaction.Besides,a computational modelling of analogous intramolecular RE/P systems indicates that the size of the central metal and the length of the chain connecting Lewis pairs play an important role in the catalytic activity.
基金supported by National Natural Science Foundation of China(no.22522101,22271001,22003001).
文摘Although rare-earth-catalysed C-H addition to unsaturated hydrocarbons has emerged as a powerful and atom-economical strategy,the mechanistic principles governing selectivity in reactions involving conjugated dienes remain poorly understood.Here,density functional theory(DFT)calculations are employed to elucidate the mechanistic origins of divergent selectivity in rare-earth-catalysed pyridine C-H alkylation and aldimine annulation reactions with conjugated dienes.The results indicate that,despite producing formal 1,4-and 1,2-insertion products,respectively,both transformations proceed through a preferred 1,4-cis-insertion pathway to generate η^(3)-allyl intermediates.Comprehensive computational analyses reveal that the divergence arises from distinct post-insertion pathways:sterically favored protonation at the terminal carbon in pyridine alkylation,versus electronically and sterically driven cyclization at the internal carbon in aldimine annulation.These results demonstrate that product selectivity is dictated primarily by the site-selective evolution of the η^(3)-allyl intermediate rather than by the initial insertion event.This work establishes a unified mechanistic framework for diene-enabled rare-earth-catalysed C-H functionalization and provides theoretical insights into selectivity control through post-insertion reactivity.
基金supported by the NSFC(21674014,U1862115)Y.L.and G.L.thank the Fundamental Research Funds for the Central Universities(DUT18GJ201,DUT18RC(3)002)+1 种基金PLD thanks the National Science Foundation for grant CHE-1809116The authors also thank RICC(RIKEN Integrated Cluster of Clusters)and the Network and Information Center of Dalian University of Technology for part of computational resources.
文摘Redox-switchable polymerization has drawn increasing attention,in particular for the ring-opening polymerization(ROP)of biomass-derived monomers.However,an understanding of how the switch determines the observed changes is still limited.In this study,DFT calculations were employed to understand the redox-switchable ROP mechanism ofε-caprolactone catalyzed by group 4 metal complexes bearing[OSSO]-type ferrocene ligands.Our results suggest that two oxidized forms show higher reactivity because of the higher Lewis acidity of their catalytic metal centers in comparison with that of the corresponding reduced states.In one case,however,a lower activity of the oxidized species was observed that is likely due to the increased stability of the substrate-catalyst intermediate leading to a high activation barrier.In addition,other analogous metal complexes were computationally modelled by changing the metal center or modifying the ancillary ligand with different bridging-heteroatoms,and the results provide useful information on the development of new redox-switchable polymerization catalysts.
基金supported by the National Key R&D Program of China(No.2022ZD0161300)the National Natural Science Foundation of China(Nos.U24A20325,62321005 and 62376134).
文摘Large language models(LLMs)have opened up new possibilities for intelligent agents,endowing them with human-like thinking and cognitive abilities.In this work,we delve into the potential of large language models(LLMs)in autonomous driving(AD).We introduce DriveMLM,an LLM-based AD framework that can perform close-loop autonomous driving in realistic simulators.To this end,(1)we bridge the gap between the language decisions and the vehicle control commands by standardizing the decision states according to the off-the-shelf motion planning module.(2)We employ a multimodal LLM(MLLM)to model the behavior planning module of a module AD system,which uses driving rules,user commands,and inputs from various sensors(e.g.,camera,LiDAR)as input and makes driving decisions and provide explanations.This model can plug-and-play in existing AD systems such as Autopilot and Apollo for close-loop driving.(3)We design an effective data engine to collect a dataset that includes decision state and corresponding explanation annotation for model training and evaluation.We conduct extensive experiments and show that replacing the decision-making modules of the Autopilot and Apollo with DriveMLM resulted in significant improvements of 3.2 and 4.7 points on the CARLA Town05 Long,respectively,demonstrating the effectiveness of our model.We hope this work can serve as a baseline for autonomous driving with LLMs.
基金supported by the National Natural Science Foundation of China(21872160,U1832208)the National Science Fund for Distinguished Young Scholars(21825204)+2 种基金the National Key R&D Program of China(2017YFA0700101 and 2018YFB1501602)the Youth Innovation Promotion Association CAS(2017204)Natural Science Foundation of Shanxi Province(201901D211591)。
文摘The design of efficient iron-based catalysts remains a great challenge for selective cyclohexane oxidation to cyclohexanone under mild conditions.Because of the complex distribution of iron location on the support,the selectivity is always low.Here,we report a general strategy to selectively deposit highly-dispersed FeO_(x) into the micropore of ZSM-5 by atomic layer deposition(ALD).The framework of ZSM-5 and the Bronsted acid sites are intact during ALD,and the Fe species are selectively deposited onto the defect and Lewis acid sites of ZSM-5.Besides,more Fe–O–Si bonds are formed over FeO_(x)/ZSM-5 with a low loading of Fe,while FeO_(x) nanoparticles are generated at high Fe loading.They cannot be realized by the traditional solution method.The obtained FeO_(x)/ZSM-5 catalysts perform high selectivity of cyclohexanone(92%–97%),and ALD cycle numbers of FeO_(x) control the activity.Compared with the Fe nanoparticles,the Fe–O–Si species performs higher turnover frequency and stability in the oxidation reaction.
基金This work was supported by the National Natural Science Foundation of China(No.21674014)Y.L.thanks the FundamentalResearch Funds for the Central Universities(DUT18GJ201)The authors also thank the Network and lnformation Center of Dalian University of Technology and the High-performance Computing Platform of Anhui University for part of computational resources.
文摘of main observation and conclusion The mechanism of Rh-catalyzed C(sp^3)—H amination has been computationally investigated.The reaction mechanism mainly involves sequential C(sp^3)—H activation,decarboxylation,nitrene migration insertion,and protonation steps.Competitive concerted metalation deprotonation(CMD)and external base assisted deprotonation(EBAD)pathways are found for the involved C(sp^3)—H activation in both Rh and Co analogous systems.This is different from the previously reported C(sp^2)—H activation,where the CMD is dominant.The key mechanistic difference between the two systems is found to be in the C(sp^3)—H activation step.In comparison with Rh species,the lower activity of Co complex toward the C(sp^3)—H activation could be ascribed to smaller atomic size of Co and thus larger steric repulsion between ancillary ligand and substrate along with the CMD pathway.In view of the EBAD pathway,however,the lower activity of Co species could be imputed to the triplet nature of Co center,which is against the electron transfer from the electron-rich carbon atom of the deprotonating C(sp^3)—H bond to the Co center.As to the subsequent decarboxylation and nitrene insertion steps,compared with the Co system,the relatively lower reactivity of Rh species is partially due to the stronger Rh—N bond,and the higher Ti(Rh—N)and n^*(Rh—N)orbital energies of the corresponding transition state structure.
