The potential energy surfaces for the C-C, C-Br and C-Cl dissociations of BrCH 2 COCl(S 1 ) are investigated at the CAS(8,7)/6 31G * and MR CI/cc pVDZ levels of theory, which provides some new insights into the mechan...The potential energy surfaces for the C-C, C-Br and C-Cl dissociations of BrCH 2 COCl(S 1 ) are investigated at the CAS(8,7)/6 31G * and MR CI/cc pVDZ levels of theory, which provides some new insights into the mechanism of the BrCH 2 COCl photodis sociation at 248nm. It is found that the relative strength of the C-C and C-Cl α bonds is one of the factors that influence the selectivity of the α bond fissions. However, the selectivity is mainly determined by the mechanism of dissociation upon n→π * excitation. The preference of the C-Cl α bond fission over the C-Br β bond cleavage is attributed to the nonadiabatic recrossing in previous studies. The present calculations predict that distance dependence of intramolecular energy relaxation is another important factor that influences the selectivity of the α and β bond cleavages.展开更多
Excited-state double proton transfer(ESDPT)is a controversial issue which has long been plagued with theoretical and experimental communities.Herein,we took 1,8-dihydroxy-2-naphthaldehyde(DHNA)as a prototype and used ...Excited-state double proton transfer(ESDPT)is a controversial issue which has long been plagued with theoretical and experimental communities.Herein,we took 1,8-dihydroxy-2-naphthaldehyde(DHNA)as a prototype and used combined complete active space selfconsistent field(CASSCF)and multi-state complete active-space second-order perturbation(MS-CASPT2)methods to investigate ESDPT and excited-state deactivation pathways of DHNA.Three different tautomer minima of S1-ENOL,S1-KETO-1,and S1-KETO-2 and two crucial conical intersections of S1 S0-KETO-1 and S1 S0-KETO-2 in and between the S0 and S1 states were obtained.S1-KETO-1 and S1-KETO-2 should take responsibility for experimentally observing dual-emission bands.In addition,two-dimensional potential energy surfaces(2 D-PESs)and linear interpolated internal coordinate paths connecting relevant structures were calculated at the MS-CASPT2//CASSCF level and confirmed a stepwise ESDPT mechanism.Specifically,the first proton transfer from S1-ENOL to S1-KETO-1 is barrierless,whereas the second one from S1-KETO-1 to S1-KETO-2 demands a barrier of ca.6.0 kcal/mol.The linear interpolated internal coordinate path connecting S1-KETO-1(S1-KETO-2)and S_(1) S0-KETO-1(S1 S0-KETO-2)is uphill with a barrier of ca.12.0 kcal/mol,which will trap DHNA in the S_(1) state while therefore enabling dual-emission bands.On the other hand,the S1/S0 conical intersections would also prompt the S_(1) system to decay to the S_(0) state,which could be to certain extent suppressed by locking the rotation of the C5-C8-C9-O10 dihedral angle.These mechanistic insights are not only helpful for understanding ESDPT but also useful for designing novel molecular materials with excellent photoluminescent performances.展开更多
The role of the intersection between two potential energy surfaces has been more generally emphasizing on than before.In the present system,the intersections between S1,T1 and S0 surfaces were optimized with the state...The role of the intersection between two potential energy surfaces has been more generally emphasizing on than before.In the present system,the intersections between S1,T1 and S0 surfaces were optimized with the state-averaged CAS(8,7)/6-31G method.The comparison of their optimized structures demonstrates that the intersection points of S1/S0 and S1/T1 locate in the same region,referred to as S1/T1/S0 point.The existence of S1/T1/S0 point and its high possibility of radiationless transition via intersystem crossing or internal conversion,would make the system have the most efficient funnel to generate the ground- and triplet-state products,which is consistent with the experimental facts.展开更多
文摘The potential energy surfaces for the C-C, C-Br and C-Cl dissociations of BrCH 2 COCl(S 1 ) are investigated at the CAS(8,7)/6 31G * and MR CI/cc pVDZ levels of theory, which provides some new insights into the mechanism of the BrCH 2 COCl photodis sociation at 248nm. It is found that the relative strength of the C-C and C-Cl α bonds is one of the factors that influence the selectivity of the α bond fissions. However, the selectivity is mainly determined by the mechanism of dissociation upon n→π * excitation. The preference of the C-Cl α bond fission over the C-Br β bond cleavage is attributed to the nonadiabatic recrossing in previous studies. The present calculations predict that distance dependence of intramolecular energy relaxation is another important factor that influences the selectivity of the α and β bond cleavages.
基金supported by the National Key Research and Development Program of China for BinBin Xie(No.2019YFA0709400)the National Natural Science Foundation of China for Bin-Bin Xie(No.21903068)+1 种基金Xiang-Yang Liu(No.22003043)Natural Science Foundation of Zhejiang Province for Bin-Bin Xie(No.LQ19B030007)。
文摘Excited-state double proton transfer(ESDPT)is a controversial issue which has long been plagued with theoretical and experimental communities.Herein,we took 1,8-dihydroxy-2-naphthaldehyde(DHNA)as a prototype and used combined complete active space selfconsistent field(CASSCF)and multi-state complete active-space second-order perturbation(MS-CASPT2)methods to investigate ESDPT and excited-state deactivation pathways of DHNA.Three different tautomer minima of S1-ENOL,S1-KETO-1,and S1-KETO-2 and two crucial conical intersections of S1 S0-KETO-1 and S1 S0-KETO-2 in and between the S0 and S1 states were obtained.S1-KETO-1 and S1-KETO-2 should take responsibility for experimentally observing dual-emission bands.In addition,two-dimensional potential energy surfaces(2 D-PESs)and linear interpolated internal coordinate paths connecting relevant structures were calculated at the MS-CASPT2//CASSCF level and confirmed a stepwise ESDPT mechanism.Specifically,the first proton transfer from S1-ENOL to S1-KETO-1 is barrierless,whereas the second one from S1-KETO-1 to S1-KETO-2 demands a barrier of ca.6.0 kcal/mol.The linear interpolated internal coordinate path connecting S1-KETO-1(S1-KETO-2)and S_(1) S0-KETO-1(S1 S0-KETO-2)is uphill with a barrier of ca.12.0 kcal/mol,which will trap DHNA in the S_(1) state while therefore enabling dual-emission bands.On the other hand,the S1/S0 conical intersections would also prompt the S_(1) system to decay to the S_(0) state,which could be to certain extent suppressed by locking the rotation of the C5-C8-C9-O10 dihedral angle.These mechanistic insights are not only helpful for understanding ESDPT but also useful for designing novel molecular materials with excellent photoluminescent performances.
文摘The role of the intersection between two potential energy surfaces has been more generally emphasizing on than before.In the present system,the intersections between S1,T1 and S0 surfaces were optimized with the state-averaged CAS(8,7)/6-31G method.The comparison of their optimized structures demonstrates that the intersection points of S1/S0 and S1/T1 locate in the same region,referred to as S1/T1/S0 point.The existence of S1/T1/S0 point and its high possibility of radiationless transition via intersystem crossing or internal conversion,would make the system have the most efficient funnel to generate the ground- and triplet-state products,which is consistent with the experimental facts.
