We report the first disubstituted hetero-ten-vertex closo cluster [(CrGe_(9))Cr_(2)(CO)_(13)]^(4-)with three adjacent Cr(CO);units adopting both η^(5) and η^(1) coordination modes,which was synthesized through the r...We report the first disubstituted hetero-ten-vertex closo cluster [(CrGe_(9))Cr_(2)(CO)_(13)]^(4-)with three adjacent Cr(CO);units adopting both η^(5) and η^(1) coordination modes,which was synthesized through the reaction of "KGe;" with(MeCN)_(3)Cr(CO)_(4)and Cr(CO)_(6)in ethylenediamine(en) solution.In contrast to the η^(1)-Cr atoms forming localized two-center two-elelctron(2 c-2 e) Cr-Ge bonds,the hetero atom η^(5)-Cr exhibits versatile bonding mechanisms including three 5 c-2 e and five 8 c-2 e delocalized bonds which account for Hückel aromaticity.Intricate multi-center bonding patterns delineate the multiple local σ-aromatic characters of the title cluster displaying explicit spherical aromaticity.展开更多
Novel expanded porphyrinoids with advanced structure features(such as multiple-inner-ring-fusion)have a wide range of benefits(such as multi-metal coordination and facile tunable aromaticity)not offered by their norma...Novel expanded porphyrinoids with advanced structure features(such as multiple-inner-ring-fusion)have a wide range of benefits(such as multi-metal coordination and facile tunable aromaticity)not offered by their normal porphyrin analogues,and have found wide applications as sensors,fluorescent probes,novel ligands and functionalized NIR organic dyes in various research fields.However,the structures of these expanded porphyrinoids are scarce due to their limited synthetic accessibility.Herein,we summarized the lately reported efficient synthesis of novel expanded porphyrinoids with multipleinner-ring-fusion(up to six-inner-ring-fusion)and smaragdyrins with tunable aromaticity.Their synthesis is either based on an oxidative ring cyclization on linear/macrocyclic oligopyrroles containing N-confused pyrrole unit(s)or a straightforward double SNAr reaction on readily available 3,5-dibromoBODIPY,respectively.展开更多
We use density functional theory and time-dependent together with a set of extensive mul- tidimensional visualization techniques to characterize the influence of keto effect on charge distribution at ground state and ...We use density functional theory and time-dependent together with a set of extensive mul- tidimensional visualization techniques to characterize the influence of keto effect on charge distribution at ground state and electronic transitions for neutral and charged hexaphyrin aromaticity with and without keto-defect. It is found that the aromaticity is the key fac- tor to influence the ground state Mulliken charges distribution properties, other than the meso-aryl-substituted effect. But with the enhancement of the keto-defect, the distribution changes of Mulliken charges on the hexaphyrin groups are larger than those on the pentaflu- orophenyl substituted groups, following with the aromaticity changes from nonaromatic to aromatic. Furthermore, through characterizing by transition density and charge difference density, direct visual evidence for neutral and charged aromaticity with and without keto- defect can be clearly derived, and the ability of charge transfer between units of monoradical （nonaromaticity） and singlet biradical （aromaticity） forms is much stronger than that of neutral forms.展开更多
Clusters XY2Z species are theoretically investigated with density functional theory （DFT） method. The results show that for LiP2C, LiAs2Ge and KAs2C species, the C2v isomer is the most stable planar structure, while...Clusters XY2Z species are theoretically investigated with density functional theory （DFT） method. The results show that for LiP2C, LiAs2Ge and KAs2C species, the C2v isomer is the most stable planar structure, while for other species the Cs isomer is the most stable planar structure at the B3LYP/6-311＋G＊ level. Wiberg Bond Index （WBI） and Nucleus-Independent Chemical Shift （NICS） values indicate the existence of delocalization in stable planar structures. A detailed Molecular Orbital （MO） analysis further reveals that planar isomers of these species have strong aromatic character, which strengthens the structural stability and makes them closely connect with the concept of aromaticity.展开更多
The simple homodinuclear M-M single bonds for group II and XII elements are difficult to obtain as a result of the fulfilled s2electronic configurations,consequently,a dicationic prototype is often utilized to design ...The simple homodinuclear M-M single bonds for group II and XII elements are difficult to obtain as a result of the fulfilled s2electronic configurations,consequently,a dicationic prototype is often utilized to design the M^+-M^+single bond.Existing studies generally use sterically bulky organic ligands L^-to synthesize the compounds in the L^--M^+-M^+-L-manner.However,here we report the design of Mg-Mg and Zn-Zn single bonds in two ligandless clusters,Mg2B7-and Zn2B7-,using density functional theory methods.The global minima of both of the clusters are in the form of M2^2+(B7^3-),where the M-M single bonds are positioned above a quasi-planar hexagonal B7 moiety.Chemical bonding analyses further confirm the existence of Mg-Mg and Zn-Zn single bonds in these clusters,which are driven by the unusually stable B7^3-moiety that is bothσandπaromatic.Vertical detachment energies of Mg2B7-and Zn2B7-are calculated to be 2.79 e V and 2.94 e V,respectively,for the future comparisons with experimental data.展开更多
The structures, energies and aromaticity （the nuclear-independent chemical shifts,NICS） of AlCO-substituted semibullvalenes were investigated at the B3LYP/6-311＋G＊＊ level.Similar to BCO-substituted analogues, [2,...The structures, energies and aromaticity （the nuclear-independent chemical shifts,NICS） of AlCO-substituted semibullvalenes were investigated at the B3LYP/6-311＋G＊＊ level.Similar to BCO-substituted analogues, [2,6]-AlCO-semibullvalene is neutral bishomoaromatic.The NICS values reveal that the aromaticity of AlCO-substituted structures is smaller than that of BCO analogues.展开更多
Alkaline-earth(Ae) metals have attracted a wealth of interdependent research from synthetic chemists.In Ae-catalyzed organometallic reactions,β-diketiminate is a typical ligand used to stabilize Ae catalysts by formi...Alkaline-earth(Ae) metals have attracted a wealth of interdependent research from synthetic chemists.In Ae-catalyzed organometallic reactions,β-diketiminate is a typical ligand used to stabilize Ae catalysts by forming six-membered rings comprising Ae metals.Herein,studies focusing on the configuration of β-diketiminate-coordinated Ae compounds observed that the C-C and C-N bonds are homogeneous and unchanged.Furthermore,energetic studies observed that the formation of the Ae-incorporated sixmembered rings results in enhanced stability of>20 kcal/mol.The nucleus-independent chemical shifts,anisotropy of the induced current density,and molecular orbital analyses demonstrated the nonaromaticity of the β-diketiminate-coordinated Ae compounds.The improved stability of these compounds can be explained by the delocalization of the π electrons derived from the β-diketiminate moiety.展开更多
The aromaticity of all possible substituted fullerene isomers of C18N2, C18B2, C18BN, and their molecular ions which originate from the C20 （Ih） cage were studied by the topological resonance energy （TRE） and the ...The aromaticity of all possible substituted fullerene isomers of C18N2, C18B2, C18BN, and their molecular ions which originate from the C20 （Ih） cage were studied by the topological resonance energy （TRE） and the percentage topological resonance energy methods. The relationship between the aromaticity of C18BxNy isomers and the sites where the heteroatoms dope at the C20 （Ih） cage is discussed. Calculation results show that at the neutral and cationic states all the isomers are predicted to be antiaromatic with negative TREs, but their polyvalent anions are predicted to be aromatic with positive TREs. The most stable isomer is formed by heteroatom doping at the 1,11-sites in C18N2. C18B2, and C18BN. Heterofullerenes are more aromatic than C20. The stability order in the neutral states is C18N2〉C18BN〉C18B2〉C20. The stability order in closed-shell is C18B2^8- 〉C20^6- 〉C18BN^6- 〉C18N2^4-. This predicts theoretically that their polyvalent anions have high aromaticity.展开更多
Aromaticity,in general,can promote a given reaction by stabilizing a transition state or a product via a mobility ofπelectrons in a cyclic structure.Similarly,such a promotion could be also achieved by destabilizing ...Aromaticity,in general,can promote a given reaction by stabilizing a transition state or a product via a mobility ofπelectrons in a cyclic structure.Similarly,such a promotion could be also achieved by destabilizing an antiaromatic reactant.However,both aromaticity and transition states cannot be directly measured in experiment.Thus,computational chemistry has been becoming a key tool to understand the aromaticity-driven reaction mechanisms.In this review,we will analyze the relationship between aromaticity and reaction mechanism to highlight the importance of density functional theory calculations and present it according to an approach via either aromatizing a transition state/product or destabilizing a reactant by antiaromaticity.Specifically,we will start with a particularly challenging example of dinitrogen activation followed by other small-molecule activation,Csingle bondF bond activation,rearrangement,as well as metathesis reactions.In addition,antiaromaticity-promoted dihydrogen activation,CO_(2)capture,and oxygen reduction reactions will be also briefly discussed.Finally,caution must be cast as the magnitude of the aromaticity in the transition states is not particularly high in most cases.Thus,a proof of an adequate electron delocalization rather than a complete ring current is recommended to support the relatively weak aromaticity in these transition states.展开更多
Understanding the structure-property relationships in polycyclic conjugated hydrocarbons(PCHs)is crucial in controlling their electronic properties and developing new optically functional materials.Aromaticity is a fu...Understanding the structure-property relationships in polycyclic conjugated hydrocarbons(PCHs)is crucial in controlling their electronic properties and developing new optically functional materials.Aromaticity is a fundamentally important and intriguing property of numerous organic chemical structures and has stimulated a myriad of experimental and theoretical investigations.Exploiting aromaticity rules for the rational design of optoelectronic materials with the desired photophysical characteristics is a challenging yet fascinating task.Herein we present an in-depth computational and spectroscopic study on the structure-property relationships of dinaphthopentalenes(DNPs).Results highlight that the different fusion patterns between 4nπand 4n+2πunits endow these PCHs with the tunable aromaticity in the ground state/excited state,which leads to the diverse electronic structures and consequently the distinctive excited state photophysics.Accordingly,we propose a combined aromaticity design strategy for rationally modulating and tailoring electronic and optical properties of PCH skeletons.These outcomes not only present a full picture of the excited state dynamics of the DNP system and afford a new class of efficient singlet fission-active materials but also provide some basic guidelines for exploiting aromaticity rules to design and develop new optical function materials.展开更多
During the past few years we have carried out in our Institute and Research Laboratory a series of systematic crystal structure analyses and chemical reactivity. studies on
The Hückel’s rule,Baird’s rule,and electronic shell closure model are classical and well-established concepts in chemistry,which have long been employed in rationalizing the aromaticity/antiaromaticity of organ...The Hückel’s rule,Baird’s rule,and electronic shell closure model are classical and well-established concepts in chemistry,which have long been employed in rationalizing the aromaticity/antiaromaticity of organic species and stability of inorganic clusters.Thus,the observation of unique species featuring properties out of the fundamental frameworks of these rules is challenging but significant and helps in drawing a complete picture of fascinating concepts in chemistry.展开更多
The measurement of aromaticity in biochars is generally conducted using solid state 13C nuclear magnetic resonance spectroscopy,which is expensive,time-consuming,and only accessible in a small number of researchintens...The measurement of aromaticity in biochars is generally conducted using solid state 13C nuclear magnetic resonance spectroscopy,which is expensive,time-consuming,and only accessible in a small number of researchintensive universities.Mathematical modelling could be a viable alternative to predict biochar aromaticity from other much easier accessible parameters(e.g.elemental composition).In this research,Genetic Programming(GP),an advancedmachine learning method,is used to develop newpredictionmodels.In order to identify and evaluate the performance of prediction models,an experimental data set with 98 biochar samples collected from the literature was utilized.Due to the benefits of the intelligence iteration and learning of GP algorithm,a kind of underlying exponential relationship between the elemental compositions and the aromaticity of biochars is disclosed clearly.The exponential relationship is clearer and simpler than the polynomial mapping relationships implicated by Maroto-Valer,Mazumdar,and Mazumdar-Wang models.In this case,a novel exponential model is proposed for the prediction of biochar aromaticity.The proposed exponential model appears better prediction accuracy and generalization ability than existing polynomial models during the statistical parameter evaluation.展开更多
An octahedral Nb6 structural unit with space aromaticity is identified for the first time in a transition–metal monoxide crystal Nb3O3 by ab initio calculations.The strong Nb–Nb metallic bonding facilitates the form...An octahedral Nb6 structural unit with space aromaticity is identified for the first time in a transition–metal monoxide crystal Nb3O3 by ab initio calculations.The strong Nb–Nb metallic bonding facilitates the formation of stable octahedral Nb6 structural units and the release of delocalization energy.Moreover,the Nb atoms in continuously connected Nb6 structural units share their electrons with each other in a continuous space of framework,so that the electrons are uniformly distributed.The newly discovered aromaticity in the octahedral Nb6 structural units extends the range of aromatic compounds and broadens our vision in structural chemistry.展开更多
The dynamic transformations of conformations and aromatic properties of [32]octaphyrins（1.0.1.0.1.0.1.0） through rotating the pyrrolic ring of the macrocycles are demonstrated by theoretical simulations in CH2Cl2 so...The dynamic transformations of conformations and aromatic properties of [32]octaphyrins（1.0.1.0.1.0.1.0） through rotating the pyrrolic ring of the macrocycles are demonstrated by theoretical simulations in CH2Cl2 solution. Facile multistep isomeriza- tions involving antiaromatic-Htickel and aromatic-Mobius topologies were also predicted by density functional theory （DFT）. The understanding of changes in topologies and aromaticities of free-base expanded porphrins may provide useful information to build new macrocycles with unique properties.展开更多
Theoretical calculations of Double Hanging Ring Molecule(DHRM) [(GnHn-1^m)(GnHn-1^m)](G=C,Si,Ge;n=3,5,6,7,8;m=+1,-1,0,+1,+2) were performed via Gaussian 09 with the method of Density Functional Theory(DFT). Geometrica...Theoretical calculations of Double Hanging Ring Molecule(DHRM) [(GnHn-1^m)(GnHn-1^m)](G=C,Si,Ge;n=3,5,6,7,8;m=+1,-1,0,+1,+2) were performed via Gaussian 09 with the method of Density Functional Theory(DFT). Geometrical optimization, Potential Energy surface Scan(PES), Degree of Aromaticity(DOA) and Nucleus Independent Chemical Shift(NICS) were computed to study the optimal structures and aromaticity of DHRMs. Ring Stretching Vibration Raman Spectroscopy(RSVRSF) was predicted to seek the relation between RSVRSF and aromaticity of DHRMs. The results show optimal structures of DHRMs[(GnH(n-1)~m)(GnH(n–1)~m)](n = 3, 5~8);DA = 90° is the stable structure when n = 3, 7, 8;while n = 5 corresponds to DA = 30°, n = 6 corresponds to DA = 50°;the correlation between DOA and NICS of DHRMs is quadratic;the value of RSVRSF of DHRM approximates to its corresponding single ring molecule, which could act as characteristic frequency of ring molecule to identify its aromaticity;the correlation between RSVRSF and DOA is quadratic, and that between RSVRSF and NICS is linear.展开更多
The localized molecular orbitals and energy levels for four typical conjugated six-membered ring systems C_6H_6, C_3N_3H_3, B_3N_3H_6, and (B_3O_6)^(3-) as well as a non-aromatic reference molecule N_3Cl_6 have been ...The localized molecular orbitals and energy levels for four typical conjugated six-membered ring systems C_6H_6, C_3N_3H_3, B_3N_3H_6, and (B_3O_6)^(3-) as well as a non-aromatic reference molecule N_3Cl_6 have been calculated by using Edmiston-Ruedenberg energy localization technique under the CNDO/2 approximation in order to investigate the nature of aromaticity or quasi-aromaticity of the six-membered ring systems studied. The contour maps for π-type localized MO's (LMO) have been plotted to illustrate the bonding characteristics of the five ring systems studied. These LMO calculations show that for all the conjugated six-membered ring systems considered there exists local delocalization of π-bonds or three-centered and occasionally four-centered two-electron π-bonds in our terminology, and the cooperative effect among these π-bonds leading to the formation of a closed continuous x-conjugation system around the ring, which is necessary for the creation of aromaticity in the systems studied. We have been able to discuss the properties of these three-centered π-bonds in terms of the constituent atoms and electrons and the relevant orbitals involved.展开更多
Results of ab initio self-consistent-field (SCF) and density functional theory (DFT) calculations of the gas-phase structure, acidity (free energy of deprotonation, ΔG*) and aromaticity of tetraselenosquaric acid (3,...Results of ab initio self-consistent-field (SCF) and density functional theory (DFT) calculations of the gas-phase structure, acidity (free energy of deprotonation, ΔG*) and aromaticity of tetraselenosquaric acid (3, 4-diselenyl-3-cyclobutene-1,2-diselenone, H2 C4 Se4)are reported. The global minimum found on the potential energy surface of tetraselenosquaric acid presents a planar conformation. The ZZ isomer was found to have the lowest energy among the three planar conformers and the ZZ and ZE isomers are very dose in energy. The optimized geometric parameters exhibit a bond length equalization relative to reference compounds, cyclobutanediselenone, and cyclobutanediselenol. The computed aromatic stabilization energy (ASE) by homodesmotic reaction is -77.4 (MP2(fu)/6–311+G** /RHF/6 - 311 + G** ) and - 54.8 kJ/mol (B3LYP/6 - 311 + G** //B3LYP/6 -311 + G**). The aromaticity of tetraselenosquaric acid is indicated by the calculated diamagnetic susceptibility exaltation (A) -19.13 (CSGT(IGAIM)-RHF/6–311 + G**// RHF/6–311 + G** and -32.91 (4π·10?6 m?3/mol)(CSGT(I-GAIM)-B3LYP/6 - 311 + G* * //B3LYP/6 - 311 + G**). Thus, tetraselenosquaric acid fulfils the geometric, energetic and magnetic criteria of aromaticity. The calculated gas-phase acidity is ΔG1*(298k) = 1257.7 and ΔG*2 (298k) = 1617.1 kJ/mol. Hence, tetraselenosquaric acid is the strongest acid among the three squaric acids (3, 4-dihydroxy-3-cyclobutene-1, 2-dione, H2 C4 3,4-dithiohydroxy-3-cyclobutene-1,2-dithione, H2C4 S4, 3, 4-diselenyl-3-cyclobutene-1,2-diselenone, H2C4Se4).展开更多
Novel benzo-bridged hexaphyrin(2.1.2.1.2.1)and its copper complex were synthesized.Single-crystal structures showed typical figure-of-eight Huckel topologies.NMR,NICS,HOMA,ACID,and EDDB analysis supported their non-ar...Novel benzo-bridged hexaphyrin(2.1.2.1.2.1)and its copper complex were synthesized.Single-crystal structures showed typical figure-of-eight Huckel topologies.NMR,NICS,HOMA,ACID,and EDDB analysis supported their non-aromatic properties owning to the strong local aromatic benzo rings cutting the global aromatic ring of the benzo-bridged figure-of-eight hexaphyrin(2.1.2.1.2.1).The redox properties and degenerate HOMOs and LUMOs levels indicate multielectron donating and accepting abilities.展开更多
Aromaticity has always been an intriguing chemistry topic,which is considered to have close relations with materials'stability and chemical reactivity due to special energy profiles.For conjugated cycles,Hück...Aromaticity has always been an intriguing chemistry topic,which is considered to have close relations with materials'stability and chemical reactivity due to special energy profiles.For conjugated cycles,Hückel's rule,proposed in 1931,suggests that annulenes having[4n+2]and[4n]πelectrons present aromatic and antiaromatic characters with closed and open electronic configurations,respectively[1].展开更多
基金supported by the National Natural Science Foundation of China (No. 21971118 to Z.M. Sun and21573179 to J. Zhu)the Natural Science Foundation of Tianjin City (No. 20JCYBJC01560)。
文摘We report the first disubstituted hetero-ten-vertex closo cluster [(CrGe_(9))Cr_(2)(CO)_(13)]^(4-)with three adjacent Cr(CO);units adopting both η^(5) and η^(1) coordination modes,which was synthesized through the reaction of "KGe;" with(MeCN)_(3)Cr(CO)_(4)and Cr(CO)_(6)in ethylenediamine(en) solution.In contrast to the η^(1)-Cr atoms forming localized two-center two-elelctron(2 c-2 e) Cr-Ge bonds,the hetero atom η^(5)-Cr exhibits versatile bonding mechanisms including three 5 c-2 e and five 8 c-2 e delocalized bonds which account for Hückel aromaticity.Intricate multi-center bonding patterns delineate the multiple local σ-aromatic characters of the title cluster displaying explicit spherical aromaticity.
基金the National Nature Science Foundation of China(Nos.21672006,21672007 and 21871006)for supporting this work
文摘Novel expanded porphyrinoids with advanced structure features(such as multiple-inner-ring-fusion)have a wide range of benefits(such as multi-metal coordination and facile tunable aromaticity)not offered by their normal porphyrin analogues,and have found wide applications as sensors,fluorescent probes,novel ligands and functionalized NIR organic dyes in various research fields.However,the structures of these expanded porphyrinoids are scarce due to their limited synthetic accessibility.Herein,we summarized the lately reported efficient synthesis of novel expanded porphyrinoids with multipleinner-ring-fusion(up to six-inner-ring-fusion)and smaragdyrins with tunable aromaticity.Their synthesis is either based on an oxidative ring cyclization on linear/macrocyclic oligopyrroles containing N-confused pyrrole unit(s)or a straightforward double SNAr reaction on readily available 3,5-dibromoBODIPY,respectively.
文摘We use density functional theory and time-dependent together with a set of extensive mul- tidimensional visualization techniques to characterize the influence of keto effect on charge distribution at ground state and electronic transitions for neutral and charged hexaphyrin aromaticity with and without keto-defect. It is found that the aromaticity is the key fac- tor to influence the ground state Mulliken charges distribution properties, other than the meso-aryl-substituted effect. But with the enhancement of the keto-defect, the distribution changes of Mulliken charges on the hexaphyrin groups are larger than those on the pentaflu- orophenyl substituted groups, following with the aromaticity changes from nonaromatic to aromatic. Furthermore, through characterizing by transition density and charge difference density, direct visual evidence for neutral and charged aromaticity with and without keto- defect can be clearly derived, and the ability of charge transfer between units of monoradical （nonaromaticity） and singlet biradical （aromaticity） forms is much stronger than that of neutral forms.
基金supported by the 111 Project B07012 of China and the National Natural Science Foundation of China (No.20773014)
文摘Clusters XY2Z species are theoretically investigated with density functional theory （DFT） method. The results show that for LiP2C, LiAs2Ge and KAs2C species, the C2v isomer is the most stable planar structure, while for other species the Cs isomer is the most stable planar structure at the B3LYP/6-311＋G＊ level. Wiberg Bond Index （WBI） and Nucleus-Independent Chemical Shift （NICS） values indicate the existence of delocalization in stable planar structures. A detailed Molecular Orbital （MO） analysis further reveals that planar isomers of these species have strong aromatic character, which strengthens the structural stability and makes them closely connect with the concept of aromaticity.
基金supported by the National Key R&D Program of China(No.2018YFE0115000)the Natural Science Foundation of Tianjin City(No.19JCYBJC19600)。
文摘The simple homodinuclear M-M single bonds for group II and XII elements are difficult to obtain as a result of the fulfilled s2electronic configurations,consequently,a dicationic prototype is often utilized to design the M^+-M^+single bond.Existing studies generally use sterically bulky organic ligands L^-to synthesize the compounds in the L^--M^+-M^+-L-manner.However,here we report the design of Mg-Mg and Zn-Zn single bonds in two ligandless clusters,Mg2B7-and Zn2B7-,using density functional theory methods.The global minima of both of the clusters are in the form of M2^2+(B7^3-),where the M-M single bonds are positioned above a quasi-planar hexagonal B7 moiety.Chemical bonding analyses further confirm the existence of Mg-Mg and Zn-Zn single bonds in these clusters,which are driven by the unusually stable B7^3-moiety that is bothσandπaromatic.Vertical detachment energies of Mg2B7-and Zn2B7-are calculated to be 2.79 e V and 2.94 e V,respectively,for the future comparisons with experimental data.
基金This work was financially supported by NNSFC (20471034) and the Youth Foundation of Shanxi Province (20051011)
文摘The structures, energies and aromaticity （the nuclear-independent chemical shifts,NICS） of AlCO-substituted semibullvalenes were investigated at the B3LYP/6-311＋G＊＊ level.Similar to BCO-substituted analogues, [2,6]-AlCO-semibullvalene is neutral bishomoaromatic.The NICS values reveal that the aromaticity of AlCO-substituted structures is smaller than that of BCO analogues.
基金supported by the National Natural Science Foundation of China (Nos.21822303,21772020)the Basic and Frontier Research Project of Chongqing Science and Technology Commission (Nos.cstc2018jcyjAX0827)+4 种基金the Project of Science and Technology Collaborative Innovation Platform Construction of Chongqing University of Education (No.2017XJPT01)the Project of Scientific and Technological Research Program of Chongqing Municipal Education Commission (No.KJQN201801603)the Cultivation for National Science Foundation of Chongqing University of Education (No.18GZKP01)funded by Children’s Research Institute of National Center for Schooling Development Programme and Chongqing University of Education (No. CRIKT201909)the Fundamental Research Funds for the Central Universities (Chongqing University,No.2018CDPTCG0001/4)
文摘Alkaline-earth(Ae) metals have attracted a wealth of interdependent research from synthetic chemists.In Ae-catalyzed organometallic reactions,β-diketiminate is a typical ligand used to stabilize Ae catalysts by forming six-membered rings comprising Ae metals.Herein,studies focusing on the configuration of β-diketiminate-coordinated Ae compounds observed that the C-C and C-N bonds are homogeneous and unchanged.Furthermore,energetic studies observed that the formation of the Ae-incorporated sixmembered rings results in enhanced stability of>20 kcal/mol.The nucleus-independent chemical shifts,anisotropy of the induced current density,and molecular orbital analyses demonstrated the nonaromaticity of the β-diketiminate-coordinated Ae compounds.The improved stability of these compounds can be explained by the delocalization of the π electrons derived from the β-diketiminate moiety.
文摘The aromaticity of all possible substituted fullerene isomers of C18N2, C18B2, C18BN, and their molecular ions which originate from the C20 （Ih） cage were studied by the topological resonance energy （TRE） and the percentage topological resonance energy methods. The relationship between the aromaticity of C18BxNy isomers and the sites where the heteroatoms dope at the C20 （Ih） cage is discussed. Calculation results show that at the neutral and cationic states all the isomers are predicted to be antiaromatic with negative TREs, but their polyvalent anions are predicted to be aromatic with positive TREs. The most stable isomer is formed by heteroatom doping at the 1,11-sites in C18N2. C18B2, and C18BN. Heterofullerenes are more aromatic than C20. The stability order in the neutral states is C18N2〉C18BN〉C18B2〉C20. The stability order in closed-shell is C18B2^8- 〉C20^6- 〉C18BN^6- 〉C18N2^4-. This predicts theoretically that their polyvalent anions have high aromaticity.
基金the National Natural Science Foundation of China(22073079,22025105 and 21873079)the Ministry of Education of China(H20200504)+2 种基金the Top-Notch Young Talents Program of China is gratefully acknowledgedM.S.thanks the Ministerio de Ciencia e Innovación of Spain(project PID2020-113711GB-I00)the Generalitat de Catalunya(project 2017SGR39).
文摘Aromaticity,in general,can promote a given reaction by stabilizing a transition state or a product via a mobility ofπelectrons in a cyclic structure.Similarly,such a promotion could be also achieved by destabilizing an antiaromatic reactant.However,both aromaticity and transition states cannot be directly measured in experiment.Thus,computational chemistry has been becoming a key tool to understand the aromaticity-driven reaction mechanisms.In this review,we will analyze the relationship between aromaticity and reaction mechanism to highlight the importance of density functional theory calculations and present it according to an approach via either aromatizing a transition state/product or destabilizing a reactant by antiaromaticity.Specifically,we will start with a particularly challenging example of dinitrogen activation followed by other small-molecule activation,Csingle bondF bond activation,rearrangement,as well as metathesis reactions.In addition,antiaromaticity-promoted dihydrogen activation,CO_(2)capture,and oxygen reduction reactions will be also briefly discussed.Finally,caution must be cast as the magnitude of the aromaticity in the transition states is not particularly high in most cases.Thus,a proof of an adequate electron delocalization rather than a complete ring current is recommended to support the relatively weak aromaticity in these transition states.
基金supported by the National Natural Science Foundation of China(grant nos.22005210,21833005,and 22231009).
文摘Understanding the structure-property relationships in polycyclic conjugated hydrocarbons(PCHs)is crucial in controlling their electronic properties and developing new optically functional materials.Aromaticity is a fundamentally important and intriguing property of numerous organic chemical structures and has stimulated a myriad of experimental and theoretical investigations.Exploiting aromaticity rules for the rational design of optoelectronic materials with the desired photophysical characteristics is a challenging yet fascinating task.Herein we present an in-depth computational and spectroscopic study on the structure-property relationships of dinaphthopentalenes(DNPs).Results highlight that the different fusion patterns between 4nπand 4n+2πunits endow these PCHs with the tunable aromaticity in the ground state/excited state,which leads to the diverse electronic structures and consequently the distinctive excited state photophysics.Accordingly,we propose a combined aromaticity design strategy for rationally modulating and tailoring electronic and optical properties of PCH skeletons.These outcomes not only present a full picture of the excited state dynamics of the DNP system and afford a new class of efficient singlet fission-active materials but also provide some basic guidelines for exploiting aromaticity rules to design and develop new optical function materials.
文摘During the past few years we have carried out in our Institute and Research Laboratory a series of systematic crystal structure analyses and chemical reactivity. studies on
基金supported by the Taishan Scholars Project of Shandong Province(no.ts201712011)the National Natural Science Foundation of China(NSFC)(nos.21603119 and 21705093)+4 种基金the Natural Science Foundation of Shandong Province(nos.ZR2017BB061 and ZR2016BQ09)the Natural Science Foundation of Jiangsu Province(no.BK20170396)the Project for Scientific Research Innovation Team of Young Scholar in Colleges and Universities of Shandong Province(no.2019KJC025)the Young Scholars Program of Shandong University(YSPSDU)(no.2018WLJH48)the Qilu Youth Scholar Funding of Shandong University,and the Fundamental Research Funds of Shandong University(no.2017TB003).
文摘The Hückel’s rule,Baird’s rule,and electronic shell closure model are classical and well-established concepts in chemistry,which have long been employed in rationalizing the aromaticity/antiaromaticity of organic species and stability of inorganic clusters.Thus,the observation of unique species featuring properties out of the fundamental frameworks of these rules is challenging but significant and helps in drawing a complete picture of fascinating concepts in chemistry.
文摘The measurement of aromaticity in biochars is generally conducted using solid state 13C nuclear magnetic resonance spectroscopy,which is expensive,time-consuming,and only accessible in a small number of researchintensive universities.Mathematical modelling could be a viable alternative to predict biochar aromaticity from other much easier accessible parameters(e.g.elemental composition).In this research,Genetic Programming(GP),an advancedmachine learning method,is used to develop newpredictionmodels.In order to identify and evaluate the performance of prediction models,an experimental data set with 98 biochar samples collected from the literature was utilized.Due to the benefits of the intelligence iteration and learning of GP algorithm,a kind of underlying exponential relationship between the elemental compositions and the aromaticity of biochars is disclosed clearly.The exponential relationship is clearer and simpler than the polynomial mapping relationships implicated by Maroto-Valer,Mazumdar,and Mazumdar-Wang models.In this case,a novel exponential model is proposed for the prediction of biochar aromaticity.The proposed exponential model appears better prediction accuracy and generalization ability than existing polynomial models during the statistical parameter evaluation.
基金financially supported by National Key R&D Program of China(2016YFB0700600)Soft Science Research Project of Guangdong Province(2017B030301013)Shenzhen Science and Technology Research Grant(ZDSYS201707281026184).
文摘An octahedral Nb6 structural unit with space aromaticity is identified for the first time in a transition–metal monoxide crystal Nb3O3 by ab initio calculations.The strong Nb–Nb metallic bonding facilitates the formation of stable octahedral Nb6 structural units and the release of delocalization energy.Moreover,the Nb atoms in continuously connected Nb6 structural units share their electrons with each other in a continuous space of framework,so that the electrons are uniformly distributed.The newly discovered aromaticity in the octahedral Nb6 structural units extends the range of aromatic compounds and broadens our vision in structural chemistry.
基金supported by the National Basic Research Program of China(2011CB808600)the National Natural Science Foundation of China(21273102)
文摘The dynamic transformations of conformations and aromatic properties of [32]octaphyrins（1.0.1.0.1.0.1.0） through rotating the pyrrolic ring of the macrocycles are demonstrated by theoretical simulations in CH2Cl2 solution. Facile multistep isomeriza- tions involving antiaromatic-Htickel and aromatic-Mobius topologies were also predicted by density functional theory （DFT）. The understanding of changes in topologies and aromaticities of free-base expanded porphrins may provide useful information to build new macrocycles with unique properties.
基金Supported by the National Natural Science Foundation of China(No.21563023)the Graduate Education Innovation Program funded Projects of Inner Mongolia(No.S20161013506)inner Mongolia Normal University Graduate Students'Research&Innovation Fund(No.CXJJS16090)。
文摘Theoretical calculations of Double Hanging Ring Molecule(DHRM) [(GnHn-1^m)(GnHn-1^m)](G=C,Si,Ge;n=3,5,6,7,8;m=+1,-1,0,+1,+2) were performed via Gaussian 09 with the method of Density Functional Theory(DFT). Geometrical optimization, Potential Energy surface Scan(PES), Degree of Aromaticity(DOA) and Nucleus Independent Chemical Shift(NICS) were computed to study the optimal structures and aromaticity of DHRMs. Ring Stretching Vibration Raman Spectroscopy(RSVRSF) was predicted to seek the relation between RSVRSF and aromaticity of DHRMs. The results show optimal structures of DHRMs[(GnH(n-1)~m)(GnH(n–1)~m)](n = 3, 5~8);DA = 90° is the stable structure when n = 3, 7, 8;while n = 5 corresponds to DA = 30°, n = 6 corresponds to DA = 50°;the correlation between DOA and NICS of DHRMs is quadratic;the value of RSVRSF of DHRM approximates to its corresponding single ring molecule, which could act as characteristic frequency of ring molecule to identify its aromaticity;the correlation between RSVRSF and DOA is quadratic, and that between RSVRSF and NICS is linear.
文摘The localized molecular orbitals and energy levels for four typical conjugated six-membered ring systems C_6H_6, C_3N_3H_3, B_3N_3H_6, and (B_3O_6)^(3-) as well as a non-aromatic reference molecule N_3Cl_6 have been calculated by using Edmiston-Ruedenberg energy localization technique under the CNDO/2 approximation in order to investigate the nature of aromaticity or quasi-aromaticity of the six-membered ring systems studied. The contour maps for π-type localized MO's (LMO) have been plotted to illustrate the bonding characteristics of the five ring systems studied. These LMO calculations show that for all the conjugated six-membered ring systems considered there exists local delocalization of π-bonds or three-centered and occasionally four-centered two-electron π-bonds in our terminology, and the cooperative effect among these π-bonds leading to the formation of a closed continuous x-conjugation system around the ring, which is necessary for the creation of aromaticity in the systems studied. We have been able to discuss the properties of these three-centered π-bonds in terms of the constituent atoms and electrons and the relevant orbitals involved.
基金Project supported by the Natural Science Foundation of Fujian Province
文摘Results of ab initio self-consistent-field (SCF) and density functional theory (DFT) calculations of the gas-phase structure, acidity (free energy of deprotonation, ΔG*) and aromaticity of tetraselenosquaric acid (3, 4-diselenyl-3-cyclobutene-1,2-diselenone, H2 C4 Se4)are reported. The global minimum found on the potential energy surface of tetraselenosquaric acid presents a planar conformation. The ZZ isomer was found to have the lowest energy among the three planar conformers and the ZZ and ZE isomers are very dose in energy. The optimized geometric parameters exhibit a bond length equalization relative to reference compounds, cyclobutanediselenone, and cyclobutanediselenol. The computed aromatic stabilization energy (ASE) by homodesmotic reaction is -77.4 (MP2(fu)/6–311+G** /RHF/6 - 311 + G** ) and - 54.8 kJ/mol (B3LYP/6 - 311 + G** //B3LYP/6 -311 + G**). The aromaticity of tetraselenosquaric acid is indicated by the calculated diamagnetic susceptibility exaltation (A) -19.13 (CSGT(IGAIM)-RHF/6–311 + G**// RHF/6–311 + G** and -32.91 (4π·10?6 m?3/mol)(CSGT(I-GAIM)-B3LYP/6 - 311 + G* * //B3LYP/6 - 311 + G**). Thus, tetraselenosquaric acid fulfils the geometric, energetic and magnetic criteria of aromaticity. The calculated gas-phase acidity is ΔG1*(298k) = 1257.7 and ΔG*2 (298k) = 1617.1 kJ/mol. Hence, tetraselenosquaric acid is the strongest acid among the three squaric acids (3, 4-dihydroxy-3-cyclobutene-1, 2-dione, H2 C4 3,4-dithiohydroxy-3-cyclobutene-1,2-dithione, H2C4 S4, 3, 4-diselenyl-3-cyclobutene-1,2-diselenone, H2C4Se4).
基金partly supported by the National Natural Science Foundation of China(No.22301108)the Project Startup Foundation for Distinguished Scholars of Jiangsu University(Nos.4111310026 and 5501310014).
文摘Novel benzo-bridged hexaphyrin(2.1.2.1.2.1)and its copper complex were synthesized.Single-crystal structures showed typical figure-of-eight Huckel topologies.NMR,NICS,HOMA,ACID,and EDDB analysis supported their non-aromatic properties owning to the strong local aromatic benzo rings cutting the global aromatic ring of the benzo-bridged figure-of-eight hexaphyrin(2.1.2.1.2.1).The redox properties and degenerate HOMOs and LUMOs levels indicate multielectron donating and accepting abilities.
基金supported by the National Natural Science Foundation of China(No.22073045 to H.Ma and Nos.22173114 and 22333003 to Y.Ma)Strategic Priority Research Program of Chinese Academy of Sciences(XDB0500001)Youth Innovation Promotion Association of Chinese Academy of Sciences(No.2022168)
文摘Aromaticity has always been an intriguing chemistry topic,which is considered to have close relations with materials'stability and chemical reactivity due to special energy profiles.For conjugated cycles,Hückel's rule,proposed in 1931,suggests that annulenes having[4n+2]and[4n]πelectrons present aromatic and antiaromatic characters with closed and open electronic configurations,respectively[1].
