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 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
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
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
Singlet fission(SF)offers the potential to improve the efficiency of photovoltaic devices(PVs)by harnessing high-energy photons to produce doubled photocurrents.However,progress in SF-based PVs is hindered by limited ...Singlet fission(SF)offers the potential to improve the efficiency of photovoltaic devices(PVs)by harnessing high-energy photons to produce doubled photocurrents.However,progress in SF-based PVs is hindered by limited SF materials as a result of stringent requirements for atypical energetic arrangement and high ambient stability.Here we show that excited-state antiaromaticity(ESAA)relief can be used to simultaneously regulate the energy separation between T_(1) and S_(0) and design SF-capable materials with favorable energetic conditions and excellent stability.We achieve this by facilitatingπ-electron migration between the seven-and fivemembered rings in acepleiadylene(APD),which alleviates Baird’s antiaromaticity in the T_(1) state while maintaining Hückel’s aromaticity in S_(0).This leads to a lowered T_(1)’s energy relative to S_(0).Aromaticity index calculations reveal the aromaticity reversal and electron density redistribution between S_(0) and T_(1) to mitigate ESAA.This results in an energetic relationship suitable for SF,enabling a rapid fission process with an impressive yield of 165%.Moreover,ESAA relief endows APD with superior stability under ambient conditions.Our work not only introduces a new SF scaffold based on nonbenzenoid hydrocarbons,but it also provides valuable insights for the design of stable SF-active materials.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
This study presents a thorough investigation into the use of single and twin-tailed cationic and anionic surfactant-modified chitosan(SMCS)hydrogel beads as effective adsorbents for the elimination of hazardous polycy...This study presents a thorough investigation into the use of single and twin-tailed cationic and anionic surfactant-modified chitosan(SMCS)hydrogel beads as effective adsorbents for the elimination of hazardous polycyclic aromatic hydrocarbons(PAHs)from aqueous solutions.The Chitosan(CS)hydrogel beads were modified with single/twin-tailed anionic surfactants,sodium dodecyl sulfate(SDS)and sodium bis(2-ethylhexyl)sulfosuccinate(AOT),and cationic surfactants,dodecyltrimethylammonium bromide(DTAB)and didodecyldimethylammonium bromide(DDAB),to enhance their adsorption capacity of PAHs.The CS and SMCS beads were evaluated for their structural,mechanical,and adsorption properties using a range of techniques,including infrared spectroscopy(IR),energy-dispersive X-ray spectroscopy(EDX),rheometry,and field emission scanning electron microscopy(FESEM).Adsorption experiments of naphthalene(Nap),acenaphthene(Ace),and phenanthrene(Phe)on SMCS beads demonstrate that they have significantly higher adsorption capacities than CS beads,due to increase in hydrophobic interactions.Adsorption capacity followed the trend,Phen>Ace>Nap for all the beads revealing that twin-tailed SMCS bead possess much higher adsorption capacities(Qmax)compared to single-tailed SMCS beads.For twin tailed surfactants,the maximum adsorption capacities for Nap,Ace and Phe varied as CS-AOT(CS-DDAB):430.0(323.8)611.60(538.18)633.39(536.99)mg/g respectively,outperforming other reported hydrogel beads.The study highlights the simplicity,eco-friendliness,and enhanced performance of surfactant modification for developing high-efficiency adsorbents,paving the way for cost-effective solutions in water re-mediation.展开更多
Along with decrease of fine particulate matter(PM_(2.5))concentration in recent years in China,secondary species become increasingly important.This work focuses on characterizing secondary components,and a few importa...Along with decrease of fine particulate matter(PM_(2.5))concentration in recent years in China,secondary species become increasingly important.This work focuses on characterizing secondary components,and a few important groups of organics including organic nitrogen(ON),organonitrates(OrgN),organosulfates(OS)and polycyclic aromatic hydrocarbons(PAHs),via online measurement of submicron aerosols(PM_(1))in Nanjing,China,during 2022 summer.The average PM_(1) concentration was 15.39μg/m^(3),dominated by secondary components(69.1%),which were even more important at higher PM_(1) levels.The primary organic aerosols(POA)were from traffic,industry and cooking;the two secondary OA factors were both closely linked with photochemistry,with one(OOA1)being relatively fresh and important in early afternoon and another(OOA2)being aged and important in late afternoon.Sulfate formation was also governed by photochemistry but resembled that of OOA2 not OOA1;nitrate formation was associated strongly with heterogeneous hydrolysis and thermodynamic equilibrium.Results also reveal a possible photochemical reaction channel from POA to OOA1,then to OOA2.Case studies show that formations of secondary components responded differently to different weather conditions and governed summer PM_(1) pollution.The average ON,OrgN,OS and PAHs concentrations were determined to be 122.8,84.4,45.6 and 3.3 ng/m^(3),respectively.ON was dominated by primary sources(53.8%).OrgN varied similarly to nitrate.OS formation was linked with aqueous-phase reactions,which were insignificant therefore its level was low.PAHs was mainly from traffic,and photochemical oxidation might be its important sink during afternoon.展开更多
Despite the widespread presence and frequent detection of polycyclic aromatic hydrocarbons(PAHs)in various aspects of life,there is limited research on their exposure levels in pregnant women and cumulative exposure f...Despite the widespread presence and frequent detection of polycyclic aromatic hydrocarbons(PAHs)in various aspects of life,there is limited research on their exposure levels in pregnant women and cumulative exposure from the living environment.This study included 1311 women in late pregnancy from the Zunyi birth cohort and measured the urinary concentrations of 10 hydroxylated PAH metabolites(OH-PAHs).Risk assessment was conducted based on the estimated daily intake to calculate the hazard quotient and hazard index(HI).A linear regression model was used to analyze the relationship between creatinine-adjusted OH-PAHs concentrations and living environment and lifestyle factors,while principal component analysis was applied to trace the sources of PAHs exposure.1-OHPYR was detected in all participants’urine,with naphthalene metabolites having the highest concentrations among creatinine-adjusted PAHs.OH-PAHs concentrations were associated with housing type,room number,cooking frequency,household size,exercise frequency,fuel type,distance from main road,and drinking water source.Pregnant women using traditional fuels and living in bungalows had higher health risks than those using clean energy and living in buildings.Those living within 100 m of a main road had higher HI than those farther away.Coal combustion was identified as the primary source of PAHs exposure.The study emphasizes the importance of reducing PAHs exposure,especially for pregnant women living in polluted environments.It recommends public health interventions such as improving indoor ventilation and providing clean energy to reduce related health risks.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 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supported by the National Natural Science Foundation of China(grant nos.22173062,21833005,22090022,and 22275125)the Beijing Natural Science Foundation of China(grant nos.Z230019 and 2212005)the Youth Innovative Research Team of Capital Normal University.
文摘Singlet fission(SF)offers the potential to improve the efficiency of photovoltaic devices(PVs)by harnessing high-energy photons to produce doubled photocurrents.However,progress in SF-based PVs is hindered by limited SF materials as a result of stringent requirements for atypical energetic arrangement and high ambient stability.Here we show that excited-state antiaromaticity(ESAA)relief can be used to simultaneously regulate the energy separation between T_(1) and S_(0) and design SF-capable materials with favorable energetic conditions and excellent stability.We achieve this by facilitatingπ-electron migration between the seven-and fivemembered rings in acepleiadylene(APD),which alleviates Baird’s antiaromaticity in the T_(1) state while maintaining Hückel’s aromaticity in S_(0).This leads to a lowered T_(1)’s energy relative to S_(0).Aromaticity index calculations reveal the aromaticity reversal and electron density redistribution between S_(0) and T_(1) to mitigate ESAA.This results in an energetic relationship suitable for SF,enabling a rapid fission process with an impressive yield of 165%.Moreover,ESAA relief endows APD with superior stability under ambient conditions.Our work not only introduces a new SF scaffold based on nonbenzenoid hydrocarbons,but it also provides valuable insights for the design of stable SF-active materials.
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.
基金the Department of Science and Technology(DST),Govt.of India for providing funds under the FIST program and PURSE grant vide No.SR/PURSE/2020/31 to the department of Chemistry,University of Kashmir.
文摘This study presents a thorough investigation into the use of single and twin-tailed cationic and anionic surfactant-modified chitosan(SMCS)hydrogel beads as effective adsorbents for the elimination of hazardous polycyclic aromatic hydrocarbons(PAHs)from aqueous solutions.The Chitosan(CS)hydrogel beads were modified with single/twin-tailed anionic surfactants,sodium dodecyl sulfate(SDS)and sodium bis(2-ethylhexyl)sulfosuccinate(AOT),and cationic surfactants,dodecyltrimethylammonium bromide(DTAB)and didodecyldimethylammonium bromide(DDAB),to enhance their adsorption capacity of PAHs.The CS and SMCS beads were evaluated for their structural,mechanical,and adsorption properties using a range of techniques,including infrared spectroscopy(IR),energy-dispersive X-ray spectroscopy(EDX),rheometry,and field emission scanning electron microscopy(FESEM).Adsorption experiments of naphthalene(Nap),acenaphthene(Ace),and phenanthrene(Phe)on SMCS beads demonstrate that they have significantly higher adsorption capacities than CS beads,due to increase in hydrophobic interactions.Adsorption capacity followed the trend,Phen>Ace>Nap for all the beads revealing that twin-tailed SMCS bead possess much higher adsorption capacities(Qmax)compared to single-tailed SMCS beads.For twin tailed surfactants,the maximum adsorption capacities for Nap,Ace and Phe varied as CS-AOT(CS-DDAB):430.0(323.8)611.60(538.18)633.39(536.99)mg/g respectively,outperforming other reported hydrogel beads.The study highlights the simplicity,eco-friendliness,and enhanced performance of surfactant modification for developing high-efficiency adsorbents,paving the way for cost-effective solutions in water re-mediation.
基金supported by the National Natural Science Foundation of China(Nos.22361162668 and 42021004)the National Key Research and Development Program of China(No.2023YFC3706203).
文摘Along with decrease of fine particulate matter(PM_(2.5))concentration in recent years in China,secondary species become increasingly important.This work focuses on characterizing secondary components,and a few important groups of organics including organic nitrogen(ON),organonitrates(OrgN),organosulfates(OS)and polycyclic aromatic hydrocarbons(PAHs),via online measurement of submicron aerosols(PM_(1))in Nanjing,China,during 2022 summer.The average PM_(1) concentration was 15.39μg/m^(3),dominated by secondary components(69.1%),which were even more important at higher PM_(1) levels.The primary organic aerosols(POA)were from traffic,industry and cooking;the two secondary OA factors were both closely linked with photochemistry,with one(OOA1)being relatively fresh and important in early afternoon and another(OOA2)being aged and important in late afternoon.Sulfate formation was also governed by photochemistry but resembled that of OOA2 not OOA1;nitrate formation was associated strongly with heterogeneous hydrolysis and thermodynamic equilibrium.Results also reveal a possible photochemical reaction channel from POA to OOA1,then to OOA2.Case studies show that formations of secondary components responded differently to different weather conditions and governed summer PM_(1) pollution.The average ON,OrgN,OS and PAHs concentrations were determined to be 122.8,84.4,45.6 and 3.3 ng/m^(3),respectively.ON was dominated by primary sources(53.8%).OrgN varied similarly to nitrate.OS formation was linked with aqueous-phase reactions,which were insignificant therefore its level was low.PAHs was mainly from traffic,and photochemical oxidation might be its important sink during afternoon.
基金supported by the National Key R&D Program of China(Nos.2018YFC1004300 and 2018YFC1004302)the Science&Technology Program of Guizhou Province(Nos.QKHHBZ[2020]3002,QKHPTRC-GCC[2022]039-1 and QKHPTRCCXTD[2022]014)the Scientific Research Program of Guizhou Provincial Department of Education(No.QJJ[2023]019).
文摘Despite the widespread presence and frequent detection of polycyclic aromatic hydrocarbons(PAHs)in various aspects of life,there is limited research on their exposure levels in pregnant women and cumulative exposure from the living environment.This study included 1311 women in late pregnancy from the Zunyi birth cohort and measured the urinary concentrations of 10 hydroxylated PAH metabolites(OH-PAHs).Risk assessment was conducted based on the estimated daily intake to calculate the hazard quotient and hazard index(HI).A linear regression model was used to analyze the relationship between creatinine-adjusted OH-PAHs concentrations and living environment and lifestyle factors,while principal component analysis was applied to trace the sources of PAHs exposure.1-OHPYR was detected in all participants’urine,with naphthalene metabolites having the highest concentrations among creatinine-adjusted PAHs.OH-PAHs concentrations were associated with housing type,room number,cooking frequency,household size,exercise frequency,fuel type,distance from main road,and drinking water source.Pregnant women using traditional fuels and living in bungalows had higher health risks than those using clean energy and living in buildings.Those living within 100 m of a main road had higher HI than those farther away.Coal combustion was identified as the primary source of PAHs exposure.The study emphasizes the importance of reducing PAHs exposure,especially for pregnant women living in polluted environments.It recommends public health interventions such as improving indoor ventilation and providing clean energy to reduce related health risks.
