Diradical polycyclic hydrocarbons(PHs)have unique open-shell structures and interesting physical prop-erties.However,owing to high reactivity of unpaired electrons,such open-shell organic diradicaloids are usually les...Diradical polycyclic hydrocarbons(PHs)have unique open-shell structures and interesting physical prop-erties.However,owing to high reactivity of unpaired electrons,such open-shell organic diradicaloids are usually less stable than closed-shell systems,limiting their practical applications.In this study,we report P=O-attaching of diradical PHs as a new strategy to enhance their stability while maintaining diradi-cal properties.Three P=O-attached PHs containing the indeno[1,2-b]fluorene,fluoreno[3,2-b]fluorene and indeno[2,1-b]fluoreneπ-skeletons,respectively,were designed and synthesized.As theoretically and ex-perimentally proved,two of them have the relatively large diradical characters and open-shell singlet diradical nature.In comparison to their all-carbon analogues,the attached electron-withdrawing P=O groups endow them with much lower LUMO/HOMO energy levels but preserved magnetic activities and physical properties,such as thermally accessible triplet species and multi-redox ability.Moreover,the P=O groups effectively decrease their oxidation activities and thereby lead to their remarkably excellent ambient stabilities.Thus,this P=O-attaching strategy will be applicable to other diradical PH systems and may promote the generation of stable organic diradicaloids for radical chemistry and materials.展开更多
The parent and radical-modified chitin units are computationally studied and the parent chitin unit possesses closed-shell singlet(CS)state as its ground state.Two radicals(CH_(3)·and CH_(3)CH_(2)·)are chose...The parent and radical-modified chitin units are computationally studied and the parent chitin unit possesses closed-shell singlet(CS)state as its ground state.Two radicals(CH_(3)·and CH_(3)CH_(2)·)are chosen to modify the parent chitin unit.Calculations predict that CH_(3)CH_(2)·-modified chitin unit possesses the open-shell broken-symmetry(BS)singlet diradical ground state,different from that CH_(3)·-modified chitin unit is a triplet diradical.That is to say,the magnetic conversion can occur from nonmagnetic exchange coupling to antiferromagnetic(AFM)or ferromagnetic(FM)exchange coupling by means of the radical modification method.The present work helps to get a basic understanding of structures and electronic properties of chitin and its radical-modified derivatives at the atomistic level.Moreover,it also provides a feasible way to design new chitin-based magnetic materials and organic magnetic switches.展开更多
The polarizability（α） and second hyperpolarizability（γ） were systemically investigated for singlet diradical complex involving X（X=B,Al,Ga） atom.The results show that both the α and γ can be effectively tune...The polarizability（α） and second hyperpolarizability（γ） were systemically investigated for singlet diradical complex involving X（X=B,Al,Ga） atom.The results show that both the α and γ can be effectively tuned by varying the distance R（between compound A and a water molecule） and acceptor atom X.The lone pair of electrons from the O atom of the water molecule entered into the vacant p orbital of atom X,which increased the diradical character and led to the increase of the α and γ values.Furthermore,the polarizable continuum model（PCM） was used to test the effects of H2O and CCl4 solvents on the α and γ values.Both the α and γ values of the studied diradical complex 1a（1b,1c） in H2O and CCl4 were uniformly enhanced.And the solvent effects of H2O on either α or γ were larger than those of CCl4.展开更多
The development of efficient and stable perovskite solar cells(PSCs)continues to face commercialization challenges,with long-term operational stability remaining a critical bottleneck despite considerable progress in ...The development of efficient and stable perovskite solar cells(PSCs)continues to face commercialization challenges,with long-term operational stability remaining a critical bottleneck despite considerable progress in power conversion efficiency(PCE).This challenge is particularly pronounced at the hole-selective interface,where high-performance contacts frequently lack the necessary robustness,thereby limiting device reliability and durability.The recent development of stable organic diradical self-assembled monolayers(SAMs)represents a significant advancement in interfacial contact engineering for perovskite devices.展开更多
Open-shell chiral diradicals that feature both the unique chiroptical properties and tunable spin states have kindled numerous interests in organic synthesis and material science.We present a new class of such model s...Open-shell chiral diradicals that feature both the unique chiroptical properties and tunable spin states have kindled numerous interests in organic synthesis and material science.We present a new class of such model systems based on theπ-extended planar chiral pillar[5]arene derivatives P5Flu and P5Cz,where the pillar[5]arene-based chiral scaffolds are coupled with sterically encumbered fluorenyl and carbazolyl moieties as highly luminescent redox-active emitters,respectively.Both molecules in neutral states can readily undergo chemical oxidations leading toπ-conjugated chiral diradicals of the dehydrogenated P5Flu^(2·)and a positively charged dication P5Cz^(2+2)·.Characterization of the resulting Müller’s open-shell species by variable-temperature electron spin resonance(VT-ESR),UV-vis-NIR absorption,VT-NMR and by computational studies revealed a singlet(ΔE_(S-T)=-1.63 kcal mol^(-1))and a nearly degenerate singlet-triplet ground state(ΔE_(S-T)=0.05 kcal mol^(-1),with a diradical character index y0=0.89)for P5Cz^(2+2)·and P5Flu^(2·),respectively.We particularly show in this work a new journey for pillar[5]arenes from the conventionally available closed-shell structures to different open-shell spin states with potential applications in chirospintronics and NIR-active chiroptoelectronic materials.展开更多
Knowledge about electronic structures is important to gain an understanding of the unique functional properties of diradicaloids.In this study,we synthesized and characterized a diradicaloid in which two phenalenyl ra...Knowledge about electronic structures is important to gain an understanding of the unique functional properties of diradicaloids.In this study,we synthesized and characterized a diradicaloid in which two phenalenyl radical sites are coupled antiferromagnetically via a through-space interaction.The results of quantum chemical,physicochemical(^(1)H NMR,electronic absorption,cyclic voltammetry,SQUID,ESR),and chemical reactivity studies show that this diradicaloid has singlet diradical character.An assessment of the nature of the bonding interaction between two radical sites in this species using DFT calculations demonstrates that a small spatial overlap between the two SOMOs in this diradicaloid provides an efficient electron exchange path for the singlet state to be substantially lower in energy than the triplet state.展开更多
Two tetraazacyclophane dications(1^(2+) and 2^(2+)) with different remote substituents have been synthesized, isolated and characterized.Their electronic structures and physical property were studied by various spectr...Two tetraazacyclophane dications(1^(2+) and 2^(2+)) with different remote substituents have been synthesized, isolated and characterized.Their electronic structures and physical property were studied by various spectroscopic techniques, single crystal X-ray diffraction,super conducting quantum interference device(SQUID) measurements and theoretical calculations. The dications have triplet ground states with ferromagnetic interaction exceeding the thermal energy at room temperature. The solid-state structures of these species were tunable by substituent effect, with 1^(2+) as a monomer and 2^(2+) as a dimer.展开更多
Two-electron oxidations of three 1,2-di（bisphenylamino）-benzenes afforded a class of nitrogen analogues of o-quinodimethane. Their elec-tronic structures in the ground state were studied by spectroscopic techniques ...Two-electron oxidations of three 1,2-di（bisphenylamino）-benzenes afforded a class of nitrogen analogues of o-quinodimethane. Their elec-tronic structures in the ground state were studied by spectroscopic techniques including EPR and UV-vis absorption spectroscopy. They have open-shell singlet ground states with thermally accessible triplet states. One of them （12＋2） has been crystalized and isolated. SQUID measurements, single crystal X-ray diffraction and theoretical calculat ons show I has unexpected non-Kekule diradical character, sharply different from o-quinodirnethane.展开更多
By using weakly coordinating anions we succeeded in the stabilization and isolation of two Wfirster＇s blue-based diradicaloid dications with saturated spacers. Their geometries and electronic structures were investig...By using weakly coordinating anions we succeeded in the stabilization and isolation of two Wfirster＇s blue-based diradicaloid dications with saturated spacers. Their geometries and electronic structures were investigated by various experiments in conjunction with DFT calculations. Both one-dimensional alkylate-bridged dications show considerable diradical character with spacer-dependent singlet-triplet energy gaps. One of them displays a much enhanced diradical character and could basically be viewed as a pure diradical with degeneracy of singlet and triplet states.展开更多
Air stable diradicaloid polycyclic aromatic hydrocarbon(PAH)materials possess unique electronic and magnetic properties for various applications.In general,long conjugated distances between two radical centers are req...Air stable diradicaloid polycyclic aromatic hydrocarbon(PAH)materials possess unique electronic and magnetic properties for various applications.In general,long conjugated distances between two radical centers are required to improve the air stability,thereby complicating the synthetic procedures.Herein,the chalcogen containing rubicenes(O-,S-,and Se-rubicenes)were systematically investigated to understand the chalcogen effects on chalcogen-rubicene physicochemical properties.Impressively,these rubicenes presented unprecedented diradical characterwithin one simple benzene ring and excellent air stabilities.Theirdiradicalcharacterweremanifested by single-crystal X-ray studies,variable-temperature nuclear magnetic resonance,and electron spin resonance.Furthermore,the nucleus independent chemical shifts andthe anisotropy of the induced currentdensity calculations revealed that the formation of diradical was caused by a pro-aromaticity driving force.Importantly,the diradical character of rubicenes are visualizedbyFractionalOccupationNumberWeighted Electron Density(FOD)plots,which present high NFOD values from 1.651 to 1.830.This contribution provided distinctive insights into the structure and property relationship of PAH diradicals.展开更多
An unexpected bistricyclic aromatic ene AF was synthesized in a tin(Ⅱ)chloride-mediated reductive aromatization reaction.The obtained AF showed a highly overcrowded structural conformation as revealed by X-ray crysta...An unexpected bistricyclic aromatic ene AF was synthesized in a tin(Ⅱ)chloride-mediated reductive aromatization reaction.The obtained AF showed a highly overcrowded structural conformation as revealed by X-ray crystallography.Interestingly,AF exhibited reversible high-contrast mechanochromism and thermochromism between pale and red color.The obvious chromism is likely ascribed to the conformation transformation and trace amount of diradical species formation upon stimulus.展开更多
Homogeneous formation of polychlorinated dibenzothiophenes/thianthrenes（PCDT/TAs）,sulfurated compounds analogous to polychlorinated dibenzo-p-dioxin/dibenzofurans（PCDD/Fs）, has been well-documented to occur via ra...Homogeneous formation of polychlorinated dibenzothiophenes/thianthrenes（PCDT/TAs）,sulfurated compounds analogous to polychlorinated dibenzo-p-dioxin/dibenzofurans（PCDD/Fs）, has been well-documented to occur via radical–radical coupling reactions from chlorinated thiophenol precursors. However, the current understanding of the formation mechanism of PCDT/TAs is exclusively limited to the inherent point of view that chlorothiophenoxy radicals act as the only required intermediates for PCDT/TAs. This study investigates reaction pathways for the formation of PCDT/TAs involving two new types of radical species, i.e., substituted phenyl radicals and substituted thiophenoxyl diradicals. Taking 2-chlorothiophenol（2-CTP） as a model compound for chlorothiophenols,we found that apart from the mostly discussed chlorothiophenoxy radicals, substituted phenyl radicals and substituted thiophenoxyl diradicals could also be readily formed via the reaction of 2-CTP with H radicals. Furthermore, direct self-and cross-coupling of these radicals can result in the formation of PCDT/TAs, including 1-monochlorothianthrene（1-MCTA）, 1,6-dichlorothianthrene（1,6-DCTA）, 4,6-dichlorodibenzothiophene（4,6-DCDT）and 1,6-dichlorodibenzothiophene（1,6-DCDT）. The pathways proposed in this work are proven to be both thermodynamically and kinetically favorable. Particularly, comparisons were made between the formation mechanisms of sulfurated and oxygenated dioxin systems from an energetic point view, showing that replacing oxygen with sulfur atoms greatly reduces the activation barriers of the rate-controlling steps involved in the PCDT/TA formation processes compared with those involved for PCDD/Fs. The calculated results in this work may improve our understanding of the formation mechanism of PCDT/TAs from chlorothiophenol precursors and should be informative to environmental scientists.展开更多
The mechanism of photocycloaddition reaction between 6-azauracll and acetone was studied by using semiemptrical SCFMO AMI method. It was found that this reaction is not a concerted one. The calculated results are as f...The mechanism of photocycloaddition reaction between 6-azauracll and acetone was studied by using semiemptrical SCFMO AMI method. It was found that this reaction is not a concerted one. The calculated results are as follows:(1) A T1 state exciplex is on the T1 state energy surface; (2) T exciplex as a reactant will proceed along the energy surface of T1 state to form a diradical intermediate. The energy barrier of this reaction step is 63. 6 kJ/mol; (3) The T1 state diradical intermediate happens to be close in energy to the ground state intermediate with a similar geometry. Such a situation turns out to be very favorable for an intersystem crossing (jump from the T, state to the ground state) ; (4) The final product will be formed from the ground S0 state intermediate via an energy barrier 88. 2 kJ/mol.展开更多
The aromaticity and electronic properties of monocyclic or polycyclicπ-conjugated molecules have been widely studied.However,the related research on fullyπ-conjugated multicyclic macrocycles(MMCs)remains limited mai...The aromaticity and electronic properties of monocyclic or polycyclicπ-conjugated molecules have been widely studied.However,the related research on fullyπ-conjugated multicyclic macrocycles(MMCs)remains limited mainly due to the synthetic challenges.Herein,we report a straightforward synthesis of two MMCs(T8 and T12)in which unilateral and bilateral thiophene-based macrocycles merged with a cyclooctatetrathiophene unit by employing intramolecular Yamamoto coupling reactions of the designed precursors(8 and 12)followed by oxidative dehydrogenation.The neural compounds,their dications,and even tetracations were isolated in single-crystal form.Their geometry,aromaticity,open-shell diradical character,and physical properties were investigated by experiments such as X-ray crystallographic analysis,nuclear magnetic resonance(NMR),electron spin resonance(ESR),and theoretical calculations,which revealed changes in local/global aromatic/antiaromatic characteristics at different oxidation states.展开更多
Quinoidal small molecule semiconductors hold huge potential in ambipolar organic field-effect transistors(OFETs)and organic spintronic devices.Here,two quinoidal molecules with methylthio side chains were synthesized ...Quinoidal small molecule semiconductors hold huge potential in ambipolar organic field-effect transistors(OFETs)and organic spintronic devices.Here,two quinoidal molecules with methylthio side chains were synthesized to develop molecular semiconductors with high ambipolar mobility,designated QBDTS and QTBDTS.The theoretical calculation results reveal that QBDTS has a closed-shell structure while QTBDTS showed an open-shell structure with a biradical character(y0)of 0.46 and its magnetic properties were further investigated using electron paramagnetic resonance(EPR)and superconducting quantum interference device(SQUID)methods.The methyl side chains showed a large impact on the molecular orbital levels.The HOMO/LUMO levels of QBDTS and QTBDTS were measured to be-5.66/-4.56 and-5.27/-4.48 eV,respectively,which are favorable for ambipolar charge transport in OFETs.Importantly,the spin-coated QBDTS displayed hole and electron mobilities of 0.01 and 0.5 cm^(2)V^(-1)s^(-1)while QTBDTS showed a record high hole mobility of 1.8 cm^(2)V^(-1)s^(-1)and electron mobility of 0.3 cm^(2)V^(-1)s^(-1).Moreover,comparative studies of the thin film morphologies also manifested the beneficial influence of methyl side chains on film crystallinity and molecule orientation.These results strongly proved that methyl side chain engineering can be a simple but efficient strategy for modulating electronic properties and molecular stacking behaviors.This work also represents a big advancement for quinoidal molecular semiconductors in ambipolar OFET applications.展开更多
The block correlated coupled cluster (BCCC) method, with the complete active-space self-consistent-field (CASSCF) reference function, has been applied to investigating the singlet-triplet gaps in several substituted c...The block correlated coupled cluster (BCCC) method, with the complete active-space self-consistent-field (CASSCF) reference function, has been applied to investigating the singlet-triplet gaps in several substituted carbenes including four halocarbenes (CHCl, CF2, CCl2, and CBr2) and two hydroxycar-benes (CHOH and C(OH)2). A comparison of our results with the experimental data and other theoretical estimates shows that the present approach can provide quantitative descriptions for all the studied carbenes. It is demonstrated that the CAS-BCCC method is a promising theoretical tool for calculating the electronic structures of diradicals.展开更多
Recent years have witnessed breakthroughs in the study of zigzag hydrocarbon belts.However,the synthesis of heterocycle-containing zigzag molecular belts remains very rare and challenging despite their interesting str...Recent years have witnessed breakthroughs in the study of zigzag hydrocarbon belts.However,the synthesis of heterocycle-containing zigzag molecular belts remains very rare and challenging despite their interesting structures and potential applications in chemistry and materials science.Here,we report the expeditious construction of a highly strained belt[4]arene[4](1,4-dihydropyridine)structure using the fjords-stitching strategy.The synthesis comprised four-fold abnormal m-bromination of four Npivaloylaniline units and Pd_(2)(dba)_(3)/4-Me_(2)NC_(6)H_(4)Pt Bu_(2)-catalyzed intramolecular C-N bond-forming reactions.Subsequent functionalization through Narylations produced a variety of tetraza-embedded octahydrobelt[8]arenes.Further oxidation of p-methoxyphenyl-substituted belt[4]arene[4](1,4-dihydropyridine)with Ag[Al(O^(t)Bu^(F))^(4)]yielded a singlet diradical dication N-doped zigzag belt.展开更多
Benzo[1,2-c;4,5-cʹ]bis[1,2,5]thiadiazole(BBT)has intrinsic diradical character and herein it is used to construct organic near-infrared(NIR)dyes together with the aromatic porphyrin unit.Three BBT-porphyrin hybrid dye...Benzo[1,2-c;4,5-cʹ]bis[1,2,5]thiadiazole(BBT)has intrinsic diradical character and herein it is used to construct organic near-infrared(NIR)dyes together with the aromatic porphyrin unit.Three BBT-porphyrin hybrid dyes 1-3 with different linkage modes are synthesized by Pd-catalyzed Sonogashira crosscoupling between meso-ethynylene porphyrin units and monobromo-/dibromo-BBT,or through unexpected homocoupling between the BBT units.They all possess small open-shell diradical character and display intense NIR absorption in the range of 800-1000 nm.They also exhibit amphoteric redox behavior.BBT-based diradicaloids are thus good candidates for organic NIR dyes.展开更多
基金supported by Jilin Scientific and Technological Development Program(Nos.20220101054JC,20220201085GX)National Natural Science Foundation of China(Nos.22175074,52373182).
文摘Diradical polycyclic hydrocarbons(PHs)have unique open-shell structures and interesting physical prop-erties.However,owing to high reactivity of unpaired electrons,such open-shell organic diradicaloids are usually less stable than closed-shell systems,limiting their practical applications.In this study,we report P=O-attaching of diradical PHs as a new strategy to enhance their stability while maintaining diradi-cal properties.Three P=O-attached PHs containing the indeno[1,2-b]fluorene,fluoreno[3,2-b]fluorene and indeno[2,1-b]fluoreneπ-skeletons,respectively,were designed and synthesized.As theoretically and ex-perimentally proved,two of them have the relatively large diradical characters and open-shell singlet diradical nature.In comparison to their all-carbon analogues,the attached electron-withdrawing P=O groups endow them with much lower LUMO/HOMO energy levels but preserved magnetic activities and physical properties,such as thermally accessible triplet species and multi-redox ability.Moreover,the P=O groups effectively decrease their oxidation activities and thereby lead to their remarkably excellent ambient stabilities.Thus,this P=O-attaching strategy will be applicable to other diradical PH systems and may promote the generation of stable organic diradicaloids for radical chemistry and materials.
基金Natural Science Foundation of Shandong Province,China(Nos.ZR2016BL13 and ZR2015EQ021)National Natural Science Foundation of China(No.51505065)Foundation for Science and Technology of Shandong Provincial Universities,China(No.J16LC55)。
文摘The parent and radical-modified chitin units are computationally studied and the parent chitin unit possesses closed-shell singlet(CS)state as its ground state.Two radicals(CH_(3)·and CH_(3)CH_(2)·)are chosen to modify the parent chitin unit.Calculations predict that CH_(3)CH_(2)·-modified chitin unit possesses the open-shell broken-symmetry(BS)singlet diradical ground state,different from that CH_(3)·-modified chitin unit is a triplet diradical.That is to say,the magnetic conversion can occur from nonmagnetic exchange coupling to antiferromagnetic(AFM)or ferromagnetic(FM)exchange coupling by means of the radical modification method.The present work helps to get a basic understanding of structures and electronic properties of chitin and its radical-modified derivatives at the atomistic level.Moreover,it also provides a feasible way to design new chitin-based magnetic materials and organic magnetic switches.
基金Supported by the National Natural Science Foundation of China(No.20873017)the Natural Science Foundation of Jilin Province,China(No.20101154)
文摘The polarizability（α） and second hyperpolarizability（γ） were systemically investigated for singlet diradical complex involving X（X=B,Al,Ga） atom.The results show that both the α and γ can be effectively tuned by varying the distance R（between compound A and a water molecule） and acceptor atom X.The lone pair of electrons from the O atom of the water molecule entered into the vacant p orbital of atom X,which increased the diradical character and led to the increase of the α and γ values.Furthermore,the polarizable continuum model（PCM） was used to test the effects of H2O and CCl4 solvents on the α and γ values.Both the α and γ values of the studied diradical complex 1a（1b,1c） in H2O and CCl4 were uniformly enhanced.And the solvent effects of H2O on either α or γ were larger than those of CCl4.
文摘The development of efficient and stable perovskite solar cells(PSCs)continues to face commercialization challenges,with long-term operational stability remaining a critical bottleneck despite considerable progress in power conversion efficiency(PCE).This challenge is particularly pronounced at the hole-selective interface,where high-performance contacts frequently lack the necessary robustness,thereby limiting device reliability and durability.The recent development of stable organic diradical self-assembled monolayers(SAMs)represents a significant advancement in interfacial contact engineering for perovskite devices.
基金supported by the National Natural Science Foundation of China(22471014,22271013)。
文摘Open-shell chiral diradicals that feature both the unique chiroptical properties and tunable spin states have kindled numerous interests in organic synthesis and material science.We present a new class of such model systems based on theπ-extended planar chiral pillar[5]arene derivatives P5Flu and P5Cz,where the pillar[5]arene-based chiral scaffolds are coupled with sterically encumbered fluorenyl and carbazolyl moieties as highly luminescent redox-active emitters,respectively.Both molecules in neutral states can readily undergo chemical oxidations leading toπ-conjugated chiral diradicals of the dehydrogenated P5Flu^(2·)and a positively charged dication P5Cz^(2+2)·.Characterization of the resulting Müller’s open-shell species by variable-temperature electron spin resonance(VT-ESR),UV-vis-NIR absorption,VT-NMR and by computational studies revealed a singlet(ΔE_(S-T)=-1.63 kcal mol^(-1))and a nearly degenerate singlet-triplet ground state(ΔE_(S-T)=0.05 kcal mol^(-1),with a diradical character index y0=0.89)for P5Cz^(2+2)·and P5Flu^(2·),respectively.We particularly show in this work a new journey for pillar[5]arenes from the conventionally available closed-shell structures to different open-shell spin states with potential applications in chirospintronics and NIR-active chiroptoelectronic materials.
基金the JSPS for KAKENHI funding(Grant No.JP21H01918 and JP20K21194)a Grant-in-Aid for Transformative Research Areas(A)“Condensed Conjugation”(JSPS for KAKENHI funding Grant No.JP20H05865)from MEXT,Japan.
文摘Knowledge about electronic structures is important to gain an understanding of the unique functional properties of diradicaloids.In this study,we synthesized and characterized a diradicaloid in which two phenalenyl radical sites are coupled antiferromagnetically via a through-space interaction.The results of quantum chemical,physicochemical(^(1)H NMR,electronic absorption,cyclic voltammetry,SQUID,ESR),and chemical reactivity studies show that this diradicaloid has singlet diradical character.An assessment of the nature of the bonding interaction between two radical sites in this species using DFT calculations demonstrates that a small spatial overlap between the two SOMOs in this diradicaloid provides an efficient electron exchange path for the singlet state to be substantially lower in energy than the triplet state.
基金supported by the National Natural Science Foundation of China(21525102,21690062)the Natural Science Foundation of Jiangsu Province(BK20140014)
文摘Two tetraazacyclophane dications(1^(2+) and 2^(2+)) with different remote substituents have been synthesized, isolated and characterized.Their electronic structures and physical property were studied by various spectroscopic techniques, single crystal X-ray diffraction,super conducting quantum interference device(SQUID) measurements and theoretical calculations. The dications have triplet ground states with ferromagnetic interaction exceeding the thermal energy at room temperature. The solid-state structures of these species were tunable by substituent effect, with 1^(2+) as a monomer and 2^(2+) as a dimer.
文摘Two-electron oxidations of three 1,2-di（bisphenylamino）-benzenes afforded a class of nitrogen analogues of o-quinodimethane. Their elec-tronic structures in the ground state were studied by spectroscopic techniques including EPR and UV-vis absorption spectroscopy. They have open-shell singlet ground states with thermally accessible triplet states. One of them （12＋2） has been crystalized and isolated. SQUID measurements, single crystal X-ray diffraction and theoretical calculat ons show I has unexpected non-Kekule diradical character, sharply different from o-quinodirnethane.
基金supported by the National Natural Science Foundation of China(21525102,2169002)the Natural Science Foundation of Jiangsu Province(BK20140014)
文摘By using weakly coordinating anions we succeeded in the stabilization and isolation of two Wfirster＇s blue-based diradicaloid dications with saturated spacers. Their geometries and electronic structures were investigated by various experiments in conjunction with DFT calculations. Both one-dimensional alkylate-bridged dications show considerable diradical character with spacer-dependent singlet-triplet energy gaps. One of them displays a much enhanced diradical character and could basically be viewed as a pure diradical with degeneracy of singlet and triplet states.
基金The work was supported by the NSFC(grant nos.51925306,21774130,and 21905277)National Key R&D Program of China(grant no.2018FYA 0305800)+2 种基金Key Research Program of the Chinese Academy of Sciences(grant no.XDPB08-2)the Strategic Priority Research Program of Chinese Academy of Sciences(grant no.XDB28000000)Fundamental Research Funds for the Central University.DFT results described in this short communication are obtained on the National Super-computing Center in Shenzhen(Shenzhen Cloud Computing Center).
文摘Air stable diradicaloid polycyclic aromatic hydrocarbon(PAH)materials possess unique electronic and magnetic properties for various applications.In general,long conjugated distances between two radical centers are required to improve the air stability,thereby complicating the synthetic procedures.Herein,the chalcogen containing rubicenes(O-,S-,and Se-rubicenes)were systematically investigated to understand the chalcogen effects on chalcogen-rubicene physicochemical properties.Impressively,these rubicenes presented unprecedented diradical characterwithin one simple benzene ring and excellent air stabilities.Theirdiradicalcharacterweremanifested by single-crystal X-ray studies,variable-temperature nuclear magnetic resonance,and electron spin resonance.Furthermore,the nucleus independent chemical shifts andthe anisotropy of the induced currentdensity calculations revealed that the formation of diradical was caused by a pro-aromaticity driving force.Importantly,the diradical character of rubicenes are visualizedbyFractionalOccupationNumberWeighted Electron Density(FOD)plots,which present high NFOD values from 1.651 to 1.830.This contribution provided distinctive insights into the structure and property relationship of PAH diradicals.
基金Innovation Program of Shanghai Municipal Education Commission(No.2019-01-07-00-05-E00012)Program for Changjiang Scholars and Innovative Research Team in University for financial support+1 种基金the financial supports sponsored by Shanghai Sailing Program(No.19YF1412900)the Fundamental Research Funds for the Central Universities。
文摘An unexpected bistricyclic aromatic ene AF was synthesized in a tin(Ⅱ)chloride-mediated reductive aromatization reaction.The obtained AF showed a highly overcrowded structural conformation as revealed by X-ray crystallography.Interestingly,AF exhibited reversible high-contrast mechanochromism and thermochromism between pale and red color.The obvious chromism is likely ascribed to the conformation transformation and trace amount of diradical species formation upon stimulus.
基金supported by the National Natural Science Foundation (Nos. 21407167, 21621064, and 21607168)the Chinese Academy of Sciences (No. XDB14030500)
文摘Homogeneous formation of polychlorinated dibenzothiophenes/thianthrenes（PCDT/TAs）,sulfurated compounds analogous to polychlorinated dibenzo-p-dioxin/dibenzofurans（PCDD/Fs）, has been well-documented to occur via radical–radical coupling reactions from chlorinated thiophenol precursors. However, the current understanding of the formation mechanism of PCDT/TAs is exclusively limited to the inherent point of view that chlorothiophenoxy radicals act as the only required intermediates for PCDT/TAs. This study investigates reaction pathways for the formation of PCDT/TAs involving two new types of radical species, i.e., substituted phenyl radicals and substituted thiophenoxyl diradicals. Taking 2-chlorothiophenol（2-CTP） as a model compound for chlorothiophenols,we found that apart from the mostly discussed chlorothiophenoxy radicals, substituted phenyl radicals and substituted thiophenoxyl diradicals could also be readily formed via the reaction of 2-CTP with H radicals. Furthermore, direct self-and cross-coupling of these radicals can result in the formation of PCDT/TAs, including 1-monochlorothianthrene（1-MCTA）, 1,6-dichlorothianthrene（1,6-DCTA）, 4,6-dichlorodibenzothiophene（4,6-DCDT）and 1,6-dichlorodibenzothiophene（1,6-DCDT）. The pathways proposed in this work are proven to be both thermodynamically and kinetically favorable. Particularly, comparisons were made between the formation mechanisms of sulfurated and oxygenated dioxin systems from an energetic point view, showing that replacing oxygen with sulfur atoms greatly reduces the activation barriers of the rate-controlling steps involved in the PCDT/TA formation processes compared with those involved for PCDD/Fs. The calculated results in this work may improve our understanding of the formation mechanism of PCDT/TAs from chlorothiophenol precursors and should be informative to environmental scientists.
文摘The mechanism of photocycloaddition reaction between 6-azauracll and acetone was studied by using semiemptrical SCFMO AMI method. It was found that this reaction is not a concerted one. The calculated results are as follows:(1) A T1 state exciplex is on the T1 state energy surface; (2) T exciplex as a reactant will proceed along the energy surface of T1 state to form a diradical intermediate. The energy barrier of this reaction step is 63. 6 kJ/mol; (3) The T1 state diradical intermediate happens to be close in energy to the ground state intermediate with a similar geometry. Such a situation turns out to be very favorable for an intersystem crossing (jump from the T, state to the ground state) ; (4) The final product will be formed from the ground S0 state intermediate via an energy barrier 88. 2 kJ/mol.
基金supported financially by the Singapore Ministry of Education(MOE)Academic Research Fund(AcRF)Tier 2 grant(MOE-T2EP10222-0003)the Agency for Science,Technology and Research Manufacturing,Trade,and Connectivity(A*STAR MTC)project,Singapore(M22K2c0083).
文摘The aromaticity and electronic properties of monocyclic or polycyclicπ-conjugated molecules have been widely studied.However,the related research on fullyπ-conjugated multicyclic macrocycles(MMCs)remains limited mainly due to the synthetic challenges.Herein,we report a straightforward synthesis of two MMCs(T8 and T12)in which unilateral and bilateral thiophene-based macrocycles merged with a cyclooctatetrathiophene unit by employing intramolecular Yamamoto coupling reactions of the designed precursors(8 and 12)followed by oxidative dehydrogenation.The neural compounds,their dications,and even tetracations were isolated in single-crystal form.Their geometry,aromaticity,open-shell diradical character,and physical properties were investigated by experiments such as X-ray crystallographic analysis,nuclear magnetic resonance(NMR),electron spin resonance(ESR),and theoretical calculations,which revealed changes in local/global aromatic/antiaromatic characteristics at different oxidation states.
基金supported by the National Natural Science Foundation of China(21801201,51773160,21975194,22175134)the Research Fund for Distinguished Young Scholars of Hubei Province(2019CFA042)。
文摘Quinoidal small molecule semiconductors hold huge potential in ambipolar organic field-effect transistors(OFETs)and organic spintronic devices.Here,two quinoidal molecules with methylthio side chains were synthesized to develop molecular semiconductors with high ambipolar mobility,designated QBDTS and QTBDTS.The theoretical calculation results reveal that QBDTS has a closed-shell structure while QTBDTS showed an open-shell structure with a biradical character(y0)of 0.46 and its magnetic properties were further investigated using electron paramagnetic resonance(EPR)and superconducting quantum interference device(SQUID)methods.The methyl side chains showed a large impact on the molecular orbital levels.The HOMO/LUMO levels of QBDTS and QTBDTS were measured to be-5.66/-4.56 and-5.27/-4.48 eV,respectively,which are favorable for ambipolar charge transport in OFETs.Importantly,the spin-coated QBDTS displayed hole and electron mobilities of 0.01 and 0.5 cm^(2)V^(-1)s^(-1)while QTBDTS showed a record high hole mobility of 1.8 cm^(2)V^(-1)s^(-1)and electron mobility of 0.3 cm^(2)V^(-1)s^(-1).Moreover,comparative studies of the thin film morphologies also manifested the beneficial influence of methyl side chains on film crystallinity and molecule orientation.These results strongly proved that methyl side chain engineering can be a simple but efficient strategy for modulating electronic properties and molecular stacking behaviors.This work also represents a big advancement for quinoidal molecular semiconductors in ambipolar OFET applications.
基金Supported by the National Natural Science Foundation of China (Grant Nos. 20625309 and 20433020)the National Basic Research Program (Grant No. 2004CB719901)+1 种基金the Ministry of Education of China (Grant No. NCET-04-0450) Fok Ying Tong Education Foundation (Grant No. 91014)
文摘The block correlated coupled cluster (BCCC) method, with the complete active-space self-consistent-field (CASSCF) reference function, has been applied to investigating the singlet-triplet gaps in several substituted carbenes including four halocarbenes (CHCl, CF2, CCl2, and CBr2) and two hydroxycar-benes (CHOH and C(OH)2). A comparison of our results with the experimental data and other theoretical estimates shows that the present approach can provide quantitative descriptions for all the studied carbenes. It is demonstrated that the CAS-BCCC method is a promising theoretical tool for calculating the electronic structures of diradicals.
基金We thank the National Natural Science Foundation of China(grant nos.22050005,21732004,and 21821001)the Tsinghua University Initiative Scientific Research Program(grant no.2019Z07L01004)for generous financial support.
文摘Recent years have witnessed breakthroughs in the study of zigzag hydrocarbon belts.However,the synthesis of heterocycle-containing zigzag molecular belts remains very rare and challenging despite their interesting structures and potential applications in chemistry and materials science.Here,we report the expeditious construction of a highly strained belt[4]arene[4](1,4-dihydropyridine)structure using the fjords-stitching strategy.The synthesis comprised four-fold abnormal m-bromination of four Npivaloylaniline units and Pd_(2)(dba)_(3)/4-Me_(2)NC_(6)H_(4)Pt Bu_(2)-catalyzed intramolecular C-N bond-forming reactions.Subsequent functionalization through Narylations produced a variety of tetraza-embedded octahydrobelt[8]arenes.Further oxidation of p-methoxyphenyl-substituted belt[4]arene[4](1,4-dihydropyridine)with Ag[Al(O^(t)Bu^(F))^(4)]yielded a singlet diradical dication N-doped zigzag belt.
基金supported by NRF(NRF-NRFI05-2019-0005)MOE Tier 2 grant(MOE2018-T2-2-094).
文摘Benzo[1,2-c;4,5-cʹ]bis[1,2,5]thiadiazole(BBT)has intrinsic diradical character and herein it is used to construct organic near-infrared(NIR)dyes together with the aromatic porphyrin unit.Three BBT-porphyrin hybrid dyes 1-3 with different linkage modes are synthesized by Pd-catalyzed Sonogashira crosscoupling between meso-ethynylene porphyrin units and monobromo-/dibromo-BBT,or through unexpected homocoupling between the BBT units.They all possess small open-shell diradical character and display intense NIR absorption in the range of 800-1000 nm.They also exhibit amphoteric redox behavior.BBT-based diradicaloids are thus good candidates for organic NIR dyes.
