The singlet-triplet splitting energy gap ΔEs-T= Es - ET is calculated for the ortho-, meta-, and para-xylylenes and their heteroatomic analogous by means of AM1-CI approach. It is shownthat when the radical centers R...The singlet-triplet splitting energy gap ΔEs-T= Es - ET is calculated for the ortho-, meta-, and para-xylylenes and their heteroatomic analogous by means of AM1-CI approach. It is shownthat when the radical centers R(R=H2C- ,H2N+- or HN’- ) are twisted sufficiently far out ofconjugation with the benzene ring, ΔEs-T tends to zero or is negative, i.e. ortho-, meta-, and para-phenylenes turn into weak ferromagnetic or antiferromagnetic coupling unit, while they are strong ferromagnetic (meta-isomers) or antiferromagnetic (ortho-, para-isomers) coupling units under planar conformation. It is suggested that serious twisted conformation is not recommended candidate for the design of novel high-spin molecules with stable high-spin ground states by ortho-or para-phenylene coupling unit.展开更多
Dinuclear copper complex with biradicals [Cu(hfac)2]2PhBNM(PhBNM = 2,5-bimethyl-1,4-bis(4,4,5,5-tetramethyllimidazoline-1-oxyl-3-oxide)phenyl,hfac=hexafluoroacetylacetonate) has been synthesized and characterized. It ...Dinuclear copper complex with biradicals [Cu(hfac)2]2PhBNM(PhBNM = 2,5-bimethyl-1,4-bis(4,4,5,5-tetramethyllimidazoline-1-oxyl-3-oxide)phenyl,hfac=hexafluoroacetylacetonate) has been synthesized and characterized. It crystallized in the monoclinic system, with space group C2/c, a=1.9012(4), b=1.3718(3), c=2.1620(4) nm, β=97.55(3)°, Z=4. The X-ray structure analysis shows that the molecular structure consists of two kinds of conformations. The ratio of them is 7:3. The energy of two conformations, calculated with molecular mechanics, are different, E1=740 kJ/mol, and E2=771 kJ · mol-1. The CNDO/k results on the complex indicate that the orbital energy of low spin state is lower than that of high spin state, which correspond with the results of magnetic measurement.展开更多
Photochromism due to organometallic ring-closure through C−C linkage has never been attained.In this work,we report a preliminary approach to achieve T-type photochromism by creating a metallacyclopentadiene biradical...Photochromism due to organometallic ring-closure through C−C linkage has never been attained.In this work,we report a preliminary approach to achieve T-type photochromism by creating a metallacyclopentadiene biradical under light irradiation.A class of CuPt2 phenylacetylide compounds was prepared with distinguished photochromic recyclability and durability,which involved the formation of thermally sensitive copper(I)-butadienyl,five-membered ring through copper(I)-participated ring-closure.Upon UV light irradiation,the metallacyclopentadiene with copper(I)center chelated by 1,3-butadiene-1,4-diyl biradical was generated through photochemical C-C linkage of two face-to-face oriented ethynyl units in close proximity,giving rise to a drastic change in UV-vis absorption spectrum.When UV light irradiation was ceased,decoloration occurred through thermal cycloreversion,which endowed the photochromic CuPt2 complexes with self-recovery characteristics.Electron paramagnetic resonance(EPR)spectral study confirmed a biradical feature of a ring-closed isomer.The thermal decoloration half-lives at ambient temperature were regulated from seconds to hours by increasing F substituents in phenylethynyl ligands.展开更多
Five novel complexes of formula [Ln(hfac)3] · BNPhOM, where La = Gd, Ho, Dy, Y, Er; Mac = hexfluoracetylacetonate; BNPhOM=1,3-[bis-2,2′,-(4,4,5,5-tetramethyl-4,5-di-hydro-1H-imidazolyl-1-oxyl-3-oxide) phenoxy] p...Five novel complexes of formula [Ln(hfac)3] · BNPhOM, where La = Gd, Ho, Dy, Y, Er; Mac = hexfluoracetylacetonate; BNPhOM=1,3-[bis-2,2′,-(4,4,5,5-tetramethyl-4,5-di-hydro-1H-imidazolyl-1-oxyl-3-oxide) phenoxy] propane, have been prepared and characterized by elemental analysis, molar conductances, IR and electronic spectra. The temperature dependence of the magnetic susceptibility for Gd(III) and radical was measured (2—-300 K). The observed data were successfully simulated giving the exchange integral J = 0.28 cm?1, J' = - 0.33 cm?1. These results indicate a weak ferromagnetic spin exchange interaction between Gd(III) ion and the radical and a weak antiferromagnetic spin exchange interaction between the radical and radical.展开更多
Three biradical-bridged heterometallic chains,[LnCu_(2)(hfac)7(bisNITPhPy)]n(Ln^(Ⅲ)=Gd,1;Tb,2;Ho,3),were synthesized by means of a nitronyl nitroxide biradical bisNITPhPy([5-(4-pyridyl)-1,3-bis(1’-oxyl-3’-oxide-4...Three biradical-bridged heterometallic chains,[LnCu_(2)(hfac)7(bisNITPhPy)]n(Ln^(Ⅲ)=Gd,1;Tb,2;Ho,3),were synthesized by means of a nitronyl nitroxide biradical bisNITPhPy([5-(4-pyridyl)-1,3-bis(1’-oxyl-3’-oxide-4’,4’,5’,5’-tetramethyl-4,5-hydro-1H-imidazol-2-yl)]benzene;hfac=hexafluoroacetylacetonate).In these structures,the bisNITPhPy biradical serves as a pentadentate ligand to hold one Ln^(Ⅲ)ion through two neighboring aminoxyl(NO)moieties in chelating mode,while other two NO groups are coordinated to Cu(hfac)_(2)units,leading to a 1D Cu-Ln-birad chain.An additional terminal Cu(hfac)_(2)unit linked to a pyridine-N atom is found at the periphery.The magnetic susceptibility data of compound Gd have been analyzed with a closed ring model comprising three[Cu-Rad-Gd-Rad]units,which indicates ferromagnetic Gd(Ⅲ)-nitroxide and Cu(Ⅱ)-axial nitroxide interactions.The Tb derivative was found to behave as a single chain magnet with an energy barrier for magnetization reversal of 26 K.展开更多
The reaction of the biradical[(μ-NTer)P•]_(2) with thiophosgene,SCCl_(2),leads to a cyclic phospha-aza thiourea derivative in very good yields.This synthetic approach represents a new possibility to prepare cyclic th...The reaction of the biradical[(μ-NTer)P•]_(2) with thiophosgene,SCCl_(2),leads to a cyclic phospha-aza thiourea derivative in very good yields.This synthetic approach represents a new possibility to prepare cyclic thioketones starting from four-membered cyclo-diphosphadiazanediyls by formal CS insertion with simultaneous oxidation of the two phosphorus atoms by the two chlorine atoms.When the phospha-aza thiourea derivative is reduced with magnesium chips,a deep blue,highly labile cyclic thioketone is formed,which can be regarded as a biradical heterocyclopentane-1,3-diyl.This new biradical can be converted to a housane species by light,which triggers transannular P-P bond formation.A thermal backreaction was not observed,but scavenging reactions with CS_(2) or PhCHO clearly indicate the intermediate formation of the labile,biradical cyclic thioketone.Various intercepted products,such as[2.2.1]bicyclic cage compounds could be isolated and structurally characterized.Freshly in situ generated biradical thioketone can be utilized to activate small molecules.展开更多
Metal-organic photothermal conversion materials are vital for the efficient utilization of renewable energy to relieve freshwater shortage.Driven by the aspiration to pursue performant photothermal conversion material...Metal-organic photothermal conversion materials are vital for the efficient utilization of renewable energy to relieve freshwater shortage.Driven by the aspiration to pursue performant photothermal conversion materials,extensive efforts have been committed to regulating the photothermal effect.Decoration of the molecular skeleton represents the traditional design idea for adjusting the photophysical features.Distinctively,here,we introduced a more easy-to-operate heterometallic selection tactic that allowed for fine adjustment of the photothermal conversion ability as exemplified by a series of nitronyl nitroxide biradical-based 3d-4f macrocycles,namely,DyCo-1,YbCo-2,DyZn-3 and GdCo-4.The comparative investigation of DyCo-1/YbCo-2 and DyCo-1/DyZn-3 revealed that photothermal conversion efficiency follows the trend DyCo-1 (75.5%) > YbCo-2 (71.9%) > DyZn-3 (57.3%) on account of the 3d/4f metal modulation,suggesting that the Dy-Co combination achieved the optimization of photothermal performance.Furthermore,DyCo-1 was successfully applied to solar-driven water evaporation with an efficiency of 53.1%.To the best of our knowledge,macrocyclic compounds 1-3 represent the first example of nitronyl nitroxide-3d-4f photothermal materials.The work offers a feasible heterometallic modulation strategy to elaborately design molecular photothermal agents as well as a new material selection for solar-driven water evaporation and freshwater production to alleviate water scarcity.展开更多
Radical-mediated reactions have many advantages in the construction of complex molecular scaffolds by forging chemical bonds of high challenge.Diazenes,including 1,1-diazenes and 1,2-diazenes,can generate biradical sp...Radical-mediated reactions have many advantages in the construction of complex molecular scaffolds by forging chemical bonds of high challenge.Diazenes,including 1,1-diazenes and 1,2-diazenes,can generate biradical species via nitrogen extrusion under thermal or photochemical conditions.The superior reactivity of the generated biradical enables various types of synthetic transformations with excellent chemoselectivity and has been applied to the complex natural products synthesis.In this mini-review,the modes of reaction are summarized and discussed,namely ring contraction via nitrogen deletion,homo or heterodimerization,trimethylenemethane(TMM)-diyl cycloaddition.Applications of these classes of reactions in complex natural product synthesis are illustrated.Last but not least,the current state,future directions,and opportunities for dinitrogen extrusion reaction from diazenes are highlighted and discussed.展开更多
Novel stable high-spin molecules possessing three different arranging fashions were designed with —^＊N—S— as a spin-containing （SC） fragment, an aromatic group, such as benzene （ 1 ）, pyridine （2）, pyridazi...Novel stable high-spin molecules possessing three different arranging fashions were designed with —^＊N—S— as a spin-containing （SC） fragment, an aromatic group, such as benzene （ 1 ）, pyridine （2）, pyridazine （3） , pyrimidine （4）, pyrazine （5） or triazine （6） as end groups （EG）, and phenyl as a ferromagnetic coupling （FC） unit. The effects of different EG on the spin multiplicities of the ground states and their stabilities were investigated by means of the AM1-CI approach. All the investigated molecules corresponded to the FC and possessed high-spin ground states. The spin on the two atoms of the SC fragment was not in agreement with the delocalization results in the specific stability of —^＊N—S—. In those molecules, the stabilities of the triplet states decreased when the distance between the atoms of central SC fragments （—N—） increased. The stabilities of the triplet states of compounds 1a-n, 1b-n and 1c-n, with heterocycles as EG were higher than those of the triplet states of those compounds with phenyl as EG. Furthermore, the stahilities of the triplet states of the compounds with pyrimidine and triazine as EG were higher than those with pyridine, pyridazine or pyrasine as EG.展开更多
Novel stable high spin molecules possessing three different arranged fashions are designed with - · N-N< as a spin-containing(SC) fragment, phenylene as an end group and various aromatic molecules, such as ben...Novel stable high spin molecules possessing three different arranged fashions are designed with - · N-N< as a spin-containing(SC) fragment, phenylene as an end group and various aromatic molecules, such as benzene(1), 2,6-pyridine(2), 3,5-pyridine(3), pyridazine(4), 4,6-pyrimidine(5), 2,6-pyrimidine(6), pyrazine(7) and triazine(8), as a ferromagnetic coupling(FC) unit. The effects of the different coupling units on the spin multiplicities of the ground states and their stabilities were investigated by means of AM1-CI approach. It has been found that the spin densities on the two atoms of the SC fragment are different from delocalization results in the specific stability of - · N-N<. In these molecules, the stabilities of the triplet states decrease when the distance between the atoms of central SC(-N-) increases. It is shown that the heterocycles as the coupling units have influence on the stabilities of the high-spin ground states. That the heteroatom lying in m -phenyl can improve ferromagnetic coupling, while the heteroatom lying in o -phenyl or p -phenyl is not in favor of the ferromagnetic coupling.展开更多
The series of biradicals with m phenylene coupling unit and hetero spin centers were calculated compared with those possessing homo spin centers using AM1 CI method. A simple rule was proposed to design high s...The series of biradicals with m phenylene coupling unit and hetero spin centers were calculated compared with those possessing homo spin centers using AM1 CI method. A simple rule was proposed to design high spin molecules with ferromagnetic coupling unit and hetero spin centers. Two neutral (or charged) hetero spin centers resulted in high spin ground state, one neutral and another charged hetero spin centers correspond to low spin ground state. The latter was ascribed to the huge splitting of two partially occupied molecular orbitals.展开更多
文摘The singlet-triplet splitting energy gap ΔEs-T= Es - ET is calculated for the ortho-, meta-, and para-xylylenes and their heteroatomic analogous by means of AM1-CI approach. It is shownthat when the radical centers R(R=H2C- ,H2N+- or HN’- ) are twisted sufficiently far out ofconjugation with the benzene ring, ΔEs-T tends to zero or is negative, i.e. ortho-, meta-, and para-phenylenes turn into weak ferromagnetic or antiferromagnetic coupling unit, while they are strong ferromagnetic (meta-isomers) or antiferromagnetic (ortho-, para-isomers) coupling units under planar conformation. It is suggested that serious twisted conformation is not recommended candidate for the design of novel high-spin molecules with stable high-spin ground states by ortho-or para-phenylene coupling unit.
文摘Dinuclear copper complex with biradicals [Cu(hfac)2]2PhBNM(PhBNM = 2,5-bimethyl-1,4-bis(4,4,5,5-tetramethyllimidazoline-1-oxyl-3-oxide)phenyl,hfac=hexafluoroacetylacetonate) has been synthesized and characterized. It crystallized in the monoclinic system, with space group C2/c, a=1.9012(4), b=1.3718(3), c=2.1620(4) nm, β=97.55(3)°, Z=4. The X-ray structure analysis shows that the molecular structure consists of two kinds of conformations. The ratio of them is 7:3. The energy of two conformations, calculated with molecular mechanics, are different, E1=740 kJ/mol, and E2=771 kJ · mol-1. The CNDO/k results on the complex indicate that the orbital energy of low spin state is lower than that of high spin state, which correspond with the results of magnetic measurement.
基金This work was supported by the National Natural Science Foundation of China(grant nos.92061202,22175181,and 21531008)the Fujian Science and Technology Project(grant no.2020L3022)the Strategic Priority Research Program of the Chinese Academy of Sciences(grant no.XDB20000000).
文摘Photochromism due to organometallic ring-closure through C−C linkage has never been attained.In this work,we report a preliminary approach to achieve T-type photochromism by creating a metallacyclopentadiene biradical under light irradiation.A class of CuPt2 phenylacetylide compounds was prepared with distinguished photochromic recyclability and durability,which involved the formation of thermally sensitive copper(I)-butadienyl,five-membered ring through copper(I)-participated ring-closure.Upon UV light irradiation,the metallacyclopentadiene with copper(I)center chelated by 1,3-butadiene-1,4-diyl biradical was generated through photochemical C-C linkage of two face-to-face oriented ethynyl units in close proximity,giving rise to a drastic change in UV-vis absorption spectrum.When UV light irradiation was ceased,decoloration occurred through thermal cycloreversion,which endowed the photochromic CuPt2 complexes with self-recovery characteristics.Electron paramagnetic resonance(EPR)spectral study confirmed a biradical feature of a ring-closed isomer.The thermal decoloration half-lives at ambient temperature were regulated from seconds to hours by increasing F substituents in phenylethynyl ligands.
基金Project supported by the National Natural Science Foundation of China (Nos. 29871019 and 29631040) and the Natural Science Foundation of Yunnan Province (No. 1999B0003M).
文摘Five novel complexes of formula [Ln(hfac)3] · BNPhOM, where La = Gd, Ho, Dy, Y, Er; Mac = hexfluoracetylacetonate; BNPhOM=1,3-[bis-2,2′,-(4,4,5,5-tetramethyl-4,5-di-hydro-1H-imidazolyl-1-oxyl-3-oxide) phenoxy] propane, have been prepared and characterized by elemental analysis, molar conductances, IR and electronic spectra. The temperature dependence of the magnetic susceptibility for Gd(III) and radical was measured (2—-300 K). The observed data were successfully simulated giving the exchange integral J = 0.28 cm?1, J' = - 0.33 cm?1. These results indicate a weak ferromagnetic spin exchange interaction between Gd(III) ion and the radical and a weak antiferromagnetic spin exchange interaction between the radical and radical.
基金supported by the National Key R&D Program of China(2018YFA0306002)the National Natural Science Foundation of China(No.21773122 and 21471083)and the 111 Project(B12015).
文摘Three biradical-bridged heterometallic chains,[LnCu_(2)(hfac)7(bisNITPhPy)]n(Ln^(Ⅲ)=Gd,1;Tb,2;Ho,3),were synthesized by means of a nitronyl nitroxide biradical bisNITPhPy([5-(4-pyridyl)-1,3-bis(1’-oxyl-3’-oxide-4’,4’,5’,5’-tetramethyl-4,5-hydro-1H-imidazol-2-yl)]benzene;hfac=hexafluoroacetylacetonate).In these structures,the bisNITPhPy biradical serves as a pentadentate ligand to hold one Ln^(Ⅲ)ion through two neighboring aminoxyl(NO)moieties in chelating mode,while other two NO groups are coordinated to Cu(hfac)_(2)units,leading to a 1D Cu-Ln-birad chain.An additional terminal Cu(hfac)_(2)unit linked to a pyridine-N atom is found at the periphery.The magnetic susceptibility data of compound Gd have been analyzed with a closed ring model comprising three[Cu-Rad-Gd-Rad]units,which indicates ferromagnetic Gd(Ⅲ)-nitroxide and Cu(Ⅱ)-axial nitroxide interactions.The Tb derivative was found to behave as a single chain magnet with an energy barrier for magnetization reversal of 26 K.
基金support by the Deutsche Forschungsgemeinschaft(DFGSCHU 1170/12-2)Moreover,we wish to thank the ITMZ at the University of Rostock for access to the cluster computer,and especially Malte Willert for his assistance with the queuing system and software installations.
文摘The reaction of the biradical[(μ-NTer)P•]_(2) with thiophosgene,SCCl_(2),leads to a cyclic phospha-aza thiourea derivative in very good yields.This synthetic approach represents a new possibility to prepare cyclic thioketones starting from four-membered cyclo-diphosphadiazanediyls by formal CS insertion with simultaneous oxidation of the two phosphorus atoms by the two chlorine atoms.When the phospha-aza thiourea derivative is reduced with magnesium chips,a deep blue,highly labile cyclic thioketone is formed,which can be regarded as a biradical heterocyclopentane-1,3-diyl.This new biradical can be converted to a housane species by light,which triggers transannular P-P bond formation.A thermal backreaction was not observed,but scavenging reactions with CS_(2) or PhCHO clearly indicate the intermediate formation of the labile,biradical cyclic thioketone.Various intercepted products,such as[2.2.1]bicyclic cage compounds could be isolated and structurally characterized.Freshly in situ generated biradical thioketone can be utilized to activate small molecules.
基金financially supported by the Key Laboratory of Advanced Energy Materials Chemistry(Ministry of Education of the People’s Republic of China)Fundamental Research Program of Shanxi Province(202403021221203)Shanxi Patent Transformation Program Project(202401004).
文摘Metal-organic photothermal conversion materials are vital for the efficient utilization of renewable energy to relieve freshwater shortage.Driven by the aspiration to pursue performant photothermal conversion materials,extensive efforts have been committed to regulating the photothermal effect.Decoration of the molecular skeleton represents the traditional design idea for adjusting the photophysical features.Distinctively,here,we introduced a more easy-to-operate heterometallic selection tactic that allowed for fine adjustment of the photothermal conversion ability as exemplified by a series of nitronyl nitroxide biradical-based 3d-4f macrocycles,namely,DyCo-1,YbCo-2,DyZn-3 and GdCo-4.The comparative investigation of DyCo-1/YbCo-2 and DyCo-1/DyZn-3 revealed that photothermal conversion efficiency follows the trend DyCo-1 (75.5%) > YbCo-2 (71.9%) > DyZn-3 (57.3%) on account of the 3d/4f metal modulation,suggesting that the Dy-Co combination achieved the optimization of photothermal performance.Furthermore,DyCo-1 was successfully applied to solar-driven water evaporation with an efficiency of 53.1%.To the best of our knowledge,macrocyclic compounds 1-3 represent the first example of nitronyl nitroxide-3d-4f photothermal materials.The work offers a feasible heterometallic modulation strategy to elaborately design molecular photothermal agents as well as a new material selection for solar-driven water evaporation and freshwater production to alleviate water scarcity.
基金Fuzhou University for the funding support(No.GXRC21051)the Award Program for Minjiang Scholar Professorship。
文摘Radical-mediated reactions have many advantages in the construction of complex molecular scaffolds by forging chemical bonds of high challenge.Diazenes,including 1,1-diazenes and 1,2-diazenes,can generate biradical species via nitrogen extrusion under thermal or photochemical conditions.The superior reactivity of the generated biradical enables various types of synthetic transformations with excellent chemoselectivity and has been applied to the complex natural products synthesis.In this mini-review,the modes of reaction are summarized and discussed,namely ring contraction via nitrogen deletion,homo or heterodimerization,trimethylenemethane(TMM)-diyl cycloaddition.Applications of these classes of reactions in complex natural product synthesis are illustrated.Last but not least,the current state,future directions,and opportunities for dinitrogen extrusion reaction from diazenes are highlighted and discussed.
基金Supported by the National Natural Science Foundation of Chana(Nos. 29804002, 20274006) and Tianjin Polytechnic Univer-sity Item(Nos. 029307, 029302).
文摘Novel stable high-spin molecules possessing three different arranging fashions were designed with —^＊N—S— as a spin-containing （SC） fragment, an aromatic group, such as benzene （ 1 ）, pyridine （2）, pyridazine （3） , pyrimidine （4）, pyrazine （5） or triazine （6） as end groups （EG）, and phenyl as a ferromagnetic coupling （FC） unit. The effects of different EG on the spin multiplicities of the ground states and their stabilities were investigated by means of the AM1-CI approach. All the investigated molecules corresponded to the FC and possessed high-spin ground states. The spin on the two atoms of the SC fragment was not in agreement with the delocalization results in the specific stability of —^＊N—S—. In those molecules, the stabilities of the triplet states decreased when the distance between the atoms of central SC fragments （—N—） increased. The stabilities of the triplet states of compounds 1a-n, 1b-n and 1c-n, with heterocycles as EG were higher than those of the triplet states of those compounds with phenyl as EG. Furthermore, the stahilities of the triplet states of the compounds with pyrimidine and triazine as EG were higher than those with pyridine, pyridazine or pyrasine as EG.
基金Supported by the National Natural Science Foundation of China( No.2 980 4 0 0 2,2 0 2 74 0 0 6 ) ,FokYingTungEducationFoundation( No.710 13) and Foundation of Northeast Normal University( No.1114 34)
文摘Novel stable high spin molecules possessing three different arranged fashions are designed with - · N-N< as a spin-containing(SC) fragment, phenylene as an end group and various aromatic molecules, such as benzene(1), 2,6-pyridine(2), 3,5-pyridine(3), pyridazine(4), 4,6-pyrimidine(5), 2,6-pyrimidine(6), pyrazine(7) and triazine(8), as a ferromagnetic coupling(FC) unit. The effects of the different coupling units on the spin multiplicities of the ground states and their stabilities were investigated by means of AM1-CI approach. It has been found that the spin densities on the two atoms of the SC fragment are different from delocalization results in the specific stability of - · N-N<. In these molecules, the stabilities of the triplet states decrease when the distance between the atoms of central SC(-N-) increases. It is shown that the heterocycles as the coupling units have influence on the stabilities of the high-spin ground states. That the heteroatom lying in m -phenyl can improve ferromagnetic coupling, while the heteroatom lying in o -phenyl or p -phenyl is not in favor of the ferromagnetic coupling.
文摘The series of biradicals with m phenylene coupling unit and hetero spin centers were calculated compared with those possessing homo spin centers using AM1 CI method. A simple rule was proposed to design high spin molecules with ferromagnetic coupling unit and hetero spin centers. Two neutral (or charged) hetero spin centers resulted in high spin ground state, one neutral and another charged hetero spin centers correspond to low spin ground state. The latter was ascribed to the huge splitting of two partially occupied molecular orbitals.
