磁性双核Ni(Ⅱ)配合物的BS-DFT理论研究

基于对称性破损态方法结合密度泛函理论,运用不同方法和基组,对典型的μ1,1-N3铁磁性双核Ni(Ⅱ)配合物[L1 Ni_2(N_3)](NO_3)2(1)和μ1,3-N3反铁磁性双核Ni(Ⅱ)配合物[L_2Ni_2(N_3)](ClO_4)_2(2)的磁性进行了研究.结果表明,杂化密度泛函方法能够准确描述2个配合物的磁特性,计算结果与实验值吻合很好.配合物1中单占据分子轨道(SOMOs)能量劈裂较小,表现为近简并,有利于铁磁耦合相互作用;配合物2中SOMOs能量劈裂较大,导致反铁磁性相互作用.配合物1中存在2条磁通道,其中pyrazolate配体的N原子间存在p轨道重叠,有利于反铁磁相互作用,叠氮基和金属Ni中心之间为正交磁轨道,有利于铁磁相互作用,2个磁通道作用的总结果使得体系宏观上显示为弱铁磁性;配合物2中,2条磁通道的配体pyrazolate和叠氮基中的N原子之间都存在p轨道重叠,导致反铁磁耦合.     

羧酸桥对反铁磁性EO叠氮铜双核配合物磁性影响的理论研究

基于密度泛函理论结合对称性破损态(DFT-BS)方法,运用不同的密度泛函和基组对反铁磁性EO叠氮铜双核配合物[Cu2(dmpe)2(μ1,1-N3)2(CH3COO)]+的磁性质进行研究.结果显示,杂化泛函计算的结果与实验数据非常吻合,能够准确描述反铁磁性EO叠氮铜双核配合物的磁性质.磁轨道分析表明,配合物中存在3个磁通道(2个叠氮桥、1个羧酸桥),磁通道中N原子、O原子与顺磁中心二价铜离子间都存在p d轨道重叠,对体系反铁磁性耦合相互作用都有贡献.从自旋布居分布角度来看,该配合物中顺磁中心间主要是自旋离域作用.配合物中羧酸桥传递强反铁磁性相互作用,使得顺磁中心间磁轨道的重叠增加,体系的反铁磁性相互作用增强.     

叠氮/吡啶苯甲酸氮氧化物共配叠氮铜配合物磁学性质理论研究

基于DFT-BS方法,采用不同泛函和基组研究了叠氮/吡啶苯甲酸氮氧化物共配叠氮铜配合物[Cu（4,3-opybz）(μ-N₃)]_n的磁学性质.结果表明,在B3P86/TZVP水平下计算的磁耦合常数(48.20 cm^-1)与实验值(49.70 cm^-1)最吻合,可准确描述其磁学性质.磁轨道分析表明,Cu（Ⅱ）离子的未成对电子主要集中在3d_x²-y²轨道上.顺磁中心与桥联配体间存在强轨道相互作用,其磁轨道主要来源于顺磁中心Cu（1）和Cu（2）的3d_x²-y²轨道、吡啶苯甲酸氮氧化物桥联配体羧酸根离子的离域π键和叠氮配体的p轨道.顺磁中心Cu（Ⅱ）主要是自旋离域机理,顺磁中心的自旋离域作用使得与其配位的原子获得了少量的自旋电子.     

甲酸根桥联双核铜配合物磁学性质理论研究

基于DFT-BS方法,选择不同的泛函方法和基组,研究anti,anti甲酸桥联双核铜配合物的磁学性质.结果表明,在B3P86/TZV水平计算得到顺磁中心Cu(Ⅱ)离子间磁耦合常数为-55.63 cm^-1,与实验值-55.60 cm^-1最接近,可准确描述甲酸桥联双核铜配合物的磁学性质.顺磁中心Cu(Ⅱ)与甲酸根桥联配体间有较强的轨道作用,其磁轨道主要来源于Cu(Ⅱ)离子的3dyz轨道、桥联配体甲酸根离子的离域π键,顺磁中心Cu(Ⅱ)离子为自旋离域机理.在不同桥联模式的甲酸桥联双核铜配合物中,随顺磁中心Cu(1)自旋密度增加,Cu(Ⅱ)离子间的反铁磁性贡献逐渐增加,其磁耦合常数J值逐渐减小.     

吡唑/草酸根混合配位的非对称双核铜配合物磁性的理论研究

基于密度泛函理论结合对称性破损态方法,选择不同的泛函方法和基组研究吡唑/草酸根混合配位的非对称双核铜配合物的磁学性质。结果表明,在B3LYP/def2-TZVP水平计算的磁耦合常数为-127.24cm~(-1),与实验值-129cm~(-1)基本吻合,可准确描述吡唑/草酸根混合配位的非对称双核铜配合物的磁学性质。磁轨道和自旋布居分析表明,顺磁中心Cu(Ⅱ)与桥联配体草酸根离子间存在较强的轨道相互作用,其磁轨道主要由顺磁中心Cu(Ⅱ)的3d_x2_(-y)2轨道、桥联配体草酸根离子的π键组成,顺磁中心Cu(Ⅱ)主要是自旋离域机理。配合物磁性与结构关系的研究表明,随着结构参数τ的增加,顺磁中心HS态和BS态自旋密度的平方差和自然磁轨道间重叠积分的平方随之增大,反铁磁性相互作用的贡献增大,配合物磁耦合常数J值减小。     

氢键桥联双核铜配合物磁耦合的密度泛函研究

在密度泛函理论的基础上,应用对称性破损方法研究了氢键桥联双核铜模型配合物的磁耦合行为以及磁耦合常数随O-O距离的变化趋势.计算结果表明,反铁磁耦合作用来源于Cu原子的d_x²-y²和氧原子的p_x或p_y磁轨道的部分重叠,而H原子不参与磁耦合作用.磁耦合常数J与O-O距离r之间存在指数关系,而不是线性关系.     

溶剂对4-叠氮苯甲酸共配叠氮铜配合物磁学性质影响的理论研究

基于DFT-BS方法,在不同泛函方法和基组下研究μ-1,1叠氮、4-叠氮苯甲酸、溶剂共配的叠氮铜配合物[Cu2(4-aba)3(N3)3(CH3OH)3]2-的磁学性质。结果显示,在B2PLYP/TZVP水平下计算得到顺磁中心间的磁耦合常数为33.48 cm-1,与实验值33.80 cm-1最吻合,可准确描述其磁学性质。配合物[Cu2(4-aba)3(N3)3(CH3OH)3]2-的分子磁轨道主要贡献来自于顺磁中心Cu(1)、Cu(2)的3dx2-y2轨道、N3-离子的π型轨道、4-叠氮苯甲酸的π型轨道和溶剂甲醇氧原子的p轨道。在4-叠氮苯甲酸共配的叠氮铜配合物中引入共配溶剂水及醇类,随溶剂R基供电子效应的增加,反铁磁性部分对磁耦合常数的贡献减小,其磁耦合常数J值随之增大。     

新型三核配合物[ CuL( DMF) 2] 2Zn( N3) 2的合成及其性质

以含草酰胺桥的单核配合物CuL(H₂L=2,3-二氧-5,6 ∶13,14-二联苯基-9,10-环己基-1,4,8,11-四氮杂十四环-7,12-二烯烃)为前驱体, Zn(ClO₄)₂·6H₂O为金属中心,NaN₃为辅助配体,DMF为溶剂,采用扩散法合成了一例新的三核金属配合物[CuL(DMF)₂]₂Zn(N₃)₂,并通过元素分析,X-射线粉末衍射、X-射线单晶衍射、红外光谱、紫外-可见光谱、磁性分析对其进行了表征。结构分析表明：该配合物(CCDC:1835721)属于三斜晶系,P₁空间群,晶胞参数分别为a=9.618 8(19) , b=9.878 5(18) , c=14.555(3) , α=100.898(3)°, β=101.384(3)°, γ=109.661(3)°, V=1 226. 9(4) ³, Z=1。磁性研究表明：配合物中顺磁金属离子Cu(II)之间存在弱的反铁磁性相互作用。     

金属串配合物[Ni3(L)4(NCS)2](L = dpa-, mpta-, mdpa-, mppa-)结构和磁性的理论研究

应用密度泛函理论BP86方法结合自然键轨道分析方法对具有分子导线潜在应用前景的金属串配合物[Ni₃(L)₄(NCS)₂](L = dpa^- (1), mpta^- (2), mdpa^- (3), mppa^- (4))进行研究,分析了桥联配体L对Ni―Ni相互作用和磁耦合性质的影响.结果得到: (1)配合物的基态均是对应于五重态(HS)的反铁磁(AF)单重态, HS的能量和结构与AF态相近, Ni₃⁶⁺链形成了三中心四电子σ键(σ₂σ_nb¹σ^*1). (2) dpa^-引入甲基成为mdpa^-,对Ni―Ni、Ni―N距离影响不大; 3H-吡咯环和噻唑环取代吡啶环后, N1―N2、Ni―Ni距离增大, Ni2―N2键长缩短,但噻唑环的影响较小;故Ni―Ni相互作用强度为1 ≈ 3 > 2 > 4. (3)预测了3和4的J_ab值为-103和-88 cm^-1,随Ni―Ni相互作用增强磁耦合效应增大. Ni―Ni相互作用越大,通过Ni₃⁶⁺链σ型轨道的直接磁耦合越强; Ni2―N2键越强,通过涉及桥联配体的间接磁耦合越强,直接磁耦合比间接磁耦合更强.     

一维交替铁磁-反铁磁耦合的海森堡链[Mn(N_3)_2(pybox)]_n(英文)

合成了一种叠氮锰一维链状化合物([MnⅡ(N3)2(pybox)]n,1),该化合物采用2,6-吡啶双噁唑啉(pybox)三齿配体和叠氮作为共配体。用单晶X射线衍射的方法对其晶体结构进行了表征,结果表明二价锰离子通过双EO叠氮桥和双EE桥交替桥连成链状结构,其中锰离子分别与4个叠氮根和1个pybox配体上的3个氮原子配位,为七配位模式。变温磁化率数据表明,交替的EO叠氮桥和EE叠氮桥分别传递铁磁和反铁磁耦合相互作用形成一维交替的海森堡链。通过S=5/2交替铁磁-反铁磁耦合一维体系的理论模型,我们获得其磁耦合常数为:J1=9.19 cm-1,J2=-19.89 cm-1。化合物1在低温表现出反铁磁有序。     

Theoretical studies on the magnetic bistability of dinickel complex tuned by azide

The magnetic-structural correlation in magnetic switchable dinickel(II) complex [LNi2(N3)3] (L- is a pyrazolate-based compartmental ligand) has been investigated on the basis of various unrestricted density functional theory (UDFT) combined with the broken symmetry (BS) approach. The calculated exchange coupling constants were in good agreement with experimental result by using the PBE0 method with LANL2DZ basis set. The antiferromagnetic interaction between the Ni(II) ions is mainly due to the large energy difference of the singly occupied molecular orbitals (SOMOs), and the p orbital overlap for nitrogen atoms on azido and the pyrazolate bridge groups. The analysis of the spin density distribution reveals that both the spin polarization and spin delocalization contribute to the antiferromagnetic interaction. Furthermore, the bistable magnetic behavior for this system (strong antiferromagnetic interaction in low-temperature phase and the week antiferromagnetic in high-temperature phase) results from the change of the Ni-NNN-Ni dihedral angle (tau) in mu1,3-N3. The increase of tau is the key role in decreasing the SOMOs energy difference and weakening the antiferromagnetic interaction. Therefore, the abrupt modulation of the magnitude of M-NNN-M dihedral angle tau in the binuclear-azide complex by external perturbations provides new possibilities for the design of molecular magnetic switching devices.     

新型二维网状双席夫碱银配合物的合成与结构

席夫碱配体由于在合成上具有极大的灵活性和良好的配位能力 ,因而席夫碱 -金属配合物的研究一直受到广泛重视 .多年来 ,席夫碱配体由简单的单齿发展到多齿和大环配体 .此外 ,过渡金属的席夫碱配合物具有独特的结构、性能和广泛的应用 ,如氧化还原 [1] 、催化 [2 ] 以及生物体系的化学模拟 [3 ] ;另一方面 ,由于银原子配位方式的多样性 (二、三、四和五配位 ) ,便于人们对超分子化合物的组装规律进行系统研究 ,因而银配合物的研究正日益引起人们极大的兴趣 [4～ 7] .鉴于此 ,我们设计合成了一个新的四齿席夫碱配体 L ,研究了其与 CF3 SO3 …     

Crystal structures and magnetic properties of 2,3,5,6-tetrakis(2-pyridyl)pyrazine (tppz)-containing copper(II) complexes

Four new copper(II) complexes of formula [Cu(2)(tppz)(dca)(3)(H(2)O)].dca.3H(2)O (1), [Cu(5)(tppz)(N(3))(10)](n)() (2), [[Cu(2)(tppz)(N(3))(2)][Cu(2)(N(3))(6)]](n)() (3), and [Cu(tppz)(N(3))(2)].0.33H(2)O (4) [tppz = 2,3,5,6-tetrakis(2-pyridyl)pyrazine and dca = dicyanamide anion] have been synthesized and structurally characterized by X-ray diffraction methods. The structure of complex 1 is made up of dinuclear tppz-bridged [Cu(2)(tppz)(dca)(3)(H(2)O)](+) cations, uncoordinated dca anions, and crystallization water molecules. The copper-copper separation across bis-terdentate tppz is 6.5318(11) A. Complex 2 is a sheetlike polymer whose asymmetric unit contains five crystallographically independent copper(II) ions. These units are building blocks in double chains in which the central part consists of a zigzag string of copper atoms bridged by double end-on azido bridges, and the outer parts are formed by dinuclear tppz-bridged entities which are bound to the central part through single end-on azido bridges. The chains are furthermore connected through weak, double out-of-plane end-on azido bridges, yielding a sheet structure. The intrachain copper-copper separations in 2 are 6.5610(6) A across bis-terdentate tppz, 3.7174(5) and 3.8477(5) A across single end-on azido bridges, and from 3.0955(5) to 3.2047(7) A across double end-on azido bridges. The double dca bridge linking the chains into sheets yields a copper-copper separation of 3.5984(7) A. The structure of 3 consists of centrosymmetric [Cu(2)(tppz)(N(3))(2)](2+) and [Cu(2)(N(3))(6)](2)(-) units which are linked through axial Cu.N(azido) (single end-on and double end-to-end coordination modes) type interactions to afford a neutral two-dimensional network. The copper-copper separations within the cation and anion are is 6.5579(5) A (across the bis-terdentate tppz ligand) and 3.1034(6) A (across the double end-on azido bridges), whereas those between the units are 3.6652(4) A (through the single end-on azido group) and 5.3508(4) A (through the double end-to-end azido bridges). The structure of complex 4 is built of neutral [Cu(tppz)(N(3))(2)] mononuclear units and uncoordinated water molecules. The mononuclear units are grouped by pairs to give a rather short copper-copper separation of 3.9031(15) A. The magnetic properties of 1-4 have been investigated in the temperature range 1.9-300 K. The magnetic behavior of complexes 1 and 4 is that of antiferromagnetically coupled copper(II) dimers with J = -43.7 (1) and -2.1 cm(-)(1) (4) (the Hamiltonian being H = -JS(A).S(B)). An overall ferromagnetic behavior is observed for complexes 2 and 3. Despite the structural complexity of 2, its magnetic properties correspond to those of magnetically isolated tppz-bridged dinuclear copper(II) units with an intermediate antiferromagnetic coupling (J = -37.5 cm(-)(1)) plus a ferromagnetic chain of hexanuclear double azido-bridged copper(II) units (the values of the magnetic coupling within and between the hexameric units being +61.1 and +0.0062 cm(-)(1), respectively). Finally, the magnetic properties of 3 were successfully analyzed through a model of a copper(II) chain with regular alternating of three ferromagnetic interactions, J(1) = +69.4 (across the double end-on azido bridges in the equatorial plane), J(2) = +11.2 (through the tppz bridge), and J(3) = +3.4 cm(-)(1) (across the single end-on azido bridge).     

双臂套索冠醚双核铜(Ⅱ)配合物的磁性质研究

测定了双臂套索冠醚双核铜(Ⅰ)配合物[Cu₂L(OH)](ClO₄)₃Me₂CO(L=N,N'-二(8-喹啉甲基)-1,4,10,13-四氧-7,16-二氮环八环)的变温磁化率(4～300K),所加场强为5.O×10⁵A/m.拟合了变温磁化率数据,得到J=-279.cm^-1;加上分子场校正后,得J=-257.7cm^-1,Zj'=-30.1cm^-1.拟合结果表明,分子间存在反铁磁性交换作用,而分子内的磁交换(J＜500cm^-1)还未大到使其反铁磁性交换作用变为抗磁性.用自旋倾斜体系解释了其反常的χm-H图.晶体结构和Cu²⁺3d轨道的分析表明,磁交换作用是通过OH桥进行的.比较了另外2个类似的双核铜(Ⅰ)大环OH桥联配合物,得出了J值和轨道重叠之间的关系.     

Crystal structure, magnetism and spectroscopy of bis(tetraphenylphosphonium)tetrakis(dicyanamido)cobaltate(II) with bridging and pendant dicyanamide ligands

The synthesis, structure and magnetic properties of the cobalt(II) complex, (Ph₄P)₂[Co(NCNCN)₄] (1) is reported. The compound crystallises in the monoclinic system, space group C2/c, with cell constants: β=105.65(2)°, Z=4 and The structure of 1 consists of octahedral CoN₆ chromophores with uni- and bidentate N(CN)₂ ligands. Cobalt atoms are doubly bridged by bidentate NCNCN groups forming infinite ribbons along the crystallographic b-axis. As first representative of an anionic dicyanamide complex 1 behaves as a weak ferromagnet at low temperatures.     

Synthesis, spectral and structural characterization of three zinc(II) azide complexes with aminopyrazine

The reaction between zinc(II) azide, Zn(N₃)₂ and aminopyrazine (ampyz) afforded the complexes: [Zn(N₃)₂(ampyz)₂] (1), [Zn(N₃)₂(ampyz)]_n (2) and [Zn₃(N₃)₆(ampyz)₂]_n (3). These complexes are characterized by spectroscopic and crystallographic methods. The IR spectra of these compounds are measured and discussed. The structure of 1 consists of isolated tetrahedral zinc atom surrounded by two mono-dentate N-ampyz and two terminal azido ligands. Complex 2 features a zigzag chain of zinc centers in which each zinc is surrounded by alternate di-EO (end-on) and di-EE (end-to-end) azide bridges, the chain thus contains alternate four-membered Zn₂N₂ and eight-membered Zn₂(NNN)₂ rings. The two ampyz ligands are located in cis-arrangement and each of them further binds another zinc atom giving rise to a 3D network. Complex 3 contains two structurally different zinc atoms; the six-coordinate Zn(1) center links two di-EO azido bridges and two trans ampyz, thus having ZnN₆ chromophore. The five-coordinate Zn(2) center binds two di-EO bridging azido groups and the fifth position is occupied by an N atom from a bridging ampyz molecule. Both zinc centers, therefore participate in the formation of a 1D chain of cyclic Zn₂N₂ units. Each ampyz ligand binds another zinc atom via the second pyrazinic N atom giving another cross-chain and thus the structure consists of 2D sheets. In these three complexes the azido ligands of all types are asymmetric and linear within the experimental error.     

Synthesis, spectral and structural characterization of two polymeric 1:1 complexes of 2,3-dimethylpyridine and 5-ethyl-2-methylpyridine with copper(II) azide; Cu(2,3-dimethylpyridine) (N3)2 and Cu(2-methyl-5-ethylpyridine) (N3)2

Two new 1:1 ligand complexes of copper(II) azide with disubstituted pyridine ligands, namely catena-di-μ(1,3)-azido-[di-μ(1,1)-azidobis(2,3-lutidine)dicopper(II)] (1) and catena-di-μ(1,1)-azido[di-μ(1,1)-azidobis(2-methyl-5-ethylpyridine)dicopper(II)] (2), have been synthesized and characterized by spectroscopic and X-ray crystallographic methods. The polymeric complex 1 features monodentate 2,3-lut ligands, centrosymmetric di-μ(1,1)-azido-bridged Cu₂N₂ rings, distorted square-pyramidal copper(II) coordination geometry and di-μ(1,3)-azido bridges which link the centrosymmetric binuclear Cu₂(2,3-lut)₂(N₃)₂ moieties to form sheets within the ab plane. In the monoclinic crystals of complex 2, the copper(II) centres are pentacoordinated via N(11), N(21), N(11b) and N(21a) from the azido ligands [Cu---N distances 1.971(5)–2.286(5) Å] and N(1) from the organic molecule at a Cu---N bond length of 2.001(5) Å. Both azido ligands function as μ(1,1) bridges to form chains of polyhedra along the short a-axis of the unit cell. The IR absorption spectra reveal that each of these complexes contains two independent azide ligands. The solid and solution electronic spectra of complexes 1 and 2 show at least three and two strong absorption bands, respectively, associated with N₃⁻ → Cu^II charge transfer transitions. The EPR spectra of powder samples and DMSO solutions at room temperature were recorded and are discussed.     

Structurally diverse copper(II) complexes of polyaza ligands containing 1,2,3-triazoles: site selectivity and magnetic properties

Copper(II) acetate mediated coupling reactions between 2,6-bis(azidomethyl)pyridine or 2-picolylazide and two terminal alkynes afford 1,2,3-triazolyl-containing ligands L(1)-L(6). These ligands contain various nitrogen-based Lewis basic sites including two different pyridyls, two nitrogen atoms on a 1,2,3-triazolyl ring, and the azido group. A rich structural diversity, which includes mononuclear and dinuclear complexes as well as one-dimensional polymers, was observed in the copper(II) complexes of L(1)-L(6). The preference of copper(II) to two common bidentate 1,2,3-triazolyl-containing coordination sites was investigated using isothermal titration calorimetry and, using zinc(II) as a surrogate, in (1)H NMR titration experiments. The magnetic interactions between the copper(II) centers in three dinuclear complexes were analyzed via temperature-dependent magnetic susceptibility measurements and high-frequency electron paramagnetic resonance spectroscopy. The observed magnetic superexchange is strongly dependent on the orientation of magnetic orbitals of the copper(II) ions and can be completely turned off if these orbitals are arranged orthogonal to each other. This work demonstrates the versatility of 1,2,3-triazolyl-containing polyaza ligands in forming metal coordination complexes of a rich structural diversity and interesting magnetic properties.     

Structures with tunable strong ferromagnetic coupling: from unordered (1D) to ordered (Discrete)

The X-ray crystal structures, magnetic susceptibilities from 2 to 300 K, and theoretical analyses of the magnetism for 1D and trinuclear azido Cu(II) carboxylate complexes [Cu(1.5)(hnta)(N(3))(2)(H(2)O)](n) (1) and [Cu(3)(hnta)(4)(N(3))(2)(H(2)O)(3)] (2), respectively, where hnta is 6-hydroxynicotinate, are described. Although both exhibit strong ferromagnetic coupling, discrete complex 2 exhibits long-range ferromagnetic ordering, while the very similar 1D system 1 does not. Density functional calculations provided accurate J values and allowed rationalization of the ferromagnetic coupling in terms of the magnetic orbitals and spin densities.