首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >Mono-, di- and trinuclear 2,3,5,6-tetrakis(2-pyridyl)pyrazine (tppz)-containing copper(II) complexes: syntheses, crystal structures and magnetic properties
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Mono-, di- and trinuclear 2,3,5,6-tetrakis(2-pyridyl)pyrazine (tppz)-containing copper(II) complexes: syntheses, crystal structures and magnetic properties

机译:单,二和三核含2,3,5,6-四(2-吡啶基)吡嗪(tppz)的铜(II)配合物:合成,晶体结构和磁性

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摘要

Three new copper(II) complexes of formula [Cu(tppz) (NCO)(2)] . 0.4H(2)O(1), [Cu-2(tppz) Br-4] (2) and [Cu-3(tppz) (C5O5)(3)(H2O)(3)] . 7H(2)O(3) [tppz = 2,3,5,6-tetrakis(2-pyridyl) pyrazine; C5O52- = croconate, dianion of 4,5-dihydroxycyclopent-4-ene-1,2,3-trione] have been synthesised and structurally characterized by X-ray diffraction methods. The structure of complex 1 is made up of neutral [Cu(tppz) (NCO)(2)] mononuclear units and uncoordinated water molecules. The mononuclear units are grouped by pairs to give a rather short copper copper distance of 3.9244(4) Angstrom. The structure of complex 2 consists of neutral tppz-bridged [Cu-2(tppz)Br-4] dinuclear units, the copper copper separation across tppz being 6. 6198(1) Angstrom. The dinuclear units are further connected through weak, double out-of-plane Cu-Br ... Cu bridges [Br( 1) ... Cu(1a) 4.0028(17) Angstrom] creating tetranuclear entities, the copper copper separation through this interaction being 4.3299(21) Angstrom. The structure of complex 3 is built of neutral [Cu-3(tppz) (C5O5)(3)(H2O)(3)] trinuclear units and uncoordinated water molecules. Tppz and one of the croconate groups act as bridging ligands, the former exhibiting the bis-terdentate coordination mode and the latter adopting an unusual asymmetrical bis-bidentate bridging mode through three adjacent oxygen atoms. The other two croconate groups exhibit the bidentate coordination mode. The intramolecular copper copper separations are 6. 5417( 9) ( across tppz) and 4.3234(9) Angstrom (through bis-bidentate croconato). The magnetic properties of 2 and 3 have been investigated in the temperature range 1.9-300 K. The magnetic behaviour of complex 2 is that of an antiferromagnetically coupled copper(II) dimer (J = -40.9 cm(-1), the Hamiltonian being (H) over cap = -J (S) over cap (A).(S) over cap (B)). In the case of compound 3, the chi(M) T vs. T plot is typical of an overall antiferromagnetic coupling with a low-lying spin doublet being fully populated at T < 10 K. The values of the intramolecular antiferromagnetic interactions in 3 are -19.9 (across tppz) and -32.9 cm(-1) ( through bridging croconato). Density functional type calculations were performed on model dinuclear fragments of 3 in order to analyze the efficiency of the exchange pathways involved and also to substantiate the coupling parameters.
机译:三种新的式[Cu(tppz)(NCO)(2)]的铜(II)配合物。 0.4H(2)O(1),[Cu-2(tppz)Br-4](2)和[Cu-3(tppz)(C5O5)(3)(H2O)(3)]。 7H(2)O(3)[tppz = 2,3,5,6-四(2-吡啶基)吡嗪;合成了C 5 O 52- = croconate,4,5-二羟基环戊-4-烯-1,2,3-三酮的二价阴离子,并通过X射线衍射法对其结构进行了表征。配合物1的结构由中性[Cu(tppz)(NCO)(2)]单核单元和未配位的水分子组成。单核单元按对分组,以得到相当短的铜铜距离,为3.9244(4)埃。配合物2的结构由中性的tppz桥联[Cu-2(tppz)Br-4]双核单元组成,tppz上的铜铜间隔为6 6198(1)埃。双核单元通过弱的双平面Cu-Br ... Cu桥[Br(1)... Cu(1a)4.0028(17)埃)进一步连接,形成四核实体,通过这种相互作用为4.3299(21)埃。配合物3的结构由中性[Cu-3(tppz)(C5O5)(3)(H2O)(3)]三核单元和未配位的水分子组成。 Tppz和一个crocroate基团充当桥接配体,前者表现出双齿配位模式,而后者则通过三个相邻的氧原子采用不寻常的不对称双齿桥接模式。其他两个鳄鱼组表现出双齿协调模式。分子内铜的铜间距为6. 5417(9)(横跨tppz)和4.3234(9)埃(通过双齿croconato)。在1.9-300 K的温度范围内研究了2和3的磁性。配合物2的磁性是反铁磁耦合的铜(II)二聚体(J = -40.9 cm(-1),哈密顿量为(H)超过上限= -J(S)超过上限(A)。(S)超过上限(B))。在化合物3的情况下,chi(M)T与T的关系图是整体反铁磁耦合的典型特征,其中低层自旋双峰在T <10 K时完全填充。在3中的分子内反铁磁相互作用的值为-19.9(横跨tppz)和-32.9 cm(-1)(通过桥接croconato)。在模型双核碎片3上进行密度泛函类型计算,以分析涉及的交换途径的效率并证实偶联参数。

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