作为寡吡啶模拟物的Verdazyl自由基：1,5-二甲基-3-(2,2'-联吡啶-6-基)-6-氧代Verdazyl的M(II)配合物（M = Mn、Ni、Cu、Zn）的结构和磁性

Verdazyl radicals as oligopyridine mimics: structures and magnetic properties of M(II) complexes of 1,5-dimethyl-3-(2,2'-bipyridin-6-yl)-6-oxoverdazyl (M = Mn, Ni, Cu, Zn).

作者信息

Barclay Tosha M, Hicks Robin G, Lemaire Martin T, Thompson Laurence K

机构信息

Department of Chemistry, Mississippi State University, Box 9573, State College, Mississippi 39762, USA.

出版信息

Inorg Chem. 2003 Apr 7;42(7):2261-7. doi: 10.1021/ic020520q.

DOI:10.1021/ic020520q

PMID:12665359

Abstract

The verdazyl radical 1,5-dimethyl-3-(2,2'-bipyridin-6-yl)-6-oxoverdazyl (3) was prepared, and its homoleptic metal complexes M(3)(2)(2+).2X(-) (5, M = Mn(II); 6, M = Ni(II); 7, M = Cu(II); 8, M = Zn(II); X = ClO(4), PF(6)) were characterized by single-crystal X-ray diffraction and variable-temperature magnetic susceptibility measurements. Relevant crystallographic parameters are as follows: 5, monoclinic space group Pna2(1), a = 18.755(4) A, b = 11.154(3) A, c = 16.594(4) A, alpha = 90.00 degrees, beta = 90.00 degrees, gamma = 90.00 degrees, V = 3471.4(13) A(3), and Z = 4; 7, triclinic space group Ponedblac;, a = 9.4638(18) A, b = 9.8442(19) A, c = 18.769(4) A, alpha = 103.746(3) degrees, beta = 92.925(3) degrees, gamma = 94.869(3) degrees, V = 1687.8(6) A(3), and Z = 2; 8, triclinic space group Ponedblac;, a = 9.4858(14) A, b = 9.7919(14) A, c = 18.889(3) A, alpha = 104.196(3) degrees, beta = 92.855(3) degrees, gamma = 94.216(3) degrees, V = 1692.1(4) A(3), and Z = 2. In all cases, the two verdazyl-based ligands bind almost perpendicular to each other in meridional positions, yielding pseudooctahedral metal complexes whose general structural features are strongly reminiscent of metal bis(terpyridine) complexes. The intramolecular metal-verdazyl magnetic exchange coupling is strongly ferromagnetic in 6 (J(Ni-vd) = +240 cm(-1)), and strongly antiferromagnetic in 5 (J(Mn-vd) = -93 cm(-1)). Complex 7 exhibits weak ferromagnetic coupling (J(Cu-vd) = -4.5 cm(-1)). Intramolecular radical-radical coupling in the zinc complex 8 was found to be weakly antiferromagnetic (J(vd-vd) = -8 cm(-1)). Intramolecular radical-radical exchange was generally weak in the four metal complexes, ranging from -10 cm(-1) (for 5) to +2 cm(-1) (for 7). The low-temperature magnetic behavior of 7 and 8 is complex, possibly arising from a combination of intra- and intermolecular interactions.

摘要

制备了氮氧自由基1,5-二甲基-3-(2,2'-联吡啶-6-基)-6-氧代氮氧自由基(3)，并通过单晶X射线衍射和变温磁化率测量对其同配金属配合物M(3)₂(2⁺)·2X⁻(5，M = Mn(II)；6，M = Ni(II)；7，M = Cu(II)；8，M = Zn(II)；X = ClO₄⁻，PF₆⁻)进行了表征。相关晶体学参数如下：5，单斜空间群Pna2(1)，a = 18.755(4) Å，b = 11.154(3) Å，c = 16.594(4) Å，α = 90.00°，β = 90.00°，γ = 90.00°，V = 3471.4(13) Å³，Z = 4；7，三斜空间群P-1，a = 9.4638(18) Å，b = 9.8442(19) Å，c = 18.769(4) Å，α = 103.746(3)°，β = 92.925(3)°，γ = 94.869(3)°，V = 1687.8(6) Å³，Z = 2；8，三斜空间群P-1，a = 9.4858(14) Å，b = 9.7919(14) Å，c = 18.889(3) Å，α = 104.196(3)°，β = 92.855(3)°，γ = 94.216(3)°，V = 1692.1(4) Å³，Z = 2。在所有情况下，两个基于氮氧自由基的配体在子午位置几乎相互垂直结合，形成伪八面体金属配合物，其一般结构特征与金属双(三联吡啶)配合物非常相似。分子内金属-氮氧自由基磁交换耦合在6中为强铁磁性(J(Ni-vd) = +240 cm⁻¹)，在5中为强反铁磁性(J(Mn-vd) = -93 cm⁻¹)。配合物7表现出弱铁磁性耦合(J(Cu-vd) = -4.5 cm⁻¹)。发现锌配合物8中的分子内自由基-自由基耦合为弱反铁磁性(J(vd-vd) = -8 cm⁻¹)。在这四种金属配合物中，分子内自由基-自由基交换通常较弱，范围从-10 cm⁻¹(对于5)到+2 cm⁻¹(对于7)。7和8的低温磁行为很复杂，可能是由分子内和分子间相互作用共同引起的。