Department of Chemistry, University of Guelph , Guelph, Ontario N1G 2W1, Canada.
J Am Chem Soc. 2013 Sep 11;135(36):13298-301. doi: 10.1021/ja4067783. Epub 2013 Aug 30.
A binuclear metal coordination complex of the first thiazyl-based biradical ligand 1 is reported (1 = 4,6-bis(1,2,3,5-dithiadiazolyl)pyrimidine; hfac =1,1,1,5,5,5,-hexafluoroacetylacetonato-). The Mn(hfac)2-biradical-Mn(hfac)2 complex 2 is a rare example of a discrete, molecular species employing a neutral bridging biradical ligand. It is soluble in common organic solvents and can be easily sublimed as a crystalline solid. Complex 2 has a spin ground state of S(T) = 4 resulting from antiferromagnetic coupling between the S(birad) = 1 biradical bridging ligand and two S(Mn) = 5/2 Mn(II) ions. Electrostatic contacts between atoms with large spin density promote a ferromagnetic arrangement of the moments of neighboring complexes in ribbon-like arrays. Weak antiferromagnetic coupling between these high-spin ribbons stabilizes an ordered antiferromagnetic ground state below 4.5 K. This is an unusual example of magnetic ordering in a molecular metal-radical complex, wherein the electrostatic contacts that direct the crystal packing are also responsible for providing an efficient exchange coupling pathway between molecules.
报道了首例噻唑基双自由基配体 1 的双核金属配位配合物（1=4,6-双（1,2,3,5-四氢恶二唑基）嘧啶；hfac=1,1,1,5,5,5-六氟乙酰丙酮酸根）。Mn(hfac)2-双自由基-Mn(hfac)2 配合物 2 是一种罕见的采用中性桥联双自由基配体的离散、分子物种。它可溶于常见有机溶剂，并且可以很容易地升华得到结晶固体。配合物 2 的自旋基态为 S(T) = 4，这是由于 S(birad) = 1 双自由基桥联配体和两个 S(Mn) = 5/2 Mn(II)离子之间的反铁磁耦合所致。具有大自旋密度的原子之间的静电接触促进了相邻配合物在带状阵列中磁矩的铁磁排列。这些高自旋 ribbons 之间的弱反铁磁耦合稳定了在 4.5 K 以下的有序反铁磁基态。这是分子金属-自由基配合物中磁有序的一个不寻常例子，其中指导晶体堆积的静电接触也负责提供分子之间有效的交换耦合途径。
