A carboxylic acid-substituted picolinic hydrazone ligand (pcoap) forms a homoleptic [2 × 2] tetranuclear Cu(II)4 complex with four six-coordinate Cu(II) centers bridged by μ-O alkoxide groups in a square grid structure. The terminal carboxylic groups complete the six-coordinate structures at each copper centre, capping off external coordination positions, with two functioning as carboxylates, and two in neutral carboxylic acid form. Despite very large Cu–O–Cu bridge angles (139.2–140.6°), and short Cu–Cu distances (3.97–4.05 Å), which would normally be expected to propagate antiferromagnetic exchange interactions within the grid, strictly orthogonal bridging connections between the metal centers lead to intramolecular ferromagnetic exchange (J
= 7.2(3) cm−1), and an S
= 4/2 magnetic ground state.
一种
羧酸取代的皮科啉腙
配体(pcoap)形成了一种同色[2 × 2]四核 Cu(II)4 复合物,其四个六配位的 Cu(II) 中心在方形网格结构中由μ-O 氧化烷基桥接。末端的羧基使每个
铜中心的六配位结构更加完整,并封顶外部配位,其中两个为
羧酸盐,两个为中性
羧酸形式。尽管 Cu-O-Cu 桥角非常大(139.2-140.6°),Cu-Cu 间距也很短(3.97-4.05 Å),这通常会在网格内传播反
铁磁交换相互作用,但
金属中心之间严格正交的桥接连接导致了分子内
铁磁交换(J = 7.2(3) cm-1)和 S = 4/2 磁基态。