The nano-scale molecule with the longest delocalized metal–metal bonds: linear heptacobalt(<scp>ii</scp>) metal string complexes [Co<sub>7</sub>(µ<sub>7</sub>-L)<sub>4</sub>X<sub>2</sub>]
作者:Wen-Zhen Wang、Rayyat Huseyn Ismayilov、Gene-Hsiang Lee、Isiah Po-Chun Liu、Chen-Yu Yeh、Shie-Ming Peng
DOI:10.1039/b614661a
日期:——
A new type of pyrazine-modulated oligo-α-pyridylamino ligands, N2-(pyrazin-2-yl)-N6-(6-(pyrazin-2-ylamino)pyridin-2-yl)pyridine-2,6-diamine (H3pzpz) (1) and N2-(pyrazin-2-yl)-N6-(6-(pyridin-2-ylamino)pyridin-2-yl)pyridine-2,6-diamine (H3tpz) (2), were synthesized and characterized by IR, 1H NMR and MS(FAB). Using 1 and 2, the linear heptacobalt(II) metal string complexes [Co7(µ7-L)4X2] (L = pzpz3â, X = Clâ (3), NCSâ (4); L = tpz3â, X = Clâ (5), X = NCSâ (6)) were synthesized and structurally characterized. The structures showed the shortest CoâCo distance (2.194 Ã
) and the longest Co chain (13.5 Ã
) obtained to date with direct CoâCo bonds. The CoâCo distances are in the range 2.194â2.309 Ã
. Electrochemical studies showed two reversible oxidations and one reversible reduction, while all the redox reactions of H3pzpz complexes, 3 and 4, occurred at higher potentials than H3tpz complexes, 5 and 6. The complexes 3â6 are fairly stable to oxidation. Temperature-dependent magnetic research on 3â6 revealed anomalous magnetic behavior with intermediate magnetic moment values between quartet and doublet states, and deviation from the CurieâWeiss law.
一种新型吡嗪调节的寡δ-吡啶氨基配体,N2-(吡嗪-2-基)-N6-(6-(吡嗪-2-基氨基)吡啶-2-基)吡啶-2、合成了 N2-(吡嗪-2-基)-N6-(6-(吡嗪-2-基氨基)吡啶-2-基)吡啶-2,6-二胺 (H3pzpz) (1) 和 N2-(吡嗪-2-基)-N6-(6-(吡嗪-2-基氨基)吡啶-2-基)吡啶-2,6-二胺 (H3tpz) (2),并通过红外光谱、1H NMR 和 MS(FAB) 进行了表征。利用 1 和 2 合成了线性七钴(II)金属弦配合物[Co7(µ7-L)4X2](L = pzpz3â, X = Clâ (3), NCSâ (4);L = tpz3â, X = Clâ (5), X = NCSâ (6)),并对其进行了结构表征。这些结构显示了迄今为止通过直接 CoCo 键获得的最短 CoâCo 距离(2.194 Ã)和最长 Co 链(13.5 Ã)。CoâCo距离范围为2.194â2.309 Ã。电化学研究表明,H3pzpz 复合物 3 和 4 发生了两次可逆氧化反应和一次可逆还原反应,而 H3tpz 复合物 5 和 6 的所有氧化还原反应都发生在较高的电位下。复合物 3â6 对氧化相当稳定。对 3â6 进行的随温度变化的磁性研究发现,其磁性行为异常,磁矩值介于四重态和双重态之间,并且偏离居里-魏斯定律。