三吡啶二胺配基的異金屬錯合物之合成與導電度研究

Abstract

以三吡啶二胺配基 (tripyridyldiamino ligand)為配基，簡稱H2tpda，成功合成出五核混金屬，[Mo2Co3(μ5-tpda)4(X)2] 【X = Cl (1)，NCS (2)】，兩個鉬金屬和三個鈷金屬被四個tpda架橋配基以螺旋式纏繞成全順向式配位而構成直線型，軸向基配位在一個鉬原子和一個鈷原子上， (1)、(2) 的M1-M2 (M1 = M2 = 50 % Mo + 50 % Co)距離約為2.17 A，其鍵長接近Mo2有金屬四重鍵 (2.09 A)和Co-Co單鍵 (2.30 A)的平均值。 使用同樣的配基，成功合成出四核混金屬串，[MoCo3(μ5-tpda)4(NCS)2] (3)，其中一個鉬金屬和三個鈷金屬被四個tpda架橋配基，以螺旋式纏繞成全順向式配位而構成直線型，軸向基配位分別在不同的終端鈷原子上。 最後更成功合成出在五核對稱混金屬 [Mo4Ni1(μ5-tpda)4(Cl)2] (4)，軸向基配位在不同的終端鉬原子上。 電化學分析下，(1)、(2)、(3)皆具有良好的可逆氧化還原的特性，(1)、(2)有三對可逆的氧化還原對，在氧化的部份都有兩對氧化還原對且在還原部份都有一對氧化還原對，而 (3)有四對可逆的氧化還原對。進行OTTLE光譜測量，由高回復率再次驗證具有好的氧化還原特性。 以超導量子干涉儀量測磁性，可知錯合物 (1)-(3)可能具自旋交叉 (spin-crossover)現象，350 K時的μeff = 4.06 B.M. (1)，μeff = 2.686 B.M. (2)，μeff = 2.94 B.M. (3)。 進行單分子導電度量測，(2)其導電值為4×10-5G0，推測原因Mo-Mo間具四重鍵，造成電子傳導較容易。

A series of asymmetric heteronuclear metal string complexes, [Mo2Co3(μ5-tpda)4(X)2] 【X = Cl (1)，NCS (2)】(tpda = tripyridyldiamino anion) are synthesized, axial ligands are bonded to one Mo ion and one Co ion. The crystal structure shows M1-M2 (M1 = M2 = 50 % Mo + 50 % Co) bond distance of (1) and (2) are about 2.17 A and it corresponds to an average of metal-metal quadruple bond and single bond. The tetranuclear linear metal string [MoCo3(μ5-tpda)4(NCS)2] (3) is helically wrapped by four all syn type ligands. The Mo4+ is chelated by one pyridine N atom and the amido N atom of each of tpda2- and is surrounded by four ligating tpda2-, axial ligands are bonded to different cobalt ions. Another symmetric heteronuclear metal string complex, [Mo4Ni1(μ5-tpda)4(Cl)2] (4) which axial ligands are bonded to different Mo ions. In the CV analysis, the linear pentanuclear complexes (1) and (2) all have good reversible redox properties. It shows two pairs of reversible redox couples in oxidation and one pair of reversible redox couples in reduction. The linear tetranuclear complex (3) also has good reversible redox properties. It shows three pairs of reversible redox couples in oxidation and one pair of reversible redox couples in reduction. All the complexes tested by OTTLE and the good redox properties are once again verified by the high response rate. The magnetic susceptibility shows that complex (1)-(3) are spin-crossover. The μeff values of (1) (4.06 B.M.), (2) (2.89 B.M.), (3) (2.94 B.M.) at 350K. In complex (1)-(3), the electronic configuration (S=0) of Mo24+ bimetal clusters is diamagnetic, the Mo4+ ion is paramagnetic and the tricobalt ion exhibits spin-crossover. From STM-bj data, the conductance of value of single molecular complex (2) is 4×10-5G0. The quadruple bond between Mo-Mo causes easier electronic communication.