Dipartimento di Chimica Generale, Università di Pavia, 27100 Pavia, Italy.
Inorg Chem. 2010 Feb 1;49(3):997-1007. doi: 10.1021/ic9019684.
The racemic form of 5 ((RR)5 + (SS)5) gives dinuclear complexes of 2:2 stoichiometry both with Cu(II), acting as a bis-terdentate ligand, and with Cu(I), acting as a bis-bidentate ligand. Single crystal X-ray diffraction studies have shown that the Cu(II) complex exists as double-strand homochiral helicate molecules: P,P-Cu(2)(II)((RR)5)(2) and M,M-Cu(2)(II)((SS)5)(2); in which the two trans-1,2-cyclohexanediamine subunits have the same chirality for of the two strands. Each Cu(II) metal center is six-coordinated according to a cis-octahedral geometry and interacts with a NNO donor subunit of each strand. The Cu(I) complex, when crystallized from THF in the presence of (rac)5, gives a double-strand homochiral helicate complex and in the solid state forms a racemic mixture of the homochiral metal complexes M,M-Cu(2)(I)((RR)5)(2) and P,P-Cu(2)(I)((SS)5)(2). When crystallizing from a MeCN solution, Cu(I) and (rac)5 give rise to the heterochiral nonhelicate dimeric complex Cu(2)(I)((RR)5)((SS)5), in which the two strands of the dimer have inverse configuration of the trans-1,2-cyclohexanediamine subunits and are assembled side-by-side. In both structural architectures, the Cu(I) centers are four-coordinated by two nitrogen atoms from each strand, according to a distorted tetrahedral geometry. In MeCN solution, the dinuclear Cu(II) complex disassembles to give the mononuclear species, which, on reduction at a platinum electrode in a cyclic voltammetry experiment, gives two Cu(I) mononuclear complexes that quickly assemble to give the dinuclear Cu(I) complex. This complex undergoes two consecutive one-electron oxidation processes, but the dinuclear Cu(II) species that forms decomposes in less than 1 s. On the contrary, the Cu(2)(I)((rac)5)(2) complex is stable in MeCN solution and undergoes two one-electron oxidation processes to give a form of dinuclear Cu(II) complex that lasts in solution for more than 20 s.
（RR）5 和（SS）5 的外消旋形式给出了具有 2:2 化学计量比的双核配合物，与 Cu(II) 结合时，它作为双齿配体，与 Cu(I) 结合时，它作为双齿配体。单晶 X 射线衍射研究表明，Cu(II) 配合物存在双链同手性螺旋分子：P，P-[Cu(2)(II)((RR)5)(2)]（4+）和 M，M-[Cu(2)(II)((SS)5)(2)]（4+）；其中两个反式-1,2-环己二胺亚基对于两条链具有相同的手性。每个 Cu(II) 金属中心根据顺式八面体几何结构进行六配位，并与每条链的一个 NNO 供体亚基相互作用。Cu(I) 配合物在 THF 中结晶并存在（rac）5 时，会得到双链同手性螺旋配合物，在固态下形成 M，M-[Cu(2)(I)((RR)5)(2)]（2+）和 P，P-[Cu(2)(I)((SS)5)(2)]（2+）同手性金属配合物的外消旋混合物。从 MeCN 溶液中结晶时，Cu(I) 和（rac）5 生成异手性非螺旋二聚体配合物[Cu(2)(I)((RR)5)((SS)5)]（2+），其中二聚体的两条链具有反式-1,2-环己二胺亚基的相反构型，并排组装。在这两种结构架构中，Cu(I) 中心通过来自每个链的两个氮原子四配位，形成扭曲的四面体几何形状。在 MeCN 溶液中，双核 Cu(II) 配合物解组装为单核物种，该单核物种在循环伏安实验中在铂电极上还原时，生成两个快速组装成双核 Cu(I) 配合物的单核 Cu(I) 配合物。该配合物经历两个连续的单电子氧化过程，但形成的双核 Cu(II) 物种在不到 1 秒内分解。相反，[Cu(2)(I)((rac)5)(2)]（2+）配合物在 MeCN 溶液中稳定，并经历两个单电子氧化过程，生成一种在溶液中持续超过 20 秒的双核 Cu(II) 配合物。
