Adaptive Self-Assembly: Environment-Induced Formation and Reversible Switching of Polynuclear Metallocyclophanes
摘要:
Ligand 3 has been shown to self-assemble under coordination of copper(II) cations in a 1:1 ratio in acetonitrile to give equilibrating mixtures of a [2 x 2] grid-type tetranuclear structure 1 and a hexanuclear achitecture of hexagonal shape 2. The latter was confirmed by determination of the crystal structure which further indicated that 2 contained acetonitrile molecules and hydroxo groups bound to the copper(II) centers, which are therefore five-coordinate. The structures assigned to 1 and 2 were further supported by the spectral (mass, UV/Vis) data. The self-assembly process is strongly dependent on the conditions of the medium. An increase in concentration in acetronitrile increases the relative amount of hexamer 2, which appears to be the favored entity at the highest concentrations that can be reached before precipitation occurs. On the other hand, in nitromethane only the tetranuclear complex 1 was detected by mass spectrometry. Replacement of nitromethane by acetonitrile and vice versa indicated the reversible switching between a solution containing either 1 alone or an equilibrium mixture of 1 and 2, respectively. In conclusion, the system described presents several remarkable features: 1) self-assembly with substrate binding, 2) dynamic combinatorial structure generation, and 3) environment-induced structural switching amounting in effect to a process of adaptive self-assembly.
Ligand 3 has been shown to self-assemble under coordination of copper(II) cations in a 1:1 ratio in acetonitrile to give equilibrating mixtures of a [2 x 2] grid-type tetranuclear structure 1 and a hexanuclear achitecture of hexagonal shape 2. The latter was confirmed by determination of the crystal structure which further indicated that 2 contained acetonitrile molecules and hydroxo groups bound to the copper(II) centers, which are therefore five-coordinate. The structures assigned to 1 and 2 were further supported by the spectral (mass, UV/Vis) data. The self-assembly process is strongly dependent on the conditions of the medium. An increase in concentration in acetronitrile increases the relative amount of hexamer 2, which appears to be the favored entity at the highest concentrations that can be reached before precipitation occurs. On the other hand, in nitromethane only the tetranuclear complex 1 was detected by mass spectrometry. Replacement of nitromethane by acetonitrile and vice versa indicated the reversible switching between a solution containing either 1 alone or an equilibrium mixture of 1 and 2, respectively. In conclusion, the system described presents several remarkable features: 1) self-assembly with substrate binding, 2) dynamic combinatorial structure generation, and 3) environment-induced structural switching amounting in effect to a process of adaptive self-assembly.
Bimetallic Iridium(III) Complexes Consisting of Ir(ppy)<sub>2</sub> Units (ppy = 2-Phenylpyridine) and Two Laterally Connected N<sup>∧</sup>N Chelates as Bridge: Synthesis, Separation, and Photophysical Properties
analysis of each fraction indicates high diastereomeric purity. Electronic circular dichroism properties and comparison with literature data establish their absolute configuration. The absorption and emission properties of the three stereoisomers show only very small variations. The anisotropic properties can be interpreted as distinct interactions of the isomers with the chiral resolving Delta-TRISPHAT
前体络合物Ir2(ppy)4Cl2(ppy = 2-苯基吡啶)与桥联配体3,8-二吡啶基-4,7-菲咯啉(L)的反应以94%的收率提供了环金属化铱双核络合物[(ppy )2Ir(mu-L)Ir(ppy)2] 2+(12+)作为三种立体异构体的混合物。该混合物由内消旋形式的Delta,Lambda和外消旋形式(对映体对Delta,Delta和Lambda,Lambda)以1:1.5的比例组成。内消旋体形式的高氯酸盐的单晶X射线表征揭示了(i)桥接配体因平面度而发生的变形以及(ii)两个铱亚基在桥接配体中平面上方和下方的位置。用Delta-TRISPHAT阴离子(TRISPHAT =三(四氯苯并二羟基氨基甲酸)磷酸(V))作为离子对的离子对色谱可分离三种立体异构体。每个部分的1 H NMR光谱分析表明非对映异构体纯度高。电子圆二色性和与文献数据的比较建立了它们的绝对构型。三种立体异构体的吸收和