Rotational isomers in stacked macrocycles: Synthesis and spectroscopic properties of peripherally substituted (mu-oxo)bis(phthalocyaninatosilicon) compounds
Rotational isomers in stacked macrocycles: Synthesis and spectroscopic properties of peripherally substituted (mu-oxo)bis(phthalocyaninatosilicon) compounds
复制标题
DOI：
10.1021/ja962663f
复制
发表时间：
1997-11-05
影响因子：
15
通讯作者：
Hanack, M
中科院分区：
文献类型：
--
作者：
Kleinwachter, J;Hanack, M
（RO）(8)PcSi(OSiMe(2)tBu)L和mu-氧桥接二聚体[(RO)(8)PcSi(OSiMe(2)tBu)](2)O (R = H17C8-, H25C12-, （+/-)-3,7- me -2- c8h15 -, (+/-)-2- et - c6h12 -）的合成和光谱性质L = -OSiMe(2)tBu, -OSiMe3, -F, -OH)。所有二聚体的光学吸收光谱都表现出强烈的溶剂致变色行为，而单体则没有。在非芳香族溶剂中，如二氯甲烷，二聚体的q波段在560 ~ 760 nm之间分裂成至少5个宽波段，质子核磁共振谱显示低温下芳香信号的强烈分裂（δ δ = 1 ppm），表明环之间的扭转角类似于20-30度。在芳香族溶剂中，如苯、甲苯或1-甲基萘，可观察到二聚体的热致变色。这是由温度依赖的光学吸收光谱显示，这是由于第二异构体的存在，只发现在芳香溶剂的溶液。在639 nm处有一个非常强而锐利的q波段，在670 nm处有一个弱肩带，在830 nm处有一个非常宽而弱的吸收光谱。这个同分异构体的质子核磁共振谱，即使在-88℃，芳香质子也只有一个信号，显示出两个环的完全交错或重叠构象。两个同分异构体的比例取决于芳香溶剂分子的性质和浓度以及附着在大环上的烷基链R的空间需求。讨论了两种异构体中吸收带的分配与激子耦合理论和芳香溶剂与大环之间的pi-pi相互作用有关，这可能也解释了在单体和二聚体中观察到的强芳香溶剂诱导的核磁共振位移（ASIS）。
The synthesis and spectroscopic properties of a series of soluble octaalkoxy-substituted silicon phthalocyanine monomers, (RO)(8)PcSi(OSiMe(2)tBu)L, and mu-oxo-bridged dimers, [(RO)(8)PcSi(OSiMe(2)tBu)](2)O (R = H17C8-, H25C12-, (+/-)-3,7-Me-2-C8H15-, (+/-)-2-Et-C6H12-; L = -OSiMe(2)tBu, -OSiMe3, -F, -OH), are reported. The optical absorption spectra of all dimers show strong solvalochromic behavior whereas the monomers do not. In nonaromatic solvents like, e.g., dichloromethane, the Q-band of the dimers is split into at least five broad bands between 560 and 760 nm, and proton NMR spectra show a strong splitting (Delta delta = 1 ppm) of the aromatic signal at low temperature, indicating a torsion angle of similar to 20-30 degrees between the rings. In aromatic solvents such as, e.g., benzene, toluene, or 1-methylnaphthalene, thermochromism of the dimers is observed. This is shown by temperature-dependent optical absorption spectroscopy to be due to the presence of a second isomer exclusively found in solutions of aromatic solvents. It shows a rather different absorption spectrum with a very intense and sharp Q-band at 639 nm, a weak shoulder at similar to 670 nm, and a very broad and weak absorption at similar to 830 nm. Proton NMR spectra of this isomer shaw, even at -88 degrees C, only one signal for the aromatic protons, demonstrating a fully staggered or eclipsed conformation of the two rings. The ratio between the two isomers is dependent on the nature and concentration of the aromatic solvent molecules and the steric demand of the alkyl chains R attached to the macrocycle. The assignment of the absorption bands in both isomers is discussed in relation to exciton coupling theory and inter-ring pi-pi interactions between the aromatic solvent and the macrocycles, which are likely to account also for the strong aromatic solvent-induced NMR shifts (ASIS) observed for the monomers as well as for the dimers.