79357-13-4Relevant articles and documents
Controlled Hierarchical Self-Assembly of Catenated Cages
Li, Pan,Li, Zi-Ying,Li, Zimu,Liu, Xiaoyun,Nomura, Yoshiaki,Sun, Zhongwei,Xu, Shijun,Zhang, Shaodong
, p. 10833 - 10840 (2020)
Constructing hierarchical superstructures to achieve comparable complexity and functions to proteins with four-level hierarchy is challenging, which relies on the elaboration of novel building blocks with complex structures. We present a series of catenated cages with unique structural complexity and tailorability. The rational design was realized as such: A catenane of two symmetric cages (CSC), CSC-1, with all rigid imine panels was converted to a catenane of two dissymmetric cages (CDC), CDC-1, with two exterior flexible amine panels, and CDC-5 was tailored from CDC-1 by introducing an additional methyl group on each blade to increase lateral hindrance. CDC-1s with the most irregular and flexible configuration formed supramolecular dimers, which self-organized into 3D continuous wavelike plank with a three-level hierarchy, previously undiscovered by conventional building blocks. A drastically different 3D triclinic crystalline phase with a four-level hierarchy and trigonal phase with a three-level hierarchy were constructed of distorted CSC-1s and the most symmetric CDC-5s, respectively. The wavelike plank exhibited the lowest order, and the triclinic phase had a lower order than the trigonal phase which had the highest order. It correlates with the configuration of the primary structures, namely, the most disordered shape of CDC-1, the low-order configuration of CSC-1, and the most ordered geometry of CDC-5. The catenated cages with subtle structural differences therefore provide a promising platform for the search of emerging hierarchical superstructures that might be applied to proton conductivity, ferroelectricity, and catalysis.
The VCD spectrum of 2-methylthietane: measured (800-1500 cm-1) and computed with semi-empirical models
Shaw, R. A.,Ibrahim, N.,Wieser, H.
, p. 345 - 356 (2007/10/02)
The vibrational circular dichroism (VCD) spectrum (800 to 1500 cm-1) is reported for 2-methylthietane (2MT).Fixed partial charge (FPC), atomic polar tensor (APT), and charge flow (CF) methods are used to compute the VCD spectra for both stable conformers (CH3 in the axial or equatorial orientation) for the complete range of fundamental vibrations, based on 3-21G and 6-31G* harmonic force fields.The experimental and computed absorption and VCD spectra of R-(+)-2MT are compared to the previously reported spectra of R-(-)-2-methyloxetane.The success of the APT and CFmodels for reproducing the dominant ring stretching IR and VCD features of that compound is rationalized by a comparison of APT and FPC intensity expressions.Further comparison of the APT and FPC calculated electric dipole moment derivatives are interpreted to suggest values for the diagonal CS and CH stretching charge flow terms for 2MT.These investigations then provide a rationale for previously reported successes of the FPC model, and permit identification of specific vibrational modes of 2MT that are amenable to FPC-VCD modeling.The previously established conformational mixture of ca. 30percent axial and 70percent equatorial is shown to be in accord with FPC-VCD predictions for the most appropriate (β-CH2 wagging) mode. Key words: vibrational circular dichroism, 2-methylthietane, fixed partial charge, atomic polar tensor, charge flow.
