Thermodynamic forecasting of mechanically interlocked switches.
Thermodynamic forecasting of mechanically interlocked switches.
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机械联锁开关的热力学预测。
DOI：
10.1039/b911874h
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发表时间：
2009
影响因子：
3.2
通讯作者：
Stoddart,JFraser
中科院分区：
文献类型：
--
作者：
Olson,MarkA;Braunschweig,AdamB;Ikeda,Taichi;Fang,Lei;Trabolsi,Ali;Slawin,AlexandraMZ;Khan,SaeedI;Stoddart,JFraser
机械互锁分子（MIM）开关的形式，[2]轮烷和[2]索烃已被证明是一个现实和可行的替代硅芯片密度的挑战时，在分子电子器件（MED）和纳米机电系统（NEMS）。结构修饰和化学环境可以对分子运动的弛豫热力学产生很大的影响，例如负责基于MIM的设备的操作的顺式轮烷和索烃中的平移和旋转。结构修饰对可切换MIM中平衡过程的自由能差（ΔGo）的影响可以通过考虑其前体伪轮烷中存在的相互作用来预测。通过采用等温滴定量热法（ITC）调查的热力学参数，一系列的单取代，受体主机cyclophanes与各种捐助者的客人，结合X-射线晶体学数据，一个明显的联系之间的非共价键的相互作用在pseudotaxanes和MIM生存的机械键的形成后，可以确定。因此，在不同的准轮烷形成过程中的自由能差的变化（ΔΔGo值）可以随后外推，以预测与类似MIM开关中的开关相关的热力学的ΔGo值，采用相同的供体-受体识别组分。以这种方式，已经建立了设计和调节可切换MIM和基于MIM的材料的系统的和预测的热力学方法。此外，这些热力学关系让人想起长期被遗忘的概念的“parachor”作为一个分子描述符相对于化学系统中的物理性质的加和性，具体处理定量结构性质-活性关系（QSPR/QSAR）。
Mechanically interlocked molecular (MIM) switches in the form of bistable [2]rotaxanes and [2]catenanes have proven to be—when incorporated in molecular electronic devices (MEDs) and in nanoelectromechanical systems (NEMS)—a realistic and viable alternative to the silicon chip density challenge. Structural modifications and chemical environment can have a large impact on the relaxation thermodynamics of the molecular motions, such as translation and circumrotation in bistable rotaxanes and catenanes responsible for the operation of devices based on MIMs. The effects of structural modifications on the difference in free energy (ΔGo) for the equilibrium processes in switchable MIMs can be predicted by considering, firstly, the interactions present in their precursor pseudorotaxanes. By employing isothermal titration microcalorimetry (ITC) to investigate the thermodynamic parameters governing pseudorotaxane formation for a series of monosubstituted, acceptor host cyclophanes with various donor guests, in conjunction with X-ray crystallographic data, an obvious link between the noncovalent bonding interactions in pseudorotaxanes and MIMs that survive following the formation of the mechanical bond can be identified. It follows that the changes (ΔΔGo values) in the difference of free energy during the formation of different pseudorotaxanes can subsequently be extrapolated to predict ΔGo values for the thermodynamics associated with switching in analogous MIM switches, employing the same donor–acceptor recognition components. In this manner, a systematic and predictive thermodynamic approach to designing and tuning switchable MIMs and MIM-based materials has been established. Additionally, these thermodynamic relationships are reminiscent of the long forgotten concept of the ‘parachor’ as a molecular descriptor with respect to the additivity of physical properties in chemical systems dealing specifically with quantitative structure property-activity relationships (QSPR/QSAR).