Crowley James D, Goshe Andrew J, Steele Ian M, Bosnich Brice
Department of Chemistry, The University of Chicago, 5735 South Ellis Avenue, Chicago, IL 60637, USA.
Chemistry. 2004 Apr 19;10(8):1944-55. doi: 10.1002/chem.200305620.
A dicationic molecular receptor bearing two cofacially disposed terpyridyl-Pd-Cl units forms stable 1:1 host-guest complexes with planar, neutral platinum(II) complexes. When the guest is modified to incorporate a pyridine group, the now basic guest is protonated by trifluoroacetic acid in acetonitrile solutions. The basic yellow guest forms a stable, deep red 1:1 host-guest complex with the yellow palladium receptor. Addition of trifluoroacetic acid to this host-guest complex leads to the displacement of the guest from the receptor. It is proposed that the dissociation of the guest is caused by electrostatic repulsion between the dicationic receptor and the positively charged protonated guest. Addition of base restores the host-guest complex. This protonmotive translocation of the guest from the host to the solution is discussed in terms of the mechanisms that drive molecular motors, the power stroke and the Brownian ratchet. It is concluded that the system is best described as a molecular switch that operates by the same mechanism as one stroke of a molecular motor
一种带有两个共面排列的三联吡啶-钯-氯单元的双阳离子分子受体与平面中性铂（II）配合物形成稳定的1:1主客体配合物。当客体经修饰引入吡啶基团时，这种呈碱性的客体在乙腈溶液中会被三氟乙酸质子化。呈碱性的黄色客体与黄色钯受体形成稳定的深红色1:1主客体配合物。向该主客体配合物中加入三氟乙酸会导致客体从受体上解离。据推测，客体的解离是由双阳离子受体与带正电荷的质子化客体之间的静电排斥引起的。加入碱可恢复主客体配合物。从驱动分子马达的机制、动力冲程和布朗棘轮的角度讨论了客体从主体到溶液的这种质子动力易位。得出的结论是，该系统最好被描述为一种分子开关，其运作机制与分子马达的一个冲程相同。
