Visible-Light-Driven Rotation of Molecular Motors in Discrete Supra­molecular Metalla­cycles

The organization of molecular motors
in supra­molecular assemblies
to allow the amplification and transmission of motion and collective
action is an important step toward future responsive systems. Metal-coordination-driven
directional self-assembly into supra­molecular metalla­cycles
provides a powerful strategy to position several motor units in larger
structures with well-defined geometries. Herein, we present a pyridyl-modified
molecular motor ligand (MPY) which upon coordination
with geometrically distinct di-Pt­(II) acceptors assembles into discrete
metalla­cycles of different sizes and shapes. This coordination
leads to a red-shift of the absorption bands of molecular motors,
making these motorized metalla­cycles responsive to visible light.
Photochemical and thermal isomerization experiments demonstrated that
the light-driven rotation of the motors in the metalla­cycles
is similar to that in free MPY in solution. CD studies
show that the helicity inversions associated with each isomerization
step in the rotary cycle are preserved. To explore collective motion,
the trimeric motor-containing metalla­cycle was aggregated with
heparin through multiple electrostatic interactions, to construct
a multi-component hierarchical system. SEM, TEM, and DLS measurements
revealed that the photo- and thermal-responsive molecular motor units
enabled selective manipulation of the secondary supra­molecular
aggregation process without dissociating the primary metalla­cycle
structures. These visible-light-responsive metalla­cycles, with
intrinsic multiple rotary motors, offer prospects for cooperative
operations, dynamic hierarchical self-assembled systems, and adaptive
materials.

分子马达在超分子组装中的组织结构，旨在实现运动和集体行为的放大与传递，是迈向未来响应性系统的重要步骤。金属配位驱动的方向性自组装进入超分子金属环，为在具有明确几何形状的大型结构中定位多个马达单元提供了一种强大的策略。在本研究中，我们介绍了一种吡啶修饰的分子马达配体（MPY），当与几何上不同的二Pt(II)受体配位时，可组装成不同大小和形状的离散金属环。这种配位导致分子马达的吸收带红移，使这些机动金属环对可见光敏感。光化学和热异构化实验表明，在金属环中光驱动的马达旋转与在溶液中自由MPY的旋转相似。圆二色谱研究表明，在旋转周期中每个异构化步骤相关的螺旋反转都被保留。为了探索集体运动，含有三聚马达的金属环通过与肝素的多重静电相互作用聚集，构建了一个多组分分层系统。扫描电子显微镜（SEM）、透射电子显微镜（TEM）和动态光散射（DLS）测量揭示了光和热响应的分子马达单元能够在不破坏初级金属环结构的情况下，对二级超分子聚集过程进行选择性操控。这些对可见光敏感的金属环，具有内在的多个旋转马达，为协同操作、动态分层自组装系统和自适应材料提供了前景。