Nanopatterning of Surfaces with Monometallic and Heterobimetallic 1D Coordination Polymers: A Molecular Tectonics Approach at the Solid/Liquid Interface

The self-assembly
of multiple molecular components into complex
supramolecular architectures is ubiquitous in nature and constitutes
one of the most powerful strategies to fabricate multifunctional nanomaterials
making use of the bottom-up approach. When spatial
confinement in two dimensions on a solid substrate is employed, this
approach can be exploited to generate periodically ordered structures
from suitably designed molecular tectons. In this study we demonstrate
that physisorbed directional periodic arrays of monometallic or heterobimetallic
coordination polymers can be generated on a highly oriented pyrolitic
graphite surface by combinations of a suitably designed directional
organic tecton or metallatecton based on a porphyrin or nickel­(II)
metalloporphyrin backbone bearing both a pyridyl unit and a terpyridyl
unit acting as coordinating sites for CoCl2. The periodic
architectures were visualized at the solid/liquid interface with a
submolecular resolution by scanning tunneling microscopy and corroborated
by combined density functional and time-dependent density functional
theory calculations. The capacity to nanopattern the surface for the
first time with two distinct metallic centers exhibiting different
electronic and optical properties is a key step toward the bottom-up
construction of robust multicomponent and, thus, multifunctional molecular
nanostructures and nanodevices.

多分子组分自组装形成复杂超分子结构的现象在自然界中普遍存在，亦是利用自下而上策略制备多功能纳米材料的最有效手段之一。当采用固体衬底上的二维空间限域手段时，该策略可通过合理设计的分子构造基元（molecular tectons）制备出周期性有序结构。本研究证明，通过合理设计基于卟啉（porphyrin）或镍(II)金属卟啉骨架的定向有机构造基元或金属构造基元，该骨架同时带有可作为CoCl₂配位位点的吡啶基与三联吡啶基，可在高定向热解石墨（highly oriented pyrolitic graphite）表面制备出物理吸附的单金属或双金属配位聚合物定向周期性阵列。研究人员通过扫描隧道显微镜（scanning tunneling microscopy）在固液界面以亚分子分辨率观测到了该周期性结构，并结合密度泛函理论（density functional theory）与含时密度泛函理论（time-dependent density functional theory）计算对其进行了验证。本研究首次实现了带有两种具有不同电子与光学特性的独立金属中心的表面纳米图案化，这为构建稳定的多组分乃至多功能分子纳米结构与纳米器件的自下而上制备路径提供了关键进展。