Organisch-Chemisches Institut, Universität Münster, Corrensstraße 36, 48149 Münster, Germany.
J Am Chem Soc. 2021 May 12;143(18):7164-7175. doi: 10.1021/jacs.1c02384. Epub 2021 Apr 29.
Halogens play a crucial role in numerous natural processes and synthetic materials due to their unique physicochemical properties and the diverse interactions they can engage in. In the field of supramolecular polymerization, however, halogen effects remain poorly understood, and investigations have been restricted to halogen bonding or the inclusion of polyfluorinated side groups. Recent contributions from our group have revealed that chlorine ligands greatly influence molecular packing and pathway complexity phenomena of various metal complexes. These results prompted us to explore the role of the halogen nature on supramolecular polymerization, a phenomenon that has remained unexplored to date. To address this issue, we have designed a series of archetypal bispyridyldihalogen Pt complexes bearing chlorine (), bromine (), or iodine () and systematically compared their supramolecular polymerization in nonpolar media using various experimental methods and theory. Our studies reveal a remarkably different supramolecular polymerization for the three compounds, which can undergo two competing pathways with either slipped (kinetic) or parallel (thermodynamic) molecular packing. The halogen exerts an inverse effect on the energetic levels of the two self-assembled states, resulting in a single thermodynamic pathway for , a transient kinetic species for , and a hidden thermodynamic state for . This seesaw-like bias of the energy landscape can be traced back to the involvement of the halogens in weak N-H···X hydrogen-bonding interactions in the kinetic pathway, whereas in the thermodynamic pathway the halogens are not engaged in the stabilizing interaction motif but rather amplify solvophobic effects.
卤素由于其独特的物理化学性质以及它们能够参与的各种相互作用，在许多自然过程和合成材料中都起着至关重要的作用。然而，在超分子聚合领域，卤素效应的研究还很不充分，研究仅限于卤素键合或包含全氟化侧基。我们小组最近的研究表明，氯配体极大地影响了各种金属配合物的分子堆积和路径复杂性现象。这些结果促使我们探索卤素性质对迄今尚未探索的超分子聚合的作用。为了解决这个问题，我们设计了一系列典型的双吡啶二卤代铂配合物，分别带有氯（）、溴（）或碘（），并使用各种实验方法和理论系统地比较了它们在非极性介质中的超分子聚合。我们的研究揭示了这三种化合物具有非常不同的超分子聚合行为，它们可以通过两种竞争途径进行，要么是滑动（动力学）要么是平行（热力学）的分子堆积。卤素对两个自组装态的能级产生相反的影响，导致对于，只有一个热力学途径；对于，是瞬态动力学物种；对于，是隐藏的热力学状态。这种能量景观的跷跷板式偏见可以追溯到卤素参与动力学途径中弱的 N-H···X 氢键相互作用，而在热力学途径中，卤素不参与稳定相互作用模式，而是放大溶剂化效应。
