The coordination of iron(II) ions by a homoditopic ligand L with two tridentate chelates leads to the tautomerism-driven emergence of complexity, with isomeric tetramers and trimers as the coordination products. The structures of the two dominant [Fe^II₄L₄]⁸⁺ complexes were determined by X-ray diffraction, and the distinctness of the products was confirmed by ion-mobility mass spectrometry. Moreover, these two isomers display contrasting magnetic properties (Fe^II spin crossover vs. a blocked Fe^II high-spin state). These results demonstrate how the coordination of a metal ion to a ligand that can undergo tautomerization can increase, at a higher hierarchical level, complexity, here expressed by the formation of isomeric molecular assemblies with distinct physical properties. Such results are of importance for improving our understanding of the emergence of complexity in chemistry and biology.

Die Koordination eines Liganden L mit Fe^II-Metallionen führt zum tautomeriegetriebenen Auftreten von Komplexität, welche sich in der parallelen Bildung von jeweils isomeren Tetrameren und Trimeren als Koordinationsprodukten zeigt. Die Molekülstruktur der zwei vorherrschenden isomeren [Fe^II₄L₄]⁸⁺-Komplexe vom [2×2]-Gittertypus wurde mittels Einzelkristallröntgenbeugung bestimmt. Die divergente Identität der Tautomeriekonformere wurde durch Ionenmobilitätsmassenspektrometrie bestätigt, und es konnte zusätzlich gezeigt werden, dass die beiden Isomere stark kontrastierende magnetische Eigenschaften (Fe^II-Spinübergang vs. blockierter Fe^II-High-Spin-Zustand) aufweisen. Die Ergebnisse zeigen, wie die Tautomerisierung eines homoditopen bis-dreizähnigen Liganden durch die Koordination von Metallionen zu einer Akkumulation von Komplexität (d. h. für den vorliegenden Fall die parallele Bildung von isomeren, molekularen Strukturen) auf einer hierarchisch höheren Ebene (hier Gitterkomplexe mit unterschiedlichen physikalischen Eigenschaften) führt. Diese Ergebnisse sind von Bedeutung für das Verständnis der grundlegenden Vorgänge, die Komplexität auf molekularer Ebene in chemischen und biologischen Systemen generieren.

This Feature Article reports on the controlled formation and structure-functionality aspects of vacuum-deposited self-assembled organic and metal-organic networks at metal surfaces using ditopic linear and nonlinear molecular bricks, namely di-carbonitrile polyphenyls. Surface confined supramolecular organization of linear aromatic molecules leads to a fascinating variety of open networks. Moreover, cobalt-directed assembly of the same linear linkers reveals highly regular, open honeycomb networks with tunable pore sizes representing versatile templates for the organization of molecular guests or metal clusters and the control of supramolecular dynamers. In addition, the 2D nanopore organic networks act as arrays of quantum corrals exhibiting confinement of the surface-electronic states of the metallic substrate. A reduction of the linker symmetry leads to the formation of disordered, glassy coordination networks, which represent a structural model for amorphous materials.

This Feature Article reports on the controlled formation and structure-functionality aspects of vacuum-deposited self-assembled organic and metal-organic networks at metal surfaces using ditopic linear and nonlinear molecular bricks, namely di-carbonitrile polyphenyls. Surface confined supramolecular organization of linear aromatic molecules leads to a fascinating variety of open networks. Moreover, cobalt-directed assembly of the same linear linkers reveals highly regular, open honeycomb networks with tunable pore sizes representing versatile templates for the organization of molecular guests or metal clusters and the control of supramolecular dynamers. In addition, the 2D nanopore organic networks act as arrays of quantum corrals exhibiting confinement of the surface-electronic states of the metallic substrate. A reduction of the linker symmetry leads to the formation of disordered, glassy coordination networks, which represent a structural model for amorphous materials.