Kristall‐Engineering: eine holistische Darstellung

Abstract

Kristall‐Engineering, d. h. das Konstruieren von molekularen Festkörpern, ist das Synthetisieren von funktionalen Festkörperstrukturen aus neutralen oder ionischen Baueinheiten, wobei die Aufbaustrategie intermolekulare Wechselwirkungen einbezieht. Wasserstoffbrücken, Koordinationsbindungen und andere, schwächer gerichtete Wechselwirkungen definieren Unterstrukturmuster, die in der Literatur als supramolekulare Synthone oder sekundäre Baueinheiten bezeichnet werden. Das Kristall‐Engineering weist beträchtliche Überlappungen mit der supramolekularen Chemie, der Röntgenkristallographie, den Materialwissenschaften und der Festkörperchemie auf, es bildet aber dennoch eine eigenständige Disziplin. Das Gebiet hebt die herkömmlichen Trennungslinien von organischer, anorganischer und physikalischer Chemie auf, sodass Ideen und Techniken aus unterschiedlichsten Forschungsbereichen einfließen. Der vorliegende Aufsatz soll einige aktuelle Herausforderungen in diesem sich schnell entwickelnden Gebiet beleuchten. Zu den behandelten Themen gehören die Beschaffenheit von intermolekularen Wechselwirkungen, deren Rolle beim Konstruieren von Kristallstrukturen, die oft voneinander abweichenden Auffassungen über die geometrischen und chemischen Modelle eines Molekülkristalls, die Beziehung dieser Modelle zur Polymorphie, die wissensgestützte Computervorhersage von Kristallstrukturen sowie Versuche zum Abbilden des Reaktionswegs der Kristallisation.

Formation of a Hydrogen‐Bonded Heptazine Framework by Self‐Assembly of Melem into a Hexagonal Channel Structure

“…[1,2] In supramolecular chemistry or crystal engineering, complex chemical structures determined by several types of noncovalent interactions such as hydrogen bonds, ionic, hydrophobic, van der Waals, or dispersive forces are formed. Next to the ambition to understand the principles of molecular self-assembly in the solid state, the synthesis of solids that exhibit desired structural motifs such as ordered channels or cavities reminiscent of zeolites, is a relevant goal in crystal engineering.…”

Fast Molecular Rotor Dynamics Modulated by Guest Inclusion in a Highly Organized Nanoporous Organosilica

“…[13] This is a rare observation of host-guest interactions, revealed by the change in the host properties. As depicted in Figure 3, it is possible to drastically reduce the molecular mobility of the empty material by diffusing a guest inside the channels (+ Guest); removing it (ÀGuest) causes reversion to the initial value.…”

Construction of Hydrogen‐Bonded Ternary Organic Crystals Derived from L‐Tartaric Acid and Their Application to Enantioseparation of Secondary Alcohols

“…Therefore, smaller secondary aliphatic alcohols (4) were selected as target compounds. 1 H NMR spectroscopy analysis of 1 a·2 c crystallized from acetonitrile in the presence of an excess amount of 2-butanol (4 a) and 2-pentanol (4 b) revealed that both of them gave the corresponding 1:1:1 inclusion crystals and the isolated alcohols showed high ee values (Table 3, entries 12 and 13). As stated above, compounds 4 a and 4 b can be included by 1 a alone; however, compound 1 a has no chiral recognition ability for these small aliphatic alcohols.…”

“…The resulting solution was kept at room temperature to allow slow evaporation of the solvent and afford ternary crystals. The collected crystals were characterized by 1 H NMR spectroscopy and the incorporated alcohol was isolated by preparative-scale TLC, followed by HPLC analyses to determine the enantiomeric excess (ee). In the case of aliphatic alcohols, the included alcohols were derivatized to their corresponding phenyl carbamates prior to isolation and determination of the ee values by HPLC.…”

“…[1] One of the enthusiastically studied topics in this field is the design and synthesis of multicomponent, metal-free organic crystals, including cocrystals and organic salts. Multicomponent organic crystals not only serve to deepen the understanding of supramolecular chemistry, but have also been successfully applied to the control of the solubility of pharmaceuticals, in catalysis, in gas storage, and so forth.…”