Crystalline Ammonium Complexes of Trimethyl‐ and Triethylbenzene‐Based Tripodal Compounds Bearing Pyrazole and Indazole Groups

• Published in: European journal of organic chemistry Vol. 2018; no. 31; pp. 4317 - 4330
• Main Authors: Schulze, Mathias M., Koch, Niklas, Seichter, Wilhelm, Mazik, Monika
• Format: Journal Article
• Language: English
• Published: WEINHEIM Wiley 23.08.2018; Wiley Subscription Services, Inc
• Subjects: Bearing; Chemistry; Chemistry, Organic; Conformation; Crystal structure; Crystallinity; Derivatives; Halogen bond; Host; Hydrogen bonds; Molecular recognition; Physical Sciences; Pyrazole; Receptors; Science & Technology; Supramolecular motif; Trimethylbenzene; X-ray diffraction; GRAPH-SET ANALYSIS; CENTER-DOT-N; SELECTIVE RECOGNITION; Host; TERMINAL PYRIDINE; Receptors; Supramolecular motif; Hydrogen bonds; HEXA-HOST; Halogen bond; HYDROGEN-BOND PATTERNS; PI INTERACTIONS; Molecular recognition; SECONDARY INTERACTIONS; Conformation
• ISSN: 1434-193X; 1099-0690
• DOI: 10.1002/ejoc.201800480

Crystalline complexes of NH4+PF6– with trimethyl‐ and triethylbenzene‐based tripodal compounds, bearing either pyrazole or indazole groups, were prepared and characterized by X‐ray diffraction studies. The supramolecular motifs observed in the crystal structures and the conformations of the tripodal molecules have been the subject of a detailed analysis and are described in this paper. The pyrazole‐bearing side arms of the hosts with a trimethylbenzene scaffold are arranged in an aaa fashion and form a cavity including the ammonium ion. In the case of the triethylbenzene derivatives, the fully alternating arrangement of the pyrazole/indazole and ethyl groups is observed and by taking the ethyl groups into account, the conformation can be defined as ab′ab′ab′. The conformations observed in the crystals of the free host molecules can be defined as ab′ab′ba′ with the indazole‐bearing arms arranged in an aab fashion. The crystal packings of the complexes are, among other things, characterized by the presence of NH···F and CH···F hydrogen bonds as well as by CBr···N and CBr···π halogen bonds in the case of the bromo‐substituted derivatives. Ammonium complexes of pyrazole‐ or indazole‐bearing benzene‐based tripodal hosts were prepared and analysed by X‐ray diffraction. The crystal packings of the complexes are characterized by the presence of N–H/C–H···F hydrogen bonds as well as C–Br···N/π halogen bonds. Information about the conformations which adopt the tripodal molecules in the crystalline state is also provided by the performed analyses.