Molecular Tectonics. Hydrogen-Bonded Networks Built from Tetra- and Hexaanilines

Abstract

A series of compounds with multiple PhNH 2 groups were synthesized and crystallized, and their structures were solved by X-ray diffraction to assess the ability of -NH 2 groups in anilines to direct molecular crystallization. 2,2′,7,7′-Tetraamino-9,9′-spirobi[9H-fluorene] (1c) forms an inclusion complex held together in part by donation of hydrogen bonds from -NH 2 groups to guest molecules. Surprisingly, the -NH 2 groups do not engage in hydrogen bonding with each other. Tetrakis(4-aminophenyl)methane (2c) crystallizes to form a guest-free closepacked diamondoid network in which each -NH 2 group donates and accepts one N-H‚‚‚N hydrogen bond. Tetrakis-[(4-aminophenoxy)methyl]methane (3c), a more flexible analogue, also crystallizes as a close-packed structure maintained by an extensive network of N-H‚‚‚N hydrogen bonds. Despite the structural similarity of tetraanilines 2c and 3c, their hydrogen-bonding patterns and network topologies are different. A flexible hexaaniline, 1,1′-oxybis-[3-(4-aminophenoxy)-2,2-bis[(4-aminophenoxy)methyl]]propane (4c), produces a close-packed network joined by both N-H‚‚‚N and N-H‚‚‚O hydrogen bonds. Tetrakis(4-aminophenyl)ethylene ( 5) crystallizes as a hydrate to yield a structure consisting of layered hydrogen-bonded sheets. The diverse hydrogen-bonding motifs observed show that crystal engineering using direct interactions of the -NH 2 group of anilines is a challenging endeavor, and other intermolecular interactions can compete effectively with N-H‚‚‚N hydrogen bonds to determine how crystallization occurs.

Porous Hydrogen-Bonded Organic Frameworks

“…Later on, Wuest and other prominent supramolecular chemists devoted themselves to another backbones, namely RB1 – 8 (see Table 1 and Figure 2 ). They initially investigated diverse NH 2 tetrasubstituted backbones ( RB4 – 8 ) [ 19 , 20 , 21 , 22 ]. Unfortunately, X-ray diffraction examinations of crystals demonstrated that, although HOFs possessing RB4 and RB7 backbones were less packed, the porosities of the corresponding HOFs (see Table 1 ) were generally below 18%.…”

p-Phenylenediamine and its dihydrate: two-dimensional isomorphism and mechanism of the dehydration process, and N—H...N and N—H...π interactions

“…Among these structures, 48 were formed by aromatic, 27 by aliphatic and four by vinyl amines, and one by a mixed aromatic/aliphatic amine. The same search requesting additionally the presence of a water molecule in the crystal structure gave 23 hydrates but only one of them was formed by an aromatic amine, with one molecule of water included per three tetraamine molecules (CSD refcode RARROS; Laliberté et al, 2005). The search shows that inclusion of water molecules in the crystal structures of primary aromatic monoand polyamines is less feasible than in the case of their aliphatic analogues.…”

Synthesis and Topological Determination of Hexakis‐Substituted 1,4‐Ditritylbenzene and Nonakis‐Substituted 1,3,5‐Tritritylbenzene Derivatives: Building Blocks for Higher Supramolecular Assemblies

“…We were among the first to use them as sixfold connecting tectons 32–34. To the best of our knowledge only two other purely organic structures bearing six anchor points have been reported so far;35 one is a flexible hexaaniline35a and the second is based on rigid hexasubstituted centrohexaindanes 35b,35c…”