Molecular tectonics — Use of urethanes and ureas derived from tetraphenylmethane and tetraphenylsilane to build porous chiral hydrogen-bonded networks

Abstract

Tetraphenylmethane, tetraphenylsilane, and simple derivatives with substituents that do not engage in hydrogen bonding typically crystallize as close-packed structures with essentially no space available for the inclusion of guests. In contrast, derivatives with hydrogen-bonding groups are known to favor the formation of open networks that include significant amounts of guests. To explore this phenomenon, we synthesized six new derivatives 5a–5e and 6a of tetraphenylmethane and tetraphenylsilane with urethane and urea groups at the para positions, crystallized the compounds, and determined their structures by X-ray crystallography. As expected, all six compounds crystallize to form porous three-dimensional hydrogen-bonded networks. In the case of tetraurea 5e, 66% of the volume of the crystals is accessible to guests, and guests can be exchanged in single crystals without loss of crystallinity. Of special note are: (i) the use of tetrakis(4-isocyanatophenyl)methane (1f) as a precursor for making enantiomerically pure tetraurethanes and tetraureas, including compounds 5b, 5c; and (ii) their subsequent crystallization to give porous chiral hydrogen-bonded networks. Such materials promise to include chiral guests enantioselectively and to be useful in the separation of racemates, asymmetric catalysis, and other applications.Key words: crystal engineering, molecular tectonics, hydrogen bonding, networks, porosity, urethanes, ureas, tetraphenylmethane, tetraphenylsilane.

Crystal structure of chlorido(η2-phenyl isothiocyanate-κ2C,S)-mer-tris(trimethylphosphane-κP)iridium(I)

“…The first entry in Table 1 shows the average values for all 16 structures, the next four entries are the specific non-complexed aryl isothiocyanates, the next six entries are other examples from the CCDC in which phenyl isothiocyanate is complexed to a metal and the last entry is the data from the title compound. For the structures of several uncomplexed aryl isothiocyanates, see: Majewska et al (2007Majewska et al ( , 2008; Laliberté et al (2004); Biswas et al (2007). For the structures of a cobalt and a nickel complex of phenyl isothiocyanate, see: Bianchini et al (1984).…”

Interplay between Polymorphism and Isostructurality in the 2-Fur- and 2-Thenaldehyde Semi- and Thiosemicarbazones

“…Through the years, crystal engineering principles have been developed on the basis of crystallographic data. The hydrogen bond rules [8,9], exchange rule [10,11], synthon hierarchy for some functional group [12][13][14][15][16], and molecular tectonics [17][18][19] are the most important principles among all of the studied ones. They are very helpful in predicting the results of crystal formation, but are still insufficient.…”

“…The presented study demonstrates the complexity of the problem of the self-assembly of different isomorphous molecules (i.e., 5-nitro-2-furaldehyde thiosemicarbazone (1), 5-nitro-2-thiophene thiosemicarbazone (2), 5-nitro-2-furaldehyde semicarbazone (3), 5-nitro-2-thiophene semicarbazone (4), Scheme S1). Only one compound of this group was previously structurally determined (i.e., the 3 [17][18][19]) and it created three monoclinic polymorphic forms 3α [22], 3β, and 3γ [23,24]. The introduction of additional species (different acids) to 3 distinctly affects the present synthons and hydrogen bonding schemes.…”

Fourfold Suzuki–Miyaura and Sonogashira Cross‐Coupling Reactions on Tetrahedral Methane and Adamantane Derivatives

“…Even peripheral chiral bricks leading to enantiomerically pure networks can be generated by either grafting four enantiopure extensions [8] or by fourfold asymmetric reaction on the core structures. [9] Müllen et al [10] pioneered the field of polyphenyl dendrimers based on rigid tetraalkyne structures.…”