“…1 cations lying between the hydrogen-bonded sheets. The structure of 3 has the same gross features as that previously reported for [NBu 4 ]Cl?2tu, 14 although there are some subtle differences. In [NBu 4 ]Cl?2tu, the thiourea tapes are flat, with an angle of 167u between neighbouring chains.…”
“…1 cations lying between the hydrogen-bonded sheets. The structure of 3 has the same gross features as that previously reported for [NBu 4 ]Cl?2tu, 14 although there are some subtle differences. In [NBu 4 ]Cl?2tu, the thiourea tapes are flat, with an angle of 167u between neighbouring chains.…”
“…The rather open framework of DCBP molecules does not collapse because the channels are filled by the urea ribbons. 10 The extended ribbon variation of I is present in LUTDUR, CRWNUR and TOZHOF, as in 1. The anti Hatoms of each urea ribbon form bifurcated N᎐Hؒ ؒ ؒN≡C hydrogen bonds with the DCBP layers via synthon III leading to the three-dimensional supramolecular structure.…”
“…‡ In the inclusion compounds with tetraalkylammonium halides, the halide ion acts as a spacer unit that interconnects the urea ribbons. 10 The extended ribbon variation of I is present in LUTDUR, CRWNUR and TOZHOF, as in 1. The C᎐Hؒ ؒ ؒN hydrogen bonds in 1 are considerably longer when compared with other occurrences of synthon II in say, 1,4dicyanobenzene and 1,2,4,5-tetracyanobenzene.…”
The crystal chemistry and engineering of a new family of host-guest complexes is described. 4,4Ј-Dicyanobiphenyl (DCBP) forms a 1:1 complex, 1 with urea wherein the DCBP host forms large hexagonal channels via C᎐Hؒ ؒ ؒN hydrogen bonds and the urea guest molecules are arranged in N᎐Hؒ ؒ ؒO ribbons which fit completely within the host channels. By analogy, 4,4Ј-bipyridine N,NЈ-dioxide (BPNO) was selected as a molecule that can form a corresponding C-Hؒ ؒ ؒO based channel. BPNO forms complexes with urea (2), thiourea (3) and water (4). Structures 2 and 3 provide some points of comparison with the structure of 1 but are not fully equivalent to it. In structure 4, the smaller guest water is able to fit neatly within the smaller hexagonal channel of BPNO and in this sense, the degree of structural predictability is satisfactory. To obtain another structure similar to that of 1, 4,4Ј-dinitrobiphenyl (DNBP) was identified as an alternative host compound. This choice was justified by the structure of its 1:1 complex, 5 with urea. In all cases, the guest molecules interact with each other via strong hydrogen bonds and form an essential template for the weak hydrogen bonded assembly of the host network structure but the latter is still of some significance. One finds consequently, in complexes 1-5, a constructive interplay of strong and weak hydrogen bonds.
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