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Assembly of pamoic acid (H2PA) with piperazine (PIPO) or 4,4′-bipyridyl (BIPY) results in two distinct supramolecular complexes [(PA)·(H2PIPO)]·3H2O (1) and [(H2PA)·(BIPY)] (2). The former displays triple-helix host arrays via charge-assisted N+−H···O−interactions with the inclusion of helical water chains, whereas the latter represents the first cocrystal of pamoic acid sustaining by the familiar carboxyl-pyridyl H-bonding synthons. Notably, the structure of 1can be dehydrated/rehydrated with retention of crystallinity. [ABSTRACT FROM AUTHOR]

The mol­ecular structure of the neutral mononuclear complex [Fe(NCS)2(3-bpo)2(H2O)2], in which 3-bpo denotes 2,5-di-3-pyrid­yl-1,3,4-oxadiazole (C12H8N4O), is centrosymmetric, with FeII located on an inversion center. This complex is octa­hedral, and the FeII atom is trans coordinated by two monodentate NSC− ligands, two monodentate 3-bpo ligands and two water mol­ecules. Each complex is linked to four others, forming a (011) sheet, by O—H⋯N hydrogen bonding. Weak C—H⋯S inter­actions link each (011) sheet to the two adjacent sheets, hence forming a three-dimensional array. There is also some slipped π stacking within each sheet. [ABSTRACT FROM AUTHOR]

A survey of the Cambridge Structural Database (CSD) indicates that 79% of complexes that contain both imidazole and carboxyl groups generate imidazolium-carboxylate supramolecular heterosynthons rather than carboxyl or imidazole supramolecular homosynthons. In the absence of other competing factors, the occurrence of such heterosynthons is increased to 100%. This observation is further supported by the crystal structures of seven new complexes that contain tris(2-benzimidazylmethyl)amine (TBMA) and a variety of carboxylic acids, including benzoic acid (HBA), p-methoxybenzoic acid (HPMBA), phthalic acid (H2PA), terephthalic acid (H2TPA), isophthalic acid (H2PIA), trimesic acid (H3TMA), and pyromellitic acid (H4PMA). In all seven complexes, (H2TBMA)·(BA)2·DMF (1), (HTBMA)·(PMBA)·(TBMA)·(HPMBA)2·2DMF·H2O (2), (HTBMA)·(H2TBMA)·(HPA)·(PA)·3DMF·H2O (3), (HTBMA)2·(TPA)·2DMF (4), (HTBMA)2·(PIA)·2DMF (5), (H2TBMA)·(HTMA)·0.5DMF·H2O (6), and (HTBMA)2·(H2PMA)·2DMF·H2O (7), proton transfer occurs from acid to aromatic nitrogen of benzimidazole (partial proton transfer for 3, 6, and 7). Analysis of the H-bonding synthons and their effect on crystal packing is also presented in the context of crystal engineering and host−guest chemistry. In the structure of 1, discrete acid/base hexamers are formed via synthons III, V, and VI, while in 2−5, self-recognition via synthons IV, V, and VIresults in one-dimensional (1-D) chains, and these structures are extended to high-dimensional architectures (two-dimensional (2-D) structures in 3and three-dimensional (3-D) structures in 2, 4, and 5) via additional C−H···O, C−H···π and π···π interactions. Interestingly, salts 6and 7display the 3-D supramolecular networks via synthons III, IV, V, and VI, which have 1-D channels that are occupied by DMF guests. [ABSTRACT FROM AUTHOR]