)] (II), each feature a bidentate, bridging bipyridyl-type ligand encompassing a di-amide group. In (I), the binuclear compound is disposed about a centre of inversion, leading to an open conformation, while in (II), the complete molecule is completed by the application of a twofold axis of symmetry so that the bridging ligand has a Ushape. In each of (I) and (II), the dithiocarbamate ligands are chelating with varying degrees of symmetry, so the zinc atom is within an NS 4 set approximating a square-pyramid for (I) and a trigonal-bipyramid for (II). The solvent dimethylformaide (DMF) molecules in (I) connect to the bridging ligand via amide-N-HÁ Á ÁO(DMF) and various amide-, DMF-C-HÁ Á ÁO(amide, DMF) interactions. The resultant three-molecule aggregates assemble into a three-dimensional architecture via C-HÁ Á Á(pyridyl, chelate ring) interactions. In (II), undulating tapes sustained by amide-N-HÁ Á ÁO(amide) hydrogen bonding lead to linear supramolecular chains with alternating molecules lying to either side of the tape; no further directional interactions are noted in the crystal.
Chemical contextThe potential of self-association between amide functionalities via amide-N-HÁ Á ÁO(amide) hydrogen-bonding has long been recognized (MacDonald & Whitesides, 1994). In this way, eight-membered {Á Á ÁHNCO} 2 synthons can be formed. Alternatively, extended aggregation patterns based on a single point of contact repeat associations leading to supramolecular chains or double-connections (edge-shared) leading to tapes. In this connection, isomeric di-amide structures of the general formula (n-NC 5 H 4 )CH 2 N(H)C( O)-C( O)N(H)CH 2 -(C 5 H 4 N-n), for n = 2, 3 and 4, hereafter abbreviated as n LH 2 , have long attracted interest for their potential to form supramolecular tapes. For example, as realized in the twodimensional structure formed in the 1:1 co-crystal of 4 LH 2 and the conformer, bi-functional 1,4-di-iodobuta-1,3-diyne (Goroff et al., 2005). Here, the amide tapes are orthogonal to the NÁ Á ÁI halogen bonding. In the realm of metal-containing species, a three-dimensional architecture can be assembled in A similar coordination/hydrogen-bonding arrangement is found in the three-dimensional assembly in crystals of et al., 2008). Motivated by these results, investigations were commenced exploring the coordination ability of n LH 2 with zinc(II) dithiocarbamates functionalized with hydrogen-bonding potential, i.e. Zn[S 2 CN(R)CH 2 CH 2 OH] 2 , for R = alkyl, CH 2 CH 2 OH. As discussed in more detail in the Database survey, none of these crystals exhibited self-association of the amide residues. For example, in the crystal of binuclear {Zn[S 2 CN(Me)CH 2-CH 2 OH] 2 } 2 ( 3 LH 2 ), supramolecular chains are constructed as a result of hydroxy-O-HÁ Á ÁO(hydroxy) hydrogen bonding that leads to the formation of sterically unencumbered 28-membered {Á Á ÁHOC 2 NCSZnSCNC 2 O} 2 synthons. Two chains inter-weave through these rings and are held in place by hydroxy-O-HÁ Á ÁO(amide) hydrogen bonding (Poplaukhin & Tiekink, 2010). I...