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Reaction of transition metal(II) salts with 2,2′-biimidazole (H2biim) and co-ligands formed a series of new complexes, [M(H2biim)2(bipy)2](NO3)2·2H2O (1–3) (M = Co, Ni, Zn), [Co(H2biim)2(bipy)](ClO4)2·3H2O (4), {[Cu(H2biim)2]3(μ-C3H3O4)2 (C3H2O4)2}·6H2O (5), [Co(H2biim)2(H2O)2](C3H3O4)2 (6) (bipy = 4,4′-bipyridine, C3H2O4 = malonate dianion, C3H3O4 = malonate anion). These complexes were characterized by single-crystal X-ray diffraction, and elemental analysis. All complexes except 4 were also characterized by luminescence spectra and thermogravimetric analysis. The crystal packing of these six complexes shows that cationic M(II)(2,2′-biimidazole) fragments are self-assembled to construct the 3D supramolecular networks by hydrogen bonding and π–π interactions. The 3D supramolecular networks are significantly affected by counter anion and co-ligands. In complexes 1–3, there are two sets of (4,4) nets which pass through each other to form inclined 2D interpenetration. Complex 4 is obtained by similar reactions as 1 Compared with 1, the only difference in 4 with the reactant Co(NO3)2·6H2O replaced by Co(ClO4)2·6H2O, but it has a very different structure. In 4, the 3D networks containing cavities of 23 × 23 A is formed. In complex 5, the uncoordinated waters form an infinite 1D pipe structure which is embedded in the 3D porous network. The acid–water ring and R22(9) synthons in complex 6 lead to the formation of (4,4) 2D network.

Reactions of transition metal(II) nitrate with 2,2′-biimidazole and 1,10-phenanthroline generated three new isostructural complexes, [Co(H2biim)3][Co(H2biim)2(phen)](NO3)4·2CH3OH·H2O (1), [Ni(H2biim)3][Ni(H2biim)2(phen)](NO3)4·3.5H2O (2), and [Zn(H2biim)3][Zn(H2biim)2(phen)](NO3)4·4H2O (3) (H2biim = 2,2′-biimidazole, phen = 1,10-phenanthroline). These complexes were characterized by single-crystal X-ray diffraction, elemental analysis, luminescent spectra and thermogravimetric analysis. The crystal packing of the complexes show that cationic [M(H2biim)3]2+ fragments are self-assembled to construct the 2-D supramolecular networks by hydrogen bonding and π–π interactions. The guest molecule [M(H2biim)2phen]2+ is well recognized by the N–H⋯O and O–H⋯O hydrogen bonds. In complexes 1–3, chiral guest molecules recognize the chirality of the host cations [M(H2biim)3]2+, which are assembled into 2-D nets with alternating Δ and Λ chirality resulting in the structure of racemates. The data observed in this paper suggest that the diverse hydrogen bonding modes between the nitrate and H2biim ligand identified here play a crucial role in the formation of 1–3.

The reactions of silver salts AgX [X = OTf (OTf = CF3SO3), ClO4 and BF4] and bis(diphenylphosphino)methane (dppm) with 4,4′-bipyridine (bipy) and its derivations [1,2-di(4-pyridyl)ethane (dpa), 1,2-di(4-pyridyl)ethylene (dpe), 1,3-bis(4-pyridyl)propane (bpp)] lead to six silver(I) complexes: {[Ag2(dppm)2(OTf)]2(μ-bipy)}(OTf)2·2CH3OH (1), {[Ag2(dppm)2(μ-bpp)(OTf)](OTf)·CH3OH}n (2), {[Ag2(dppm)2(CH3CN)]2(μ-dpa)}(ClO4)4·2CH3CN (3), [Ag2(dppm)3](ClO4)2 (4), {[Ag2(dppm)2(μ-bipy)(CH3CN)](BF4)2}n (5) and {[Ag2(dppm)2(μ-dpe)(CH3CN)](BF4)2}n (6). Complexes 1 and 3 are tetranuclear complexes with two eight-membered Ag2P4C2 rings bridged by bipy and dpa respectively. 2, 5 and 6 are of infinite chain structures formed by [Ag2(dppm)2] units linked by bpp, bipy and dpe respectively. 4 is a binuclear compound with two silver atoms bridged by three dppm ligands. All complexes are characterized by X-ray diffraction, fluorescence, 1H and 31P NMR spectroscopy and terahertz time-domain spectroscopy (THz-TDS).