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Lone pair–π interaction is an important but less studied binding force. Naphthalene diimides (NDIs) are ideal to form such an interaction because their quadrupole moment is exceptionally positive. Here, we report the combination of NDI ligands bearing two divergently oriented pyridyl units with different metal nitrates in different solvents resulting in six neutral 1-D coordination networks, in which the nitrate anions not only serve as capping ligands to coordinate to metal centers but also provide lone pairs to interconnect with the π-acidic NDI ligands through lone pair–π interactions. Interestingly, such lone pair–π interactions are found to have a synergic effect on the coordination interactions of the aforementioned NDI ligands with metal ions. In other words, metal-ion-directed self-assembly of NDI ligands is supposed to be driven by cooperative lone pair–π and coordination interactions.

Using the hydrothermal synthetic method, two cadmium complexes (1 and 2) with an identical chemical formula of [Cd(ABTC)2]n (ABTC = 2-aminobenzothiazole-6-carboxylic acid) but completely different topologies were prepared at two different pH values of reaction solution, 5.3 and 7.3, respectively. Reaction with a pH in between resulted in a mixture of 1 and 2, and the ratio of two products was proportional to pH value of the reaction condition.

Hydrothermal reactions of divalent transition metal salts with two different-sized tetrazole-yl acylamide ligands, N-(1H-tetrazol-5-yl)acetamide (H-NTAA) and N-(1H-tetrazol-5-yl)propionamide (H-NTPA), led to six crystalline coordination polymers, named Cd(NTAA)2 (1), Zn(NTAA)2·∼H2O (2), Cu(NTAA)2 (3), Mn(NTAA)2 (4), Cd(NTPA)2 (5), Mn(NTPA)2 (6), respectively. The X-ray diffraction analysis revealed that compound 2 is a 1D zigzag chain, compounds 3 and 4 exhibit an interesting 2D 44-sql network, while compounds 1, 5 and 6 possess a 3D non-interpenetrated diamondoid framework. Wherein, compounds 1, 4, 5 and 6 crystallized in an acentric space group with significant second harmonic generation (SHG) efficiencies. The effect of metal ions and that of small aliphatic acyl side-groups in semirigid tetrazole-yl acylamide ligands on the structural topologies and symmetries of generated coordination polymers are discussed.