Dicarboxylate anion-dependent assembly of Ni(II) coordination polymers with 4,4′-dipyridyl sulfide

Four new coordination polymers, [Ni(isop)(bps)(H₂O)]_2n·5H₂O (1), [Ni(O₂N–BDC)(bps)(H₂O)]_2n (2), [Ni(OH–BDC)(bps)₂(H₂O)]_n (3) and {[Ni₂(H₂O)(tbip)₂(bps)₂]}_n (4) (bps = 4,4′-dipyridyl sulfide, H₂isop= isophthalic acid, O₂N–BDC = 5-nitroisophthalic acid, OH–BDC = 5-hydroxyisophthalic acid, H₂tbip = 5-tert-butyl isophthalic acid), have been isolated from parallel hydrothermal reactions of Ni(OAc)₂·4H₂O and bps with isop, O₂N–BDC, OH–BDC and H₂tbip, respectively.

Compound 1 is an unusual 2D double layered supramolecular motif generated by hydrogen bonding interactions of two single 2D (4,4) networks. Compound 2 has a highly puckered 2D (4,4) sheet and further stack via OO intermolecular contacts to form a 3D supramolecular structure.

Compound 3 features a 2D rectangular grid layer with terminal bps ligands projecting into the interlayer space, leading to a highly interdigitated packing motif and further expansion to generate a 3-D network through interlayer C–Hπ stacking interactions. Compound 4 contains [Ni₂(H₂O)]⁴⁺ dimers bridged by pairs of ligands into a single 3D diamond network with alternately left-handed and right-handed helical channels. As compared to isop, the coexistence of electron-donating (–OH, –C(CH₃)₃) or electron-withdrawing (–NO₂) groups in the dicarboxylate derivatives has a significant effect on the molecular self-assembly. Variable-temperature magnetic susceptibility measurements reveals the existence of weak ferromagnetic interactions between the nickel centers in 4.