Hydrothermal reaction of Ln(NO₃)·6H₂O with benzimidazole-5,6-dicarboxylic acid (H₃bidc) and KSCN afforded a series of new two- and three-dimensional coordination polymers, namely [Ln₂(Hbidc)₂(SO₄)(H₂O)₃]_n (Ln = La (1), Pr (2), Sm (3), Gd (4)) and [Ln₄(Hbidc)₄(SO₄)₂]_n·2nH₂O (Ln = Eu (5), Tb (6), Dy (7), Er (8)). The sulfates were in situ generated by catalytic oxidation of KSCN. These complexes were characterized by single crystal X-ray diffraction, IR spectroscopy, thermal analysis, fluorescent spectra and magnetic measurements. Complexes 1–4 are isomorphous and comprise a 2D network based upon planar tetranuclear lanthanide secondary building units. The 2D layers extend to a 3D framework by π–π stacking between imidazole rings and hydrogen bonding interactions. The complexes 5–8 are also isomorphous and have similar 3D frameworks fabricated through Hbidc²⁻ and SO₄ ²⁻ bridging dinuclear lanthanide secondary building units, and the guest water molecules are trapped in the lattice. The luminescent properties of complexes 5 and 6 exhibit characteristic europium and terbium luminescence, while 4 involves ligand-to-metal charge transfer. The magnetic properties of four complexes were also investigated.

The bifunctional salt [Co(terpy)₂](TCNQ)₃·CH₃CN (terpy = 2,2′;6′,2′′-terpyridine, TCNQ = 7,7,8,8-tetracyanoquino-dimethane) exhibits a high room temperature conductivity of 0.13 S cm⁻¹ and an anomaly in conductivity at ∼190 K as evidenced by variable temperature structural, magnetic and conductivity studies. The anomaly in the conductivity at 190 K has been correlated with the temperature dependent structural breathing and Jahn–Teller distortion of the low spin state of the SCO units, as well as the charge fluctuations and supramolecular π-stacking interactions of partially charged TCNQ radicals. The modular synthetic approach leads to an accessible source of partially charged TCNQ radicals for the facile preparation of bifunctional molecular materials with high electrical conductivity.