Variable architectures of Zinc coordination polymers modeled by tetra-pyridine ligands with different anions

Abstract

Solvothermal reactions of tetrakis(4-pyridyloxymethyl)methane (TPOM) and tetrakis(3-pyridyloxymethyl)methane (TPOM2) with different counter-anions (Cl⁻, deprotonated benzoate (L1) and 1,4-benzenedicarboxylic acid (L2)) in the presence of zinc ions under different synthesis temperatures produced six new coordination polymers (CPs), namely, {[Zn₂(TPOM2)₂(Cl)₄]}_n (1), {[Zn₂(TPOM2)(L1)₄]·4H₂O}_n (2), {[Zn₄(TPOM2)(L2)₄]·DMF·4H₂O}_n (3), {[Zn(TPOM)(Cl)₂]}_n (4), {[Zn₂(TPOM)(L1)₄]·2H₂O}_n (5), and {[Zn₂(TPOM)(L2)₂]·4H₂O}_n (6). These complexes were characterized by elemental analysis, IR spectroscopy, and X-ray single-crystal diffraction. Complexes 1, 2 and 4 reveal 1D crystal structures with novel 2,2,4-connected 3-nodal, 2₂,4-connected 2-nodal and 2,2-unidonal topology constructed from the connection of Zn centers and tetra-pyridine ligands, which were further neutralized by the mono-dentate Cl⁻ and L1 ligands coordinated to the Zn ions. In contrast, complex 5 exhibits a two-fold interpenetrating 2D structure with a novel 2,2,4-connected 3-nodal net. Interestingly, complex 3 exhibits a distinct 3D framework constructed by the connection of typical neutral {Zn₂(L2)₂}_n square-grid and 4-connected TPOM2 ligands, compared to the distinct 3D structure of 6. Structural results for these complexes show that the different counter-anions play an important role in constructing CPs with flexible ligands.