Temperature, Cooling Rate, and Additive-Controlled Supramolecular Isomerism in Four Pb(II) Coordination Polymers with an in Situ Ligand Transformation Reaction

Solvothermal reactions of Pb(Ac)2 with a new flexible 1,3-bis(4-pyridyl-3-cyano)propane (1, BPCP) ligand under different synthesis conditions via an in situ ligand transformation reaction produced three true coordination polymorphs, namely, [PbL2–]n (for 2 and 3) and [Pb3L2–3]n (4), as well as their polymorphic framework [(Pb2L2–)·2H2O]n (5) (H2L = 1,3-bis(4-pyridyl-3-carboxyl)propane). These compounds were characterized by elemental analysis, IR, TG, PXRD, and single-crystal X-ray diffraction. In these compounds, the L2–ligand exhibits different coordination conformations and modes tuned by different synthesis conditions, including reaction temperature, cooling rate, and additive, and constructs various architectures by bridging a variety of building units. Polymorphs 2 and 3 display a 3D framework with 1D channels built up from dinuclear ringlike [Pb2L2–2] units and dinuclear semi-ring-like [Pb2L2–] units, respectively. Polymorph 4 also features a 3D architecture constructed from dinuclear ringlike [Pb2...