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 [Pb3L32-](n) (4), as well as their polymorphic framework [(Pb2L2-)center dot 2H(2)O](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 L(2-)ligancl 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 ID channels built up from dinuclear ringlike [Pb2L22-] units and dinuclear semi-ring-like [Pb2L2-] units, respectively. Polymorph 4 also features a 3D architecture constructed from dinuclear ringlike [Pb2L22-] units interlinked by the L2- ligand. Interestingly, the framework of 4 is big enough to allow the other net to penetrate to form a 2-fold interpenetrating framework with a trinodal (3,6,10) connected topology with a point symbol of (4(3))(4(4).6(10).8)(4(8).6(24).8(9).10(4)). For 5, there exists two kinds of dinuclear ringlike [Pb2L22-] units. These [Pb2L22-] units are interconnected by Pb atoms to afford a 2D undulant network that is further connected by the hydrogen-bonding interactions and weak interactions to afford a 3D supramolecular network. In addition, the photoluminescence properties of 1-5 and the H2L ligand in the solid state at room temperature were also investigated.