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)<sub>2</sub> with a new flexible 1,3-bis­(4-pyridyl-3-cyano)­propane (<b>1</b>, BPCP) ligand under different synthesis conditions via an in situ ligand transformation reaction produced three true coordination polymorphs, namely, [PbL<sup>2–</sup>]<sub><i>n</i></sub> (for <b>2</b> and <b>3</b>) and [Pb<sub>3</sub>L<sup>2–</sup><sub>3</sub>]<sub><i>n</i></sub> (<b>4</b>), as well as their polymorphic framework [(Pb<sub>2</sub>L<sup>2–</sup>)·2H<sub>2</sub>O]<sub><i>n</i></sub> (<b>5</b>) (H<sub>2</sub>L = 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<sup>2–</sup>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 <b>2</b> and <b>3</b> display a 3D framework with 1D channels built up from dinuclear ringlike [Pb<sub>2</sub>L<sup>2–</sup><sub>2</sub>] units and dinuclear semi-ring-like [Pb<sub>2</sub>L<sup>2–</sup>] units, respectively. Polymorph <b>4</b> also features a 3D architecture constructed from dinuclear ringlike [Pb<sub>2</sub>L<sup>2–</sup><sub>2</sub>] units interlinked by the L<sup>2–</sup> ligand. Interestingly, the framework of <b>4</b> 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<sup>3</sup>)­(4<sup>4</sup>·6<sup>10</sup>·8)­(4<sup>8</sup>·6<sup>24</sup>·8<sup>9</sup>·10<sup>4</sup>). For <b>5</b>, there exists two kinds of dinuclear ringlike [Pb<sub>2</sub>L<sup>2–</sup><sub>2</sub>] units. These [Pb<sub>2</sub>L<sup>2–</sup><sub>2</sub>] 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 <b>1</b>–<b>5</b> and the H<sub>2</sub>L ligand in the solid state at room temperature were also investigated.