Solution and solid-state photoluminescence of bis{succinatobis[2,6-bis(2-benzimidazolyl)] lead(II)}: A comment on the lone-pair stereochemistry and its effect on supramolecular interaction

A new Pb(II) coordination compound, namely [Pb(suc)(H2bbp)]2 (1) has been synthesized by treating succinic acid (H2suc), and 2,6-bis(2-benzimidazolyl) pyridine (H2bbp) with Pb(II) nitrate under hydrothermal conditions. Dicarboxylate as a bridging ligand is used to link adjacent metal centers forming dinuclear metal complex. The arrangement of the H2bbp ligand and carboxyl groups suggest a gap in the coordination around the Pb(II) ion, occupied possibly by a stereoactive lone-pair of electrons on Pb(II) where the coordination around the lead atoms is hemidirected. At room temperature, in the solid-state, the compound displays blue luminescence at 438 nm, which is about 50 nm red-shifted compared to the emission in DMF solution, resulting from long Pb···O interactions, a closer inspection of the pack reveals π–π stacking interactions that are crucial to lowering the HOMO–LUMO energy gaps.