Blue- And white-light-emitting 2D-coordination polymers and their solid-state photodimerization reaction

Two Pb(ii) coordination polymers (CPs), namely [Pb(μ-bpe)(μ-O₂CCH₃)₂]_n(1) and [Pb(μ-bpe)(μ-O₂CH)₂]_n(2), have been isolated from the reaction of Pb(OAc)₂·3H₂O with 1,2-bis(4-pyridyl)ethene (bpe) in the presence of acetate and formate anionic ligands, respectively. Compounds1and2formed 2D sheet-like structures, constructed by bridging acetate and formate carboxylate ligands. The bpe ligand containing the olefinic C-C bonds was perfectly brought to the proximity of Schmidt topolochemical criteria for2. The 2D sheet in2underwent 67% of the photodimerization reaction in the solid state, while the 2D sheet in1was photochemically stable. Therefore, the photochemical reactivity of1and2was rationalized based on the orientation of the olefinic C-C bonds, which was brought close to each other due to the distinct bridging of the carboxylates and the Pb(ii) metal ions. The room temperature solid-state photoluminescence (PL) revealed that compound1exhibited a near white-light emission and the blue-light emission for2upon excitation at 365 nm. The differences in the emission of the two 2D-sheets were correlated with the bridging carboxylate ligands.