In Situ Ligand Modification Strategy for the Construction of One-, Two-, and Three-Dimensional Heterometallic Iodides

Three heterometallic iodides featuring the novel in situ modified ligands N,N',N″-trimethyl-2,4,6-tris(4-pyridyl)-1,3,5-triazine (Me₃tpt³⁺), N,N'-dimethyl-2,4,6-tris(4-pyridyl)-1,3,5-triazine (Me₂tpt²⁺), and N-monomethyl-2,4,6-tris(4-pyridyl)-1,3,5-triazine (Metpt⁺), [Pb₃CuI₁₀(Me₃tpt)] (1), [Pb₅Cu₂I₁₆(Me₂tpt)₂] (2), and [Pb₃Cu₆I₁₄(Metpt)₂] (3), were synthesized. Compound 1 exhibits a chain structure, in which the Pb₄I₁₆ units are connected by the CuI₃ units. The negative charge of the resulting chain is balanced by the cationic Me₃tpt³⁺ groups. 2 features a layer structure, in which the Pb-I chains are connected by the dimeric Cu₂ units. The anionic layer is decorated by the Me₂tpt²⁺ motifs via coordinating to the intralayer Cu(I) ions. 3 displays a 3D framework structure, in which the inorganic layer with an 18-membered ring is composed of the strictly alternating arrangements of trimeric Pb₃ units and hexameric Cu₆ units. The adjacent inorganic layer is further connected by a Metpt⁺ linker to form the final 3D hybrid framework. It is notable that the in situ N-methylation reaction for tpt has taken place and the resultant motif (Me₃tpt³⁺ for 1, Me₂tpt²⁺ for 2, and Metpt⁺ for 3) is captured within the corresponding structure. More importantly, the structural diversities from low-dimensional chain and layer to high-dimensional framework is accomplished via the (partial) N-methylation of tripyridine motifs in the heterometallic iodide systems. Our studies offer a new coordination mode of tripyridine motif (N-coordination together with N-methylation) and provide a general strategy to integrate the polypyridine motifs and heterometallic halide systems to generate intriguing hybrid structure and investigate the potential structure-related properties. The UV-vis spectra show that the band gaps for 1-3 are 1.48, 1.35, and 1.34 eV, respectively. Their thermal stabilities have also been studied.