Ligand-Driven Coordination Sphere-Induced Engineering of Hybride Materials Constructed from PbCl₂ and Bis-Pyridyl Organic Linkers for Single-Component Light-Emitting Phosphors

Abstract

We report design and structural characterization of six new coordination polymers fabricated from PbCl₂ and a series of closely related bis-pyridyl ligands L^I and HL^II-HL^VI, namely, [Pb₂(L^I)Cl₄]_n, [Pb(HL^II)Cl₂]_n·nMeOH, [Pb(HL^III)Cl₂]_n·0.5 nMeOH, [Pb₂(L^IV)Cl₃]_n, [Pb(HL^V)Cl₂]_n, and [Pb₃(L^VI)₂Cl₄]_n·nMeOH. The topology of the obtained networks is dictated by the geometry of the organic ligand. The structure of [Pb₂(L^I)Cl₄]_n is constructed from the [PbCl₂]_n two-dimensional (2D) sheets, linked through organic linkers into a three-dimensional framework, which exhibits a unique binodal 4,7-connected three-periodic topology named by us as sda1. Topological analysis of the 2D metal-organic sheet in [Pb(HL^II)Cl₂]_n·nMeOH discloses a binodal 3,4-connected layer topology, regardless of the presence of tetrel bonds. A one-dimensional (1D) coordination polymer [Pb(HL^III)Cl₂]_n·0.5 nMeOH is considered as a uninodal 2-connected chain. The overall structure of [Pb₂(L^IV)Cl₃]_n is constructed from dimeric tetranuclear [Pb₄(μ³-L^IV-κ⁶N:N':N″:μ³-O)₂(μ⁴-Cl)(μ²-Cl)₂]³⁺ cationic blocks linked in a zigzag manner through bridging μ²-Cl^- ligands, yielding a 1D polymeric chain. Topological analysis of this chain reveals a unique pentanodal 3,4,4,5,6-connected chain topology named by us as sda2. The structure of [Pb(HL^V)Cl₂]_n exhibits a 1D zigzaglike polymeric chain. Two chains are further linked into a 1D gridlike ribbon through the dimeric [Pb₂(μ²-Cl)₂Cl₂] blocks as bridging nodes. With the bulkiest ligand HL^VI, a 2D layered coordination polymer [Pb₃(L^VI)₂Cl₄]_n·nMeOH is formed, which network, considering all tetrel bonds, reveals a unique heptanodal 3,3,3,3,4,5,5-connected layer topology named by us as sda3. Compounds [Pb₂(L^I)Cl₄]_n, [Pb₂(L^IV)Cl₃]_n, and [Pb(HL^V)Cl₂]_n were found to be emissive in the solid state at ambient temperature. While blue emission of [Pb₂(L^I)Cl₄]_n is due to the ligand-centered transitions, bluish-green and white luminescence of [Pb₂(L^IV)Cl₃]_n and [Pb(HL^V)Cl₂]_n, respectively, was assigned to ligand-to-metal charge transfer mixed with metal-centered excited states. Molecular as well as periodic calculations were additionally applied to characterize the obtained polymers.