Phosphorescence emission and fine structures observed respectively under ambient conditions and at ca. 55 K in a coordination polymer of lead(ii)-thiophenedicarboxylate

Abstract

Under solvothermal conditions, a robust Pb2+-based coordination polymer (CP), [Pb(TDC)]n (1), where H2TDC is thiophenedicarboxylic acid, has been achieved. Structural analysis reveals that 1 crystallizes in the monoclinic space group C2/c, where the Pb2+ ions show quadrangular prism coordination geometry. CP 1 represents a 3D coordination network based on a TDC2- ligand as bridges and quadrangular prismatic PbO8 units as nodes, among which the PbO8 units are extended through edge-sharing to form a 2D layer in the bc plane. Interestingly, CP 1 emitted intense and long-lived orange phosphorescence in the solid state at room temperature, with a quantum yield of 6.7% and a phosphorescence lifetime of 1.78 ms. A fine structure is clearly observed in the phosphorescence emission spectra at temperatures below 55 K. The emission mainly arose from the electron transition within the π-type orbitals of the TDC2- ligand. This study gives a fresh impetus to achieve CP-based long-lived phosphorescent materials under ambient conditions.

Stereochemically Active and Inactive Lone Pairs in Two Room-Temperature Phosphorescence Coordination Polymers of Pb2+ with Different Tricarboxylic Acids

“…It is well-known that the heavy atom has strong spin–orbital coupling effect, which could efficiently enhance intramolecular intersystem crossing; as a result, it is possible to achieve the ligand-based phosphorescent CPs by rational design of organic ligand structure and selection of heavy metal ion to assembling CPs. In previous studies, we used such a functionality-directed crystal engineering strategy to achieve successfully a series of Pb 2+ - and Cd 2+ -based phosphorescent CPs which emit phosphorescence with high quantum yield under ambient condition. − To extend further the study of CPs emitting ligand-based phosphorescence, herein, we present two high-thermal-resistance Pb 2+ -based CPs, [Pb 2 (HBTC) 2 (DMF)] ( 1 ) and [Pb­(HPTC)] ( 2 ), which are comprised of Pb 2+ ions with rigid aromatic tricarboxylic acids ligands, 1,3,5-benzenetricarboxylic acid (H 3 BTC) and 2,4,6-pyridine tricarboxylic acid (H 3 PTC), respectively, and the two Pb 2+ -based CPs emit intense greenish phosphorescence under ambient condition.…”

Dual stimuli-responsive phosphorescence of a Pb(ii) coordination polymer to acidic vapors and thermal treatment

“…More importantly, a heavy atom effect of the Pb(II) center can induce spin-orbit coupling interactions in luminescent CPs. 14,15 The strong coupling efficiently promotes the intersystem crossing process, which enables the spin forbidden (T 1 → S 0 ) transition, generating phosphorescence emission at room temperature. Also, the effective utilization of the light of triplet excitons is facilitated, allowing a high quantum efficiency of phosphorescent Pb(II) CPs, 16,17 which can bring about their high-contrast emission signal change upon external stimulations.…”