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. 2025 Jul 29;16(35):16004-16015.
doi: 10.1039/d5sc04306a. eCollection 2025 Sep 10.

Topochemical photocycloaddition in two-dimensional lead-halide coordination polymers with tunable phosphorescence

Zhongwei Chen  1 , Jin Wu  1 , Zeyu Deng  2 , Congcong Chen  3 , Jianning Feng  1 , Baixu Ma  3 , Lizhi Tao  3 , Lingling Mao  3 , Haipeng Lu  1
Affiliations

Topochemical photocycloaddition in two-dimensional lead-halide coordination polymers with tunable phosphorescence

Zhongwei Chen et al. Chem Sci. .

Abstract

Topochemical transformation in which the parent structural motifs are preserved has become a powerful strategy to access new advanced materials. Solid-state topochemical conversion in a single-crystal-to-single-crystal (SCSC) fashion is particularly attractive as it provides design principles with unequivocal structural details. Here, we report a series of two-dimensional (2D) lead-halide coordination polymers with bipyridyl ethylene (bpe) ligands that can undergo quantitative SCSC [2 + 2] photocycloaddition. The chemical and structural diversity of 2D lead-halide coordination polymers allows systematic modulation of the rate of SCSC [2 + 2] photocycloaddition by changing the halide and bpe ligands. Our work reveals the structure-property relationship in lead-halide coordination polymers during the dynamic [2 + 2] photocycloaddition process. The photo-transformed coordination polymers with cyclobutane linkages show drastically different properties in optical absorption and emission. We present a viable strategy to modify the structure and properties of lead-halide coordination polymers by post-synthetic modification.

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Conflict of interest statement

The authors declared that they have no conflicts of interest.

Figures

Scheme 1
Scheme 1. Schematic illustration for the design of lead halide coordination polymers and their solid-state [2 + 2] photocycloaddition process.
Fig. 1
Fig. 1. Structures of bpe-based lead-halide CPs. (a–d) Front view of the 2D structures of 44bpe-PbX2 (X = Cl, Br, I), 22bpe-PbBr2, 24bpe-PbI2, and 22bpe-PbI2. (e–h) Side view of the 2D structures of 44bpe-PbX2, 22bpe-PbBr2, 24bpe-PbI2, and 22bpe-PbI2. (i–k) Parallel packing of 44bpe, 22bpe, and 24bpe. (l) Criss-cross packing of 22bpe. Green, blue, brown, purple, and dark spheres denote the Cl, N, Br, I, and Pb atoms, respectively. Gray sticks denote the C atoms.
Fig. 2
Fig. 2. (a) Absorption spectra of the bpe-PbX2 CPs. (b) 1H NMR spectra of 44bpe-PbCl2 under different irradiation times. (c) Photocycloaddition rates of the bpe-PbX2 CPs with different double bond distances. (d) The relationship between the photocycloaddition rates and bandgap.
Fig. 3
Fig. 3. Different conformations of cyclobutane photoproducts. (a) rctt. (b) rtct.
Fig. 4
Fig. 4. [2 + 2] Photocycloaddition induced SCSC transformation in bpe-PbX2 CPs. (a) 44bpe-PbCl2-P; the inset shows the single crystal after illumination, scale bar is 100 μm. (b) 44bpe-PbBr2-P. (c) 44bpe-PbI2-P. (d) 22bpe-PbBr2-P. (e) 24bpe-PbI2-P.
Fig. 5
Fig. 5. Absorption spectrum changes in bpe-PbX2 CPs after photocycloaddition. (a) 44bpe-PbCl2. (b) 44bpe-PbBr2. (c) 44bpe-PbI2. (d) 22bpe-PbBr2. (e) 22bpe-PbI2. (f) 24bpe-PbI2.
Fig. 6
Fig. 6. Photocycloaddition-induced PL spectrum changes in 44bpe-PbCl2 (a), 44bpe-PbBr2 (b), 44bpe-PbI2 (c), 22bpe-PbBr2 (d), and 24bpe-PbI2 (e). (f) PL lifetime of the bpe-PbX2 CPs.
Fig. 7
Fig. 7. Band decomposed partial charge densities of 22bpe-PbBr2 (top panel) and 22bpe-PbBr2-P (bottom panel) at VBM (left and middle panels) and CBM (right panel), respectively.
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