Tuning Triplet Exciton Pathways via Molecular Aggregation in a Family of Coordination Polymers.

Feng, Rui; Li, Zi-Ying; Huang, Shi-Shuang; Yu, Mei-Hui; Wei, Fengxia; Hou, Jingwei; Li, Wei; Bu, Xian-He · Nano Lett · 2025

basic_science · Level V

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Abstract

Molecular aggregation is the key factor in determining the triplet exciton pathways of room-temperature phosphorescence (RTP) materials; however, controlling different aggregation forms and understanding their synergistic effects remain challenging. In this work, we report three coordination polymers (CPs) with cofacial translational stacking (H-aggregation), cofacial-staggered translational stacking (H-J aggregation) and cofacial translational-crossing stacking (H-X aggregation): [Zn(3,4-PyDC)(TPT)]·TPT (<b>1</b>; 3,4-PyDC = 3,4-pyridinedicarboxylate; TPT = 2,4,6-tri(4-pyridyl)-1,3,5-triazine), [Zn(IPA)(TPT)<sub>2</sub>]·H<sub>2</sub>O (<b>2</b>; IPA = isophthalate) and [Zn<sub>3</sub>(3,5-PyC)<sub>2</sub>(TPT)<sub>3</sub>(H<sub>2</sub>O)<sub>2</sub>] (<b>3</b>; 3,5-PyC = 3,5-pyrazoledicarboxylate). By changing the aggregation modes, these CPs exhibit tunable triplet exciton pathways, enabling distinct fluorescent, phosphorescent, and photochromic properties. Single-crystal X-ray diffraction, time-resolved emission spectroscopy and theoretical analysis demonstrate that enhanced charge migration in <b>2</b> with H-J aggregation promotes charge-separated photochromism, while differentiated orbital energies in <b>3</b> with H-X aggregation enables wavelength-responsive room temperature phosphorescence. These findings provide a route to hybrid CPs with designated triplet-exciton pathways and associated optical properties by manipulating molecular aggregation.