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

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)₂]·H₂O (<b>2</b>; IPA = isophthalate) and [Zn₃(3,5-PyC)₂(TPT)₃(H₂O)₂] (<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.