Coordination-Driven Strategy to Access Dual-State Emissive Helically Twisted bis-Zn(II) Complexes of Dipyrroethene-Based Ligands

Abstract

Herein, we present a coordination-driven strategy to access a novel class of dual-state emissive helically twisted bis-Zn(II) complexes in good yields by treating aggregation-induced emission (AIE)-active α-functionalized (E)-5,6-ditolyldipyrroethene ligands with Zn(OAc)2 under optimum reaction conditions. Comprehensive X-ray crystallographic studies in combination with detailed photophysical and density functional theory (DFT) analysis revealed a very interesting structure–property relationship. The complexes exhibit a discrete double-stranded dimeric tetrahedral bis-Zn(II) architecture in which metal coordination induces a pronounced conformational rigidification of the AIE-active ligands. While conventional AIEgens, including tetraphenylethylene (TPE) or 5,6-ditolyldipyrroethene (DPE), depend primarily on external aggregation effects, the present strategy utilizes intrinsic coordination-induced locking with reduced π···π stacking to regulate excited-state relaxation processes. As a result, the complexes suppress nonradiative decay and exhibit strong fluorescence in both solution and solid states with good quantum yields. This work establishes Zn(II) coordination-induced helically twisted architecture as an effective molecular design strategy to access dual-state luminescence materials and highlights α-functionalized dipyrroethene ligands as promising building blocks for photofunctional coordination architectures.