Blue-shifted mechanochromism of a dimethoxynaphthalene-based crystal with aggregation-induced emission

In this study, we report a diaminomaleonitrile-functionalized dimethoxynaphthalene molecule (N-MN), with intramolecular charge transfer and aggregation-induced emission properties. Moreover, N-MN is a remarkable blue-shifted mechanochromic luminescent (ML) material. Upon external mechanical force, the orange emissive N-MN crystal is changed to yellow emission, accompanying with a blue-shifted fluorescence of 39 nm (from 607 to 568 nm). Single-crystal X-ray diffraction analysis indicates that the initial crystal of N-MN has a tight antiparallel packing mode with abundant intermolecular interactions. External mechanical force destroys the intermolecular interactions and partly changes the packing mode, resulting in the blue-shifted emission. This study provides further understanding of the relationship between intermolecular interactions, molecular packing mode and the blue-shifted emission properties.