Phenanthroimidazole derivatives with minor structural differences: crystalline polymorphisms, different molecular packing, and totally different mechanoluminescence

Abstract

Two crystalline polymorphs of tPTI-Bpin displayed opposite mechanoluminescence (ML) performance, and had different space groups of P2₁/c (ML-active tPTI-B1) and P (ML-inactive tPTI-B2), respectively. For comparison, another analogue molecule of PTI-Bpin was designed. Careful analysis of their crystal structures demonstrated that the special triangle-like molecular packing mode of tPTI-B1 mainly accounted for its distinctive ML behavior. Regardless of its minor difference in chemical structure from that of tPTI-Bpin, PTI-B without the ML property has similar parallelogram-like molecular packing to tPTI-B2, further confirming that the ML property is highly related to the molecular packing rather than the chemical structure.