Diphenylpyridyl Amine Substituted Phosphorescent Cu(I)‐Halide Complexes: Reversible Mechanochromism and Aggregation‐Induced Emission Properties

ABSTRACT A series of luminescent Cu(I) complexes incorporating the N,N ‐diphenylpyridin‐4‐amine (DPPA) and PPh 3 were synthesized and characterized, revealing intriguing photophysical and stimuli‐responsive properties. Single‐crystal X‐ray diffraction studies confirmed the formation for Cu 2 X 2 (DPPA) 2 (PPh 3 ) 2 (X = I, Br, Cl for C 1 , C 2 , and C 3 ) having Cu 2 X 2 rhomboid core. These complexes exhibit intense blue to cyan‐blue solid‐state emission, with λ em at 436 ( C 1 ), 462 ( C 2 ), and 491 nm ( C 3 ). Remarkably, C 2 and C 3 show high photoluminescence quantum yields (PLQY) of 65% and 48%, respectively. Temperature‐dependent photoluminescence and lifetime studies suggest phosphorescence. Additionally, these complexes exhibit reversible mechanochromic properties: grinding induces a significant red‐shift in emission ( C 1 : 436 nm → 502 nm; C 2 : 462 nm → 531 nm; C 3 : 491 nm → 540 nm). The reversible mechanochromism is attributed to the loss in crystallinity and disruption of weak C─H⋯π interactions. The complexes also demonstrate pronounced aggregation‐induced emission (AIE) behavior in DMSO/water mixtures, with a significant increase in emission at 90% water fraction. Dynamic light scattering (DLS) and scanning electron microscopy (SEM) analyses revealed the formation of spherical nanoaggregates. These results demonstrate the potential of DPPA‐based Cu(I) complexes as stimuli‐responsive materials for various applications.