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Diphenylpyridyl Amine Substituted Phosphorescent Cu(I)-Halide Complexes: Reversible Mechanochromism and
Dilip Pandey1, Savita Chand2, Rajneesh Kumar Yadav1
1Department of Chemistry, Indian Institute of Technology Indore, Madhya Pradesh, India.
Abstract:
A series of luminescent Cu(I) complexes incorporating the N,N-diphenylpyridin-4-amine (DPPA) and PPh3 were synthesized and characterized, revealing intriguing photophysical and stimuli-responsive properties. Single-crystal X-ray diffraction studies confirmed the formation for [Cu2X2(DPPA)2(PPh3)2] (X = I, Br, Cl for C1, C2, and C3) having Cu2X2 rhomboid core. These complexes exhibit intense blue to cyan-blue solid-state emission, with λem at 436 (C1), 462 (C2), and 491 nm (C3). Remarkably, C2 and C3 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 (C1: 436 nm → 502 nm; C2: 462 nm → 531 nm; C3: 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.
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