Thermo-, Mechano-, and Vapochromic Dinuclear Cuprous-Emissive Complexes with a Switchable CH 3 CN-Cu Bond.

A thermo-, mechano-, and vapochromic bimetallic cuprous-emissive complex has been reported, and the origin and application of its tri-stimuli-responsive luminescence have been explored. As revealed by single-crystal structure analysis, thermo- and vapochromic luminescence adjusted by heating at 60 °C and CH 3 CN vapor fuming, accompanied by a crystalline-to-crystalline transition, is due to the breaking and rebuilding of the CH 3 CN-Cu bond, as supported by 1 H nuclear magnetic resonance (NMR), Fourier-transform infrared (FT-IR) spectroscopy, powder X-ray diffraction (PXRD), thermogravimetry (TG), and time-dependent density functional theory (TD-DFT) analyses of the CH 3 CN-coordinated species [Cu 2 (μ-dppa) 2 (μ-η 1 (N)η 2 (N,N)-fptz)(CH 3 CN)](ClO 4 )·H 2 O ( 1 ) and its CH 3 CN-removed derivative [Cu 2 (μ-dppa) 2 (μ-η 1 (N)η 2 (N,N)-fptz)](ClO 4 )·H 2 O ( 2 ). Luminescence mechanochromism, mixed with a crystalline-to-amorphous transition where the initial crystalline is different for 1 and 2 , is mainly assigned as the destruction of the CH 3 CN-Cu bonding and/or the O···HN dppa and OH···N triazolyl hydrogen bonds. It is also suggested that a rational use of switchable coordination such as weak metal-solvent bonding is a feasible approach to develop multi-stimuli-responsive luminescent materials and devices.