Upon
mechanical stimulation, 9-anthryl gold(I) isocyanide complex <b>3</b> exhibited a bathochromic shift of its emission color from
the visible to the infrared (IR) region, which is unprecedented in
its magnitude. Prior to exposure to the mechanical stimulus, the polymorphs <b>3α</b> and <b>3β</b> exhibit emission wavelength
maxima (λ<sub>em,max</sub>) at 448 and 710 nm, respectively.
Upon grinding, the λ<sub>em,max</sub> of <b>3α</b><sub>ground</sub> and <b>3β</b><sub>ground</sub> are
bathochromically shifted to 900 nm, i.e., Δλ<sub>em,max</sub> (<b>3α</b>) = 452 nm or 1.39 eV. Polymorphs <b>3α</b> and <b>3β</b> thus represent the first examples of mechanochromic
luminescent materials with λ<sub>em,max</sub> in the IR region