“…When heated to the temperatures of 303 K, 333 K, 363 K, and 383 K, the absorption edges of the (PED)CuCl 4 were observed at 596 nm, 613 nm, 635 nm, and 659 nm, respectively.F or (BED) 2 CuCl 6 ,t he absorption edges were observed at 574 nm, 617 nm, 659 nm, and 677 nm, upon heating to 303 K, 363 K, 423 K, and 443 K, respectively.T he red shift of the absorption edge with the temperature rise confirms the chromatic variation of the samples. [36] By extrapolating the linear region of the absorption edge to the energy-axis intercept, we have determined the optical band gaps of the two crystals.For (PED)CuCl 4 ,the band gap changed from 2.08 eV to 1.88 eV when the temperature varied from 303 Kt o3 83 K. In comparison, the band gap of the (BED) 2 CuCl 6 reduced from 2.16 eV to 1.83 eV, when the temperature varied from 303 Kt o4 43 K ( Figure S6,S7). This band gap narrowing is consistent with the observed color changes at different temperatures.…”