Synthesis and mechanochromic luminescence of a novel cationic iridium(Ⅲ) complex

A cationic iridium(Ⅲ) complex (ppy)₂Ir(DPPTA)PF₆ was synthesized by using 2-phenylpyridine (ppy) as main ligand and N, N-diphenyl-4-(4-phenyl-5-(pyridin-2-yl)-4H-1,2,4-triazol-3-yl)aniline (DPPTA) as ancillary ligand. This complex showed mechanochromic luminescence with high contrast. When it was just obtained via precipitating from CH₂Cl₂ solution, it emitted green light and the maximum emission wavelength (λ_em,max) was 525 nm. It emitted yellow light (λ_em,max=576 nm) after it was ground, then it emitted yellow-green light (λ_em,max=531 nm) when it was fumed by CH₂Cl₂. The color changes caused by grinding and fumigation can be repeated for many times with high stability, the difference of the λ_em,max in two states was as high as 45 nm. The emissive color of (ppy)₂Ir(DPPTA)PF₆ was sensitive to mechanical force and being fumed by organic solvents, but it was not sensitive to temperature changes, which was different from many reported mechanochromic luminescence materials.