Thermo- and Mechano-Triggered Luminescence ON/OFF Switching by Supercooled Liquid/Crystal Transition of Platinum(II) Complex Thin Films

Trihexyltetradecylphosphonium (P-6,P-6,P-6,P-14) salts of luminescent anionic Pt(II) complexes, (P-6,P-6,P-6,P-14)[PtX2(ppy)] (X = Cl-, Br-; ppy = 2-phenylpyridinate), are synthesized and photofunctional thin films with crystal/liquid bi-stability are fabricated. In particular, the chloride complex provides a thin film exhibiting thermo- and mechano-triggered luminescence ON/OFF switching at ambient temperature, which is based on the control of the supercooled liquid phase and bright luminescent crystalline phase. The photophysical properties of the complexes are investigated and compared with those of the bromide complex and tetra(n-butyl)ammonium salts of the complexes. Furthermore, detailed photophysical analysis reveals a large contribution of the charge-transfer character to the ligand-centered (3)pi pi* excited state, which results in intense phosphorescence in the crystal and high-contrast luminescence ON/OFF by the phase transition of the chloride complex

Surface Tension of Tricyanomethanide- and Tetracyanoborate-Based Imidazolium Ionic Liquids by Using the Pendant Drop Method

The surface tension of nine tricyanomethanide ([C­(CN)₃]⁻)- and tetracyanoborate ([B­(CN)₄]⁻)-based ionic liquids (ILs) carrying a homologous series of the 1-alkyl-3-methylimidazolium ([alkyl-MIM]⁺) cations [EMIM]⁺ (ethyl), [BMIM]⁺ (butyl), [HMIM]⁺ (hexyl), [OMIM]⁺ (octyl), and [DMIM]⁺ (decyl) was measured with the pendant drop method in the temperature range between (283 and 353) K at atmospheric pressure with an estimated uncertainty of 2 % (<i>k</i> = 2). For the probed ILs, the surface tension decreases with increasing temperature and increasing alkyl chain length of the cation. Smaller values for the [B­(CN)₄]⁻-based ILs compared to the [C­(CN)₃]⁻-based ILs having the same cation were observed. The measured surface tensions agree with the limited number of experimental data found in the literature for the two IL families. A simple prediction based on the surface tension measured at 293 K and the temperature dependence of density showed good agreement with the measured temperature-dependent data. In comparison to other [alkyl-MIM]⁺-based ILs with anions of varying molecular size, the fairly large surface tensions of the ILs investigated in this study could be attributed to the strong charge delocalization in their relatively small anions