High-Spin (S=1) Blatter-Based Diradical with Robust Stability andElectrical Conductivity

摘要

riplet ground-state organic molecules are of interest with respectto several emerging technologies but usually show limited stability, especially asthinfilms. We report an organic diradical, consisting of two Blatter radicals, thatpossesses a triplet ground state with a singlet-triplet energy gap,Delta EST approximate to 0.4-0.5kcal mol-1(2J/k approximate to 220-275 K). The diradical possesses robust thermal stability,with an onset of decomposition above 264 degrees C (TGA). In toluene/chloroform,glassy matrix, andfluid solution, an equilibrium between two conformations with Delta EST approximate to 0.4 kcal mol-1and Delta EST approximate to-0.7 kcal mol-1is observed, favoring thetriplet ground state over the singlet ground-state conformation in the 110-330 K temperature range. The diradical with the tripletground-state conformation is found exclusively in crystals and in a polystyrene matrix. The crystalline neutral diradical is a goodelectrical conductor with conductivity comparable to the thoroughly optimized bis(thiazolyl)-related monoradicals. This is surprisingbecause the triplet ground state implies that the underlying pi-system is cross-conjugated and thus is not compatible with either goodconductance or electron delocalization. The diradical is evaporated under ultra-high vacuum to form thinfilms, which are stable inair for at least 18 h, as demonstrated by X-ray photoelectron and electron paramagnetic resonance (EPR) spectroscopies