Emissive silver(i) cyclic trinuclear complexes with aromatic amine donor pyrazolate derivatives: way to efficiency

Abstract

3-Trifluoromethyl-pyrazoles containing strong fluorophore groups: triphenylamine (TPAPz) and carbazole (CarbPz), and their trinuclear silver(I) complexes are found to be emissive in solution and the solid state, giving the first example of silver pyrazolate adducts emissive in solution at room temperature. The electronic coupling was observed for pyrazole with a structurally flexible triphenylamine substituent, determining the intraligand charge-transfer (ILCT) nature of the excited states. The association–dissociation of the trinuclear complex core with the heavy atom effect leads to the intense phosphorescence of the triphenylamine-containing complex. The structural rigidity of the N-ethyl carbazole substituent allows only twisting via the bond to the pyrazolate core leading to typical carbazole-centered (LC) fluorescence in solution. In the solid-state, aggregation plays the primary role in emission properties. The observed behavior is in good agreement with the theoretical calculations.