Synthesis and Photophysical Properties of Monometallic C^C* Platinum(II) Formamidinate Complexes using Sterically Demanding Ligands

Abstract

AbstractA novel class of cyclometalated platinum(II) complexes—previously considered to be inaccessible—was synthesized by an improved synthetic route utilizing ligands predicted by density functional theory calculations. Based on a concise quantum chemical screening three model ligands with varying steric demand were chosen and a series of six photoluminescent C^C* cyclometalated platinum(II) formamidinate complexes was obtained. The least sterically demanding ligand led to a bimetallic complex in two isomeric forms, which could be separated and confirmed by the corresponding solid‐state structures. Sterically more hindered amidinate ligands gave the monometallic complexes supporting the theoretical predictions. The monometallic complexes show a significant hypsochromic shift of the emission wavelength, explained by the loss of the metal‐metal interactions. Depending on the cyclometalating ligand quantum yields up to 87 % with short decay times were found for this new class of phosphorescent green‐blue to pure blue platinum(II) emitters.