Supramolecular luminescent Pt(ii) tweezers: aggregation studies and 1O2 production

Abstract

Four series of Pt(II) tweezer compounds have been designed and synthesized in order to explore their ability to form supramolecular assemblies with luminescence ability. The compounds present the general chemical structure (diphos)Pt(N^N^N), where diphos is a diphosphane that differs in the flexibility and chain length (diphos = bis(diphenylphosphanyl)methane, dppm; 1,2-bis(diphenylphosphanyl)ethane, dppe and 1,2-bis(diphenylphosphanyl)benzene, dppbz) and confers the tweezer structure to the complexes. The four series are defined as a function of the substituents of the N^N^N ligands with different electronic properties (hydrogen vs. chloride) and bulkiness (p-tolyl vs. CF₃). We can identify the presence of intra- and intermolecular Pt⋯Pt, Pt⋯π and π⋯π interactions based on the spectroscopic absorption and emission profiles and supported by DFT calculations giving rise to aggregates with different stabilities. The aggregation process has been carefully analyzed both in solution and in the solid state. The resulting emission properties are affected by aggregation, exemplified by the phosphorescence emission enhancement in the absence of the chloride substituent.