Dinuclear Ruthenium(II)-Pyrrolide Complexes Linked by Different Organic Units as PDT Photosensitizers: Computational Study of the Linker Influence on the Photophysical Properties*

A new family of bis[pyrrolyl Ru(II)] triad scaffolds, consisting of two [Ru(bpy)2]2+ centers separated by a variety of organic linkers, has been recently reported as efficient compounds for in vitro photodynamic therapy (PDT). Among all the complexes, the one carrying the pyrenyl group in the organic linker, namely 4 h, has emerged as an extremely potent photosensitizer for in vitro PDT. Here, we present a computational study based on both DFT and TDA-TDDFT methods, to investigate the photochemical properties of this promising complex. In order to evaluate the influence of the organic chromophore on the photochemical properties, our investigation was further extended to the complex 4 e, whose linker includes the benzothiadiazole group, which has yielded the longest-wavelength absorption maxima overall (but with a reduced intensity compared to 4 h). Eventually, the role of the second [Ru(bpy)2]2+ moiety was evaluated by comparison with the mononuclear complex.