Following the results we previously reported on a series of xanthene and xanthone derivatives as G-quad-ruplex stabilizing ligands, in order to obtain a more selective compound with respect to the previous generation of derivatives, we decided to modify the structure of the core ligand, specifically its aromatic extension. In particular, here we report the design, synthesis and activity data of a new compound obtained by dimerization of the xanthene core (HELIXA4C). The reported results show that extension of the aromatic core and the increase of the number of polar side chains led to a great enhancement of G-quadruplex selectivity and telomere damage capability, as derived using ESI-MS evaluation, in vitro cancer screening and specific immunofluorescence assays.