Macrocyclic NHC complexes of group 10 elements with enlarged aromaticity for biological studies

Two sets of macrocyclic, bio-inspired, non-heme ligands are utilized for the synthesis of NiII, PdII and PtII complexes. The ligands consist of a 16-atom macrocycle, formed by four methylene bridged NHC moieties, with imidazole or benzimidazole as building blocks. The complexes exhibit a square planar coordination geometry and are characterized by NMR, ESI-MS, elemental analysis, SC-XRD and UV/Vis. For complexes incorporating benzimidazole, an evaluation of luminescence properties is performed, and is found that phosphorescence is present for the PdII derivative and there is fluorescence for the PtII derivative. Stability studies in cell culture medium are performed for subsequent MTT assays. Here, the NiII complexes show low to no activity, and PdII and PtII complexes exhibit remarkable low IC50 values in cisplatin resistant A2780cisR cells.