Gold(I) Complexes Incorporating Emissive Mercapto‐Pteridine Ligands: Syntheses, X‐ray Structure, Luminescence and Preliminary Cytotoxic Evaluation

Abstract

The syntheses of six new mixed P/S‐donor two‐coordinate AuI complexes are described. The complexes incorporate a pteridinyl ligand coordinated through a thiolate donor, and an ancillary tertiary phosphane (PPh3 or PCy3). The mercapto‐pteridine ligands (L1–L3) differ in the nature of the substituents on the pteridine core. An X‐ray crystal structure was obtained for one of the examples, [(L1)Au(PPh3)], revealing weak intermolecular interactions between two molecules of the complex: π–π contacts between aromatic rings appear to support an intermolecular Au–Au contact of approximately 3.05 Å. All of the complexes are luminescent in solution, with emission arising from tuneable ligand‐based excited states, and characterised as a perturbed fluorescence in nature. In this context, complexes of L3 displayed useful visible absorption and emission. Preliminary cytotoxicity assessments were conducted using the MTT assay, and the complexes each displayed impressive anti‐proliferative activities (IC50 < 5 μM) with respect to four different adenocarcinoma cell lines (MCF7, A549, PC3 and LOVO). For a given pteridine moiety, triphenylphosphane appeared to be the co‐ligand of choice for enhancing biological activity.

New avenues in the design and potential application of metal complexes for photodynamic therapy

“…80 However, the photophysical properties of many monometallic species oen rely upon a coordinated uorophore, such as a thio-naphthalimide, 81 anthraquinone (Fig. 18) 82 or mercapto-pteridine 83 species. Although the singlet oxygen generating ability of such complexes has not been investigated, the preeminence of organic chormophores in the photogeneration of singlet oxygen clearly suggests that there is much scope for exploration in the context of Au coordination chemistry.…”

Recent developments in gold(i) coordination chemistry: luminescence properties and bioimaging opportunities

“…6) obtained via the condensation of 4,5-diamino-6-hydroxy-2-mercaptopyrimidine hemisulfate hydrate with a selection of functionalised diketones. 59 Pteridines, bicyclics comprised of a fused pyrimidine and pyrazine ring, are the core structures of key biochemical systems in nature, for example pterins and folic acid 60 and have also shown potent anti-cancer activity (e.g. methotrexate).…”

Fluorescent functionalised naphthalimides and their Au(i)–NHC complexes for potential use in cellular bioimaging

“…PPh 3 ) at Au(I). 23 The importance of charge has also been noted in cytotoxic iridium(III) complexes, with cationic species proving more toxic to cell lines 24 and Gram positive bacteria 25 than neutral analogues. For the pro-ligands, [HL 6 ]PF 6 was the least toxic with IC 50 values >100 μM for each cell type.…”