Synthesis and anti-proliferative activities of amine capped Pd and Pt macrocycles of 4,4′-dipyridylselenides

Abstract

The synthesis, characterization and anti-proliferative properties of products formed from the reactions of amine-capped Pd^II and Pt^II complexes and 4,4′-dipyridylselenide/diselenide have been investigated. The addition of cis-M(N^∩N)(X)₂ with 4,4′-py₂Se_m yielded stable macrocyclic complexes [M(N^∩N)(py₂Se_m)]_n(X)_2n (M = Pd, Pt; N^∩N = en, tmeda; m = 1 or 2; X = NO₃, OTf). The ⁷⁷Se, ¹⁹⁵Pt NMR and ESI mass spectra of the product of the diselenide ligand showed the presence of two types of complexes which are indistinguishable by ¹H NMR spectroscopy. Their relative ratio depends on the nature of N^∩N and M. The major product has been confirmed as a macrocyclic dimeric complex [Pd(tmeda)(μ₂-4,4′-py₂Se₂)]₂(OTf)₄ containing a “Pd–py–Se–Se–py–Pd” linkage by single crystal XRD. In vitro evaluation of the water-soluble complexes using lung and breast carcinoma cells (A549 and MCF7) showed high anti-proliferative activity of the Pd macrocycles (IC₅₀ = 1.7–19 μM).