ESI-MS and thermal melting studies of nanoscale platinum(ii) metallomacrocycles with DNA

Abstract

The hydrophilic, long-chain diamine PEGda (O,O′-bis(2-aminoethyl)octadeca(ethylene glycol)), when complexed with cis-protected Pt(II) ions afforded water-soluble complexes of the type [Pt(N,N)(PEGda)](NO3)2 (N,N = N,N,N′,N′-tetramethyl-1,2-diaminoethane (tmeda), 1,2-diaminoethane (en), and 2,2′-bipyridine (2,2′-bipy)) featuring unusual 62-membered chelate rings. Equimolar mixtures containing either the 16-mer duplex DNA D2 or the single-stranded D2a and [Pt(N,N)(PEGda)]2+ were analyzed by negative-ion ESI-MS. Analysis of D2-Pt(II) mixtures showed the formation of 1:1 adducts of [Pt(en)(PEGda)]2+, [Pt(tmeda)(PEGda)]2+ and the previously-described metallomacrocycle [Pt2(2,2′-bipy)2{4,4′-bipy(CH2)44,4′-bipy}2]8+ with D2; the dinuclear species bound to D2 most strongly, consistent with its greater charge and aromatic surface area. D2 formed 1:2 complexes with the acyclic species [Pt(2,2′-bipy)(Mebipy)2]4+ and [Pt(2,2′-bipy)(NH3)2]2+. Analyses of D2a-Pt(II) mixtures gave results similar to those obtained with D2, although fragmentation was more pronounced, indicating that the nucleobases in D2a play more significant roles in mediating the decomposition of complexes than those in D2, in which they are paired in a complementary manner. Investigations were also conducted into the effects of selected platinum (

Interaction of metal complexes with nucleic acids

“…10d) and single and double-stranded nucleic acids. 74 Complexes 26 and 27 with the 62-membered chelate of PEGda showed very low affinity for nucleic acids while the bipyridinium complex 28 and a macrocyclic derivative of it were shown to interact more strongly with both ssDNA and dsDNA. This is likely to be due to the higher positive charge as well as the presence of a large number of aromatic rings.…”

Tuning the Structural and Photophysical Properties of Cationic Pt(II) Complexes Bearing Neutral Bis(triazolyl)pyridine Ligands

“…Platinum complexes have attracted a lot of interest for many fundamental and applied aspects that range from electronics − to sensing, − medicine, − and bioimaging. − In particular, cisplatin has been introduced in oncology for the treatment of diverse classes of cancer. ,, To improve the selectivity and efficacy of these complexes toward malicious tumors, intensive studies have been devoted to the modification of the ligands coordinated to the platinum center. ,− An alternative strategy consists of using Pt(IV) derivatives as a prodrug and to reduce the complex in vivo to the toxic Pt(II) species . In addition, cationic Pt(II) complexes have been used as intercalators for duplex and G-quadruplex DNA. ,,− Cationic complexes have also been employed for preparing luminescent Langmuir–Blodgett films by attaching alkyl chains of suitable length on the coordinated tridentate ligand taking advantage of the aggregation properties of these square planar systems . Indeed, their tendency to self-assemble has been also exploited to form various aggregates, fibers, , gels, , liquid crystals, − and micelles .…”