Synthesis, characterisation and speciation studies of heterobimetallic pyridinehydroxamate-bridged Pt(ii)/M(ii) complexes (M = Cu, Ni, Zn). Crystal structure of a novel heterobimetallic 3-pyridinehydroxamate-bridged Pt(ii)/Cu(ii) wave-like coordination polymer

Abstract

The reaction of cis-[Pt(NH3)2(3-pyhaH)2]2+ (3-pyhaH = 3-pyridinehydroxamic acid) and cis-[Pt(NH3)2(4-pyhaH)2]2+ (4-pyhaH = 4-pyridinehydroxamic acid) with Cu(II), Ni(II) or Zn(II) in aqueous solution affords novel heterobimetallic pyridinehydroxamate-bridged complexes, {cis-[Pt(NH3)2(mu-3-pyha)M(mu-3-pyha)].SO4.xH2O}n and {cis-[Pt(NH3)2(mu-4-pyha)M(mu-4-pyha)].SO4.xH2O}n respectively. The crystal and molecular structure of one of these, {cis-[Pt(NH3)2(mu-3-pyha)Cu(mu-3-pyha)]SO4.8H2O}n 3a, has been determined and was found to be a novel heterobimetallic wave-like coordination polymer, the structure of which contains interlinked pyridinehydroxamate-bridged repeating units of Pt(II) and Cu(II) ions in slightly distorted square-planar N4 and O4 coordination environments respectively and extensive hydrogen-bonding through the Pt ammines and the deprotonated hydroxamate O and via the O of the SO4(2-) counterions and the H(N) of the hydroxamate moiety. Spectrophotometric and speciation studies on the other heterobimetallic systems confirm that very similar species are being formed in solution and based on elemental analysis and spectroscopic results analogous complexes are formed in the solid-state. In this paper, we report the first examples of coordination polymers incorporating both Pt(II)/Cu(II), Pt(II)/Ni(II) and Pt(II)/Zn(II) and containing pyridinehydroxamic acids as bridging scaffolds.

Iron(III) Tris(pyridinehydroxamate)s and Related Nickel(II) and Zinc(II) Complexes: Potential Platforms for the Design of Novel Heterodimetallic Supramolecular Assemblies

“…[4] We also recently utilised 3-and 4-pyridinehydroxamic acids 3-and 4-pyhaH as bridging scaffolds in the design of Pt II /M II coordination polymers (M = Cu, Ni or Zn) because they can coordinate Pt II in a monodentate fashion through the pyridine nitrogen atom only, thus leaving the hydroxamic acid moiety free to coordinate to a separate metal ion (Figure 2). [6] …”

“…[3] The powerful metal-chelating ability of hydroxamic acids has been utilised to spectacular effect in the construction of a diverse host of fascinating metal complexes. These include hydroxamates, [4] hydroximates [4] and examples in supramolecular chemistry such as metallacrowns, [5] coordination polymers [6] and tetrahedral cluster complexes. [7] [a] Centre As ligands, hydroxamic acids typically coordinate in an O,OЈ-bidentate chelating fashion, coordinating through the carbonyl oxygen atom and the deprotonated hydroxy group to form very stable five-membered chelates.…”

A novel anti-cancer bifunctional platinum drug candidate with dual DNA binding and histone deacetylase inhibitory activity

“…Although hydroxamic acids are known to be strong metal ion chelators, 16,17 we previously reported that they have a low affinity for Pt. [18][19][20] We were therefore confident that the Pt would bind selectively to the malonato substituent. We also believed it important that the two functional entities of the Pt-HDACi conjugate, upon reaching the nucleus, would separate to allow each to work independently of the other.…”

Formation and luminescence of 1D helical polymeric excimer from Pt-MeO-salen precursor

“…Besides that, frequent solvent-induced polymorphism of Pt(II) complexes with bipyridine [10], polypyridine [11] or diimine ligands [12] that have extended p systems has been shown p-stacking and direct Pt-Pt interactions result in the formation of excimers with the characteristic luminescence shifted to lower energies with respect to the luminescence from monomers. Nevertheless, research of the role of weak coordination interactions between the well-defined monomers which modulates the luminescence properties of the chromophores is relatively limited [13].…”

“…Besides that, frequent solvent-induced polymorphism of Pt(II) complexes with bipyridine [10], polypyridine [11] or diimine ligands [12] that have extended p systems has been shown p-stacking and direct Pt-Pt interactions result in the formation of excimers with the characteristic luminescence shifted to lower energies with respect to the luminescence from monomers. Nevertheless, research of the role of weak coordination interactions between the well-defined monomers which modulates the luminescence properties of the chromophores is relatively limited [13].Based on the supramolecular photochemistry of the reported Pt-salen Schiff base systems [9], complexes of platinum(II) and MeO-substituted salen-type Schiff-base could be chosen to develop new systems, in which the outer MeO donors of MeO-salen ligand endows further coordination, definitely directing the stacking of monomers (Pt-MeO-salen) to form structurally diverse and potentially important excimers in their photochemistry applications. Herein, the self-assembly of the Pt-MeO-salen (MeO-salen = N,N 0 -bis(3-methoxy-salicylidene)-ethylene-1,2-diamine) precursor with K 2 Ni(CN) 4 leads to a polymeric complex [K 2 -(Pt-MeO-salen) 2 Ni(CN) 4 ] n Á 0.5nEt 2 O (1), and its improved photoluminescence has been examined.…”