title: Macrochelation, cyclometallation and G-quartet formation: N3- and C8-bound PdII complexes of adenine and guanine.
abstract: The reactions of Pd(II) ions with a series of chelate-tethered derivatives of adenine and guanine have been studied and reveal a difference in the reactivity of the purine bases. Reactions of [PdCl2(MeCN)2] and A-alkyl-enH x Cl (alkyl = propyl or ethyl, A adenine, en = ethylenediamine) yield the monocationic species [PdCl(A-N3-Et-en)]+ (1) and [PdCl(A-N3-Pr-en)]+ (2). Both involve co-ordination at the minor groove site N3 of the nucleobase as confirmed by single-crystal X-ray analysis. Reactions with the analogous G-alkyl-enH x Cl derivatives (G=guanine, alkyl = ethyl or propyl) were more complex with a mixture of species being observed. For G-Et-en HCI a product was isolated which was identified as [PdCl(G-C8-Et-en)]+ (3). This compound contains a biomolecular metal-carbon bond involving C8 of the purine base. Crystallography of a product obtained from reaction of G-Pr-enH x Cl and [Pd(MeCN)4][NO3]2 reveals an octacationic tetrameric complex (4), in which each ligand acts to bridge two metal ions through a combination of a tridentate binding mode involving the diamine and N3 and monodentate coordination at N7.
authors.affiliation: Department of Chemistry, University of Newcastle upon Tyne, UK. andrew.houlton@ncl.ac.uk
authors.forename: C
authors.initials: C
authors.lastname: Price
authors.forename: M A
authors.initials: MA
authors.lastname: Shipman
authors.forename: N H
authors.initials: NH
authors.lastname: Rees
authors.forename: M R
authors.initials: MR
authors.lastname: Elsegood
authors.forename: A J
authors.initials: AJ
authors.lastname: Edwards
authors.forename: W
authors.initials: W
authors.lastname: Clegg
authors.forename: A
authors.initials: A
authors.lastname: Houlton
mesh_terms: D000225:Adenine / Q000737:chemistry / Q000378:metabolism*; D020029:Base Pairing; D001665:Binding Sites; D004247:DNA / Q000378:metabolism / Q000648:ultrastructure; D006147:Guanine / Q000737:chemistry / Q000378:metabolism*; D006860:Hydrogen Bonding; D008024:Ligands; D008958:Models, Molecular; D015394:Molecular Structure; D019906:Nuclear Magnetic Resonance, Biomolecular; D010165:Palladium / Q000737:chemistry / Q000378:metabolism*
chemical_list: D008024:Ligands; D010165:Palladium; D006147:Guanine; D004247:DNA; D000225:Adenine