Macrochelation, cyclometallation and G-quartet formation: N3- and C8-bound PdII complexes of adenine and guanine.

Journal article

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: Price, C; Shipman, M; Rees, N; Elsegood, MR; Edwards, A

• Publication status: Published
• Journal: Chemistry (Weinheim an der Bergstrasse, Germany)
• Volume: 7
• Issue: 6
• Pages: 1194-1201
• Publication date: 2001-03-01
• DOI: 10.1002/1521-3765(20010316)7:6<1194::aid-chem1194>3.0.co;2-3
• EISSN: 1521-3765
• ISSN: 0947-6539
• Language: English
• Keywords: Molecular Structure; Palladium; Ligands; Guanine; Models, Molecular; Base Pairing; Nuclear Magnetic Resonance, Biomolecular; Hydrogen Bonding; Adenine; Binding Sites; DNA