Taking Advantage of Right Angles inN1,N7-Diplatinated Purine Nucleobases:  Toward Molecular Squares, Rectangles, and Meanders

Abstract

Di-and trinuclear complexes of trans-a 2 Pt II (a ) NH 3 or NH 2 CH 3 ) and the purine model nucleobases 9-methyladenine (9-MeA), 9-ethyladenine (9-EtA), 9-methylguanine (9-MeGH), and 9-ethylguanine (9-EtGH) have been prepared and characterized. The following five compounds have been studied using X-ray crystallography: 3a); a ) NH 3 , n ) 1.8 (3b)), and trans,trans,trans-{[Cl(NH 3 ) 2 Pt] 2 (N1-9-MeA-N7) 2 Pt(NH 3 ) 2 }-(ClO 4 ) 4 ‚H 2 O (5). In all diplatinated adenine species (2, 3a, 3b, and 5) the Pt-N(1) and Pt-N(7) vectors are approximately at right angles, therefore making these complexes potential building blocks for molecular squares, rectangles, and meanders. Two open nucleobase quartets, 4 and 6, consisting of three trans-diamineplatinum(II) entities and four purine nucleobases (two bridging 9-MeA′s and two terminal 9-MeGH (4) and 9-EtGH (6), respectively) have been isolated and characterized by elemental analysis and 1 H and 195 Pt NMR spectroscopy. S0020-1669(98)00081-0 CCC: $15.00

Mixed Adenine/Guanine Quartets with Threetrans‐a2PtII(a=NH3or MeNH2) Cross‐Links: Linkage and Rotational Isomerism, Base Pairing, and Loss of NH3

“…The remaining 42 isomers are given in the Supporting Information. For clarity, all linkage isomers are drawn as Z-shaped structures, with Pt-N1 and Pt-N7 vectors being approximately perpendicular, [20] but it must be kept in mind that additional rotamers are possible. For example, the Z rotamer may also adopt a U shape, and the terminal purines may likewise rotate about the MÀN(purine) bonds.…”

“…[15] However, crystal-packing patterns of nucleic acid structures (duplexes, multistranded structures, junctions) and the field now termed DNA nanotechnology provide ample opportunities to speculate about the possibilities of cross-linking of nucleobases in the presence of transition metals as well. [16] Our recent focus on adenine/guanine base pairs and larger aggregates of these two bases, both without [17] and with metal cross-links, [18] was motivated by a number of properties of this system, namely 1) by the structural variations of this mispair (A anti G anti ; A syn G anti ; AH + anti G syn ) [19] and its ready accommodation in double-stranded DNA; 2) by the obvious possibility to convert such mispairs into virtual quartets; [17] 3) by the feature that purine bases represent 90 8 fragments in complexes with metal ions at N1 and N7, [20] and 4) by unusually low pK a values of the A-N6H 2 group in particular cases.…”

Palladium(II) binding to N(7) of acyclovir: DNA interaction and herpes simplex virus (HSV-1) inhibitory activity

“…Moreover, mononuclear Pt(II) complexes of hypoxanthine derivatives bind to the N(1) atom owing to the blockage of N(7) by substituents [32][33][34][35]. Further deprotonation of the exocyclic substituent at C(2) opens the spectrum of coordination to N(7), N(1) and N(2) through the NH 2 group [35,36]. The simultaneous binding of Pt(II) and Pd(II) to N(9)-blocked guanine has been proposed as a source of N(1)-deprotonation at neutral pH [37].…”

Connectivity patterns and rotamer states of nucleobases determine acid–base properties of metalated purine quartets

“…Three principal arrangements of two hemi-deprotonated adenine ligands in head-head orientation and cross-linked by linear metal ions (M = trans-a 2 Pt II ): N1-Pt-N1, N1-Pt-N7, and N7-Pt-N7 (top to bottom). [73][74][75][76][77][78][79][80][81]. Even with a single purine base applied, e.g., 9MeA [82], yet more so in combinations with a second, different purine base [54], the number of linkage isomers becomes large.…”