title: A conformationally flexible dinuclear Pt(II) complex with differential behavior of its two states toward quadruplex DNA.
abstract: The reaction of tetrakis(pyridine-2-yl)pyrazine (tppz) with 2 equiv of (2,2'-bpy)Pt(II) in water yields two isomeric dinuclear cations, [{Pt(2,2'-bpy)}2 (tppz)](4+) , in which Pt coordination exclusively takes place through the two pairs of pyridine-2-yl nitrogen atoms. The two conformational isomers differ in their overall shape, with the formation of "Z" and "U" shapes, which are formed at 40 °C (Z isomer, 1) and under reflux conditions (U isomer, 2), respectively. X-ray crystal-structure analyses of the Z isomer, [{Pt(2,2'-bpy)}2 (tppz)](PF6 )4 ⋅3 CHCl3 ⋅4 H2 O (1 a), and of the U isomer, [{Pt(2,2'-bpy)}2 ](PF6 )4 ⋅2 CH3 CN⋅1.5 H2 O (2 a), were carried out. Co-crystallization of compound 2 with PtCl2 (2,2'-bpy) yielded [{Pt(2,2'-bpy)}2 (tppz)](BF4 )4 ⋅[PtCl2 (2,2'-bpy)]⋅4.5 H2 O (3), in which the PtCl2 (2,2'-bpy) entity was sandwiched between the two 2,2'-bpy faces of the U-shaped cation (2). Quantum chemical calculations revealed that the U isomer was more stable than the Z isomer, both in the gas phase and in an aqueous environment. These two isomers display different affinities toward duplex DNA and human telomeric quadruplex DNA (Htelo), as concluded from CD spectroscopy and FID assays. Thus, the U isomer binds significantly more strongly to quadruplex DNA (DC50 =0.38 μM) than the Z isomer (DC50 =8.50 μM).
authors.affiliation: Fakultät Chemie, Technische Universität Dortmund, Otto-Hahn-Str. 6, 44221 Dortmund, Germany.
authors.forename: Philipp
authors.initials: P
authors.lastname: von Grebe
authors.forename: Kogularamanan
authors.initials: K
authors.lastname: Suntharalingam
authors.forename: Ramon
authors.initials: R
authors.lastname: Vilar
authors.forename: Pablo J
authors.initials: PJ
authors.lastname: Sanz Miguel
authors.forename: Sonja
authors.initials: S
authors.lastname: Herres-Pawlis
authors.forename: Bernhard
authors.initials: B
authors.lastname: Lippert
mesh_terms: D056831:Coordination Complexes / Q000737:chemistry*; D018360:Crystallography, X-Ray; D004247:DNA / Q000737:chemistry / Q000378:metabolism; D054856:G-Quadruplexes; D006801:Humans; D007536:Isomerism; D008968:Molecular Conformation; D010984:Platinum / Q000737:chemistry*; D011719:Pyrazines / Q000737:chemistry; D011789:Quantum Theory; D016615:Telomere / Q000737:chemistry
chemical_list: D056831:Coordination Complexes; D011719:Pyrazines; D010984:Platinum; D004247:DNA
keywords: DNA; conformation analysis; coordination modes; molecular tweezers; platinum