A Conformationally Flexible Dinuclear Pt-II Complex with Differential Behavior of its Two States toward Quadruplex DNA

作者：von Grebe Philipp; Suntharalingam Kogularamanan; Vilar Ramon^*; Sanz Miguel Pablo J; Herres Pawlis Sonja; Lippert Bernhard

来源：Chemistry - A European Journal, 2013, 19(34): 11429-11438.

DOI：10.1002/chem.201301400

• conformation analysis
• coordination modes
• DNA
• molecular tweezers
• platinum

The reaction of tetrakis(pyridine-2-yl)pyrazine (tppz) with 2equiv 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 degrees C (Z isomer, 1) and under reflux conditions (U isomer, 2), respectively. X-ray crystal-structure analyses of the Zisomer, [{Pt(2,2-bpy)}(2)(tppz)](PF6)(4)3CHCl(3)4H(2)O (1a), and of the Uisomer, [{Pt(2,2-bpy)}(2)](PF6)(4)2CH(3)CN1.5H(2)O (2a), 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)]4.5H(2)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 Uisomer was more stable than the Zisomer, 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 Uisomer binds significantly more strongly to quadruplex DNA (DC50=0.38M) than the Zisomer (DC50=8.50M).

• 出版日期2013-8-19