Isomeric ligands usually affect the structure and biological activity of complexes. Two Complexes [Zn(tpc)₂(H₂O)₂](1) and [Zn(tfc)₂(H₂O)₂](2) were synthesized with isomeric ligands (Htpc = 5-(trifluoromethyl) pyridine-2-carboxylic acid, Htfc = 4-(trifluoromethyl) nicotinic acid). Single crystal X-ray studies revealed the structural differences between the two complexes, where the coordination mode of complex 1 is N, O chelated coordination and that of complex 2 is N, O monodentate coordination. Due to the structural variations between the two complexes, the binding activity of two complexes with bovine serum albumin (BSA) or calf thymus DNA (CT-DNA) changed. Both complexes can quench BSA statically with binding constants of 10⁵–10⁶ L mol⁻¹. Thermodynamic studies showed that the binding processes are spontaneous (ΔG < 0) and hydrogen bonding and van der Waals force play an important role in the binding processes (ΔH < 0, ΔS < 0). Complexes bind to CT-DNA through the intercalation mode, which was further verified by ethidium bromide (EB) competition experiments. Compared with complex 2, complex 1 with N, O chelated five-membered ring showed higher binding efficacy toward these biomolecules. It is speculated that the N, O chelating structure increases the binding properties of the complexes with biological macromolecules.

中文翻译：

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三氟甲基吡啶甲酸锌(II)配合物：异构体对配位和生物活性的影响

异构配体通常影响复合物的结构和生物活性。用异构配体合成了两种配合物[Zn(tpc) ₂ (H ₂ O) ₂ ]( 1 )和[Zn(tfc) ₂ (H ₂ O) ₂ ]( 2 ) ( Htpc = 5-(三氟甲基)吡啶- 2-羧酸，Htfc = 4-(三氟甲基)烟酸)。单晶X射线研究揭示了两种配合物的结构差异，配合物1的配位方式为N，O螯合配位，配合物2为N，O单齿配位。由于两种复合物之间的结构差异，两种复合物与牛血清白蛋白（BSA）或小牛胸腺DNA（CT-DNA）的结合活性发生了变化。两种复合物都可以静态猝灭 BSA，结合常数为 10 ⁵ –10 ⁶ L mol ^-1。热力学研究表明，结合过程是自发的（Δ G < 0），氢键和范德华力在结合过程中起着重要作用（Δ H < 0，Δ S < 0）。复合物通过嵌入模式与CT-DNA结合，并通过溴化乙锭（EB）竞争实验进一步验证。与配合物2相比，具有N、O螯合五元环的配合物1对这些生物分子表现出更高的结合效率。推测N、O螯合结构增加了配合物与生物大分子的结合性能。