A carbazolyl appended trans-pyridyl porphyrin (1) was synthesized and its dicationic form 2 was obtained by methylation of the pyridyl group. Copper and zinc complexes of porphyrin 2 (Cu(II), 3; Zn(II), 4) were isolated and characterized by various modern spectroscopic techniques. The DNA binding properties of 2, 3, and 4 have been explored against calf thymus-DNA (CT-DNA). DNA binding was quantized using the intrinsic binding constant (K_b) that was calculated by UV-visible absorption spectroscopy, and the value K_b = 1.6 × 10⁶ M⁻¹ for compound 2 reveals a better interaction of 2 towards CT-DNA than those of 3 (3.1 × 10⁵ M⁻¹) and 4 (3.4 × 10⁵ M⁻¹), which follows the order 2 > 4 > 3. The fluorescence quenching efficiency and ethidium bromide quenching assay also indicated a good binding affinity of all the compounds towards CT-DNA. Furthermore, the spectroscopic data suggest that the possible mode of interaction is intercalation. The docking studies were in accordance with the experimental results. Notably, DNA cleavage studies reveal that 2 shows better damage than 3 and 4 which is in accordance with the binding affinity order 2 > 4 > 3. The observed quantum yield (2: 0.65, 3: 0.33, and 4: 0.97) and no change in DNA cleavage in the presence of NaN₃ reveal the involvement of singlet oxygen. The singlet excited state lifetimes were in the range of 6.3–1.2 ns. Furthermore, these porphyrins can be investigated as interesting photosensitizers in photodynamic therapy and photochemotherapy.

中文翻译：

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咔唑附加的反式双阳离子吡啶卟啉在 DNA 结合/光切割方面优于非咔唑基类似物

合成了附加咔唑基的反式-吡啶基卟啉( 1 )，并通过吡啶基的甲基化获得其双阳离子形式2 。卟啉2 (Cu( II ), 3 ; Zn( II ), 4 ) 的铜和锌配合物通过各种现代光谱技术进行分离和表征。已针对小牛胸腺-DNA (CT-DNA) 探索了2、3和4的DNA 结合特性。使用通过紫外-可见吸收光谱计算的固有结合常数 ( K _b )量化 DNA 结合，并且值化合物2的K _b = 1.6 × 10 ⁶ M ^-1表明2对 CT-DNA 的相互作用比3 (3.1 × 10 ⁵ M ^-1 ) 和4 (3.4 × 10 ⁵ M ^-1 ) 更好，如下顺序2 > 4 > 3. 荧光猝灭效率和溴化乙锭猝灭测定也表明所有化合物对 CT-DNA 具有良好的结合亲和力。此外，光谱数据表明可能的相互作用模式是插层。对接研究与实验结果一致。值得注意的是，DNA 切割研究表明，2显示出比3和4更好的损伤，这符合2 > 4 > 3的结合亲和力顺序。观察到的量子产率（2：0.65、3 ： 0.33 和4 ：0.97）和在 NaN ₃存在下 DNA 切割没有变化揭示单线态氧的参与。单重激发态寿命在 6.3-1.2 ns 范围内。此外，这些卟啉可以作为光动力疗法和光化学疗法中有趣的光敏剂进行研究。