Interstrand DNA covalent binding of two dinuclear Ru(ii) complexes. Influence of the extra ring of the bridging ligand on the DNA interaction and cytotoxic activity

In this work, we report experimental and computational evidences for the intercalation into the DNA base pairs of the free quinones Quinizarin (Q), Naphthazain (N) and the interstrad covalent binding of their p-cymene di-Ruthenium(II) complexes (Cl2Ru2X, with X = N, Q bridging ligands). The intercalation extent for the N complex was larger than for Q, in good agreement with higher relative contour length and melting temperature for the same CX/CDNA ratio and with the computacional mean stacking distances between the ligand and the nearest base-pair (3.34Å and 3.19Å) for N and Q, respectively. However, the apparent binding constant of Q/DNA, two orders higher than that of N/DNA, denotes that the thermal stability of X/DNA complex is more related to the degree of intercalation than to the binding constants magnitude. Cl2Ru2X complexes undergo aquation, forming the aqua-derivatives [(H2O)2Ru2X]2+. These can further bind covalently to DNA via interstrand crosslinking, through both Ru centres and two N7 sites of consecutive Guanines, to give (DNA1,2)Ru2X complexes, by a mechanism similar to that of cisplatin. To the best of our knowledge, this type of interaction with dinuclear Ru(II) complexes has not been reported hitherto. The experimental and computational results reveal that the number of rings of the aromatic moiety and the covalent binding to DNA play a key role in the behaviour of the quinones and their Ru(II) derivatives. The cytotoxicity of the ligands and the corresponding Ru(II) complexes was evaluated in the MCF-7, A2780, A2780cis tumour cells and in the healthy cell line MRC-5. The cytotoxic activity was notable for the N compound and negligible for Q. The IC50 values and the resistance (RF) and selectivity (SF) factors show that the Cl2Ru2N complex is the most promising among the four studied anticancer drugs

Non-emissive RuII Polypyridyl Complexes as Efficient and Selective Photosensitizers for the Photooxidation of Benzylamines

RTI2018-100709-B-C21 CTQ (QMC)-RED2018-102471-T) Junta de Castilla y Leon (BU087G19 FEDER (BU042U16-BU305P18).Five new RuII polypyridyl complexes bearing N-(arylsulfonyl)-8-amidoquinolate ligands and three of their biscyclometalated IrIII congeners have been prepared and employed as photocatalysts (PCs) in the photooxidation of benzylamines with O2. In particular, the new RuII complexes do not exhibit photoluminescence, rather they harvest visible light efficiently and are very stable in solution under irradiation with blue light. Their non-emissive behavior has been related to the low electrochemical energy gaps and rationalized on the basis of theoretical calculations (DFT analysis) that predict low S0←T1 energy values. Moreover, the RuII complexes, despite being non-emissive, display excellent activities in the selective photocatalytic transformation of benzylamines into the corresponding imines. The presence of an electron-withdrawing group (-CF3) on the arene ring of the N-(arylsulfonyl)-8-amidoquinolate ligand improves the photocatalytic activity of the corresponding photocatalyst. Furthermore, all the experimental evidence, including transient absorption spectroscopy measurements suggest that singlet oxygen is the actual oxidant. The IrIII analogues are considerably more photosensitive and consequently less efficient photosensitizers (PSs).authorsversionpublishe