Low energy light induced DNA photocleavage with a bis-ruthenated porphyrin

Interactions of porphyrins with DNA: A review focusing recent advances in chemical modifications on porphyrins as artificial nucleases

The advance of porphyrins as artificial nucleases along the years have developed a class of compounds having potential therapeutic applications. Being an extrovert of chemistry, a variety of chemical modifications have been done on porphyrin macrocycle in order to improve the spectroscopic properties and to adapt as artificial receptors that can recognize molecules. The last twenty years has witnessed broad research in the arena of porphyrin- DNA interactions and their evolution from simple to more complex entities. In this review, we summarize the recent advances in the porphyrin-based structural modifications, with a specific emphasis on various effects of porphyrin on DNA cleavage potency. We particularly detailed the nuclease activity of cationic and anionic porphyrins, porphyrin dimers and conjugates as well as heme proteins till the third generation porphyrins as artificial nucleases.

Remarkable Electronic Effect on the meso-Tetra(thienyl)porphyrins

Complexes derived from meso-tetra(thienyl)porphyrins (TThP) and meso-tetra(pyridyl)porphyrin (TPyP) containing peripheral ruthenium complexes with general formulas {TPyP[RuCl(dppb)(5,5'-Mebipy)]₄}(PF₆)₄, {TThP[RuCl(dppb)(5,5'-Mebipy)]₄}(PF₆)₄, and {TThP-me-[RuCl(dppb)(5,5'-Mebipy)]₄}(PF₆)₄ [5,5'-Mebipy = 5,5'-dimethyl-2,2'-bipyridine and dppb = 1,4-bis(diphenylphosphino)butane] were synthesized and characterized by spectroscopy techniques (¹H- and ³¹P{¹H}-NMR, IR, UV/vis, fluorescence, and electron paramagnetic resonance (EPR)), cyclic voltammetry, coulometry, molar conductivity, and elemental analysis. Voltammetry and UV/vis studies demonstrated differentiated electronic properties for ruthenium appended with TThP and TThP-me when compared to ruthenium appended with TPyP. The UV/vis analysis for the ruthenium complex derived from TThP and TThP-me, as well as the Soret and Q bands, characteristics of porphyrins, showed a band at 700 nm referring to the Ru → S electronic transition, and porphyrin TThP-me showed another band at 475 nm from the Ru-N transition. The attribution of these bands was confirmed by spectroelectrochemical analysis. Cyclic voltammetry analysis for the ruthenium complex derived from TPyP exhibited only an electrochemical process with E_1/2 = 0.47 V assigned to the Ru(II)/Ru(III) redox pair (Fc/Fc⁺). On the other hand, two processes were observed for the ruthenium complexes derived from TThP and TThP-me, with E_1/2 around 0.17 and 0.47 V, which were attributed to the formation of a mixed valence tetranuclear species containing Ru(II) and Ru(III) ions, showing that the peripheral groups are not oxidized at the same potential. Fluorescence spectroscopic experiments show the existence of a mixed state of emission in the supramolecular porphyrin moieties. The results suggest the formation of Ru(II)-Ru(III) mixed valence complexes when oxidation potential was applied around 0.17 V in the {TThP[RuCl(dppb)(5,5'-Mebipy)]₄}(PF₆)₄ and {TThP-me-[RuCl(dppb)(5,5'-Mebipy)]₄}(PF₆)₄ species.

TiO2 modified with a Ru(ii)–N′NN′ 8-hydroxyquinolyl complex for efficient gaseous photoreduction of CO2

A rare example of a Ru(ii) pincer complex for the efficient photoreduction of CO₂ to CO/CH₄ in a gaseous system was developed.