2D Porphyrinic Metal-Organic Frameworks Featuring Rod-Shaped Secondary Building Units.

Metal-organic frameworks (MOFs) encompass a rapidly expanding class of materials with diverse potential applications including gas storage, molecular separation, sensing and catalysis. So-called 'rod MOFs', which comprise infinitely extended 1D secondary building units (SBUs), represent an underexplored subclass of MOF. Further, porphyrins are considered privileged ligands for MOF synthesis due to their tunable redox and photophysical properties. In this study, the CuII complex of 5,15-bis(4-carboxyphenyl)-10,20-diphenylporphyrin (H2L-CuII, where H2 refers to the ligand's carboxyl H atoms) is used to prepare two new 2D porphyrinic rod MOFs PROD-1 and PROD-2. Single-crystal X-ray analysis reveals that these frameworks feature 1D MnII- or CoII-based rod-like SBUs that are coordinated by labile solvent molecules and photoactive porphyrin moieties. Both materials were characterised using infrared (IR) spectroscopy, powder X-ray diffraction (PXRD) spectroscopy and thermogravimetric analysis (TGA). The structural attributes of PROD-1 and PROD-2 render them promising materials for future photocatalytic investigations.

Design, synthesis and photoinduced DNA cleavage studies of [1,2,4]-triazolo[4,3-a]quinoxalin-4(5H)-ones.

An expedient and eco-friendly synthesis of 1-aryl/heteroaryl-[1,2,4]-triazolo[4,3-a]quinoxalin-4(5H)-ones (4) has been accomplished via iodobenzene diacetate mediated oxidative intramolecular cyclization of 3-(2-(aryl/heteroarylidene)hydrazinyl)-quinoxalin-2(1H)-ones (3). Ten synthesized compounds 3 and 4 (10-40 µg) on irradiation with UV light at λmax 312 nm could lead to cleavage of supercoiled pMaxGFP DNA (Form I) into the relaxed DNA (Form II) without any additive. Further, DNA cleaving ability of triazoles was quantitatively evaluated and was found to be dependent on its structure, concentration, and strictly on photoirradiation time. Mechanistic investigations using several additives as potential inhibitors/activator revealed that the DNA photocleavage reaction involves Type-I pathway leading to formation of superoxide anion radicals (O2-) as the major reactive oxygen species responsible for photocleavage process.