Open-Shell Phenalenyl in Transition Metal-Free Catalytic C-H Functionalization.

Open-shell phenalenyl chemistry has widely been explored in the last five decades demonstrating its potential in various applications including molecular switch, spin memory device, molecular battery, cathode material, etc. In this article, we have explored another new direction of open-shell phenalenyl chemistry toward transition metal-free catalytic C-H functionalization process. A phenalenyl ligand, namely, 9-methylamino-phenalen-1-one (4a), promoted chelation-assisted single electron transfer (SET) process, which facilitates the C-H functionalization of unactivated arenes to form the biaryl products. The present methodology offers a diverse substrate scope, which can be operated without employing any dry or inert conditions and under truly transition metal based catalyst like loading yet avoiding any expensive or toxic transition metal. This not only is the first report on the application of phenalenyl chemistry in C-H functionalization process but also provides a low-catalyst loading organocatalytic system (up to 0.5 mol % catalyst loading) as compared to the existing ones (mostly 20-40 mol %), which has taken advantage of long known phenalenyl based radical stability through the presence of its low-lying nonbonding molecular orbital.

Biological studies of chalcogenolato-bridged dinuclear half-sandwich complexes.

A series of cationic chalcogenolato-bridged diruthenium complexes [(η(6)-p-MeC6H4Pr(i))2Ru2(µ-EC6H5)3](+) (E = S, 1; E = Se, 2; E = Te, 3) has been obtained in ethanol from the reaction of (η(6)-p-MeC6H4Pr(i))2Ru2(µ-Cl)2Cl2 with benzenethiol, benzeneselenol, and sodium tellurophenolate, respectively. The thiolato and selenolato derivatives are isolated in good yield as the chloride salts, while the tellurolato analogue is isolated as the hexafluorophosphate salt. Similarly, the dinuclear pentamethylcyclopentadienyl (C5Me5) rhodium and iridium complexes (η(5)-C5Me5)2M2(µ-Cl)2Cl2 react with benzenethiol, benzeneselenol, and sodium tellurophenolate in ethanol to give the corresponding cationic dinuclear complexes of the general formula [(η(5)-C5Me5)2M2(µ-EC6H5)3](+) (M = Rh, E = S, 4; E = Se, 5; E = Te, 6; M = Ir, E = S, 7; E = Se, 8; E = Te, 9). In addition, cationic dinuclear complexes with mixed thiolato-selenolato and thiolato-tellurolato bridges have been prepared, [(η(6)-p-MeC6H4Pr(i))2Ru2(µ-EC6H5)(µ-SCH2C6H4-p-Bu(t))2](+) (E = Se, 10; E = Te, 11) and [(η(5)-C5Me5)2M2(µ-EC6H5)(µ-SCH2C6H5)2](+) (M = Rh, E = Se, 12; E = Te, 13; M = Ir, E = Se, 14; E = Te, 15), starting from the neutral dinuclear complexes (η(6)-p-MeC6H4Pr(i))2Ru2Cl2(µ-SCH2C6H4-p-Bu(t))2 and (η(5)-C5Me5)2M2Cl2(µ-SCH2C6H5)2. All complexes are highly cytotoxic showing activity in the submicromolar range. The nature of the chalcogenolato bridges seems to have an impact on the activity, while the nature of the metal center plays a minor role. Among the complexes tested, the dinuclear complexes 1, 4, and 7 with the thiolato bridges show the highest activity on cancer cells and the best affinity for CT-DNA as demonstrated by cell biology and biophysical experiments.