Four derivatives of the laminate acceptor ligand dipyrido-[3,2-a:2',3'-c]phenazine (dppz) and their corresponding ruthenium complexes, [Ru(phen)2 (dppzX2 )](2+) , were prepared and characterized by NMR spectroscopy, ESI-MS, and elemental analysis. The new ligands, generically denoted dppzX2 , were symmetrically disubstituted on the distal benzene ring to give 10,13-dibromodppz (dppz-p-Br), 11,12-dibromodppz (dppz-o-Br), 10,13-dicyanodppz (dppz-p-CN), 11,12-dicyanodppz (dppz-o-CN). Solvated ground state MO calculations of the ruthenium complexes reveal that these electron-withdrawing substituents not only lower the LUMO of the dppz ligand (dppz(CN)2

The enantiomeric separation of 21 ruthenium (II) polypyridyl complexes was achieved with a novel class of cyclofructan-based chiral stationary phases (CSPs) in the polar organic mode. Aromatic derivatives on the chiral selectors proved to be essential for enantioselectivity. The R-napthylethyl carbamate functionalized cyclofructan 6 (LARIHC CF6-RN) column proved to be the most effective overall, while the dimethylphenyl carbamate cyclofructan 7 (LARIHC CF7-DMP) showed complementary selectivity. A combination of acid and base additives was necessary for optimal separations. The retention factor vs. acetonitrile/methanol ratio plot showed a U-shaped retention curve, indicating that different interactions take place at different polar organic solvent compositions. The separation results indicated that π-π interactions, steric effects, and hydrogen bonding contribute to the enantiomeric separation of ruthenium (II) polypyridyl complexes with cyclofructan chiral stationary phases in the polar organic mode.

A byproduct of the synthesis of 9,11,20,22-tetra-aza-tetrapyrido[3,2-a:2'3'-c:3'',2''-l:2''',3''']pentacene (tatpp) is the symmetrical dimer ditatpp, which is linked by a carbon-carbon bond along the central benzene ring. The structure of the dimer has been determined by X-ray crystallography and reveals a dihedral angle of 73° between the two tatpp units, which is likely due lone pair repulsion on the adjacent aza nitrogens on each tatpp unit. Because of this non-planar geometry, this ditatpp dimer is freely soluble in organic solvents, such as ethanol, very much unlike the tatpp ligand, which is sparingly soluble in all common solvents. Photolysis of ditatpp with visible light in the presence of sacrificial donors, such as triethylamine, results in multi-electron reduction on each of the tatpp units, as determined by absorption spectroscopy. As the tatpp units appear to function independently of one another, and each tatpp unit is reduced by two electrons and is doubly protonated in the final compound, the photoreduction results in a net storage of 4 electrons in the fully reduced species.

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Dipyridophenazine (dppz) is known to react with alcohols upon photoexcitation into an n‐π* transition at 378 nm to yield dihydrodipyridophenazine (dppzH2). This process occurs via H‐atom abstraction from alcohols and subsequent disproportionation of the dppzH• radical species, to the final product. This reaction shows a primary kinetic isotope effect (KIE = 4.9) in methanol/perdeuteromethanol solvents, consistent with H‐atom transfer processes. Addition of excess Zn(II) ions to the dppz solution not only accelerates the rate of photoreduction, but also lowers the KIE to 1.7, indicating a change in reaction mechanism. We postulate that the coordination of the alcoholic solvent to Zn(II) activates the alcohol α C‐H bonds toward hydride transfer processes which would be consistent with the lowered KIE and faster overall reduction of the aromatic ligand. Interestingly, this appears to be an intramolecular process in which the Zn(II) is coordinated to both the dppz ligand and the reactive alcohol, as a sharp inflection in the overall rate increase is observed at a Zn:dppz ratio of 2:1. At this ratio, the dominant dppz species involves a Zn(II) bound to one dppz and several solvent molecules (methanol and water).