Octa‐Substituted Ruthenium Phthalocyanines: The Influence of Peripheral and Nonperipheral Alkyl and Alkoxy Groups on the Electrochemical and Spectroscopical Properties

The influence of octa‐peripheral and octa‐nonperipheral alkyl, alkyloxy, and aryloxy substituents on the spectroscopic and electrochemical properties of ruthenium phthalocyanines is reported. The 1 H nuclear magnetic resonance (NMR) phenylene resonances of phthalocyanines with nonperipheral substituents are shielded relative to those of the peripheral isomers (δ H 7–8 versus 9 ppm). In addition, the UV‐Vis Q‐bands of peripherally substituted phthalocyanines (Pcs) occur in a narrow region and are blueshifted relative to those of nonperipherally substituted phthalocyanines. The pyrrole protons of the nonperipherally substituted H 2 Pcs are deshielded relative to those of the peripheral isomers in 1 H NMR spectroscopy. This trend is supported by IR (neat) hypsochromic shifts of the CO stretching frequencies of nonperipheral versus peripheral MPcs, thus confirming the higher electron density on the former ligand. Carbonyl(2,3,9,10,16,17,23,24‐octapentoxyphthalocyaninato)ruthenium(II) and its precursor ligand are outliers in various experiments. This may be due to intermolecular axial association of the peripheral oxygens with the metal (MPc) or hydrogen bond formation with the pyrrole hydrogens (H 2 Pc). The first oxidation of ruthenium phthalocyanines is ligand centered and is observed in the 0.1–0.2 V region, whereas the electrochemical HOMO–LUMO gap is within the 1.4–1.8 V range (5% CH 3 CN in CH 2 Cl 2 with 0.1 m [N( n Bu) 4 ][B(C 6 F 5 ) 4 ]).