Inorganic Chemistry, Vol.37, No.11, 2655-2662, 1998
Synthesis and spectral properties of bisaxially coordinated (octaphenyltetraazaporphyrinato)ruthenium(II) complexes
The synthesis of novel bisaxially coordinated ruthenium(II) complexes of octaphenyltetraazaporphine (L2Ru(OPTAP); L = NH3, pyridine (py), pyrazine (pyz), s-tetrazine (tz), tert-butyl isocyanide (t-BuNC), and p-diisocyanodurole (did)) is reported. Template condensation of diphenylfumaronitrile with pentaammine(dinitrogen)ruthenium(II) dichloride gives the crude compound "Ru(OPTAP)" containing mainly the bis(ammine) derivative (NH3)(2)Ru(OPTAP). Heating of "Ru(OPTAP)" with excess of L (L = py, pyz, tz, t-BuNC, did) gives L2Ru(OPTAP) which are readily soluble in organic solvents and can be purified chromatographically. In the case of the bidentate ligands (L = pyz, tz, did) refluxing of the solutions of monomers L2Ru(OPTAP) results in formation of oligomers with the bridged mu-L coordination. For L = pyz and tz, the sparingly soluble oligomers contain predominantly dimers [(L){Ru(OPTAP)}(mu-L){Ru(OPTAP)}(L)], and, for L = did, the insoluble mu-bridged polymer [(did){Ru(OPTAP)}((mu-did){Ru(OPTAP)})(x>10)(did)] is formed. UV-visible, IR, and H-1 NMR spectroscopy and mass spectrometry were used for characterization of the obtained compounds. Cyclic voltammetry study has shown one reduction (OPTAP(2-)/OPTAP(3-)) and one oxidation (Ru-II/Ru-III) process (for (py)(2)Ru(OPTAP) observed at -1.15 and 0.68 V, respectively). Comparison with the data on the corresponding phthalocyanine complexes (L2Ru(Pc)) reveals the stronger pi-back-bonding properties, the higher oxidation potential, and lower aromaticity of the porphyrazine macrocycle present in L2Ru(OPTAP). These factors along with the lesser extent of oligomerization are responsible for the lower electrical conductivity (sigma(RT) < 10(-11) S/cm) of the mu-bridged Ru(OPTAP) complexes as compared with that of the mu-bridged RuPc polymers.
Keywords:(PHTHALOCYANINATO)RUTHENIUM(II) COMPOUNDS;PHTHALOCYANINE COMPLEXES;ELECTROCHEMISTRY;RUTHENIUM(II);OXIDATION;LIGANDS;METALLOPORPHYRIN;AZAPORPHYRINS;SPECTROSCOPY;PORPHYRINS