Synthesis and Spectral Properties of Bisaxially Coordinated (Octaphenyltetraazaporphyrinato)ruthenium(II) Complexes

The synthesis of novel bisaxially coordinated ruthenium(II) complexes of octaphenyltetraazaporphine (L(2)Ru(OPTAP); L = NH(3), 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 (NH(3))(2)Ru(OPTAP). Heating of "Ru(OPTAP)" with excess of L (L = py, pyz, tz, t-BuNC, did) gives L(2)Ru(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 L(2)Ru(OPTAP) results in formation of oligomers with the bridged &mgr;-L coordination. For L = pyz and tz, the sparingly soluble oligomers contain predominantly dimers [(L){Ru(OPTAP)}(&mgr;-L){Ru(OPTAP)}(L)], and, for L = did, the insoluble &mgr;-bridged polymer [(did){Ru(OPTAP)}((&mgr;-did){Ru(OPTAP)})(x)()(>10)(did)] is formed. UV-visible, IR, and (1)H 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 (L(2)Ru(Pc)) reveals the stronger pi-back-bonding properties, the higher oxidation potential, and lower aromaticity of the porphyrazine macrocycle present in L(2)Ru(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 &mgr;-bridged Ru(OPTAP) complexes as compared with that of the &mgr;-bridged RuPc polymers.