Ultraviolet Photochemistry of Co(III)L(H(2)O)SO(3)(+) [L = Me(6)[14]dieneN(4), [14]aneN(4)] Complexes. Quandaries about the Linkage Isomerization to O-Bonded Sulfite and the Photogeneration of Cobalt(I) in Sequential Biphotonic Photolysis.

Two new macrocyclic complexes with S-bonded sulfite, Co(Me6[14]diene N4)(H2O)SO3+ and Co([14]ane N4)(H2O)SO3+, were prepared. The type of the SO32- linkage in [Co(Me6[14]dieneN4)(H2O)SO3]ClO4 was established by means of the X-ray structure (crystal system, orthorhombic; space group, P212121 (No. 19); a = 7.0342(8) A, b = 14.696(2) A, c = 23.302(5) A). In a study of the photochemical properties, transient spectra revealed the photoredox formation of Co(II) macrocycles and the photoisomerization to O-bonded sulfite. Precursors of these products were also observed and tentatively identified a an ion pair (τ = 60 and 140 ns, respectively) and an adduct of the SO3•- radical and the unsaturated macrocycle Me6[14]diene N4 (τ = 2.5 μs). The photogeneration of SO3•- was verified by means of the radical's ESR spectrum. High power laser irradiations resulted in the secondary photolysis of the intermediates and the formation of Co(I) products. The mechanism of the primary and secondary photolysis is discussed.