Ultraviolet photochemistry of Co(III)L(H2O)SO3+ [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(Me-6[14]diene N-4)( H2O)SO3+ and Co([14]ane N-4)(H2O)SO3+, were prepared. The type of the SO32- linkage in [Co(Me-6[14]diene N-4)(H2O)SO3]ClO4 was established by means of the X-ray structure (crystal system, orthorhombic; space group, P2(1)2(1)2 (1) (No. 19); a = 7.0342(8) Angstrom, b = 14.696(2) Angstrom, c = 23.302(5) Angstrom). In a study of the photochemical properties, transient spectra r evealed the photoredox formation of Co(II) macrocycles and the photoisomeri zation to O-bonded sulfite. Precursors of these products were also observed and tentatively identified a an ion pair (tau = 60 and 140 ns, respectivel y) and an adduct of the SO3.- radical and the unsaturated macrocycle Me-6[1 4]diene N-4 (tau = 2.5 mu s). 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 discus sed.