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(Me(6)[14]diene N(4))(H(2)O)SO(3)(+) and Co([14]ane N(4))(H(2)O)SO(3)(+), were prepared. The type of the SO(3)(2)(-) linkage in [Co(Me(6)[14]dieneN(4))(H(2)O)SO(3)]ClO(4) 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) Å, b = 14.696(2) Å, c = 23.302(5) Å). 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 (tau = 60 and 140 ns, respectively) and an adduct of the SO(3)(*)(-) radical and the unsaturated macrocycle Me(6)[14]diene N(4) (tau = 2.5 &mgr;s). The photogeneration of SO(3)(*)(-) 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.
Gibney
S. C.
SC
Radiation Laboratory and Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556-0579.
Ferraudi
G.
G
Shang
M.
M