Models for vanadium-tunichrome chemistry

Models for vanadium-tunichrome chemistry

ENVIRONMENTAL/TRACE METAL CHEMISTRY 353 NO27 MODELS FOR VANADIUM-TUNICHROME CHEMISTRY. Carl J. Carrano, Southwest Texas State Universitv. San Marc...

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ENVIRONMENTAL/TRACE

METAL CHEMISTRY

353

NO27

MODELS FOR VANADIUM-TUNICHROME CHEMISTRY. Carl J. Carrano, Southwest Texas State Universitv. San Marcos. Texas ‘78666, USA and Ellen Kime-Hunt, University of Vermont; Burlington VT, 05462, USA. N,N’,N”-Tris(2,3,4and 3,4,5-trihydroxybenzoyl)_1,5,10-triazadecanes have been synthesized as models for the tunichromes thought to be involved in the vanadium biochemistry of tunicates. The reaction of the model complexes with V(III), V(IV) and V(V) indicate the following: 1) Tunichromes can directly reduce V(V) to V(W) but cannot reduce it further to V(II1). 2) Tunichromes will readily complex V(II1) ions but produce red, 0x0 bridged dimers rather than mononuclear complexes. 3) The 0x0 bridged V(II1) dimers are air oxidized to produce insoluble V(W) polymeric species. These results support the notion that the V(III)_tunichrome system in the blood cells of ascidians may function as a primitive clotting or wound healing mechanism.

NO28

REACTIONS OF LOW VALENT TRANSITION-METAL COMPLEXES WITH HYDROGEN PEROXIDE. ARE THEY “FENTON-LIKE” OR NOT? Hanna Bamnolker, Mohamed- Masarwa, Haim Cohen and Dan M&e ste in Nuclear Research Centre Neaev and Chemistrv Deoartment Ben-Aurion University of the Negev, Beer-Sheva, Israel. a ’ A thermodynamic analysis of the Fenton reaction and the “Fenton-like” reactions points out that their detailed mechanisms involve the formation of a transient complex between the low-valent cation, ML,,.,“, and hydrogen peroxide of the type ML _,n-02H-. This complex might decompse into ML,,,“+1 + -OH or ML _,“+2 + R 0 or react direct1 with a substrate. Experimental data indicate #at indee & free hydrox I ra J icals are not formed durin the decomposition of (H 0 Cu+-0 H- (A ly P)Fes+.O H- and (nta)(H O)Fea+where nta= N(CH,&&),, in t6e presence of I 8.1 M alcohols. ?he natur&j the final products in the system containing iron ions and nta depends on the pH, thus indicating that the transient complex formed has a pK,.

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