ORGN 325

Enzymatic reactions often involve reactive intermediates such as carbocations and radical cations. Our research interests lie of the design of synthetic peptides with hydrophobic pockets that can stabilize these short-lived intermediates, and accordingly, a method for the rapid delivery of such intermediates was developed. The photosensitizer tris(4,4’-disubstituted-2,2’-bipyridine)Ru(II) was tethered to the hydrophobic probe N,N-dimethyl-p-toluidine (DMT) using (CH₂)₇, (CH₂)₄, and (CH₂)₃O(CH₂)₂ linkers. The effect of substitution, linker, and pH on the rate of DMT oxidation was evaluated by laser-flash photolysis, where we found that the electron transfer was most rapid (< 10 ns) under high pH, with the ether linker, and in the absence of methyl substitution. DMT oxidation occurred via Ru(II)* and Ru(III) states. In subsequent studies, we linked DAB to the Ru photosensitizer, where rapid DAB radical cation generation followed by C-C cleavage (10⁴ s^-1) resulted in the delivery of a free DAC carbocation.