Two-step one-electron transfer reaction of chromium(III) complex containing levodopa and uridine with N-bromosuccinimide

Abstract

Cr III (LD)(Urd)(H 2 O) 4 ](NO 3 ) 2 Á 3H 2 O (LD ¼ Levodopa; Urd ¼ uridine) was prepared and characterized. The product of the oxidation reaction was examined using HPLC. Kinetics of the oxidation of [Cr III (LD)(Urd)(H 2 O) 4 ] 2þ with N-bromosuccinimide (NBS) in an aqueous solution was studied spectrophotometrically, with 1.0-5.0 Â 10 À4 mol dm À3 complex, 0.5-5.0 Â 10 À2 mol dm À3 NBS, 0.2-0.3 mol dm À3 ionic strength (I), and 30-50 C. The reaction is first order with respect to [Cr III ] and [NBS], decreases as pH increases in the range 5.46-6.54 and increases with the addition of sodium dodecyl sulfate (SDS, 0.0-1.0 Â 10 À3 mol dm À3 ). Activation parameters including enthalpy, DH*, and entropy, DS*, were calculated. The experimental rate law is consistent with a mechanism in which the protonated species is more reactive than its conjugate base. It is assumed that the two-step one-electron transfer takes place via an inner-sphere mechanism. A mechanism for this reaction is proposed and supported by an excellent isokinetic relationship between DH* and DS* for some Cr III complexes. Formation of [Cr III (LD)(Urd)(H 2 O) 4 ] 2þ in vivo probably occurs with patients who administer the anti-Parkinson drug (Levodopa), since Cr III is a natural food element. This work provides an opportunity to identify the nature of such interactions in vivo similar to that in vitro.

Liquid metal-based catalysts for the electroreduction of carbon dioxide into solid carbon

“…To start, metallic additives were selected based on their capability to initiate multi-electron charge transfer, [19][20][21][22][23][24] their standard redox potential, and their solubility in the chosen liquid metal solvent. We identied ve potential metallic candidates for catalytic optimisation, including chromium (Cr), vanadium (V), hafnium (Hf), gadolinium (Gd), and cerium (Ce).…”