Synthesis, Characterization of New Tungsten(IV)?Pterin Complexes and their Reactivity Studies towards Trimethylamine N-Oxide, Sodium Borohydride and Potassium Ferricyanide

Samir S Siddhartha

doi:10.4172/2157-7064.1000198

Abstract

2-Pivaloylamino-6-acetonyl-isoxanthopterin ((1), H2L) has been reacted with Na2WO4.2H2O under suitable conditions leading to the formation of Na2[W2IV(μ–O)(L)4(CH3OH)2] (2). Na[WIV(L)2(dedtc)]. CH3OH (3) and (Ph4P)2[WIV(L)2(aet)] (4) have been prepared by the reaction of (2) with PPh3 in presence of the ancillary ligands like sodium diethyldithiocarbamate trihydrate and 2-aminoethanethiol hydrochloride, respectively. These new compounds have been purified by flash chromatography and characterized by elemental analysis, different physicochemical and spectroscopic methods. Such data particularly 1H NMR and fluorescence spectra indicate the redox noninnocent nature of the pterin ligand. Reactivities of these compounds with different substrates have been followed kinetically; using the data of (3) as their representative, it appears that the electron transfer process (kobs=1.1x10-2s-1) involving K3[Fe(CN)6] is twice as fast as the group transfer processes associated with Me3N→O and NaBH4. The corresponding negative ΔS# values are consistent with associative pathways in all these cases.

Highlights

Pterins (2-amino-4-oxopteridines) are important in a wide range of biological functions including a large number of metal–containing enzymes (e.g., Fe, Mo, W) [1,2,3]
The redox noninnocent nature of the pterin ring is associated with the ability of its pyrazine ring to exist in a number of oxidation states [4]
This redox capability of the pterin moiety is matched by the ability of the metal centres to display multiple oxidation states [5]

Summary

Introduction

Pterins (2-amino-4-oxopteridines) are important in a wide range of biological functions including a large number of metal–containing enzymes (e.g., Fe, Mo, W) [1,2,3]. This redox capability of the pterin moiety is matched by the ability of the metal centres to display multiple oxidation states [5]. This aspect has catalysed research work on the coordination chemistry of pteridines in general and pterins in particular [5,6,7,8]. (1) acts as a reducing agent towards the tungsten(VI) starting material Na2WO4.2H2O leading to the formation of the present tungsten (IV) complexes (2), (3) and (4) Their characterization aspects, spectroscopic analysis and reactivity studies towards biologically relevant substrates are delineated here [12,13,14,15]

Methods

Results

Conclusion