Dicopper(II)-EDTA Chelate as a Bicephalic Receptor Model for a Synthetic Adenine Nucleoside.

María Eugenia García-Rubiño,Antonio Frontera,Juan Niclós-Gutiérrez,Antonio Matilla-Hernández,Duane Choquesillo-Lazarte,Luis Lezama

doi:10.3390/ph14050426

María Eugenia García-Rubiño, Antonio Frontera + Show 4 more

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https://doi.org/10.3390/ph14050426

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Abstract

In the extensive field of metal ions, their interactions with nucleic acids, and their constituents, the main aim of this work is to develop a metal chelate suitable to recognize two molecules of an adenine nucleoside. For this purpose, the dinuclear chelate Cu2 (µ-EDTA) (ethylenediaminetetraacetate(4-) ion (EDTA)) is chosen as a bicephalic receptor model for N9-(2-hydroxyethyl)adenine (9heade). A one-pot synthesis is reported to obtain the compound [Cu2(µ2-EDTA)(9heade)2(H2O)4]·3H2O, which has been characterized by single-crystal X-ray diffraction and various spectral, thermal, and magnetic methods. The complex unit is a centro-symmetric molecule, where each Cu (II) center is chelated by a half-EDTA, and is further surrounded by an N7-dentate 9heade nucleoside and two non-equivalent trans-O-aqua molecules. The metal chelate-nucleoside molecular recognition is referred to as an efficient cooperation between the Cu-N7(9heade) coordination bond and a (9heade)N6-H···O(carboxyl, EDTA) interligand interaction. Theoretical calculations are also made to account for the relevance of this interaction. The extreme weakness with which each water molecule binds to the metal center disturbs the thermal stability and the infrared (FT-IR) and electron spin resonance (ESR) spectra of the compound.

Highlights

Metal chelate interactions with nucleic acid bases have aroused growing interest for decades in order to gain knowledge on the metalation processes of nucleosides, nucleotides, oligonucleotides, and nucleic acids
Metal binding patterns of nucleobases are best understood in terms of molecular recognition [1,2,3,4]
The versatility of adenine (Hade) as a ligand [2,4] is understood to consist of the basicity of its N-atoms (N9 > N1 > N7 > N3 >>N6), at the same time that the tautomerim(s) of the H(N9)-atom from its most stable tautomer, H(N9) ade

Summary

Introduction

Metal chelate interactions with nucleic acid bases (hereafter nucleobases) have aroused growing interest for decades in order to gain knowledge on the metalation processes of nucleosides, nucleotides, oligonucleotides, and nucleic acids. Metal binding patterns of nucleobases are best understood in terms of molecular recognition (a universal point of view, always reciprocal, between the involved reactants) [1,2,3,4]. In this context, the versatility of adenine (Hade) as a ligand [2,4] is understood to consist of the basicity (as proton affinity) of its N-atoms (N9 > N1 > N7 > N3 >> (exocyclic)N6), at the same time that the tautomerim(s) of the H(N9)-atom from its most stable tautomer, H(N9) ade. An example of the latter is the ternary copper(II) complex, derived from the tridentate N-benzyl-iminodiacetate(2-)

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