Metal ion binding modes of hypoxanthine and xanthine versus the versatile behaviour of adenine

Structural insights on the molecular recognition patterns between N6-substituted adenines and N-(aryl-methyl)iminodiacetate copper(II) chelates

“…Likewise, a search in the CSD restricted for neutral monodentate HdimAP ligand, with any metal ion, reveals only 4 hits [UFIDAP (Ru III ) [39], VABQOE (Re III ) [40], VABQUB (Re IV ) [40], VAZLOX (Rh I ) [41], in which HdimAP displays its most stable tautomer H(N9) and the molecular recognition consists of a coordination bond M\N3+ N9\H···Cl intra-molecular interligand H-bond. This former pattern is similar to that showed previously in compounds 1-5 but also to those containing adenine [5]. Therefore, the recognition pattern N9 + N3\H···O reported for compound 6 in this work is unprecedented for the HdimAP ligand.…”

“…Despite the N 6 -ring substituent, aliphatic (1)(2)(3) or aromatic (4)(5), and their molecular (1-4) or polymeric nature (5), in all the former compounds the Cu\N3 bond is reinforced by an intra-molecular interligand H-bonding interaction N9\H · · · O. In contrast, in the polymer of compound 6, the disubstituted ligand HdimAP exhibits the molecular recognition pattern Cu\N9 + N3\H···O.…”

“…The M\N3+ N9\H · · · O metal binding pattern has been previously described by our research group and comprises metal complexes with Cu(II)-NBzIDA-like chelates and the nucleobase adenine [5,7,8].…”

“…Indeed, during the last decades, much effort has been made to rationalize the metal binding modes of nucleobases, nucleosides and nucleotides, and/or their derivatives, with transition metal ions [2][3][4][5][6]. This is based on the idea that the in-depth study of the chemistry of this kind of ligands, including non-covalent interactions, will allow us to better understand the biochemical processes within biological systems and therefore to build up novel bio-mimetic systems with therapeutic interest.…”

“…This is based on the idea that the in-depth study of the chemistry of this kind of ligands, including non-covalent interactions, will allow us to better understand the biochemical processes within biological systems and therefore to build up novel bio-mimetic systems with therapeutic interest. In particular, our research group has been devoted to the study of the metal binding patterns of adenine, which has proved to behave as a fairly versatile ligand in its neutral form, where proton tautomerism phenomena enhance the possibilities of diverse molecular recognition patterns, but also in its different anionic and cationic forms [5]. For instance, neutral adenine (Hade) is able to recognize several Cu(II)-iminodiacetatelike chelates in different ways.…”