**1. Introduction**

Nucleobase complexes with transition metals are continuously under investigation due to their applications as advanced functional materials, their biologic importance, structural diversity and use as molecular recognition models for nucleic acids [1–6]. The majority of structural information available in these systems is mainly dedicated to the adenine nucleobase [7–16] and a variety of N-alkylated derivatives as ligands [17–31]. In contrast, available structural information in the Cambridge Structural Database (CSD) on metal complexes, co-crystals and salts with 2,6-diaminopurine (Hdap) nucleobase is much more limited, despite the fact that Hdap is an analog of adenine. Interestingly, the Hdap nucleobase is able to form the same coordination bonds than adenine and, additionally, the extra exocyclic amino group of Hdap can further function as H-bond donor. Therefore, Hdap can generate novel metal complexes, coordination polymers and supramolecular assemblies.

This study reports the synthesis, X-ray structure and density functional theory study of a new metal complex of formula H2(N3,N7)dap[Cd(HEDTA)(H2O)]·H2O (**1**). A comparison with the previously reported analog of adenine, [Cu(HEDTA)(H2O)]·2H2O [5,32], was also performed. The H-bonding networks that are established at both faces of H2dap were also studied using DFT calculations and the relative strength of each H-bond was estimated using the QTAIM theory. The antiparallel <sup>π</sup>,<sup>π</sup>-stacking interactions that were formed between the cations were also studied, focusing on the effect of the counter-ions.

## **2. Materials and Methods**
