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Nucleobases are known as suitable builders of porous materials not only due to their high number of heteroatoms leading to different coordination modes, but also because they establish strong and predictable supramolecular interactions. In this contribution, nucleobases (adenine and guanine), functionalized nucleobases (9-methyladenine) and nucleobase derivatives (6-chloropurine) have been evaluated as ligands for the construction of metal–nucleobase building blocks which can afford supramolecular porous materials, analyzing in detail the requirements that these entities must fulfill and pointing out the relevance of accomplishing the suggested requisites. More concisely, we have evaluated a paddle-wheel shaped dimeric entity, [Cu2(μ-Hade)4Cl2]Cl2·8H2O (1) (where Hade: adenine), a trimeric unit, [Co3(μ-Hade)2(μ-Cl)4Cl2(H2O)4]·2H2O (2), a dimeric entity, [Cu2(Hgua)2(H2gua)2(μ-Cl)2Cl2(H2O)][CuCl4] (3) (where Hgua: guanine, H2gua: guaninium), a monomeric unit with 9-methyladenine as the pendant ligand, [Co(9-Meade)2(H2O)4]Cl2·2H2O (4), zigzag chains, [Cu2(μ-CH3COO)4(μ-9-Meade)]n·nCH3OH (5), and a monomeric unit with 6-chloropurinato ligands, [Co(6-Clpur)2(H2O)4]·4H2O (6).

The nucleophilic attack of a series of nucleobase derivatives on the [(η6-p-cymene)RuCl(μ-Cl)]2 dinuclear entity has yielded four mononuclear complexes with the general formula [Ru(η6-p-cymene)(L)Cl2], in which L stands for cytosine (1), 2-thiouracil (2), hypoxanthine (3) and 5-aminouracil (4). Furthermore, the sieving of chlorido from compound 1, assisted by a mild base, has prompted the formation of a tetranuclear ruthenium cationic complex which crystallizes as [(η6-p-cymene)4Ru4(μ-cytosinato-κN1:κN3,O2)4](CF3SO3)4 (compound 5). The crystal structure analysis of compounds 1–4 reveals that the supramolecular packing is dominated by the self-assembly capabilities provided by the stabilized nucleobase-tautomer, which is at the same time dependent on the Ru/nucleobase coordination mode. In this regard, the assembly of the complex units is conducted through base-pairing interactions, and is also assisted by means of nucleobase/chloride hydrogen bonding. The stability of these monomeric entities in water and phosphate buffered solution is analysed by means of 1H- and 31P-NMR. The tetranuclear entity of compound 5 presents an available hydrogen-donor set (exocyclic amino group) but it lacks any available acceptor atom, which prevents the nucleobase mediated self-assembly of the complex units. Consequently, a doubly interpenetrated supramolecular network is woven by the hydrogen bonding between the triflate (CF3SO3−) anions and complex cationic entities.

Four new compounds based on zinc(II) or cadmium(II) metal ions and elongated dicarboxylate and bipyridine ligands, namely, {[Cd3(μ4-bpdc)3(H2O)2]·DMF}n (1), {[Zn3(μ4-bpdc)3(μ-bpdb)]·5DMF}n (2), {[Zn2(μ4-bpdc)2(μ-bpdb)]·7DMF}n (3), and {[Zn4(μ4-bpdc)3(DMF)(μ4-O)(H2O)]·7DMF·3H2O}n (4), (where bpdc = biphenyl-4,4′-dicarboxylate, bpdb = 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene, DMF = dimethylformamide) have been synthesised under solvothermal conditions and structurally characterised by single crystal X-ray diffraction. The crystal structures range from 2D (in 1) to 3D (2, 3, and 4) systems according to the coordination mode acquired by the bpdc ligand and the presence of an ancillary linker. Compound 1 consists of stacked Cd-bpdc neutral layers containing isolated small voids. The coordination of the bpdb ligand (2 and 3) or the formation of a tetrahedral Zn4O cluster (in 4) generates highly open 3D architectures that share the structural feature of being doubly interpenetrated. A careful computational analysis on the crystal structures permits unravelling their void systems. Moreover, characterising the photoluminescence emission of the compounds at variable excitation wavelengths provides an opportunity to couple the luminescence response with their porosity, which could signify the potential utility of these materials as photofluorescent sensors for small adsorbates.

The present work summarizes the different approaches that can be applied to achieve porous materials based on metal–nucleobase systems. The rigidity and the multiple donor sites of the nucleobases make them suitable linkers to provide coordination bond sustained metal–organic frameworks (MOFs). Furthermore, the ability of the nucleobases to establish complementary hydrogen bonding interactions allows one to achieve similar metal–nucleobase porous materials but sustained by hydrogen bond pairing interactions between the nucleobases (supramolecular metal–organic frameworks, SMOFs).

The reaction between CuCl2 and adenine in a non-aqueous solvent provides a 3D porous structure based on paddle-wheel [Cu2(µ-adenine)4Cl2]2+ cations and Cl− anions that are held together by a robust supramolecular hydrogen bonding network. The desolvated compound is able to host different guest molecules within the ∼6 A diameter 1D channels.