Bis(2,6-diamino-1H-purin-3-ium) di-μ-croconato-κ3O,O':O'';κ3O:O',O''-bis[tetraaqua(croconato-κ2O,O')neodymium(III)]

Anion–Cation Recognition Pattern, Thermal Stability and DFT-Calculations in the Crystal Structure of H2dap[Cd(HEDTA)(H2O)] Salt (H2dap = H2(N3,N7)-2,6-Diaminopurinium Cation)

The proton transfer between equimolar amounts of [Cd(H2EDTA)(H2O)] and 2,6-diaminopurine (Hdap) yielded crystals of the out-of-sphere metal complex H2(N3,N7)dap[Cd(HEDTA)(H2O)]·H2O (1) that was studied by single-crystal X-ray diffraction, thermogravimetry, FT-IR spectroscopy, density functional theory (DFT) and quantum theory of “atoms-in-molecules” (QTAIM) methods. The crystal was mainly dominated by H-bonds, favored by the observed tautomer of the 2,6-diaminopurinium(1+) cation. Each chelate anion was H-bonded to three neighboring cations; two of them were also connected by a symmetry-related anti-parallel π,π-staking interaction. Our results are in clear contrast with that previously reported for H2(N1,N9)ade [Cu(HEDTA)(H2O)]·2H2O (EGOWIG in Cambridge Structural Database (CSD), Hade = adenine), in which H-bonds and π,π-stacking played relevant roles in the anion–cation interaction and the recognition between two pairs of ions, respectively. Factors contributing in such remarkable differences are discussed on the basis of the additional presence of the exocyclic 2-amino group in 2,6-diaminopurinium(1+) ion.

Two isomorphous lanthanide crotonate complexes: di-μ-but-2-enoato-bis[diaquabis(but-2-enoato)dysprosium(III)] adenine monosolvate heptahydrate and the samarium(II) analogue

The asymmetric unit of the title dimeric compounds, [Ln(2)(C(4)H(5)O(2))(6)(H(2)O)(4)]·C(5)H(5)N(5)·7H(2)O, with Ln = Dy, (I), and Sm, (II), consists of an Ln(III) cation, three crotonate (but-2-enoate) anions and two coordinated water molecules forming the neutral complex, cocrystallized with half of an external adenine molecule and 3.5 water molecules. The metal complex has crystallographic inversion symmetry. The LnO(9) coordination polyhedra are connected through the sharing of a single edge to form isolated dimeric units, with Ln...Ln separations of 4.1766 (12) Å for (I) and 4.2340 (12) Å for (II). The unbound adenine molecule and one of the solvent water molecules are disordered around an inversion centre into two overlapping, equally populated, units. The structure is sustained by a complex hydrogen-bonding scheme involving all possible O-H and N-H groups as donors, and crotonate and water O and adenine N atoms as acceptors. The system is compared with recently published related compounds.

Poly[[diaquabis(μ2-crotonato-κ3O:O,O')(crotonato-κ2O,O')lanthanum(III)] adenine monosolvate monohydrate]

The asymmetric unit of the title compound, {[La(C(4)H(5)O(2))(3)(H(2)O)(2)]·C(5)H(5)N(5)·H(2)O}(n), consists of an La(III) cation, three crotonate (but-2-enoate) anions and two coordinated water molecules forming the neutral complex, completed by an external adenine molecule and one hydration water molecule. The LaO(10) coordination polyhedra, connected through the sharing of a single edge, form isolated chains running along the [100] direction. These one-dimensional structures are characterized by two different centrosymmetric La(2)O(2) loops, with La...La distances of 4.5394 (6) and 4.5036 (6) Å. The unbound adenine and water solvent molecules form a highly planar hydrogen-bonded array parallel to (110) (r.m.s. deviation from the mean plane < 0.10 Å) which intersects the isolated La-crotonate chains in a slanted fashion to form an extremely connected hydrogen-bonded three-dimensional structure.

Tetraaquabis(2,6-diamine-7H-purine-κN9)cobalt(II) benzene-1,2,4,5-tetracarboxylate tetrahydrate

The title compound, [Co(C(5)H(7)N(6))(2)(H(2)O)(4)](C(10)H(2)O(8))·4H(2)O, is an ionic structure comprising a [Co(Hdap)(2)(H(2)O)(4)](4+) cation (dap is 2,6-diaminopurine) in a general position, two benzene-1,2,4,5-tetracarboxylate (btc(4-)) anions straddling two different inversion centres and four solvent water molecules. The structure presents a remarkable degree of pseudosymmetry, with the Co(II) cation lying almost exactly on a noncrystallographic pseudo-inversion centre. The overall spatial arrangement can be described in terms of cationic and anionic chains running along the [111] direction and linked into a three-dimensional network by a very complex hydrogen-bonding scheme in which all the available N-H and O-H groups take part.

Two isomorphous transition metal complexes containing a protonated diaminopurine ligand: diaquabis(2,6-diamino-7H-purin-1-ium-κN9)bis(homophthalato-κO)nickel(II) tetrahydrate and the cobalt(II) analogue

The two isomorphous title compounds, [M(C(5)H(7)N(6))(2)(C(9)H(6)O(4))(2)(H(2)O)(2)]·4H(2)O or M(2+)(Hdap(+))(2)(hpt(2-))(2)(H(2)O)(2)·4H(2)O {where dap is 2,6-diaminopurine, H(2)hpt is homophthalic acid [2-(2-carboxyphenyl)acetic acid] and M is Ni(II) or Co(II)}, consist of neutral M(2+)(Hdap(+))(2)(hpt(2-))(2)(H(2)O)(2) monomers, where the M(II) cation lies on an inversion centre and its MN(2)O(4) octahedral environment is defined by one N atom (from Hdap(+)), two O atoms (from one hpt(2-) dianion and one water molecule) and their inversion images. The structures are unusual in that the Hdap(+) cation occurs in an uncommon protonated state (as 2,6-diamino-7H-purin-1-ium) and both ligands bind in an unprecedented monodentate fashion. The existence of a large number of donors and acceptors for hydrogen bonding, together with π-π interactions, leads to a rather complex three-dimensional structure.