One-Dimensional Oxalato-Bridged Cu(II), Co(II), and Zn(II) Complexes with Purine and Adenine as Terminal Ligands

Abstract

The reaction of nucleobases (adenine or purine) with a metallic salt in the presence of potassium oxalate in an aqueous solution yields one-dimensional complexes of formulas [M(mu-ox)(H(2)O)(pur)](n) (pur = purine, ox = oxalato ligand (2-); M = Cu(II) [1], Co(II) [2], and Zn(II) [3]), [Co(mu-ox)(H(2)O)(pur)(0.76)(ade)(0.24)](n)(4) and ([M(mu-ox)(H(2)O)(ade)].2(ade).(H(2)O))(n) (ade = adenine; M = Co(II) [5] and Zn(II) [6]). Their X-ray single-crystal structures, variable-temperature magnetic measurements, thermal behavior, and FT-IR spectroscopy are reported. The complexes 1-4 crystallize in the monoclinic space group P2(1)/a (No. 14) with similar crystallographic parameters. The compounds 5 and 6 are also isomorphous but crystallize in the triclinic space group P (No. 2). All compounds contain one-dimensional chains in which cis-[M(H(2)O)(L)](2+) units are bridged by bis-bidentate oxalato ligands with M(.)M intrachain distances in the range 5.23-5.57 A. In all cases, the metal atoms are six-coordinated by four oxalato oxygen atoms, one water molecule, and one nitrogen atom from a terminal nucleobase, building distorted octahedral MO(4)O(w)N surroundings. The purine ligand is bound to the metal atom through the most basic imidazole N9 atom in 1-4, whereas in 5 and 6 the minor groove site N3 of the adenine nucleobase is the donor atom. The crystal packing of compounds 5 and 6 shows the presence of uncoordinated adenine and water crystallization molecules. The cohesiveness of the supramolecular 3D structure of the compounds is achieved by means of an extensive network of noncovalent interactions (hydrogen bonds and pi-pi stacking interactions). Variable-temperature magnetic susceptibility measurements of the Cu(II) and Co(II) complexes in the range 2-300 K show the occurrence of antiferromagnetic intrachain interactions.

1D and 2D Cobalt(II) Coordination Polymers, Co(ox)(en): Synthesis, Structures and Magnetic Properties

“…The octahedral coordinate in zigzag chains can adopt terminal ligand positions by monodentate or chelating bidentate ligands, while linear chains can only adopt monodentate ligands. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] On the other hand, 2D layered structures contain bridging multidentate ligands such as 2,2'-bipyrimidine, pyrazine, and 4,4'-bipyridine (bpy), which are obviously different from chelating bidentate ligands found in 1D structures. [18][19][20][21][22][23][24][25] The geometric patterns of the layers are essentially distinguished by the facility and number of chelating ligands in the structures.…”

Molecular Recognition of Protonated Cytosine Ribbons by Metal–Oxalato Frameworks

“…12 Following these lines of investigation, we have recently reported the elaboration and solid-state characterization of supramolecular architectures isolated from aqueous solution at physiological pH in which adenine aggregates reside between neutral one-dimensional (1D) metal-oxalato-water complexes to build sheetlike structures containing sequentially arranged organic and inorganic layers. 13 The design of non-natural receptors for biomolecules is an area of active research, examples being hosts for biologically interesting guests such as barbituric acid derivatives, creatinine, or nucleobases. 14 Now, employing similar synthetic routes, we have succeeded in incorporating the protonated cytosine nucleobase into a metal-oxalato matrix to afford the compounds (1H,3H-cyt) 2 [M(ox) 2 (H 2 O) 2 ] (M(II) ) Mn (1), Co (2), Cu (3), and Zn [4]).…”

Using CdTe/ZnSe core/shell quantum dots to detect DNA and damage to DNA

“…The usual coordination mode is via the N7 atom of five-membered ring subcore of purine. [55][56][57] It is always accompanied by at least double synthons of hydrogen bond base pairing, mostly through the parts of six-membered ring subcore. This is also accompanied by π-π interactions between purines and also more closely to the five-membered ring subcore.…”