Supramolecular architectures of metal–oxalato complexes containing purine nucleobases

6-Amino-3-(prop-2-en-1-yl)-9H-purin-3-ium Tetracopper(I) Hexabromide: Synthesis and X-ray Structure Determination

6-Amino-3-(prop-2-en-1-yl)-9H-purin-3-ium tetracopper(I) hexabromide [(C5H5N5(C3H5))2Cu4Br6] (1) is synthesized in this paper. The title compound is characterized by Raman spectroscopy and single crystal X-ray diffraction: monoclinic, Sp.gr. P21/c, Z = 2, unit cell dimensions: a = 8.6870(3), b = 9.7447(2), c = 16.4418(4) Å, β = 100.681(3)°, V = 1367.72(7) Å3 at 150 K. The peculiarities of the metal coordination and distribution of weak interactions are analyzed. The significant role of hydrogen bonds in the construction of 1 crystal structure is shown.

Innovative Microstructural Transformation upon CO2 Supercritical Conditions on Metal-Nucleobase Aerogel and Its Use as Effective Filler for HPLC Biomolecules Separation

This work contributes to enlightening the opportunities of the anisotropic scheme of non-covalent interactions present in supramolecular materials. It provides a top-down approach based on their selective disruption that herein has been employed to process a conventional microcrystalline material to a nanofibrillar porous material. The developed bulk microcrystalline material contains uracil-1-propionic acid (UPrOH) nucleobase as a molecular recognition capable building block. Its crystal structure consists of discrete [Cu(UPrO)2 (4,4'-bipy)2 (H2 O)] (4,4'-bipy=4,4'-bipyridine) entities held together through a highly anisotropic scheme of non-covalent interactions in which strong hydrogen bonds involving coordinated water molecules provide 1D supramolecular chains interacting between them by weaker interactions. The sonication of this microcrystalline material and heating at 45 °C in acetic acid-methanol allows partial reversible solubilization/recrystallization processes that promote the cross-linking of particles into an interlocked platelet-like micro-particles metal-organic gel, but during CO2 supercritical drying, the microcrystalline particles undergo a complete morphological change towards highly anisotropic nanofibers. This unprecedented top-down microstructural conversion provides a nanofibrillar material bearing the same crystal structure but with a highly increased surface area. Its usefulness has been tested for HPLC separation purposes observing the expected nucleobase complementarity-based separation.

Versatile oxalato-bridging modes: a novel three-dimensional framework structure of manganese(ii) oxalate complex [MnC2O4]·0.5H2O and the relationship with other manganese(ii) oxalates

An unknown manganese(ii) oxalate complex [MnC₂O₄]·0.5H₂O (1) was discovered with a novel three-dimensional structure, exhibiting versatile bridging modes of the oxalate ligand. The thermal and magnetic behaviors of this complex were studied and the relationship with four other manganese(ii) oxalates is also discussed.

Selectivity of a thiosemicarbazonatocopper(ii) complex towards duplex RNA. Relevant noncovalent interactions both in solid state and solution

Thiosemicarbazones and their metal derivatives have long been screened as antitumor agents, and their interactions with DNA have been analysed. Herein, we describe the synthesis and characterization of compounds containing [CuL]⁺ entities (HL = pyridine-2-carbaldehyde thiosemicarbazone) and adenine, cytosine or 9-methylguanine, and some of their corresponding nucleotides. For the first time, crystal structures of adenine- and 9-methylguanine-containing thiosemicarbazone complexes are reported. To the best of our knowledge, the first study on the affinity thiosemicarbazone-RNA is also provided here. Experimental and computational studies have shown that [CuL(OH₂)]⁺ entities at low concentration intercalate into dsRNA poly(rA)·poly(rU) through strong hydrogen bonds involving uracil residues and π-π stacking interactions. In fact, noncovalent interactions are present both in the solid state and in solution. This behaviour diverges from that observed with DNA duplexes and creates an optimistic outlook in achieving selective binding to RNA for subsequent possible medical applications.

A two-dimensional zinc(II) coordination polymer based on mixed dimethyl succinate and bipyridine ligands: synthesis, structure, thermostability and luminescence properties

From the viewpoint of crystal engineering, the construction of crystalline polymeric materials requires a rational choice of organic bridging ligands for the self-assembly process. Multicarboxylate ligands are of particular interest due to their strong coordination activity towards metal ions, as well as their various coordination modes and versatile conformations. The structural chemistry of dicarboxylate-based coordination polymers of transition metals has been developed through the grafting of N-containing organic linkers into carboxylate-bridged transition metal networks. A new luminescent two-dimensional zinc(II) coordination polymer containing bridging 2,2-dimethylsuccinate and 4,4'-bipyridine ligands, namely poly[[aqua(μ2-4,4'-bipyridine-κ(2)N:N')bis(μ3-2,2-dimethylbutanedioato)-κ(4)O(1),O(1'):O(4):O(4');κ(5)O(1):O(1),O(4):O(4),O(4')-dizinc(II)] dihydrate], {[Zn2(C6H8O4)2(C10H8N2)(H2O)]·2H2O}n, has been synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction and elemental, IR and thermogravimetric analyses. In the structure, the 2,2-dimethylsuccinate ligands link linear tetranuclear Zn(II) subunits into one-dimensional chains along the c axis. 4,4'-Bipyridine acts as a tethering ligand expanding these one-dimensional chains into a two-dimensional layered structure. Hydrogen-bonding interactions between the water molecules (both coordinated and free) and carboxylate O atoms strengthen the packing of the layers. Furthermore, the luminescence properties of the complex were investigated. The compound exhibits a blue photoluminescence in the solid state at room temperature and may be a good candidate for potential hybrid inorganic-organic photoactive materials.

Synthesis, structure and characterization of a layered coordination polymer based on Zn(ii) and 6-(methylmercapto)purine

A layered coordination polymer was synthesized from Zn(ii) and 6-(methylmercapto)purine (mMP-H) in N,N-dimethylformamide (DMF). Its structure and formula [Zn₂(μ₂-mMP)₃(NO₃)(DMF)(H₂O)]_n·nDMF were determined by single crystal X-ray diffraction.

Effect of N-donor ancillary ligands on structural and magnetic properties of oxalate copper(ii) complexes

Through varying the auxiliary N-donor ligands nine new compounds have been synthesized and characterised structurally and spectroscopically. The magnetic properties of the complexes have been investigated and discussed in the context of their structures.

Semiconductive and magnetic one-dimensional coordination polymers of Cu(II) with modified nucleobases

Four new copper(II) coordination complexes, obtained by reaction of CuX2 (X = acetate or chloride) with thymine-1-acetic acid and uracil-1-propionic acid as ligands, of formulas [Cu(TAcO)2(H2O)4]·4H2O (1), [Cu(TAcO)2(H2O)2]n (2), [Cu3(TAcO)4(H2O)2(OH)2]n·4H2O (3), and [Cu3(UPrO)2Cl2(OH)2(H2O)2]n (4) (TAcOH = thymine-1-acetic acid, UPrOH = uracil-1-propionic acid) are described. While 1 is a discrete complex, 2-4 are one-dimensional coordination polymers. Complexes 2-4 present dc conductivity values between 10(-6) and 10(-9) S/cm(-1). The magnetic behavior of complex 2 is typical for almost isolated Cu(II) metal centers. Moderate-weak antiferromagnetic interactions have been found in complex 3, whereas a combination of strong and weak antiferromagnetic interactions have been found in complex 4. Quantum computational calculations have been done to estimate the individual "J" magnetic coupling constant for each superexchange pathway in complexes 3 and 4. Compounds 2-4 are the first known examples of semiconductor and magnetic coordination polymers containing nucleobases.

7-Methylguanine: protonation, formation of linkage isomers with trans-(NH3)2Pt(II), and base pairing properties

Three protonated forms of 7-methylguanine (7-MeGH, 1) with different counter ions, [7-MeGH(2)]X (X = NO(3), 1a; ClO(4), 1b; BF(4), 1c) and two Pt(II) complexes, trans-[Pt(NH(3))(2)(7-MeGH-N9)(2)](ClO(4))(2) (4) and trans-[Pt(NH(3))(2)(7-MeGH-N9)(7-MeGH-N3)](ClO(4))(2)·3H(2)O (5) are described and their X-ray crystal structures are reported. 1a-1c form infinite ribbons via pairs of intermolecular hydrogen bonds between N1H···O6 and N3···N2H(2) sites, with anions connecting individual ribbons, thereby generating extended sheets. 4 and 5 do not display unusual features, except that 5 represents a rare case of a bis(nucleobase) complex of Pt(II) in which linkage isomers occur. Unlike in a previously reported compound, [Pt(dien)(7-MeGH-N9)](NO(3))(ClO(4)), the Pt coordination planes and the 7-MeGH planes are not coplanar in 4 and 5. The hydrogen bonding behaviour of 7-MeGH, free and when platinated at N9 (complex 4), was studied in Me(2)SO-d(6). It revealed the following: (i) there is no detectable self-association of 1 in Me(2)SO solution. (ii) 1 and 1-methylcytosine (1-MeC) form Watson-Crick pairs. (iii) 4 does not self-associate. (iv) 4 associates with 1-MeC in the Watson-Crick fashion. (v) 4 and 1 interact in solution, but no model can be proposed at present. (vi) Remarkable interaction shifts between 4 and 1 occur when NH(3) is liberated from trans-(NH(3))(2)Pt(II) to give NH(4)(+) in Me(2)SO-d(6). Feasible models, which imply the presence of deprotonated 7-MeG(-) species are proposed. Finally, DFT calculations were carried out to qualitatively estimate the effect of 7-MeGH acidity in [Pt(dien)(7-MeGH-N9)](2+) in dependence of the dihedral angle between the Pt coordination plane and the nucleobase.