Angel Terrón

Experimental and theoretical study of uracil derivatives: the crucial role of weak fluorine–fluorine noncovalent interactions

We have recently communicated the important role of lone pair–π, π–π and hydrophobic interactions in the solid architecture of 5-fluoro-1-hexyluracil and 1-hexyluracil (CrystEngComm, 2010, 12, 362–365). As a matter of fact, the simple substitution of a hydrogen atom by a fluorine atom has an enormous consequence in the solid state structure. It has been demonstrated that this is due to an increase in the π-acidity of the ring. In this article we extend the study to other uracil derivatives, where we have changed the hydrophobicity of the hexyl chain by introducing hydrophilic groups in the substituent, such as hydroxyl or carboxylic groups. The latter compounds, i.e. (N1-(3-hydroxypropyl)-5-fluorouracil and N1-(4-hydroxycarbonylbutyl)-5-fluorouracil monohydrate present interesting fluorine–fluorine interactions that are very important in determining the crystal packing.

Lone pair–π vs π–π interactions in 5-fluoro-1-hexyluracil and 1-hexyluracil: a combined crystallographic and computational study

The simple substitution of a hydrogen atom by a fluorine atom in 1-hexyluracil has an enormous consequence on the solid state structure due to the increment in the π-acidity of the ring.

Interactions of d(10) metal ions with hippuric acid and cytosine. X-ray structure of the first cadmium (II)-amino acid derivative-nucleobase ternary compound.

The interactions of Zn(II), Cd(II) and Hg(II) with hippuric acid (hipH) were studied and several novel compounds were synthesized and studied by NMR. Some new metal-hippuric-cytosine ternary compounds were formed and the structure of the [Cd(hip)(2)(cyt)(H(2)O)](2) ternary complex resolved. Each cadmium (II) atom has a distorted trigonal bipyramid coordination which is linked to a water molecule, a cytosine via N(3), a carboxylic oxygen atom of a hippurate moiety and two bridging dicoordinated hippurates bound through the carboxylic oxygen atoms. To these five main bonds, two longer ancillary interactions can be observed: the second oxygen of the monocoordinated hippurate group and the carboxylic oxygen of the cytosine ligand. The compound is stabilized by an intramolecular stacking between the benzene and cytosine rings and by the hydrogen bonds between the coordinated water molecules and the ligands. This is, to our knowledge, the first structure of a cadmium-amino acid derivative-natural nucleobase compound described so far.

Some new derivatives of Co(III) with uracil, uridine and pyrimidine nucleotides

Abstract This paper describes the synthesis of compounds of Co(III) with uracil, uridine and the nucleotides 5′UMP, 5′CMP and their characterization, carried out by elemental analysis, by studying the infrared spectra, diffuse reflectance, 13 C NMR and conductivity measurements. The compounds were obtained by reaction of the starting complexes trans -[Co(en) 2 Cl 2 ]Cl and [Co(NH 3 ) 5 Cl]Cl 2 with the base, nucleoside and nucleotides. In the case of uracil (URA) and uridine (URD) compounds, indirect bonding of Co(III) to the pyrimidine ring seems to occur through the C 4 O and -NH 3 (-NH 2 ) groups of starting complexes. In the complexes of Co-nucleotide, bonding is inferred through the heterocyclic ring (for the Co(en) 2 (5′CMP)(5′CMPH)·6H 2 O complex) and through the phosphate group in the other cases.

SYNTHESIS AND CHARACTERIZATION OF A NOVEL COPPER(II)-CYTOSINE COMPLEX : TETRAKIS(CYTOSINE)COPPER(II) CHLORIDE BIS(DIMETHYLACETAMIDE) SOLVATE

Abstract The compound [Cu(C4H5N3O)4]Cl2·2DMA (DMA = N,N-dimethyl-acetamide) has been prepared in DMA-water solution from the parent compound Cu(cyt)2Cl2 (cyst = cytosine), already described, and characterized by X-ray diffraction. The cytosine compound was obtained in an attempt to synthesize the ternary cytosine-creatinine (creat) complex. In the first stage of the reaction in methanol, the yellow Cu(creat)2Cl2 complex is obtained which reacts finally with cytosine yielding the 1:4 Cu-cyt complex, the creatinine being completely displaced by cytosine. The [Cu(cyt)4]Cl2·2DMA complex has been characterized by X-ray crystallography. IR and electronic spectral data of the compound are discussed and related to the copper binding mode derived from the crystal structure determination.

X-RAY CRYSTAL STRUCTURE OF A TERNARY COPPER(II) PEPTIDE CREATININE COMPLEX, (AQUO)(CREATININE)(GLYCYLGLYCINATO) COPPER(II) SESQUIHYDRATE

Abstract The first creatinine ternary complex[Cu(gg)(H2O)(creat)]·1.5 H2O (1) [gg = glycylglycine (2−), creat = creatinine] has been crystallized from aqueous solution. The coordination geometry about the copper is approximately square pyramidal with the tridentate glycylglycine dianion and the N(1) of creatinine occupying the corners of a square. The coordination sphere about the copper is completed by an axial water molecule, CuOW(1) distance 2.496(2) A. Another water molecule OW(2), CuOW(2) distance 2.907(2) A, extends qualitatively the coordination geometry to octahedral. A third water molecule OW(3) with an occupancy factor of 0.5 is disordered and is located between two complex units. The complete crystal structure is maintained by an extensive hydrogen-bonding network in which the three types of water molecules are involved.

Ternary chromium(III)-nucleotide-amino acid complexes : L-methionine, L-serine and glycine derivatives

Abstract The first ternary Cr(III)-nucleotide-amino acid complexes (nucleotide: 5′AMP, 5′CMP; amino acid: L -serine, L -methionine, glycine) are described. The complexes have been characterized by elemental and thermogravimetric analyses, IR and electronic spectroscopy and EPR measurements. In all cases the interaction of Cr(III) with the nucleotide seems to occur mainly through the phosphate group, whereas the amino acid binds to Cr(III) through the carboxylic and amino groups. Some of the complexes show distortions from octahedral geometry, but these distortions appear to be small resulting in values of the zero field splitting parameter D −1 .

Experimental and theoretical study of thymine and cytosine derivatives: the crucial role of weak noncovalent interactions

In this paper we report the synthesis of N1-hexylthymine (1), N1-hexylcytosine (2), N1-hexylcytosine hydrobromide (3) and [(N1-hexylcytosinium)·(N1-hexylcytosine)]2·[Cl2Hg(μ-Cl)2HgCl2] (4) (the hemiprotonated form of the N1-hexylcytosine forming a CHC+ pair with carbonyl-amino symmetric and N3–N3 recognitions) and X-ray characterization of compounds 1, 3 and 4. In the solid state, N1-hexylthymine 1 follows exactly the same behaviour as N1-hexyluracil. In addition to strong hydrogen bonding interactions, various weak forces, i.e. C–H/π, carbonyl–carbonyl (CO⋯CO) and anion–π interactions (between the bromide and N1 of cytosine in 3), play a key role in stabilizing the 3D architectures of the compounds. The theoretical calculations allow estimation of the strength of these contacts and how they influence each other.

Complexation in solution of magnesium(II) and cobalt(II) with purine 5′-monophosphates and pyrimide 5′-monophosphates: a potentiometric and calorimetric study

Abstract The interaction of Mg(II) and Co (II) with purine and pyrimidine nucleoside 5′-monophosphates was studied using potentiometric and calorimetric methods, with 0.1 M tetramethylammonium bromide as the background electrolyte at 25°. The presence in solution of the complexes [Mg(AMP) 2 ] 2 −, [Co(AMP) 2 ] 2 −, [Co(GMP) 2 ] 2 − [Co(IMP) 2 ] 2 − was observed. The relationship between enthalpies and the degree of macrochelation together with the stacking interaction between purine bases in the complexes are discussed.

Ternary chromium(IlI)-nucleotide-cysteine complexes

Abstract The first ternary chromium(III)-nucleotide- cysteine complexes with purine and pyrimidine nucleotides are reported. A cysteine molecule of the starting complex is removed in some cases. With 5′ATP, ternary compounds have not been obtained because of total substitution of cysteine molecules from the starting chromium(III)-cysteine complex. The complexes have been characterized by elemental analyses, conductivity measurements, infrared and electronic spectroscopy and EPR. Distortions from octahedral geometry appear to be very small ( D −1 ).