Showing papers by "Juan J. Fiol published in 2018"

Crystal structures of N6-modified-aminoacid/peptide nucleobase analogs: hybrid adenine–glycine and adenine–glycylglycine molecules

Abstract: In this manuscript, we report the synthesis and X-ray characterization of three N6-aminoacid/peptide–adenine-derivatives; the zwitterion N6GlyAde·0.5H2O (1), its corresponding protonated form N6GlyAde·2HCl·H2O (2) and N6GlyGlyAde·H2O (3). In the zwitterion complex (1), the adenine is protonated at N(3) and the anionic carboxylate interacts with the imidazole ring of the neighbouring purine molecule. It also interacts with the water molecule that connects it to another adenine ring through N(7)–H⋯O hydrogen bonds. The hydrochloride (compound 2) crystallizes forming a laminar structure and exhibits double protonation in the adenine ring (at N1 and N7). Moreover, energetically strong anion–π interactions are important for constructing the final solid state architecture in 2. Finally, compound 3, which presents a neutral adenine ring, crystallizes in a chiral point group and forms CH⋯O and CH⋯N H-bonding interactions in the solid state. We have also studied the noncovalent interactions energetically using DFT calculations and rationalized the interactions using Molecular Electrostatic Potential surfaces and Bader's theory of “Atoms-in-Molecules”.

Cu(II)–N6-Alkyladenine Complexes: Synthesis, X-ray Characterization and Magnetic Properties

Abstract: Three new dinuclear copper(II) complexes [Cu2(μ–HLn)2(μ-Cl)2Cl2]Cl2 (1–3) have been synthesized and structurally characterized by single-crystal X-ray diffraction, where HLx, (HL1 = N6-propyladeninium, HL2 = N6-butyladeninium and HL3 = N6-isobutyladeninium) are N6-alkyl bidentate NN donor adenine bases. Complexes 1–3 exhibit a coplanar arrangement of both N6-alkyladeninium moieties with UD conformation, with the terms U(up) or D(down) referring to the coordination of each pyrimidinic N3 atoms to the upper or lower metal center. In the three complexes, both copper atoms are five-coordinated (N2Cl3 donor set), resembling a compressed trigonal bipyramid. Each adenine moiety is protonated in N1 and the positive charge balanced by chloride counterions. Magnetic measurements of complexes 1 and 3 in the 2–300 K temperature range indicate antiferromagnetic coupling with J = −156.1(7) and J = −151(2) cm−1, respectively. Density functional theory calculations have also been performed in order to estimate the exchange coupling constants in these complexes. The theoretically calculated J values are in good agreement with the experimental values.