Molecular orbital study of 8-azaxanthine derivatives and crystal structure of 1,3-dimethyl-8-azaxanthine monohydrate

Formation of 2D water morphologies in the lattice of the salt with [Cu2(OH)2(H2O)2(phen)2]2+ as cation and 4,6-dimethyl-1,2,3-triazolo[4,5-d]pyrimidin-5,7-dionato as anion

“…Phenanthroline is not coplanar with the Cu 2 O 2 core, the corresponding dihedral angle being 15:46 . The endocyclic bond angle at the nitrogen atom at position 2 is closed $ 5 with respect to the crystal structure of the free ligand [8], due to the ionization of the acidic proton located at this position, with the subsequent opening of the adjacent endocyclic angles, as it has been also previously observed in other compounds with the same anion non coordinated to metal centres [4].…”

In Vitro and in Vivo Trypanocidal Evaluation of Nickel Complexes with an Azapurine Derivative against Trypanosoma cruzi

“…For 7, the geometrical parameters are identical to those found in the literature for other complexes containing the cationic species [Ni(phen) 3 ] 2þ . 23,24 The ionization of the acidic proton of 1, located at N2 in the crystal structure of the free ligand, 25 leads to the closure of the endocyclic angle at N2 (4.1-4.4°, 4.0°, 3.7-4.5°) and the opening of the adjacent endocyclic angles at N1 (3.0-3.5°, 3.0°, 1.7-2.9°) and N3 (3.7-2.5°, 2.9°, 3.8-2.3°), respectively, but the differences with the free ligand are slightly smaller when the triazolopyrimidinato is coordinated to the nickel center, showing that the effect of the loss of the proton is partially compensated by the presence of the metal cation. Otherwise, the differences in the equivalent distances between the free heterocycle and the deprotonated form at N2 are lower than 0.04 A ˚.…”

Crystal structure of guanidinium urate monohydrate, C5H3N4O3(CH6N3) · H2O

“…An interesting feature is the distinct pyramidality at N7, which deviates 0.056(3) A from the plane of its substituents. Different binding motifs in guanidinium urate and 8-azaxanthinate [2], which presumably reflect the location of negative charge [3], are related by 180° rotation about the N1-C4 axis; the conformational flexibility of Argl76, Gln228, and Phel59 residues in the active cleft allows an induced fit for binding. It is now clear how the stereospecificity of uricase reaction may arise [4][5][6][7][8].…”