Key indicatorsSingle-crystal X-ray study T = 293 K Mean '(C±C) = 0.004 A Ê R factor = 0.036 wR factor = 0.090 Data-to-parameter ratio = 7.4For details of how these key indicators were automatically derived from the article, see http://journals.iucr.org/e. # 2002 International Union of Crystallography Printed in Great Britain ± all rights reserved The title salt, l-HisH 2 2+ Á2NO 3 À , contains two nitrate anions and one l-histidinium dication. The anions and cations are linked to each other through strong hydrogen bonds, formed by all H atoms covalently bonded to the N and O atoms of the l-histidinium dications. This three-dimensional complex network of hydrogen bonds ensures the cohesion of the ionic structure.

Key indicatorsSingle-crystal X-ray study T = 120 K Mean '(C±C) = 0.002 A Ê Disorder in solvent or counterion R factor = 0.036 wR factor = 0.105 Data-to-parameter ratio = 22.4 For details of how these key indicators were automatically derived from the article, see

Key indicatorsSingle-crystal X-ray study T = 293 K Mean '(C±C) = 0.002 A Ê R factor = 0.040 wR factor = 0.112 Data-to-parameter ratio = 11.1 For details of how these key indicators were automatically derived from the article, see

The present work describes the synthesis, structural characterization, Hirshfeld analysis, and antibacterial assays of two hydroxy Schiff bases with triazole moiety: N-[(E)-(3hydroxy)methylidene]-4H-1-2-4 triazol-4-amine (L1) and N-[(E)-(2,4dihydroxy)methylidene]-4H-1-2-4 triazol-4-amine (L2). The interaction of these two Schiff bases with AgNO 3 leads to Ag(I) dimer [Ag(L1)](NO 3) in the case of the first ligand (L1) and polymer [Ag(L2)] n (NO 3) n (H 2 O) for (L2). Crystal structure determination and Hirshfeld analysis reveal the presence of two important hydrogen bond interactions in the four compounds, O…H and H…N, involving nitrogen atoms of triazole ring. Contribution of these two types of hydrogen bonds evolves inversely from (L1) which contains one-OH, to (L2) containing two-OH, then to [Ag(L1)](NO 3) dimer and finally to [Ag(L2)] n (NO 3) n (H 2 O) polymer. Indeed, we observed an increase of the percentage to the Hirshfeld surfaces of O…H contribution from (L1) to [Ag(L2)] n (NO 3) n (H 2 O) passing by (L2) and [Ag(L1)](NO 3), while the percentage of N…H decrease in the same way. Antibacterial activity of the free ligands (L1), (L2) and their silver complexes [Ag(L1)](NO 3) and [Ag(L2)] n (NO 3) n (H 2 O) were evaluated against four Gram-negative (E. coli, Salmonella typhimurium, Klebsiella 2 pneumoniae and serratia marcescens) and two Gram-positive (Staphylococcus aureus, streptococcus) bacteria strains, using the standard antibiotics, Colistin, Fosfomycin, Gentamycin, Erythromycin, Rifampicin, Amikacin, Ofloxacin and Amoxicillin as positive controls. AgNO 3 salt was also used as second control test. The results of this evaluation reveal that, while the two Schiff bases inhibit the growth of the Serratia Marcescens bacterium only, the two Ag(I) complexes are active for all bacteria, with activities comparable to the ones of silver nitrate. However, [Ag(L2)] n (NO 3) n (H 2 O) complex appears significantly more efficient than the AgNO 3 salt against Klebsiella Pneumoniae.