There is a complex interplay between the structural and other physicochemical properties of new compounds and the molecules in living organisms. To understand the mechanism of the interactions at the molecular level, the correlations between the selected properties and their biological responses have to be examined. With this aim, in this paper, density functional theory (DFT) and LMP2 calculations were carried out for the 2-acetylpyridine-aminoguanidine ligand, L, and its copper(II) complexes containing different monoanionic ligands. In addition, several parameters, most frequently used for the prediction of drug-likeness of new compounds, were calculated. The influence of the compounds on the effectiveness of the reference chemotherapeutic drug cisplatin was determined in vitro, by comparison of their combination indices (CIs). The drug interactions between cisplatin and the earlier synthesized ligands L1 (bis(3-chloropyridazine-6-hydrazone)-2,6-diacetylpyridine) and L2 (bis(phthalazine-1-hydrazone)-2,6-diacetylpyridine) and their Co(III), Ni(II), Cu(II) and Zn(II) complexes, respectively, were also measured. The ligands L, L2, and L3, as well as their complexes, showed different interactions in combination with cisplatin from strong antagonism of L to strong synergism of 4-L1 and 4-L2. The experimental results and the calculated parameters were analyzed to evaluate their correlation with the measured interactions. The thermal stability of the LÁ2HCl ligand and its four copper(II) complexes was determined and the thermal stability data were correlated to selected calculated molecular descriptors.

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The molecular and crystal structure of a newly synthesized Co(II) complex with 2,6-diacetylpyridine bis(phenylhydrazone) (L), of the formula [CoL2]I2 are described. The reaction of warm EtOH solutions of the ligand, 2,6-diacetylpyridine bis(phenylhydrazone) and CoI2 in molar ratio 1:1 resulted in formation of black single crystals of the title complex. This is the first and so far, the only metal complex with this ligand that is characterized by single crystal X-ray crystallography. Co(II) is situated in a distorted mer-octahedral surrounding of two tridentate N3 coordinated ligand molecules. Complex crystallizes in monoclinic crystal system in C2/c space group. Besides X-ray analysis, conductometric, spectroscopic and magnetic properties of the complex are investigated.

Please cite this article as: L.S. Vojinović-Ješić, M.M. Radanović, M.V. Rodić, V. Živković-Radovanović, L.S. Jovanović, V.M. Leovac, Syntheses and characterization of 2-acetylpyridine-aminoguanidine and its copper(II) complexes: Crystallographical and antimicrobial study, Polyhedron (2016), doi: http://dx. AbstractThe syntheses, physico-chemical and microbiological properties of the ligand, 2acetylpyridine-aminoguanidine dihydrogensulfate monohydrate and its five complexes with Cu(II) are described. The compounds were characterized by single crystal X-ray crystallography. Common fragments encountered in some of the structures were compared by r.m.s. overlay calculations as well as half-normal probability plots. In these complexes the chelate ligand is coordinated in its neutral form in a tridentate N 3 -coordination mode, via pyridine, azomethine and imino nitrogen atoms of the aminoguanidine fragment. In these complexes the Cu(II) ion is situated in moderately or severely distorted square-pyramidal surroundings. The antimicrobial activity of the ligand and the complexes were examined against 6 selected bacterial and 3 fungal strains.structural and antimicrobial properties of the ligand, 2-acetylpyridine-aminoguanidine dihydrogensulfate monohydrate and its Cu(II) complexes. Experimental Materials and physical measurementsAll commercially obtained reagent-grade chemicals were used without further purification. The ligand 2-acetylpyridine-aminoguanidine dihydrogenchloride, L·2HCl, was prepared according to a previously described procedure [18] with a slight modification.Elemental analyses (C, H, N and S) of the air-dried compounds were carried out by standard micro-methods in the Center for Instrumental Analyses, ICTN in Belgrade. The chlorine content was determined by potentiometric titration using AgNO 3 . The compound was combusted using the Schoeniger method [19] and the products were absorbed in a solution of H 2 O 2 and KOH. Molar conductivity measurements of freshly prepared 1 mM solutions were performed on a Jenway 4010 conductivity meter. IR spectra were recorded on a Nicolet Nexus 670 FTIR (Thermo Scientific) spectrophotometer in the range 400-4000 cm -1 by the KBr pellet technique. Electronic spectra of DMF solutions of the ligand and the complexes were recorded on a T80+UV-Vis spectrometer (PG Instruments, Ltd.), in the spectral range 270-1000 nm. Syntheses L·2HCl, 2-acetylpyridine-aminoguanidine dihydrogenchlorideAminoguanidine-hydrogencarbonate (3.4 g, 25 mmol) was dissolved in 25 mL 2N HCl. After the addition of 2-acetylpyridine (2.8 mL, 25 mmol) the reaction mixture was heated for 1 h. The obtained microcrystalline product was evaporated nearly to dryness, using hot air, filtered in vacuo and washed with MeOH. Yield: 4.37 g (70%). Single crystals of the ligand were obtained by recrystallization from warm MeOH. Anal. Calc. for C 8 H 13 N 5 Cl 2 : C, 38.43; H, 5.20; N, 28.01; Cl, 28.34. Found: C, 38.10; H, 5.47; N, 27.76; Cl,27.99%. Conductivity [Λ M /Ω −1 cm 2 mol −1 ]: 170 (in MeOH). Selected IR ba...

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A new salt of Schiff base of aminoguanidine and 2-acetylpyridine, and its zinc(II) complex were obtained and their physicochemical and structural properties studied. The reaction of an aqueous solution of the chloride ligand salt and NH 4 NCS resulted in formation of the dithiocyanate ligand salt, L•2HNCS, while the reaction of the obtained salt with zinc(II) acetate gave a neutral complex of the formula [ZnL(NCS) 2 ]. In this complex, chelate ligand is coordinated in its neutral form, in a common tridentate NNN manner, via pyridine, azomethine and imino nitrogen atoms of the aminoguanidine fragment. This coordination mode results in formation of two strained five-membered metallocycles. Zinc(II) is situated in a distorted square-pyramidal environment of the tridentate ligand and one thiocyanate ion in the equatorial and the other thiocyanate ion in the apical position. The crystal structure of the ligand salt is stabilized by N-H … N and N-H … S interactions formed between the cationic and anionic species, while the three-dimensional crystal packing of the complex units is based on weak N-H … S interactions which involve the S acceptors from both NCS ligands.

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