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C21H20N2O3, monoclinic, P21/c (no. 14), a = 6.8892(3) Å, b = 21.8269(13) Å, c = 35.1144(19) Å, β = 90.344(5)°, V = 5280.1(5) Å3, Z = 12, R gt(F) = 0.0672, wR ref(F 2) = 0.1460, T = 170(2) K.

C18H21NO4, orthorhombic, C2221 (no. 20), a = 10.6891(2) Å, b = 11.8375(2) Å, c = 25.4410(4) Å, V = 3219.11(10) Å3, Z = 8, Rgt(F) = 0.0483, wRref(F2) = 0.1449, T = 295 K.

Aminoguanidine derivatives are the focus of research because of their various biological activities, such as antiviral, antibacterial, analgesic, antioxidant and anticancer. Their complexes with different metals are also examined and many of them show significant biological activity, too. Besides, some of the complexes show good photoluminescent properties and are used for the preparation of photoelectronic devices. Therefore, the synthesis, physicochemical, structural and thermal characterization of the complexes of 2-acetylpyridine- aminoguanidine (L) with copper (II) are described here. Under different reaction conditions, Cu(II) with L gives three complexes of different compositions. By varying the strength of basicity of the deprotonating agent used, it was proven here that the Schiff base given here could be coordinated in neutral or monoanionic form. In the presence of pyridine, a coordination polymer is obtained, while in the presence of ammonia/lithium acetate two different monomeric complexes were crystallised. Their physicochemical and thermal properties, as well as molecular and crystal structure, are determined.

Here we report a new Schiff base of aminoguanidine and 2,3-dihydroxybenzaldehyde (H2L) and its physicochemical characterization, along with an investigation into its coordination affinities towards zinc. By reacting zinc acetate with the chloride salt of the ligand in the MeCN–H2O solution, yellow single-crystals of tetranuclear, centrosymmetric complex, with the formula [Zn2(μ-L)(μ-OAc)2]2∙2MeCN, were obtained. The complex was characterized by IR spectroscopy, conductometry, elemental analysis, and single-crystal X-ray diffraction analysis. Notably, both nitrogen atoms of the aminoguanidine residue coordinate to the same zinc atom, while both deprotonated phenyl oxygen atoms achieve bridging coordination. Furthermore, two acetate anions bridge adjacent zinc atoms in addition to the Schiff base anion. Meaningful insights into the hierarchy and significance of intermolecular interactions within the crystal structure were gained by estimating the energies using the CrystalExplorer model. The calculations revealed that the crystal structure can be classified as a layer type, with notably stronger interactions occurring along the [001] and [011] directions.

Four novel conformationally restricted (–)-muricatacin analogues, bearing a methoxy group at the C-5 position and with an alkoxymethyl group аs the C-7 side chain, have been synthesised and their in vitro antiproliferative activity was evaluated against a panel of seven human tumour cell lines, as well as a single normal cell line. All analogues (9–12) showed diverse antiproliferative effects against all tested human malignant cell lines, but were devoid of any significant cytotoxicity towards the normal foetal lung fibroblasts (MRC-5). A structure–activity relationship study reveals that the introduction of tetrahydrofuran ring, the replacement of C-8 methylene group in the side chain of muricatacin analogues with the O-8 ether functionality, as well as the length of side chain may be beneficial for the antiproliferative effects of these lactones. All novel analogues were more potent than lead compound, (–)-muricatacin, against HL-60 cell line.

New thiazole hybrids were synthesized and evaluated for their in vitro cytotoxicity against a panel of human malignant cell lines. The key steps in the synthesis of hybrids 3–7 involved the initial condensation of appropriate aldononitriles with cysteine ethyl ester hydrochloride, followed by subsequent treatment of resulting thiazolines with diazabicycloundecene to form the thiazole ring. Bioisosteres 8 and 14 have been prepared after the stereoselective addition of 2-(trimethylsilyl)thiazole to the hemiacetals obtained by periodate cleavage of terminal diol functionality in the suitably protected d-glucose derivatives. The obtained analogues showed various antiproliferative activities in the cultures of several tumour cell lines. Hybrid 6 was the most potent in HeLa cells, exhibiting more than 10 and 4 times stronger activity than both leads 1 and 2, respectively. The most active compound in Raji cells was hybrid 12, which was nearly 2-fold more potent than the clinical antitumour drug doxorubicin. All analogues were more potent in A549 cells with respect to lead 1, while compounds 6 and 7 were slightly more active than doxorubicin. Preliminary structure–activity relationship analysis revealed that the presence of a cinnamate group at the C-3 position in analogues of type 7 increases the activity of resulting molecular hybrids.

C6H23I2N6NiO2.50S2, monoclinic, C2/c (no. 15), a = 8.2282(4) Å, b = 21.9200(7) Å, c = 11.4906(4) Å, β = 109.451(4)°, V = 1954.19(14) Å3, Z = 4, Rgt (F) = 0.0322, wRref (F 2) = 0.1113, T = 295.

C20H22N2O8, monoclinic, P21/c (no. 14), a = 8.7634(8) Å, b = 17.9290(18) Å, c = 12.8437(9) Å, β = 100.013(8)°, V = 1987.3(3) Å3, Z = 4, Rgt(F) = 0.0401, wRref(F2) = 0.1026, T = 170 K.

C17H14N2O3S, monoclinic, P21/c (no. 14), a = 9.8966(5) Å, b = 9.4360(4) Å, c = 16.7115(7) Å, β = 92.245(4)°, V = 1559.39(12) Å3, Z = 4, R gt(F) = 0.0358, wR ref(F 2) = 0.1013, T = 170 K.

The structures of the first two complexes with bidentate coordination of aminoguanidine Schiff base, i.e., 2-acetylpyridine-aminoguanidine (L), are reported. The complex of the formula [Cd2Cl6(HL)2] (1) was obtained in the reaction of warm aqueous solutions of chloride salts of Cd(II), Zn(II) and the ligand, while the reaction of cadmium bromide and the ligand in the presence of deprotonating agent as well as ammonium thiocyanate resulted in the formation of the complex in which Schiff base has both the role of the ligand and the counterion, viz., [HL][Cd(HL)(NCS)2XY]·H2O (2), where X is Cl- or Br-, and Y Br- or SCN-. The complexes were characterized by IR spectroscopy, elemental analysis, conductometric measurements and single crystal X-ray diffraction. The unusual bidentate coordination of the Schiff base lead to significant changes in the geometry of this molecule (from almost planar in free form and as a tridentate ligand to twisted as a bidentate ligand). Besides, in complex 1 relatively rare bridging coordination of Cl- in octahedral Cd(II) is found, while the crystal structure of complex 2 exhibits substitutional disorder, and contains four different anions: [Cd(HL)(NCS)2Br(SCN)]- (ca. 61 %), [Cd(HL)(NCS)2Cl(SCN)]- (ca. 35 %), [Cd(HL)(NCS)2Br2]- (ca. 3 %) and [Cd(HL)(NCS)2ClBr]- (ca. 1 %).

Utilizing X-ray crystallography, the crystal and molecular structures of 2,6-diacetylpyridine bis(phenylhydrazone) (L) were determined. The energetics of the intermolecular interactions in the crystal structure were assessed with computational methods, revealing that dispersion interactions are dominant. The basic structural unit of the crystal packing was revealed to be the herring- bone type arrangement of L molecules. Assignation of the IR spectrum of L with the aid of DFT calculations was performed. Furthermore, new reactions of L with CuBr2 in different solvents are described, which led to the synthesis of the mixed Cu(II)–Cu(I) complex with the formula [CuIIL2][CuI 2Br4] (1), and its structural characterization. In the complex cation, two molecules of tridentate N3 ligand are meridionally arranged in a very distorted octahedral environment of a Cu(II) ion. In [Cu2Br4]2-, the bromide ions are arranged in a trigonal- -planar geometry around each copper(I) atom. Finally, for ligand, 1, and the previously synthesized complex [CuL2]Br2, the thermal properties were examined. The thermal stability of the complexes were lower than that of the ligand and decrease in the order: L (250°C) > [CuL2]Br2 (221°C) > [CuIIL2][CuI 2Br4] (212°C). The differences in thermal stability of the complexes are due to differences in the packing efficacy of the constitutional ions.

Two square–planar complexes, [PtLCl] (1) and [PdLCl] (2), were synthesized with quinoline-2-carboxaldehyde thiosemicarbazone ligand (HL), and characterized by IR and NMR spectroscopy and single crystal X-ray diffraction analysis. In both complexes, L- is coordinated tridentately via the same donor atom set, while the fourth coordination site is occupied by a chloride ion. However, the complexes are not isostructural due to different types of non-covalent intermolecular interactions. These interactions were analyzed using Hirshfeld surfaces and two-dimensional fingerprint plots.

The syntheses, physicochemical and structural properties of the novel Cu(II) complex with 2,6-diacetylpyridine bis(phenylhydrazone) (L), of the formula [CuL 2 ]Br 2 are presented. In the reaction of warm MeOH solutions of the ligand, 2,6-diacetylpyridine bis(phenylhydrazone) and CuBr 2 in molar ratio 2:1 resulted in formation of black single crystals of the bis(ligand) complex. This is the first Cu(II) complex with this ligand that is characterized by SC-XRD. Two ligand molecules are coordinated in the usual tridentate mode, via nitrogen atoms of the pyridine ring, and two azomethine nitrogen atoms, forming distorted octahedral environments of the metal ion.

The 3-arylidene-2-thiohydantoin derivative, 3-[(2-hydroxybenzylidene) amino]-2-thioxoimidazolidin-4-one, was synthesized in a two-step condensation reaction of 2-hydroxybenzaldehyde, thiosemicarbazide and ethyl chloroacetate. The ligand was structurally characterized by NMR and IR spectroscopy, as well as by elemental analysis. In the reaction of the well-known polymeric trans-[CuCl2(DMSO)2]n complex with the polydentate thiohydantoin type ligand, instead of the corresponding copper thiohydantoin complex, unexpectedly, the dinuclear cis-[{CuCl(DMSO)2}(μ-Cl)]2 complex (1) was formed predominantly as the final stable product. The structure of the complex 1 was confirmed by single crystal X-ray diffraction analysis. The cis-complex is obtained through assisted isomerization of the trans-form, in which the thiohydantoin derivative has a crucial role.

In the reaction of acetone solutions of CoX2∙nH2O (X = Cl, Br) with methyl pyruvate semi/thiosemicarbazone (Hmps, Hmpt) the first Co(II) complexes with these ligands, i.e., [Co(Hmps)(H2O)X2] (X = Cl (1), Br (2)), [Co(Hmpt)2][CoCl4]∙2H2О (3) and [Co(Hmpt)2]Br2∙Me2CO (4) were obtained. Complexes 1 and 2 represent the first examples of metal complexes of Hmps. All the obtained compounds were characterized by elemental analysis, conductometry, magnetic measurements, and IR spectra, and for complexes 2–4, single crystal X-ray diffraction analysis was also performed. The effective magnetic moments were close to the upper limit (5 μB) for complexes 1 and 2, and close to the lower limit (4.4 μB) for complexes 3 and 4, and as such are characteristic for high-spin Co(II) complexes. Structural analysis showed that both ligands coordinate in a neutral form in a tridentate manner, via the ester oxygen, imine nitrogen and the oxygen atom of the ureido (Hmps), or the sulfur atom of the thioureido group (Hmpt). The central metal atoms are situated in a deformed octahedral coordination environment. Complex 2 has cis-Br configuration, while complexes 3 and 4 have mer-configuration. [Projects of the Serbian Ministry of Education, Science and Technological Development, Grant no. 172014 and Grant no. III41010]

The synthesis of the first Ag(I) complexes with ethyl-5-amino-1-methyl-1H-pyrazole-4-carboxylate (L) is presented. The reaction of AgClO4 with the ligand in a molar ratio of 1:1 gives a bis(ligand) complex [AgL2]ClO4 (1) in the presence of 4-formylbenzonitrile, monoperiodic polymer {[AgL2]ClO4}n (2). Characterization involved IR spectroscopy, conductometric measurements, thermogravimetric analysis, antioxidant tests, powder, and single crystal X-ray diffraction. Structural analysis revealed ligand coordination in a monodentate manner through the nitrogen atom of the pyrazole ring in both complexes. Complex 1 displayed a linear coordination environment for Ag(I), whereas, in complex 2, square-planar coordination was achieved with the additional involvement of two oxygen atoms from bridging perchlorate anions. Notably, the thermal properties of both isomers are found to be nearly identical. The significant antioxidant activity of the isomer with a reverse-oriented pyrazole-type ligand suggests its potential relevance in biological studies. [ABSTRACT FROM AUTHOR]

C16H12N2O4, triclinic, P1̄ (no. 2), a = 10.7105(5) Å, b = 11.2685(5) Å, c = 13.0145(6) Å, α = 99.292(4)°, β = 109.607(4)°, γ = 96.771(4)°, V = 1435.01(12) Å3, Z = 4, Rgt(F) = 0.0427, wRref(F2) = 0.1124, T = 295(2) K.

The reaction of copper(II) nitrate and pyridoxal S-methylisothiosemicarbazone (PLITSC) in the presence of ammonium thiocyanate resulted in the formation of two types of complexes. A dimeric complex of the formula [Cu(-PLITSC)NCS2](NCS)2·2MeOH was obtained in the presence of excess of ammonium thiocyanate, while in the presence of its nearly equimolar amount, crystals of a polymeric complex [Cu(-PLITSC)NCS]NO3∙MeOHn were formed. The complexes were characterized by elemental analysis, conductometry, IR spectroscopy, and their structures are unequivocally determined by single crystal X-ray crystallography. In both complexes, the copper atom is five-coordinated, situated in a deformed square-pyramidal environment. The basal plane of the square pyramid is defined by the oxygen atom of the deprotonated phenol group and terminal nitrogen atoms of the isothiosemicarbazide moiety of the Schiff base, as well as the nitrogen atom of the coordinated thiocyanate ion, while the apical site is occupied by the oxygen atom of the hydroxymethyl group of the neighboring asymmetric unit. This coordination mode of the PLITSC was hitherto unknown. A survey of the Cambridge Structural Database showed that the coordination of the hydroxymethyl group is rare within pyridoxal-based Schiff base metal complexes. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 172014 and Grant no. III41010]

The crystal structure of (E)-4-chloro-2-((pyridin-2-ylimino)-methyl)- phenol, recently published by Yıldırım et al. in J. Serb. Chem. Soc. 83 (2018) 707–721, is revised. Refinement of the new structural model against original X-ray diffraction data, deposited with the Cambridge Crystallographic Data Centre, proved that the compound studied by single crystal X-ray diffraction was actually (E)-4-chloro-2-((pyridin-3-ylimino)methyl)phenol.

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 NH4NCS 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. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 172014]

C22H18O10Zn, triclinic, P1̄ (no. 2), a = 7.9616(3) Å, b = 9.5386(3) Å, c = 14.2569(4) Å, α = 81.713(3)°, β = 82.724(3)°, γ = 73.103(3)°, V = 1021.03(6) Å3, Z = 2, Rgt(F) = 0.0223, wRref(F2) = 0.0603, T = 295(2) K.

Cobalt(III) complexes derived from thio- and selenosemicarbazone ligands have been studied to elucidate the nature and consequences of S to Se substitution on their possible biological activity. Solid state structures of cobalt(III) complexes with bis-tridentate coordinated 2-quinolinecarboxaldehyde thio- and selenosemicarbazone were determined by single crystal X-ray diffraction analysis. The complexes were also characterized by spectroscopic methods and cyclic voltammetry. Electronic properties of the complexes were studied using DFT and TD–DFT methods. Finally, evident in vitro antioxidant activity of the complexes was demonstrated. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 172035 and Grant no. 172055]

A terephthalate-bridged heteronuclear Cu(II)–Mn(II) complex [Cu2Mn(dipya)2(tpht)3]n, I, where dipya is 2,2′-dipyridylamine and tpht is the anion of 1,4-benzenedicarboxylic (terephthalic, H2tpht) acid was synthesized under hydrothermal conditions. The obtained complex I was characterized by a single-crystal X-ray diffraction, FTIR spectroscopy, TG/DSC analysis and magnetic measurements. The Cu(II) and Mn(II) metal centers adopt distorted octahedral geometry and they are linked by bridging tpht ligands. Two crystallographically different tpht anions are coordinated as tridentate and hexadentate ligands forming two-dimensional layers. The layers are interconnected by hydrogen bonds and additionally stabilized by non-covalent C–H···π interactions. The measurements of magnetic susceptibility proved that I is an almost perfect paramagnet. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. III45007]

Keywords: protulactone A; natural products; bicyclic lactones; medicinal chemistry; structure-activity relationship EN protulactone A natural products bicyclic lactones medicinal chemistry structure-activity relationship 1699 1703 5 08/18/23 20230901 NES 230901 Graph Fungi found in marine environments are an interesting source of biologically active compounds. This new approach also started from d -galactose, but instead of building the lactone ring at the beginning of the synthesis, we decided to build the rest of the molecule in the initial steps and to introduce the lactone ring in the final steps of the synthesis. [2] These two natural products were named protulactones A and B. The first total synthesis of (+)-protulactone A ( B PLA b ; Figure 1), the assignment of its configuration, and a preliminary study of its antiproliferative activity were described by the Gracza group in 2017. Protulactone A, natural products, bicyclic lactones, medicinal chemistry, structure-activity relationship. [Extracted from the article]