Search

The complex, trichlorido(1,4,11-triaza-8-azoniatetracyclo[6.6.2.04,16.011,15]hexadecane 1-oxide-κO)zinc(II) monohydrate, [ZnCl3(C12H23N4O)]·H2O, (I), has monoclinic symmetry (space group P21/n) at 120 K. The zinc(II) center adopts a slightly distorted tetrahedral coordination geometry and is coordinated by three chlorine atoms and the oxygen atom of the oxidized tertiary amine of the tetracycle. The amine nitrogen atom, inside the ligand cleft, is protonated and forms a hydrogen bond to the oxygen of the amine oxide. Additional hydrogen-bonding interactions involve the protonated amine, the water solvate oxygen atom, and one of the chloro ligands.

Due to the lack of new antimicrobial drug discovery in recent years and an ever-growing prevalence of multidrug-resistant “superbugs”, there is a pressing need to explore alternative ways to combat pathogenic bacterial and fungal infections. Building upon our previous work in the field of medicinal phytochemistry, the present study is focused on designing, synthesizing, and testing the altered bioactivity of new variants of two original bioactive molecules found in the Argemone mexicana plant. Herein, we report upon 14 variants of berberine and four variants of chelerythrine that have been screened against a pool of 12 microorganisms (five Gram-positive and four Gram-negative bacteria, and three fungi). Additionally, the crystal structures of two berberine variants are described. Several berberine variants show enhanced antibacterial activity compared to the unaltered plant-derived molecule. We also report promising preliminary tumor cytotoxicity effects for a number of the berberine derivatives.

Cancer resistance to chemotherapy and radiation therapies presents significant challenges, necessitating the exploration of alternative approaches. Targeting specific proteins at the molecular level, particularly their active sites, holds promise in addressing this issue. We investigated the potential of 4′-methoxy-2-nitrochalcone (MNC) as an MCL-1 inhibitor, examining its chemical and structural characteristics to elucidate its biological activity and guide the selection of potential candidates. We conducted a docking study, followed by synthesis, structural characterization, theoretical calculations, and in vitro experiments to comprehensively evaluate MNC. The docking results revealed MNC’s excellent binding within the active site of MCL-1. At 50 µM, MNC demonstrated 99% inhibition of HCT116 cell proliferation, with an IC50 value of 15.18 µM after 24 h. Treatment with MNC at 30.36 and 15.18 µM resulted in reduced cell density. Notably, MNC exhibited marked cytotoxicity at concentrations of 15.58 µM and 7.79 µM, inducing high frequencies of plasma membrane rupture and apoptosis, respectively. Our findings highlight the significant biological potential of MNC as an MCL-1 inhibitor. Furthermore, we propose exploring chalcones with hydrogen bond acceptor substituents as promising candidates for studying inhibitors targeting this protein. In conclusion, our study addresses the challenge of cancer resistance by investigating MNC as an MCL-1 inhibitor. Through detailed characterization and experimental validation, we establish the efficacof MNC in inhibiting cell proliferation and inducing cytotoxic effects. These results underscore the potential of MNC as a valuable therapeutic agent and suggest the use of chalcones with hydrogen bond acceptor substituents as a basis for developing novel MCL-1 inhibitors.

The complex, bis(N,N-diethyl-4-methyl-4-piperazine-1-carboxamide) tetrakis(isothiocyanato-κN)cobalt(II) (N,N-diethyl-4-methyl-4-piperazine-1-carboxamide = diethylcarbamazine), (C10H22N3O)2[Co(NCS)4], is presented. This complex is a blue precipitate, insoluble in water but soluble in organic solvents, that is formed from the reaction of diethylcarbamazine citrate, a protonated tertiary amine, with cobalt(II) and thiocyanate. This reaction, in the form of the Scott test, is a common presumptive test for cocaine hydrochloride. The known cobalt compound, [K2Co(NCS)4]·3H2O, has a deep-blue coloration due to the tetrahedral [Co(NCS)4]2− that is also present in the ion pair with bulky amines, and is similar to the color of other tetrahedral cobalt(II) complex ions, such as [CoCl4]2−. The structure is consistent with a previous proposal that a hydrophobic ion pair formed between [Co(NCS)4]2− and two protonated molecules of cocaine is responsible for the blue hydrophobic products formed by cocaine in the Scott test.

Three hexahydroquinoline derivatives were synthesized and crystallized in an effort to study the structure–activity relationships of these calcium-channel antagonists. The derivatives are ethyl 4-(2-methoxyphenyl)-2,7,7-trimethyl-5-oxo-1,4,5,6,7,8-hexahydroquinoline-3-carboxylate, C22H27NO4, (I), ethyl 4-(4-methoxyphenyl)-2,7,7-trimethyl-5-oxo-1,4,5,6,7,8-hexahydroquinoline-3-carboxylate, C22H27NO4, (II), and ethyl 4-(3,4-dihydroxyphenyl)-2,7,7-trimethyl-5-oxo-1,4,5,6,7,8-hexahydroquinoline-3-carboxylate, C21H24NO5, (III). In these hexahydroquinoline derivatives, common structural features such as a flat-boat conformation of the 1,4-dihydropyridine (1,4-DHP) ring, an envelope conformation of the fused cyclohexanone ring, and a substituted phenyl group at the pseudo-axial position are retained. Hydrogen bonds are the main contributors to the packing of the molecules in these crystals.

Twenty novel Mn, Fe, and Cu complexes of ethylene cross-bridged tetraazamacrocycles with potentially copolymerizable allyl and benzyl pendant arms were synthesized and characterized. Multiple X-ray crystal structures demonstrate the cis-folded pseudo-octahedral geometry forced by the rigidifying ethylene cross-bridge and show that two cis coordination cites are available for interaction with substrate and oxidant. The Cu complexes were used to determine kinetic stability under harsh acidic and high-temperature conditions, which revealed that the cyclam-based ligands provide superior stabilization with half-lives of many minutes or even hours in 5 M HCl at 50–90 °C. Cyclic voltammetry studies of the Fe and Mn complexes reveal reversible redox processes indicating stabilization of Fe2+/Fe3+ and Mn2+/Mn3+/Mn4+ oxidation states, indicating the likelihood of catalytic oxidation for these complexes. Finally, dye-bleaching experiments with methylene blue, methyl orange, and rhodamine B demonstrate efficient catalytic decolorization and allow selection of the most successful monomeric catalysts for copolymerization to produce future heterogeneous water purification materials.

The structure of tris(ethane-1,2-diamine-κ2N,N')cobalt(III) bis(iodide) triiodide, [Co(C2H8N2)3]I3(I)2, at 120 K has orthorhombic (P212121) symmetry. The diamine nitrogen atoms form N—H...I hydrogen bonds throughout the lattice, resulting in a three-dimensional network, which involves the iodide and all atoms in the triiodide anions.

The crystal structure of 1,3-dithiane 1,1,3,3-tetraoxide, C4H8O4S2, has been determined to examine the intermolecular C—H...O hydrogen bonds in a small molecule with highly polarized hydrogen atoms. The crystals are monoclinic, space group Pn, with a = 4.9472 (5), b = 9.9021 (10), c = 7.1002 (7) Å and β = 91.464 (3)° with Z = 2. The molecules form two stacks parallel to the a axis with the molecules being one a translation distance from each other. This stacking involves axial hydrogen atoms on one molecule and the axial oxygen atoms on the adjacent molecule in the stack. None of these C—H...O contacts is particularly short (all are > 2.4 Å). The many C—H...O contacts between the two stacks involve at least one equatorial hydrogen or oxygen atom. Again, no unusually short contacts are found. The whole crystal structure basically consists of a complex network of C—H...O contacts with no single, linear C—H...O contacts, only contacts that involve two (bifurcated), and mostly three or four neighbors.

Two MX2 (M = Ni, Zn; X = Cl, Br) dimethyl N-cyanodithioiminocarbonate compounds and one CrCl2 triphenylphosphine oxide complex were isolated and elucidated by single crystal X-ray crystallography. NiCl2[(CH3S)2C═NC≡N]2 (1) features inversion-related hydrogen bonded dimers linked into chains interacting through C-H···Cl growing layers along [110] whose junction into a 3D structure is enabled by H-bonds. ZnBr2[(CH3S)2C═NC≡N]2 (2) also exhibits inversion-related H-bonded dimers. In contrast with 1, the structure of 2 comprises chains along [110], connected via C-H···Br and C-H···S into a 2D layer along [-110]. CrCl2(OPPh3)2 (3) obtaining undergone redox processes, oxidizing [CH3C(O)CH2PPh3]+ to form PPh3PO, and reducing Cr from CrVI to CrII. In the structure, each molecule is linked to height neighbors through H-bonds affording a 3D network.

Tetraazamacrocycles, cyclic molecules with four nitrogen atoms, have long been known to produce highly stable transition metal complexes. Cross-bridging such molecules with two-carbon chains has been shown to enhance the stability of these complexes even further. This provides enough stability to use the resulting compounds in applications as diverse and demanding as aqueous, green oxidation catalysis all the way to drug molecules injected into humans. Although the stability of these compounds is believed to result from the increased rigidity and topological complexity imparted by the cross-bridge, there is insufficient experimental data to exclude other causes. In this study, standard organic and inorganic synthetic methods were used to produce unbridged dibenzyl tetraazamacrocycle complexes of Co, Ni, Cu, and Zn that are analogues of known cross-bridged tetraazamacrocycles and their transition metal complexes to allow direct comparison of molecules that are identical except for the cross-bridge. The syntheses of the known tetraazamacrocycles and the new transition metal complexes were successful with high yields and purity. Initial chemical characterization of the complexes was conducted by UV-Visible spectroscopy, while cyclic voltammetry showed more marked differences in electronic properties from bridged versions. Direct comparison studies of the unbridged and bridged compounds’ kinetic stabilities, as demonstrated by decomposition using high acid concentration and elevated temperature, showed that the cyclen-based complex stability did not benefit from cross-bridging. This is likely due to poor complementarity with the Cu2+ ion while cyclam-based complexes benefited greatly. We conclude that ligand–metal complementarity must be maintained in order for the topological and rigidity constraints imparted by the cross-bridge to contribute significantly to complex robustness.

Ethylene cross-bridged tetraazamacrocycles are known to produce kinetically stable transition metal complexes that can act as robust oxidation catalysts under harsh aqueous conditions. We have synthesized ligand analogs with single acetate pendant arms that act as pentadentate ligands to Mn, Fe, Co, Ni, Cu, and Zn. These complexes have been synthesized and characterized, including the structural characterization of four Co and Cu complexes. Cyclic voltammetry demonstrates that multiple oxidation states are stabilized by these rigid, bicyclic ligands. Yet, redox potentials of the metal complexes are modified compared to the “parent” ligands due to the pendant acetate arm. Similarly, gains in kinetic stability under harsh acidic conditions, compared to parent complexes without the pendant acetate arm, were demonstrated by a half-life seven times longer for the cyclam copper complex. Due to the reversible, high oxidation states available for the Mn and Fe complexes, the Mn and Fe complexes were examined as catalysts for the bleaching of three commonly used pollutant model dyes (methylene blue, methyl orange, and Rhodamine B) in water with hydrogen peroxide as oxidant. The efficient bleaching of these dyes was observed.

The crystal structures of two crystalline phases of 1,4-dithiane 1,1,4,4-tetraoxide, C4H8O4S2, have been determined in order to examine the nature of possible intermolecular hydrogen bonds. Phase 1 is monoclinic, space group C2/m, with unit-cell dimensions of a = 9.073 (8), b = 7.077 (6), c = 5.597 (5) Å and β = 105.89 (1)°. The molecule adopts 2/m symmetry and all of the molecules are related by translation and thus have the same orientation. Phase 2 is also monoclinic but in space group P21/n with unit-cell dimensions of a = 7.1305 (5), b = 5.7245 (4), c = 8.3760 (6) Å and β = 91.138 (2)°. In this phase, the molecule sits on an inversion center and the molecules within the unit cell adopt quite different orientations. In both phases, examination of the potential C—H...O hydrogen bonds around each of the independent oxygen atoms (one axial and the other equatorial) shows the general O...H patterns to be quite similar with each oxygen atom in contact with four neighboring H atoms, and each H atom contacting two neighboring O atoms. While none of the H...O contacts is particularly short (all are greater than 2.5 Å), each molecule has 32 such contacts that form an extensive intermolecular network. A 1H NMR spectrum of the compound dissolved in DMSO shows a singlet of 8H at δ 3.677 which indicates that the C—H bonds are only moderately polarized by the single adjacent –SO2– moiety: strongly polarized C—H bonds have δ values in the 5–6 range [Li & Sammes (1983). J. Chem. Soc. Perkin Trans. 1, pp. 1303–1309]. The phase 1 crystal studied was non-merohedrally twinned.

Chalcones belong to the flavonoids family and are natural compounds which show promising larvicidal property against Aedes aegypti larvae. Aiming to obtain a synthetic chalcone derivative with high larvicidal activity, herein, a bromochalcone derivative, namely (E)-3-(4-butylphenyl)-1-(4-bromophenyl)-prop-2-en-1-one (BBP), was designed, synthesized and extensively characterized by 1H- and 13C- nuclear magnetic resonance (NMR), infrared (IR), Raman spectroscopy, mass spectrometry (MS), ultraviolet–visible spectroscopy (UV-Vis), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and X-ray diffraction. Further, the quantum mechanics calculations implemented at the B3LYP/6–311+G(d)* level of the theory indicate that the supramolecular arrangement was stabilized by C–H⋯O and edge-to-face C–H⋯π interactions. The EGAP calculated (3.97 eV) indicates a good reactivity value compared with other similar chalcone derivatives. Furthermore, the synthesized bromochalcone derivative shows promising larvicidal activity (mortality up to 80% at 57.6 mg·L−1) against Ae. aegypti larvae.

The title compound, (C21H20OP)(C19H15N4)[CuCl4], was obtained by reacting CuCl2·2H2O with a mixture of one equivalent of acetonyltriphenylphosphonium chloride and one equivalent of 2,3,5-triphenyltetrazolium chloride in acetonitrile. In the structure, the Cu centre in the dianion is bonded to four chloride ligands and adopts a distorted tetrahedral geometry. The phosphonium cation likewise adopts the expected tetrahedral geometry. The tetrazolium ring forms dihedral angles of 77.68 (10), 26.85 (11) and 66.48 (10)° with the planes of the benzene rings of the substituent groups. In the crystal, weak C—H...Cl hydrogen-bonding interactions involving both cations and the anion give rise to a three-dimensional supramolecular structure.

The title complex, [Fe(C64H64N8O4)(C9H8N2)2](CF3O3S)·2C6H5Cl, has an unusual relative orientation of the two planar axial ligands [dihedral angle between the two imidazole planes = 46.55 (9)°]. The average equatorial Fe—N bond length is 1.974 (3) Å; the axial distances are 1.9628 (19) and 1.9932 (19) Å. The porphyrin core displays modest ruffling. Disorder is modeled for three of the tert-butyl groups of the pickets. In the crystal, a modest π–π interaction exists between adjacent phenyl rings related by an inversion center, and hydrogen bonds connect the trifluoromethanesulfonate oxygen atoms to the amide groups of the picket substituents.

In the asymmetric unit of the title compound, [CuBr(C18H18N4)]Br, there are three crystallographically independent cations. One of the cations exhibits positional disorder of the pyridin-2-ylmethyl groups over two sets of sites with refined occupancies of 0.672 (8) and 0.328 (8). The outer-sphere bromine counter-ion is severely disordered over multiple sites. In each cation, the CuII ion is coordinated by the four N atoms of the tris(pyridin-2-ylmethyl)amine ligand and one bromine and adopts a slightly distorted trigonal–bipyramidal geometry.

Two porphyrin complexes were studied to determine the effects of protonation on ring deformation within the porphyrin. The porphyrin 7,8,17,18-tetrabromo-5,10,15,20-tetraphenylporphyrin, C44H26Br4N4, was selected because the neutral species is readily doubly protonated to yield a dication, which was crystallized here with perchlorate counter-ions as a dichloromethane trisolvate, C44H28Br4N42+·2ClO4−·3CH2Cl2. The centrosymmetric neutral species is observed to have a mild `ruffling' of the pyrrole rings and is essentially planar throughout; intramolecular N—H...N hydrogen bonds occur. In contrast, the dication exhibits considerable deformation, with the pyrrole rings oriented well out of the plane of the porphyrin, resulting in a `saddle' conformation of the ring. The charged species forms N—H...O hydrogen bonds to the perchlorate anions, which lie above and below the plane of the porphyrin ring. Distortions to the planarity of the pyrrole rings in both cases are very minor. The characterization of the neutral species represents a low-temperature redetermination of the previous room-temperature analyses [Zou et al. (1995). Acta Cryst. C51, 760–761; Rayati et al. (2008). Polyhedron, pp. 2285–2290], which showed disorder and physically unrealistic displacement parameters.

The synthesis of the title hydrated complex salt, [Co(C6H14N2)3]Cl3·H2O, from racemic trans-1,2-diaminocyclohexane and [CoCl(NH3)5]Cl2 and its structural characterization are presented in this paper. The product was synthesized in the interest of understanding the hydrogen-bonding patterns of coordination complexes. Previous characterizations of the product in the I-42d space group have not yielded coordinates; thus, this paper provides the first coordinates for this complex in this space group. The octahedrally coordinated cation adopts twofold rotation symmetry, with outer-sphere chloride counter-ions and solvent water molecules forming a hydrogen-bonded network with amine H atoms.

The CuII atom in the title compound, [CuCl2(C14H21F3N4)], adopts a coordination geometry that is between distorted square-based pyramidal and very Jahn–Teller-elongated octahedral. It is coordinated by three N atoms from the bis(2-aminoethyl)(2-{[4-(trifluoromethyl)benzylidene]amino}ethyl)amine and two chloride ligands. The two crystallographically unique copper complexes present in the asymmetric unit exhibit noticeable differences in the coordination bond lengths. Considering the CuII atoms as having square-pyramidal geometry, the basal Cu—Cl bond lengths are typical [2.2701 (12) and 2.2777 (12) Å], while the apical distances are considerably elongated [2.8505 (12) and 2.9415 (12) Å]. For each molecule, a CuII atom from inversion-related molecules are in nearby proximity to the remaining axial CuII sites, but the Cu...Cl distances are very long [3.4056 (12) and 3.1645 (12) Å], attributable to van der Waals contacts. Nonetheless, these contacts appear to have some structure-directing properties, leading to association into dimers. These dimers associate via stacking of the aromatic rings to form extended zigzag chains.

In the structure of the title complex salt, (Et2NH2)2[CuCl4], the asymmetric unit consists of four unique diethylammonium cations and three unique tetrachloridocuprate anions. Two of the three anions are located with their copper atoms on independent crystallographic twofold axes, while the remaining tetrachloridocuprate is located at a general position of the orthorhombic space group P21212. Two of the three Cu atoms adopt a distorted square-planar/disphenoidal geometry and the third Cu atom has a regular square-planar coordination environment. The diethylammonium cations form an extensive hydrogen-bonded network through N—H...Cl interactions with the tetrachloridocuprate anions, resulting in a two-dimensional sheet-like hydrogen-bonded network parallel to the ab direction. The complex was observed to undergo a color shift from deep green at room temperature to pale yellow at temperatures above 328 K.

The crystal structure of the low-temperature monoclinic phase of the title compound, [(CH3)4N]2[CuCl4], was determined at 120 K. The structure of the room-temperature phase has been determined in the orthorhombic space group Pmcm [Morosin & Lingafelter (1961). J. Phys. Chem. 50–51; Clay et al. (1975). Acta Cryst. B31 289–290]. The asymmetric unit consists of one discrete tetrachloridocuprate anion with a distorted tetrahedral geometry and two tetramethylammonium cations. In the crystal, the cations and the anions are linked via weak C—H...Cl hydrogen bonds.

Slow co-crystallization of a solution of benzene-1,3,5-tricarboxylic acid with a large excess of 4-hydroxypyridine produces an interpenetrating, three-dimensional, hydrogen-bonded framework consisting of three 4-pyridone and one benzene-1,3,5-tricarboxylic acid molecules, C9H6O6·3C5H5NO. This structure represents an orthorhombic polymorph of the previously reported C-centered, monoclinic structure [Campos-Gaxiola et al. (2014). Acta Cryst. E70, o453–o454].

The title compound, C4H12N+·C6H6NO3S−·C6H7NO3S, consists of an ion pair and a zwitterionic neutral molecule. The cation adopts an extended conformation [C—C—N—C torsion angles = 177.1 (3) and −178.4 (3)°]. In the crystal, the components are linked by N—H...O and N—H...N hydrogen bonds, generating a three-dimensional network, which is consolidated by weak C—H...O interactions.

The SnIV atom in the centrosymmetric anion of the title salt, (C4H7N2)2[Sn2(C4H9)2(C2O4)Cl6], is coordinated in a distorted octahedral mode by two O atoms of a bridging oxalate moiety, three Cl atoms and a C atom of an n-butyl group. The latter is disordered over two sets of sites in a 0.66:0.33 occupancy ratio. N—H...O and N—H...Cl hydrogen bonds involving the 2-methylimidazolium cation and neighbouring anions result in the formation of chains extending parallel to [001].

The ZnII atom in the title complex, [ZnCl2(C4H6N2S2)2], is coordinated in a distorted tetrahedral manner by two Cl atoms and two terminal N atoms of two dimethyl N-cyanodithioiminocarbonate ligands. In the crystal, the complex molecules are connected through C—H...Cl hydrogen bonds and Cl...S contacts, leading to a two-dimensional structure extending parallel to the ab plane.

The almost planar (r.m.s. deviation = 0.055 Å) title compound, (MeS)C(O)NHC(O)NH2, was formed during an attempted crystallization of dimethyl cyanocarbonimidodithioate with CrO2Cl2; an unexpected redox reaction converted the cyanocarbonimido moiety to a urea group and removed one methylthiol group. In the crystal, hydrogen-bonding interactions from the amide and amido N—H groups to carbonyl O atoms of neighbouring molecules result in [010] ribbon-like chains.