Search

Presents a letter to the editor about an attempt to reconcile two perspectives of alternative stable states in ecosystems.

The synthesis and structures of dinuclear palladium complexes with 1,3-benz-imidazolidine-2-thione (bzimtH) and 1,3-imidazoline-2-thione (imtH) are reported, namely, bis-(μ-1 H -benzimidazole-2-thiol-ato)-κ 2 N 3 : S ;κ 2 S : N 3 -bis-[cyanido(tri-phenyl-phosphine-κ P )palladium(II)], [Pd 2 (C 7 H 5 N 2 S) 2 (CN) 2 (C 18 H 15 P) 2 ] or [Pd 2 (μ- N , S -bzimtH) 2 (CN) 2 (PPh 3 ) 2 ] ( 1 ), and bis-(μ-1 H -imidazole-2-thiol-ato)-κ 2 N 3 : S ;κ 2 S : N 3 -bis-[cyanido(tri-phenyl-phosphine-κ P )palladium(II)] aceto-nitrile 0.58-solvate, [Pd 2 (C 3 H 3 N 2 S) 2 (CN) 2 (C 18 H 15 P) 2 ]·0.58C 2 H 3 N or [Pd 2 (μ- N , S -imtH) 2 (CN) 2 (PPh 3 ) 2 ]·0.58C 2 H 3 N ( 2 ). The compound [Pd 2 (μ- N , S -bzimtH) 2 (CN) 2 (PPh 3 ) 2 ] is located on a crystallographic twofold axis while [Pd 2 (μ- N , S -imtH) 2 (CN) 2 (PPh 3 ) 2 ]. 0.58(C 2 H 3 N) contains two partially occupied aceto-nitrile solvent mol-ecules with occupancies of 0.25 and 0.33. In both of these compounds, the anionic bzimtH - and imtH - ligands coordinate through N,S-donor atoms in a bridging mode, covering four coordination sites of two metal centers and other two sites are occupied by two PPh 3 ligand mol-ecules. Finally, the remaining two sites of two metal centers are occupied by cyano groups, abstracted by the metals from the solvent during reaction. In the packing of the 1,3-benzimidazolidine- 2-thione and 1,3-imidazoline-2-thione complexes, there are intra-molecular π-π inter-actions involving the thione moiety as well as an N-H⋯N hydrogen bond linking the thione and cyano ligands. In addition, in 2 , as well as the π-π inter-action involving the thione moieties, there is an additional π-π inter-action involving one of the thione moieties and an adjacent phenyl ring from the tri-phenyl-phosphine ligand. There are also C-H⋯N inter-actions between the imidazoline rings and the aceto-nitrile N atoms., (© Lobana et al. 2023.)

Reaction of cyclohexanoneselenosemicarbazone with aldehydes and ketones containing heterocyclic rings (2-oxindole, 6-cholro-2-oxindole, 3-methyl-2-oxindole, isatin, 1-methyl isatin, furfural, pyrrole-2-carboxldehyde) in ethanol yielded, respective, selenosemicarbazones {2-oxindoleselenosemicarbazone (2-HOxsesc,H 1 L), 6-chloro-2-oxindole selenosemicarbazone (6-ClHOxsesc, H 2 L), 3-methyl-2-oxindole selenosemicarbazone (3-MeHOxses, H 3 L), isatinselenosemicarbazone (HIstsesc, H 4 L), 1-methyl isatinselenosemicarbazone (1-MeHIstsesc, H 5 L), 2-thiopheneselenosemicarbazone (2-Hthiosesc, H 6 L), 2-furfuralselenosemicarbazone (2-Hfursesc, H 7 L) and 2-pyrrole selenosemicarbazone (2-Hpysesc, H 8 L)}. However the similar reaction with aldehyde containing single aromatic ring (3-chlorobenzaldehyde and 4-chlorobenzaldehyde) formed 1, 2-bis(3-chlorobenzylidiene) hydrazine (A) and 1, 2-bis(4-chlorobenzylidiene) hydrazine (B) rather than selenosemicarbazone. All the synthesized compounds were characterized using IR and NMR ( 1 H, 13 C) spectroscopy. Structure of A and B were confirmed by single crystal X-ray crystallography. The synthesized selenosemicarbazones were tested for their anti-tubercular activities and H 1 L, H 3 L, H 5 L and H 6 L are found to exhibit excellent anti-TB activity. The experimental data will give an opportunity to examine their anti-tubercular activities and identify the lead molecule., (Copyright © 2022 Elsevier Inc. All rights reserved.)

The reaction of [Cu(CH 3 CN) 4 ](BF 4 ) with 1-methyl-1,3-imidazolidine-2-thione {SC 3 H 4 (NMe)NH}, under aerobic conditions at room temperature, yielded an unusual one-dimensional coordination polymer, namely, catena -poly[[[(1-meth-yl-1,3-imidazolidine-2-thione-κ S )copper(I)]-μ-(1-methyl-1,3-imidazolidine-2-thione)-κ 2 S : S -copper(I)-μ-[3,3'-(sulfanedi-yl)bis-(1-methyl-1,3-imidazolidine-2-thione)]-κ 5 S , S ', S '': S , S ''] bis-(tetra-fluorido-borate)], {[Cu 2 (C 4 H 8 N 2 S) 2 (C 8 H 14 N 4 S 3 )](BF 4 ) 2 } n or [Cu 4 (κ 5 : L 1 -N-S-N- L 1 ) 2 (κ 1 : L 1 -NH) 2 (κ 2 : L 1 -NH) 2 ] n (BF 4 ) 4 n 1 [ L 1 = SC 3 H 4 (NMe)NH] with sulfur-bridged {Cu I 4 S 10 } n central cores. The in situ generated bis-(1-methyl-1,3-imidazolidinyl-2-thione) sulfide [{SC 3 H 4 (NMe)NSN(NMe)C 3 H 4 S; abbrev. L 1 -N-S-N- L 1 ] ligand, in combin-ation with 1-methyl-1,3-imidazolidine-2-thione ( L 1 -NH) ligands, construct this coordination polymer. Each Cu I ion is bonded to four sulfur donor atoms in a distorted tetra-hedral geometry and the formation of this polymer solely by sulfur donor atoms with {Cu I 4 S 10 } n central cores, is the first such example in copper-heterocyclic-2-thione chemistry., (© Lobana et al. 2022.)

The goal of this study was to identify new compounds from a methanol extract of a polyherbal combination of Aristolochia indica L. and Piper nigrum L. (MECAIPN), two traditional medicinal plants used to cure envenomation, as well as to assess their antioxidant and antivenom properties. MECAIPN yielded EA1 (an essential oil), AA2 (4-(2-oxo-propyl)-cyclopentane-1,3-dione), and W3 ((2,5-dioxo-imidazolidin-4-yl)-urea) (Allantoin). Although EA1 had stronger radical scavenging activity, AA2 had higher DPPH and ferric ion radical scavenging activity, and W3 had higher molybdenum ion radical scavenging activity due to being a single molecule, the binding investigation revealed that EA1 has a greater Stern-Volmer quenching constant (Ksv) than AA2 and W3. Synchronous measurements indicated that EA1, AA2, and W3 bind to tryptophan and tyrosine residues in venom, causing denaturation of the secondary structure of the residue. Finally, the current study concludes that EA1 has more therapeutic antivenom potential, which could be related to the synergism of chemicals found in it. When it came to single compounds, AA2 had stronger antioxidant and antivenom capabilities than W3. To understand the mechanism of action and manufacture the green antivenom medication, more testing of the EA1 and compounds remains required., Competing Interests: The authors declare that there are no conflicts of interest., (Copyright © 2022 Dhivya Sivaraj et al.)

1,3-Dipolar cycloaddition of nonstabilized azomethine ylides derived from α-C-H functionalization of tetrahydroisoquinoline for regio- and diastereoselective synthesis of spirooxindole-pyrrolidines is developed. A three-component reaction of readily available cyclic amine, aryl aldehydes, and olefinic oxindoles provides a pot, atom and step economy (PASE) approach for making spiro-heterocyclic compounds with biological interest., Competing Interests: Conflicts of interest There are no conflicts to declare.

Syntheses are described for the blue/purple complexes of cobalt(II) chloride with the tetra-dentate ligands 1,4-bis-[2-(pyridin-2-yl)eth-yl]piperazine (Ppz), 1,4-bis-[2-(pyridin-2-yl)eth-yl]homopiperazine (Phpz), trans -2,5-dimethyl-1,4-bis-[2-(pyridin-2-yl)eth-yl]piperazine (Pdmpz) and tridentate 4-methyl-1-[2-(pyridin-2-yl)eth-yl]homopiperazine (Pmhpz). The CoCl 2 complexes with Ppz, namely, {μ-1,4-bis-[2-(pyridin-2-yl)eth-yl]piperazine}bis-[di-chlorido-cobalt(II)], [Co 2 Cl 4 (C 18 H 24 N 4 )] or Co 2 (Ppz)Cl 4 , and Pdmpz (structure not reported as X-ray quality crystals were not obtained), are shown to be dinuclear, with the ligands bridging the two tetra-hedrally coordinated CoCl 2 units. Co 2 (Ppz)Cl 4 and {di-chlorido-{4-methyl-1-[2-(pyridin-2-yl)eth-yl]-1,4-di-aza-cyclo-hepta-ne}cobalt(II) [CoCl 2 (C 13 H 21 N 3 )] or Co(Pmhpz)Cl 2 , crystallize in the monoclinic space group P 2 1 / n , while crystals of the penta-coordinate mono-chloro chelate 1,4-bis-[2-(pyr-id-in-2-yl)eth-yl]piperazine}chlorido-cobalt(II) perchlorate, [CoCl(C 18 H 24 N 4 )]ClO 4 or [Co(Ppz)Cl]ClO 4 , are also monoclinic ( P 2 1 ). The complex {1,4-bis-[2-(pyridin-2-yl)eth-yl]-1,4-di-aza-cyclo-hepta-ne}di-chlorido-cobalt(II) [CoCl 2 (C 19 H 26 N 4 )] or Co(Phpz)Cl 2 ( P ) is mononuclear, with a penta-coordinated Co II ion, and entails a Phpz ligand acting in a tridentate fashion, with one of the pyridyl moieties dangling and non-coordinated; its displacement by Cl - is attributed to the solvophobicity of Cl - toward MeOH. The penta-coordinate Co atoms in Co(Phpz)Cl 2 , [Co(Ppz)Cl] + and Co(Pmhpz)Cl 2 have substantial trigonal-bipyramidal character in their stereochemistry. Visible- and near-infrared-region electronic spectra are used to differentiate the two types of coordination spheres. TDDFT calculations suggest that the visible/NIR region transitions contain contributions from MLCT and LMCT character, as well as their expected d-d nature. For Co(Pmhpz)Cl 2 and Co(Phpz)Cl 2 , variable-temperature magnetic susceptibility data were obtained, and the observed decreases in moment with decreasing temperature were modelled with a zero-field-splitting approach, the D values being +28 and +39 cm -1 , respectively, with the S = 1/2 state at lower energy., (© Addison et al. 2022.)

The title compound, [Eu(C 9 H 10 BN 6 )(C 19 H 15 O 2 ) 2 (C 3 H 7 NO)] or [TpEu(Anthracac) 2 (DMF)], was synthesized by reaction of a tris-(pyrazol-yl)borate (Tp - ) Eu 3+ complex with 3-(anthracen-9-yl)pentane-2,4-dione (HAnthracac) in the presence of tri-ethyl-amine. In the title compound, Eu 3+ is located in an octa-vertex square-pyramidal coordination environment. In the two Anthracac - ligands, the anthracene and nearly planar acetyl-acetonate fragments are almost orthogonal. Neighboring mol-ecules of TpEu(Anthracac) 2 (DMF) are connected in the crystal by inter-molecular van der Waals inter-actions, while π-stacking inter-actions are limited to the edges of two anthracene rings., (© Mikhalyova et al. 2022.)

A pseudo-five-component reaction involving double decarboxylative 1,3-dipolar cycloaddition of azomethine ylides with olefinic oxindoles for the diastereoselective synthesis of bispiro[oxindole-pyrrolidine]s is developed. The major diastereomers are unique butterfly shaped compounds with a plane of symmetry. Recyclable zeolite HY acid catalyst is used to promote the reaction, and only CO 2 and H 2 O are generated as byproducts.

Structural analyses of the compounds di-μ-acetato-κ 4 O : O '-bis-{[2-meth-oxy- N , N -bis-(quinolin-2-ylmeth-yl)ethanamine-κ 4 N , N ', N '', O ]manganese(II)} bis-(tetra-phen-yl-borate) di-chloro-methane 1.45-solvate, [Mn 2 (C 23 O 2 ) 2 (C 23 H 23 N 3 O) 2 ](C 24 H 20 B)·1.45CH 2 Cl 2 or [Mn(DQMEA)(μ-OAc) 2 Mn(DQMEA)](BPh 4 ) 2 ·1.45CH 2 Cl 2 or [1] (BPh 4 ) 2 ·1.45CH 2 Cl 2 , and (acetato-κ O )[2-hy-droxy- N , N -bis(quinolin-2-ylmeth-yl)ethanamine-κ 4 N , N ', N '', O ](methanol-κ O )manganese(II) tetra-phenyl-borate methanol monosolvate, [Mn(CH 3 COO)(C 22 H 21 N 3 O)(CH 3 OH)](C 24 H 20 B)·CH 3 OH or [Mn(DQEA)(OAc)(CH 3 OH)]BPh 4 ·CH 3 OH or [2] BPh 4 ·CH 3 OH, by single-crystal X-ray diffraction reveal distinct differences in the geometry of coordination of the tripodal DQEA and DQMEA ligands to Mn II ions. In the asymmetric unit, compound [1] (BPh 4 ) 2 ·(CH 2 Cl 2 ) 1.45 crystallizes as a dimer in which each manganese(II) center is coordinated by the central amine nitro-gen, the nitro-gen atom of each quinoline group, and the meth-oxy-oxygen of the tetra-dentate DQMEA ligand, and two bridging-acetate oxygen atoms. The symmetric Mn II centers have a distorted, octa-hedral geometry in which the quinoline nitro-gen atoms are trans to each other resulting in co-planarity of the quinoline rings. For each Mn II center, a coordinated acetate oxygen participates in C-H⋯O hydrogen-bonding inter-actions with the two quinolyl moieties, further stabilizing the trans structure. Within the crystal, weak π - π stacking inter-actions and inter-molecular cation-anion inter-actions stabilize the crystal packing. In the asymmetric unit, compound [2] BPh 4 ·CH 3 OH crystallizes as a monomer in which the manganese(II) ion is coordinated to the central nitro-gen, the nitro-gen atom of each quinoline group, and the alcohol oxygen of the tetra-dentate DQEA ligand, an oxygen atom of OAc, and the oxygen atom of a methanol ligand. The geometry of the Mn II center in [2] BPh 4 ·CH 3 OH is also a distorted octa-hedron, but the quinoline nitro-gen atoms are cis to each other in this structure. Hydrogen bonding between the acetate oxygen atoms and hydroxyl (O-H⋯O) and quinolyl (C-H⋯O and N-H⋯O) moieties of the DQEA ligand stabilize the complex in this cis configuration. Within the crystal, dimerization of complexes occurs by the formation of a pair of inter-molecular O3-H3⋯O2 hydrogen bonds between the coordinated hydroxyl oxygen of the DQEA ligand of one complex and an acetate oxygen of another. Additional hydrogen-bonding and inter-molecular cation-anion inter-actions contribute to the crystal packing., (© Frey et al. 2021.)

The basic purpose of this investigation was to explore the effect on antimicrobial activity of a nitro group at an ortho- versus para-position in the 2-hydroxy-phenyl ring of nitro-salicylaldehyde-N-substituted thiosemicarbazone (X-NO2-stscH2-N1HR, X = 3 or 5; stsc-stands for salicyladehyde thiosemicarbazone) complexes with zinc. Reactions of zinc(ii) acetate with 3-nitro-salicylaldehyde-N-substituted thiosemicarbazones (3-NO2-stscH2-N1HR) and 2,2-bipyridine, or 1,10-phenanthroline as co-ligands, yielded complexes of stoichiometry, [Zn(3-NO2-stsc-N1HR)(N,N-L)] {L, R: bipy, H, 1; Me, 2; Et, 3; Ph, 4; phen, H, 5; Me, 6; Et, 7; Ph, 8}. The thio-ligands coordinate to the metal as dianions (deprotonation of -OH and -N2H moieties) through O, N3 and S donor atoms in distorted trigonal bipyramid geometry (4, 5, 7: τ = 0.718-0.576) or in distorted square pyramid geometry (8: τ = 0.349). ESI-mass spectrometry supported the formation of molecular ion peaks. Complexes displayed fluorescence with λmax = 438-473 nm. It was found that these five-coordinated [Zn(3-NO2-stsc-N1HR)(N,N-L)] complexes showed high antimicrobial activity against methicillin resistant S. aureus (MRSA), Klebsiella pneumoniae 1, Salmonella typhimurium 2 and C. albicans vis-à-vis that of 5-NO2-stscH2-N1HR zinc complexes reported earlier. However, in comparison, the antimicrobial activity of 5-nitro complexes against S. aureus was high relative to 3-nitro complexes in the present case.

In the title compounds C 23 H 21 ClN 2 O 3 [ I , namely 1-(4-chloro-phen-yl)-4-(4-methyl-phen-yl)-3,8-dioxo-1,2,5,6,7,8-hexa-hydro-quine-3-carb-oxy-lic acid] and C 24 H 22 N 2 O 3 [ II , namely 4-(4-meth-oxy-phen-yl)-1-(4-methyl-phen-yl)-2,5-dioxo-1,2,5,6,7,8-hexa-hydro-quinoline-3-carbo-nitrile], each of the cyclo-hexene and di-hydro-pyridine rings of the 1,2,5,6,7,8-hexa-hydro-quinoline moieties adopts a twisted-boat conformation. The asymmetric units of both compounds I and II consist of two independent mol-ecules ( A and B ). In II A , three carbon atoms of the cyclo-hexene ring are disordered over two sets of sites in a 0.670 (11):0.330 (11) occupancy ratio. In the crystal of I , mol-ecules are linked through classical N-H⋯O hydrogen bonds, forming inversion dimers with an R 2 2 (8) ring motif and with their mol-ecular planes parallel to the crystallographic (020) plane. Non-classical C-H⋯O hydrogen-bonding inter-actions connect the dimers, resulting in a three-dimensional network. In the crystal of II , mol-ecules are linked by C-H⋯N, C-H⋯O and C-H⋯π inter-actions, forming a three-dimensional network., (© Allah et al. 2021.)

In the title compound, C 27 H 33 NO 5 , a 3,3,6,6-tetra-methyl-tetra-hydro-acridine-1,8-dione ring system carries an ethyl acetate substituent on the acridine N atom and an o -hy-droxy-phenyl ring on the central methine C atom of the di-hydro-pyridine ring. The benzene ring is inclined to the acridine ring system at an angle of 80.45 (7)° and this conformation is stabilized by an intra-molecular O-H⋯O hydrogen bond between the hy-droxy substituent on the benzene ring and one of the carbonyl groups of the acridinedione unit. The ester C=O oxygen atom is disordered over major and minor orientations in a 0.777 (9):0.223 (9) ratio and the terminal -CH 3 unit of the ethyl side chain is disordered over two sets of sites in a 0.725 (5): 0.275 (5) ratio. In the crystal, C-H⋯O hydrogen bonds combine to link the mol-ecules into a three-dimensional network. van der Waals H⋯H contacts contribute the most to the Hirshfeld surface (66.9%) followed by O⋯H/H⋯O (22.1%) contacts associated with weak hydrogen bonds., (© Allah et al. 2021.)

A reaction of copper(i) halides (X = I, Br, Cl) and silver(i) halides with 9-anthraldehyde thiosemicarbazone (9-Hanttsc, H1L) and triphenylphosphine produced halogen-bridged dinuclear complexes, [M2(μ2-X)2(η1-S-9-Hanttsc)2(Ph3P)2] (M = Cu, X = Cl, 1; Br, 2; I, 3; M = Ag, X = Cl, 4; Br, 5). A similar reaction of 9-anthraldehyde-N1-methyl thiosemicarbazone (9-Hanttsc-N1-Me, H2L) with Ph3P and silver(i) halides yielded sulfur-bridged dimers, [Ag2X2(μ2-S-9-Hanttsc-N1-Me)2(Ph3P)2] (X = Cl, 9; Br, 10), however with copper(i) halides insoluble compounds were formed, which upon the addition of one extra mole of Ph3P gave mononuclear complexes of the formula [CuX(η1-S-9-Hanttsc-N1-Me)(Ph3P)2] (X = Cl, 6; Br, 7; I, 8). All of the complexes have been characterized by elemental analysis, NMR (1H, 13C) spectroscopy and single crystal X-ray crystallography (2, 5, 6, and 9). Both the ligands (H1L and H2L) and their complexes (1-10) were tested for their anti-tubercular and anticancer activities. The interactions of the ligands and their complexes (copper and silver) with calf thymus DNA (ct-DNA) and human serum albumin (HSA) were examined through UV-visible and fluorescence spectroscopy. Results showed that copper complex 2 displayed strong interactions with ct-DNA and HSA having binding constant values of 6.66 × 104 M-1 and 3.28 × 104 M-1, respectively, followed by silver complex 10 which gave binding constant values of 4.60 × 104 M-1 and 3.06 × 104 M-1, respectively. All of the complexes also showed good interactions with DNA in docking studies.

The basic aim of this study pertains to developing antimicrobial or anticancer agents based on N, S-donor organic ligands bonded to metals. In the present investigation, di-2-pyridylketone-N 1 -substituted thiosemicarbazone (py 2 tscH-N 1 HR 2 , Chart 2) thio-ligands were reacted with copper(I) halides in organic solvents yielding copper(II) complexes of stoichiometry, [Cu(N,N,S-py 2 tsc-N 1 HR 2 )X] (X = I, R 2  = H, 1; Me, 2; Et, 3; Ph, 4; X = Br, R 2  = H, 5; Me, 6; Et, 7; Ph, 8; X = Cl, R 2  = H, 9; Me, 10; Et, 11; Ph, 12); the formation of Cu II probably occurs through a proton coupled electron transfer (PCET) process. Electron spin resonance, ultraviolet-visible spectroscopy and X-ray crystallography (2, 3, 5, 7, 11) supported a distorted square planar geometry of these complexes. Moderate to high antimicrobial activities of these complexes against methicillin resistant Staphylococcus aureus, Gram positive bacteria, Staphylococcus aureus and Gram negative bacteria, Klebsiella pneumoniae 1, Salmonella typhimurium 2 and one yeast Candida albicans were recorded. Complexes were found to be biosafe with 88-91% cellular viability. All complexes have shown high anticancer activity against the immortalized L6 rat skeletal muscle cell line with very low IC 50 values., (Copyright © 2020 Elsevier Inc. All rights reserved.)

The structure of the title compound, [CoCl 2 (C 19 H 27 N 7 S 2 )(H 2 O)], at 173 K has monoclinic ( C 2/ c ) symmetry. We report here the synthesis, single-crystal structure, electrospray mass spectrum and NMR spectroscopy of a new six-coordinate cobalt(II) pincer complex. The pincer ligand, in this complex, which is novel, coordinates via three nitro-gen atoms (two triazole and one pyridine). The ligand is ambidentate and can coordinate via three nitro-gen atoms or two sulfur and one nitro-gen atoms. The cobalt(II) metal center has pseudo-octa-hedral geometry and based on the single-crystal structure, the pincer ligand coordinates in a meridional fashion with the metal and adjacent six-membered ring ligands all in a similar plane and forming two slightly distorted boat configurations. The other two coordinated monodentate ligands are one water mol-ecule and two chloride ions with four cobalt(II) complexes in the unit cell. The asymmetric unit of the complex is comprised of half the pyridine ring and water mol-ecule with the Co II atom at the center of the pincer situated about a twofold axis. The Co-N, Co-O, and Co-Cl bond lengths are consistent with single bonds. In the crystal, the complex forms a three-centre bifurcated weak hydrogen-bonding inter-action with a chlorine ion, forming one inter-molecular inter-action with the pincer group and a water mol-ecule and a second intra-molecular inter-action with a C-H group within the pincer group. Crystal packing is also highlighted with C 2 2 (6)> a < a infinite chains forming along [001] supported by R 2 2 (8)> a > a ring motifs, forming a three-dimensional supra-molecular network structure. While some stacking of the pyridine rings in the unit cell is observed, there are no relevant π-π inter-actions in the crystal packing. The 1 H and 13 C{ 1 H} NMR spectra of the complex are consistent with a plane of symmetry being present. The electrospray mass spectrum, which was collected in positive ion mode, showed the loss of one water mol-ecule and one chloride ligand from the complex. In the future, we plan to screen this cobalt(II) complex for electrocatalysis reactivity., (© Miecznikowski et al. 2020.)

In the title salt, [Ni(C 5 H 12 N 2 ) 2 (H 2 O) 2 ]Cl 2 , the asymmetric unit is comprised of half of the complex cation and a chloride ion with the Ni II atom of the cation situated about a twofold rotation axis. The six-coordinate Ni II atom of the cation is connected to four N atoms from two methyl-substituted ethyelenedi-amine ligands and two water mol-ecules in a slightly distorted octa-hedral environment. The five-membered chelate ring is in a slight envelope conformation. The crystal packing features O-H⋯Cl and N-H⋯Cl inter-molecular inter-actions with the Cl - ion forming weak bifurcated hydrogen bonds with nearby water mol-ecules and N-H inter-actions, leading to a three-dimensional supra-molecular network structure., (© Miecznikowski et al. 2020.)

A series of tris(pyrazolyl)borate mono-, di- and trinuclear complexes, [Tp 2 Ln] n X (Ln = Eu, Tb, Gd, Dy, X n- = various mono-, bis- and tris(β-diketonates) has been prepared. The Tb 3+ and Dy 3+ complexes are luminescent single molecular magnets (SMM) and exhibit luminescence quantum efficiencies up to 73% for the Tb 3+ and 4.4% for the Dy 3+ compounds. Similar Eu 3+ complexes display bright emission only at lower temperatures. The Dy 3+ and Tb 3+ complexes possess SMM behavior in a non-zero dc field at low temperatures, while the polynuclear Dy 3+ complexes also show slow magnetic relaxation even in zero dc field up to 8 K. U eff -values determined from dynamic magnetic measurements were up to 31 and 6 cm -1 for the Dy 3+ and Tb 3+ complexes, respectively. It was found that within a series of Dy 3+ and Tb 3+ compounds, U eff and luminescence quantum yields decreased with increasing nuclearity of the compounds and a shortening of the intramolecular Ln-Ln distance. Δ Orbach -values estimated from low-temperature luminescence spectra were significantly higher than those obtained from ac magnetic data, which may be due to involvement of additional processes in the relaxation mechanism (quantum tunneling, Raman, direct) reducing the energy barrier. Some of the Tb 3+ -compounds also display metal-centred electroluminescence, giving them potential as emitting layers in LEDs.

The interest in the present study pertains to the development of a new compound based upon a benzimidazole thiourea moiety that has unique properties related to elastase inhibition, free radical scavenging activity and its DNA binding ability. The title compound, N -(4-(1 H -benzo[ d ]imidazol-2-yl)phenyl)-3-benzoyl thiourea (C 21 H 18 N 4 O 2 SH 2 O:TUBC), was synthesized by reacting an acid chloride of benzoic acid with potassium thiocyanate (KSCN) along with the subsequent addition of 4-(1 H -benzo[ d ]imidazol-2-yl)benzenamine via a one-pot three-step procedure. The structure of the resulting benzimidazole based thiourea was confirmed by spectroscopic techniques including FTIR, 1 H-NMR, 13 C-NMR and single crystal X-ray diffraction and further examined by Hirshfeld surface analysis. TUBC was also investigated by using both in silico methodology including molecular docking for elastase inhibition along with quantum chemical studies and in vitro experimental methodology utilizing elastase inhibition and free radical scavenging assay along with DNA binding experiments. Docking results confirmed that TUBC binding was within the active region of elastase. In comparison to the reference drug oleanolic acid, the low IC 50 value of TUBC also indicated its high tendency towards elastase inhibition. TUBC scavenged 80% of DPPH˙ radicals which pointed towards its promising antioxidant activity. TUBC-DNA binding by DFT, docking, UV-visible spectroscopy and viscosity measurements revealed TUBC to be a potential drug candidate that binds spontaneously and reversibly with DNA via a mixed binding mode. All theoretical and experimental findings pointed to TUBC as a potential candidate for a variety of biological applications., Competing Interests: The authors would like to declare that there is no established conflict of interest., (This journal is © The Royal Society of Chemistry.)

The title compound, C 21 H 23 F 2 NO, consists of two fluoro-phenyl groups and one butyl group equatorially oriented on a piperidine ring, which adopts a chair conformation. The dihedral angle between the mean planes of the phenyl rings is 72.1 (1)°. In the crystal, N-H⋯O and weak C-H⋯F inter-actions, which form R 2 2 [14] motifs, link the mol-ecules into infinite C (6) chains propagating along [001]. A weak C-H⋯π inter-action is also observed. A Hirshfeld surface analysis of the crystal structure indicates that the most significant contributions to the crystal packing are from H⋯H (53.3%), H⋯C/C⋯H (19.1%), H⋯F/F⋯H (15.7%) and H⋯O/O⋯H (7.7%) contacts. Density functional theory geometry-optimized calculations were compared to the experimentally determined structure in the solid state and used to determine the HOMO-LUMO energy gap and compare it to the UV-vis experimental spectrum., (© Anitha et al. 2020.)

In the title compound, C 14 H 11 ClN 2 O 2 S, the dihedral angle between the pyrrolo-[1,2- c ]pyrimidine ring system (r.m.s. deviation = 0.008 Å) and the benzene ring is 80.2 (9)°. In the crystal, inversion dimers linked by pairs of C-H⋯O inter-actions generate R 2 2 (16) loops. Several aromatic π-π stacking inter-actions between the pyrrolo-[1,2- c ]pyrimidine rings, as well as separately between the pyrrolo and pyrimidine groups [shortest centroid-centroid separation = 3.5758 (14) Å], help to consolidate the packing., (© Narayan et al. 2020.)

Chemical model complexes are prepared to represent the active site of an enzyme. In this protocol, a family of tridentate pincer ligand precursors (each possessing two sulfur and one nitrogen donor atom functionalities (SNS) and based on bis-imidazole or bis-triazole compounds) are metallated with CoCl2·6H2O to afford tridentate SNS pincer cobalt(II) complexes. Preparation of the cobalt(II) model complexes for liver alcohol dehydrogenase is facile. Based on a quick color change upon adding the CoCl2·6H2O to acetonitrile solution that contains the ligand precursor, the complex forms rapidly. Formation of the metal complex is complete after allowing the solution to reflux overnight. These cobalt(II) complexes serve as models for the zinc active site in liver alcohol dehydrogenase (LADH). The complexes are characterized using single crystal X-ray diffraction, electrospray mass spectrometry, ultra-violet visible spectroscopy, and elemental analysis. To accurately determine the structure of the complex, its single crystal structure must be determined. Single crystals of the complexes that are suitable for X-ray diffraction are then grown via slow vapor diffusion of diethyl ether into an acetonitrile solution that contains the cobalt(II) complex. For high quality crystals, recrystallization typically takes place over a 1 week period, or longer. The method can be applied to the preparation of other model coordination complexes and can be used in undergraduate teaching laboratories. Finally, it is believed that others may find this recrystallization method to obtain single crystals beneficial to their research.

The asymmetric unit of O,O'-dimethyl [(2,3,4,5,6-pentafluorophenyl)hydrazinyl]phosphonate, C 8 H 8 F 5 N 2 O 3 P, is composed of two symmetry-independent molecules with significant differences in the orientations of the C 6 F 5 and OMe groups. In the crystal structure, a one-dimensional assembly is mediated from classical N-H...O hydrogen bonds, which includes R 2 2 (8), D(2) and some higher-order graph-set motifs. By also considering weak C-H...O=P and C-H...O-C intermolecular interactions, a two-dimensional network extends along the ab plane. The strengths of the hydrogen bonds were evaluated using quantum chemical calculations with the GAUSSIAN09 software package at the B3LYP/6-311G(d,p) level of theory. The LP(O) to σ*(NH) and σ*(CH) charge-transfer interactions were examined according to second-order perturbation theory in natural bond orbital (NBO) methodology. The hydrogen-bonded clusters of molecules, including N-H...O and C-H...O interactions, were constructed as input files for the calculations and the strengths of the hydrogen bonds are as follows: N-H...O [R 2 2 (8)] > N-H...O [D(2)] > C-H...O. The decomposed fingerprint plots show that the contribution portions of the F...H/H...F contacts in both molecules are the largest.

The basic aim of this study pertains to the synthesis of silver nitrate complexes and the study of their antimicrobial and anticancer bio-activity. A series of new silver(i) derivatives of N -substituted-imidazolidine-2-thiones (L-NR, R = Et, Pr n , Bu n , Ph), purine-6-thione (purSH 2 ), 2-thiouracil (tucH 2 ), pyrimidine-2-thione (pymSH) and pyridine-2-thione (pySH) of composition [Ag(S-L-NR)(PPh 3 ) 2 (ONO 2 )] {R = Et (1), Pr n (2), Bu n (3), Ph (4)}, [Ag 2 (N,S-purSH 2 ) 2 (μ-dppm) 2 ](NO 3 ) 2 ·2H 2 O (5) (dppm = Ph 2 P-CH 2 -PPh 2 ), [Ag(L)(PPh 3 ) 2 ](NO 3 ) {L = N,S-purSH 2 (6); S-tucH 2 (7)}, [Ag(N,S-pymS)(PPh 3 ) 2 ](CH 3 OH) (8), and [Ag(N,S-pyS)(PPh 3 ) 2 ] (9) have been synthesized and structurally characterized. These new and some previously reported complexes {[Ag 2 (L-NH) 4 (PPh 3 ) 2 ](NO 3 ) 2 (10), [Ag(L-NMe) 2 (PPh 3 )](NO 3 ) (11), and [Ag(S-bzimSH) 2 (PPh 3 ) 2 ](OAc) (12), L-NH = 1,3-imidazolidine-2-thione; L-NMe = 1-methyl-3-imidazolidine-2-thione and bzimSH 2 = benzimidazoline-2-thione)} have shown moderate to high anti-microbial activity against Gram positive bacteria, namely methicillin resistant Staphylococcus aureus (MRSA) and Staphylococcus aureus (MTCC 740), and Gram negative bacteria, namely Staphylococcus epidermidis (MTCC 435), Enterococcus faecalis (MTCC 439), Shigella flexneri (MTCC 1457) and a yeast Candida albicans (MTCC 22). These complexes have also been found to be bio-safe as studied using MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide] assay. The anti-tumor study of silver complexes against human osteosarcoma cell line (MG63) has shown IC 50 values in the range of 6-33 μM., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Nonstabilized azomethine ylides derived from decarboxylation of oxazolidin-5-ones were used for double 1,3-dipolar cycloadditions in diastereoselective synthesis of pyrrolidine-containing tetracyclic compounds. This is the first example of one-pot and five-component reactions involving two nonstabilized azomethine ylides. Only CO 2 and water were generated as byproducts.

The title compound, C 17 H 18 N 2 O 3 , is constructed from a benzodiazepine ring system linked to a pendant di-hydro-pyran ring, where the benzene and pendant di-hydro-pyran rings are oriented at a dihedral angle of 15.14 (4)°. Intra-molecular N-H Diazp ⋯O Dhydp and C-H Diazp ⋯O Dhydp (Diazp = diazepine and Dhydp = di-hydro-pyran) hydrogen bonds link the seven-membered diazepine ring to the pendant di-hydro-pyran ring, enclosing S (6) ring motifs. In the crystal, N-H Diazp ⋯O Dhydp hydrogen bonds link the mol-ecules into infinite chains along [10]. These chains are further linked via C-H Bnz ⋯O Dhydp , C-H Dhydp ⋯O Dhydp and C-H Mth ⋯O Dhydp (Bnz = benzene and Mth = meth-yl) hydrogen bonds, forming a three-dimensional network. The observed weak C-H Diazp ⋯ π inter-action may further stabilize the structure. Hirshfeld surface analysis of the crystal structure indicates that the most important contributions for the crystal packing are from H⋯H (51.1%), H⋯C/C⋯H (25.3%) and H⋯O/O⋯H (20.3%) inter-actions. Hydrogen bonding and van der Waals inter-actions are the dominant inter-actions in the crystal packing.

Sequential inter- and intramolecular [3 + 2] cycloadditions of azomethine ylides are developed for the one-pot and diastereoselective synthesis of highly condensed heterocyclic systems containing pyrrolidine and up to seven stereocenters. It has high synthetic efficiency and operational simplicity, and only water was generated as a byproduct.

The title compound, C 13 H 16 N 2 O 4 , crystallizes in the monoclinic centrosymmetric space group, P 2 1 / c , with four mol-ecules in the asymmetric unit, thus there is no crystallographically imposed symmetry and it is a racemic mixture. The structure consists of a six-membered unsaturated ring bound to a five-membered pyrrolidine-2,5-dione ring N-bound to a six-membered piperidine-2,6-dione ring and thus has the same basic skeleton as thalidomide, except for the six-membered unsaturated ring substituted for the aromatic ring. In the crystal, the mol-ecules are linked into inversion dimers by R 2 2 (8) hydrogen bonding involving the N-H group. In addition, there are bifurcated C-H⋯O inter-actions involving one of the O atoms on the pyrrolidine-2,5-dione with graph-set notation R 1 2 (5). These inter-actions along with C-H⋯O inter-actions involving one of the O atoms on the piperidine-2,6-dione ring link the mol-ecules into a complex three-dimensional array. There is pseudomerohedral twinning present which results from a 180° rotation about the [100] reciprocal lattice direction and with a twin law of 1 0 0 0 0 0 0 [BASF 0.044 (1)].

Structures are reported for eight Schiff bases derived from various salicylaldehydes: five are newly synthesized and re-investigations are reported for three previously reported structures, leading, in each case, to some revision of previous conclusions. In (E)-N-(3,4-dimethylisoxazol-5-yl)-4-[(2-hydroxybenzylidene)amino]benzenesulfonamide, C 18 H 17 N 3 O 4 S, (I), and (E)-4-[(5-bromo-2-hydroxy-3-methoxybenzylidene)amino]-N-(3,4-dimethylisoxazol-5-yl)benzenesulfonamide. C 19 H 18 BrN 3 O 5 S, (II), the isoxazole rings adopt different orientations relative to the rest of the molecules, despite the additional substituents in (II) being in the aryl ring remote from the isoxazole unit. The molecules of both (E)-4-bromo-2-[(2-hydroxyphenylimino)methyl]-6-methoxyphenol, C 14 H 12 BrNO 3 , (III), and (E)-4-bromo-2-methoxy-6-[(2-methoxyphenylimino)methyl]phenol, C 15 H 14 BrNO 3 , (IV), are both effectively planar; while (III) adopts the phenol-imine constitution, (IV) adopts the keto-amine constitution. (E)-2-Methoxy-6-[(2-methoxyphenylimino)methyl]phenol, C 15 H 15 NO 3 , (V), which was determined previously using powder X-ray data assuming the phenol-imine constitution, has now been refined from single-crystal X-ray data, confirming the phenol-imine constitution. In (E)-3-benzoyl-2-[(5-fluoro-2-hydroxybenzylidene)amino]-4,5,6,7-tetrahydrobenzo[b]thiophene, C 22 H 18 FNO 2 S, (VI), the fused carbocyclic ring exhibits conformational disorder; both disorder components, having populations of 0.705 (4) and 0.295 (4), adopt half-chair conformations. The isostructural (E)-3-benzoyl-2-[(2-hydroxybenzylidene)amino)]-4,5,6,7-tetrahydrobenzo[b]thiophene, C 22 H 19 NO 2 S, (VII), which was originally reported as having a fully ordered structure [Kaur et al. (2014). Acta Cryst. E70, o476-o477], has been rerefined using the original data set and found to exhibit the same type of disorder as found in (VI), with disordered populations having occupancies of 0.851 (3) and 0.149 (3). The triclinic polymorph of (E)-[(2-hydroxyphenylimino)methyl]phenol, C 13 H 11 NO 2 , (VIII), which crystallizes with Z' = 2 in the space group P-1, has been described variously as occurring as the keto-amine tautomer [Maciejewska et al. (1999). J. Phys. Org. Chem. 12, 875-880] and as the phenol-imine tautomer [Tunç et al. (2009). J. Chem. Crystallogr. 39, 672-676]. Rerefinement of this structure using one of the original data sets shows that both of the independent molecules exist in the keto-amine form. In the structures of compounds (I), (VI), (VII) and (VIII), hydrogen bonds generate simple chains, while a chain of rings is formed in (V). Sheets are formed by hydrogen bonds in both (II) and (III), while in (IV), the sheet structure is built from aromatic π-π stacking interactions.

A series of monomeric tetrahedral complexes of stoichiometry, [MX(HL)(Ph 3 P) 2 ] (In case of M = Cu, H 1 L, X = I, 1; Br, 2; Cl, 3; H 3 L, X = I, 4; Br, 5; Cl, 6; H 4 L, X = I, 7; Br, 8; Cl, 9 and in case of M = Ag, H 1 L, X = Cl, 13; Br, 14; H 2 L, X = Cl, 15, Br 16; H 3 L, X = Cl, 17, Br, 18) were synthesized by the reaction of copper (I) or silver (I) halides with indole-3-thiosemicarbazone (H 1 L) or 5-methoxy indole-3-thiosemicarbazone (H 2 L) or 5-methoxy indole-N 1 -methyl-3-thiosemicarbazone (H 3 L), whereas dimers of stoichiometry, [Cu 2 (μ-X) 2 (η 1 -S-H 2 L) 2 (Ph 3 P) 2 ] (X = I, 10; Br, 11; Cl, 12) were obtained by the reaction of copper (I) halides with indole-N 1 -methyl-3-thiosemicarbazone (HIntsc-N 1 -Me, H 2 L). The synthesized complexes were characterized using NMR ( 1 H and 13 C) and single crystal X-ray diffraction (H 2 L, 3, 7, 8, 10, 11 and 13) as well as elemental analysis. Anti- M. tuberculosis activity of ligands (H 1 L-H 4 L) and their metal complexes (1-18) were evaluated against M. tuberculosis H37RV strain ATCC 27294. It has been observed that there is unusual enhancement in anti TB activity of these ligands on complexation with copper (I) and silver (I). Molecular modelling studies in the active binding site are also giving complementary theoretical support for the experimental biological data acquired., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Two series of a total of ten cocrystals involving 4-amino-5-chloro-2,6-dimethylpyrimidine with various carboxylic acids have been prepared and characterized by single-crystal X-ray diffraction. The pyrimidine unit used for the cocrystals offers two ring N atoms (positions N1 and N3) as proton-accepting sites. Depending upon the site of protonation, two types of cations are possible [Rajam et al. (2017). Acta Cryst. C73, 862-868]. In a parallel arrangement, two series of cocrystals are possible depending upon the hydrogen bonding of the carboxyl group with position N1 or N3. In one series of cocrystals, i.e. 4-amino-5-chloro-2,6-dimethylpyrimidine-3-bromothiophene-2-carboxylic acid (1/1), 1, 4-amino-5-chloro-2,6-dimethylpyrimidine-5-chlorothiophene-2-carboxylic acid (1/1), 2, 4-amino-5-chloro-2,6-dimethylpyrimidine-2,4-dichlorobenzoic acid (1/1), 3, and 4-amino-5-chloro-2,6-dimethylpyrimidine-2-aminobenzoic acid (1/1), 4, the carboxyl hydroxy group (-OH) is hydrogen bonded to position N1 (O-H...N1) of the corresponding pyrimidine unit (single point supramolecular synthon). The inversion-related stacked pyrimidines are doubly bridged by the carboxyl groups via N-H...O and O-H...N hydrogen bonds to form a large cage-like tetrameric unit with an R 4 2 (20) graph-set ring motif. These tetrameric units are further connected via base pairing through a pair of N-H...N hydrogen bonds, generating R 2 2 (8) motifs (supramolecular homosynthon). In the other series of cocrystals, i.e. 4-amino-5-chloro-2,6-dimethylpyrimidine-5-methylthiophene-2-carboxylic acid (1/1), 5, 4-amino-5-chloro-2,6-dimethylpyrimidine-benzoic acid (1/1), 6, 4-amino-5-chloro-2,6-dimethylpyrimidine-2-methylbenzoic acid (1/1), 7, 4-amino-5-chloro-2,6-dimethylpyrimidine-3-methylbenzoic acid (1/1), 8, 4-amino-5-chloro-2,6-dimethylpyrimidine-4-methylbenzoic acid (1/1), 9, and 4-amino-5-chloro-2,6-dimethylpyrimidine-4-aminobenzoic acid (1/1), 10, the carboxyl group interacts with position N3 and the adjacent 4-amino group of the corresponding pyrimidine ring via O-H...N and N-H...O hydrogen bonds to generate the robust R 2 2 (8) supramolecular heterosynthon. These heterosynthons are further connected by N-H...N hydrogen-bond interactions in a linear fashion to form a chain-like arrangement. In cocrystal 1, a Br...Br halogen bond is present, in cocrystals 2 and 3, Cl...Cl halogen bonds are present, and in cocrystals 5, 6 and 7, Cl...O halogen bonds are present. In all of the ten cocrystals, π-π stacking interactions are observed.

Structural characterization of the compound [Cu(C 2 H 3 N)(C 23 H 23 N 3 O)](ClO 4 ) 2 ] or [Cu(C 2 H 3 N)(DQMEA)](ClO 4 ) 2 ] [DQMEA = 2-methoxy- N , N -bis-(quinolin-2-ylmeth-yl)ethyl-amine] {systematic name: (aceto-nitrile)[2-methoxy- N , N -bis(quinolin-2-ylmeth-yl)ethyl-amine]-copper(II) diperchlorate} by single-crystal X-ray diffraction reveals a complex cation with a tetra-dentate coordination of the DQMEA ligand along with monodentate coordination of a CH 3 CN ligand to a single Cu II center, with two perchlorate anions providing charge balance. The Cu II center has a distorted square-pyramidal geometry in which the nitro-gen atoms of the DQMEA and CH 3 CN ligands occupy the equatorial positions, while the oxygen atom of the DQMEA ligand resides in the axial position with an elongated Cu-O bond. The quinoline ring systems are nearly co-planar in the structure, while the linear CH 3 CN ligand is tilted significantly below this plane, and the central nitro-gen of DQMEA is above it. Within the complex, weak C-H⋯N hydrogen bonding takes place between the nitro-gen of CH 3 CN and a neighboring quinolyl group. The perchlorate ions are disordered within the structure, but undergo a number of weak inter-molecular C-H⋯O hydrogen-bonding inter-actions. Additional weak π-stacking inter-actions between the quinolyl groups of neighboring complexes further stabilize the crystal packing.

Structural analysis of (acetato-κ 2 O , O ')(methanol-κ O )[tris-(pyridin-2-ylmeth-yl)amine-κ 4 N , N ', N '', N ''']manganese(II) tetraphenyl-borate, [Mn(C 2 H 3 O 2 )(C 18 H 18 N 4 )(CH 3 OH)](C 24 H 20 B) or [Mn(TMPA)(Ac)(CH 3 OH)]BPh 4 [TMPA = tris-(pyridin-2-ylmeth-yl)amine, Ac = acetate, BPh 4 = tetra-phenyl-borate] by single-crystal X-ray diffraction reveals a complex cation with tetra-dentate coordination of the tripodal TMPA ligand, bidentate coordination of the Ac ligand and monodentate coordination of the methanol ligand to a single Mn II center, balanced in charge by the presence of a tetra-phenyl-borate anion. The Mn II complex has a distorted penta-gonal-bipyramidal geometry, in which the central amine nitro-gen and two pyridyl N atoms of the TMPA ligand, and two oxygen atoms of the acetate ligand occupy positions in the penta-gonal plane, while the third pyridyl nitro-gen of TMPA and the oxygen from the methanol ligand occupy the axial positions. Within the complex, the acetate O atoms participate in weak C-H⋯O hydrogen-bonding inter-actions with neighboring pyridyl moieties. In the crystal, complexes form dimers by pairs of O-H⋯O hydrogen bonds between the coordinated methanol of one complex and an acetate oxygen of the other, and weak π-stacking inter-actions between pyridine rings. Separate dimers then undergo additional π-stacking inter-actions between the pyridine rings of one moiety and either the pyridine or phenyl rings of another moiety that further stabilize the crystal.

The syntheses and crystal structures of 3-(2-chloro-eth-yl)- r -2, c -6-di-phenyl-piperidin-4-one, C 19 H 20 ClNO, (I), and 3-(2-chloro-eth-yl)- r -2, c -6-bis-(4-fluoro-phen-yl)piperidin-4-one, C 19 H 18 ClF 2 NO, (II), are described. The piperidone ring adopts a chair conformation in (I), whereas a slightly distorted chair conformation is formed in (II). The dihedral angle between the mean plane of the phenyl rings is 59.1 (1)° in (I) and 76.1 (1)° in (II). The crystal packing features weak inter-molecular N-H⋯O hydrogen bonds in each structure.

The basic objective of this investigation is to explore potential metallo-organic antimicrobial agents based on silver-heterocyclic-2-thiones. In this respect, a series of silver(I) halide complexes with imidazolidine-2-thiones (L-NR, R=H, Me, Et, Pr n , Bu n , Ph), namely, mononuclear [AgX(L-NR)(PPh 3 ) 2 ] (X, R: Cl, Bu, 1; Br, Ph, 7); [AgX(L-NR) 3 ] (Br, Bu, 5; Br, Pr n , 8) and halogen bridged dinuclear [Ag 2 (μ-X) 2 (L-NR) 2 (PPh 3 ) 2 ] (Cl, Bu n , 2; Cl, Ph, 3; Cl, Pr n , 4; Br, Ph, 6) have been synthesized and characterized using modern techniques. The thio-ligands are terminally S-bonded in all the complexes. The in vitro antimicrobial potential and biosafety evaluation of the above complexes as well as that of previously reported analogous silver complexes has been studied against Gram positive bacteria, namely, Staphylococcus aureus (MTCC 740) and Methicillin resistant Staphylococcus aureus (MRSA), Gram negative bacteria Klebsiella pneumoniae (MTCC 109), Salmonella typhimurium (MTCC 98) and a yeast Candida albicans (MTCC 227). Most of the complexes tested have shown significant antimicrobial activity with low values of minimum inhibitory concentration (MIC). Significantly, the activity against MRSA is an important outcome of this investigation. Among complexes tested for their cytotoxicity using MTT [3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide] assay, some complexes showed low cellular toxicity with high percent cell viability. A dinuclear complex [Ag 2 (μ-Cl) 2 (L-NPh) 2 (PPh 3 ) 2 ] 3 with 93.3% cell viability emerges the most important candidate for further investigations., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Correction for 'Variable coordination and C-S bond cleavage activity of N-substituted imidazolidine-2-thiones towards copper: synthesis, spectroscopy, structures, ESI-mass and antimicrobial studies' by Jaspreet K. Aulakh, et al., Dalton Trans., 2017, 46, 1324-1339.

Pyrimidines are important compounds in biology and medicine, and the aminopyrimidine fragment can be identified in three of the four bases in DNA. The targeted drug action of pharmaceuticals containing this functionality is likely to depend heavily on molecular recognition processes involving hydrogen bonding. Crystallization of an equimolar mixture of 4-amino-5-chloro-2,6-dimethylpyrimidine and 5-chloro-2-hydroxybenzoic acid yielded two forms of the 1:1 salt, C 6 H 9 ClN 3 + ·C 7 H 4 ClO 3 - , each containing a different tautomeric form of the cation. 6-Amino-5-chloro-2,4-dimethylpyrimidin-1-ium 5-chloro-2-hydroxybenzoate, (I), crystallizes in the space group P-1, with Z' = 2, and all of the component ions are fully ordered. 4-Amino-5-chloro-2,6-dimethylpyrimidin-1-ium 5-chloro-2-hydroxybenzoate, (II), also crystallizes with Z' = 2, but in the space group P2 1 /c and as a merohedral twin which closely mimics an orthorhombic unit cell. In (II), one of the cations and one of the anions is disordered, each over two sets of atomic sites having occupancies of 0.836 (2) and 0.164 (2), and 0.834 (2) and 0.166 (2). The bond lengths in the cations of (I) and (II) provide evidence for o-quinonoid and p-quinonoid bond fixation, respectively. A combination of six N-H...O hydrogen bonds links the component ions of (I) into two independent four-ion aggregates, but the ions in (II) are linked by a combination of four N-H...O and two N-H...N hydrogen bonds to form a three-dimensional framework structure. The recently reported structure of 2-amino-4,6-dimethoxypyrimidin-1-ium thiophene-2-carboxylate, C 6 H 10 N 3 O 2 + ·C 5 H 3 O 2 S - , (III), has been rerefined, using the original data set, to show that the anion is disordered over two sets of atomic sites, approximately related by a 180° rotation about the exocyclic C-C bond, and having occupancies of 0.8687 (19) and 0.1313 (19).

Using the 2-hydroxy-N'-[(E)-phenyl(pyridin-2-yl)methylidene]benzohydrazide ligand and dicarboxylate anions (succinate and malonate), two new copper(ii) complexes of formula [Cu 4 (μ-L) 4 (μ-CH 2 (COO) 2 )(H 2 O) 3 ](NO 3 ) 2 ·4H 2 O (1) and [Cu 4 (μ-L) 4 (μ-CH 2 -CH 2 (COO) 2 )(H 2 O)](NO 3 ) 2 ] (2) have been synthesized and characterized by single crystal X-ray diffraction. Complexes 1 and 2 contain a dicarboxylate bridged tetranuclear Cu(ii) cationic unit with "weighing balance shaped" topology. These compounds have also been studied by variable temperature magnetic susceptibility measurements, X-band EPR spectroscopy and electrochemistry. The unprecedented tetranuclear copper complexes 1 and 2 exhibit antiferromagnetic interactions between adjacent copper(ii) centers with magnetic exchange coupling constants (J) of J 1 = -6.8 cm -1 , J 2 = -20.6 cm -1 and g = 2.03 for 1 and J 1 = -3.1 cm -1 , J 2 = -13.9 cm -1 and g = 2.02 for 2. The goal for our research work is to understand the factors that govern the stability of the Cu-O(-O-C-O-) bond towards reactive oxygen species (ROS) in Cu-containing mimics utilizing a systematic approach. The antioxidant superoxide dismutase measurements indicate that these complexes behave as superoxide dismutase mimics.

An equimolar reaction of copper(i) iodide with N-ethyl-imidazolidine-2-thione (l-Et) in acetonitrile formed black prismatic crystals over a period of three weeks. The X-ray structure determination of black crystals revealed that the thio-ligand l-Et has transformed into a new thio-ligand, 1-ethyl-3-(1-ethyl-4,5-dihydro-1H-imidazol-2-yl)imidazolidine-2-thione (l-NEt), through C-S rupture/C-N bond formation which was coordinated in the unusual 2D polymer, {(Cu II (κ 2 -N,S-l-NEt) 2 )·(CuI 4 )·(CuI 2 )} n 1. An ESR spectrum supported the presence of divalent Cu II in the polymer. In contrast, reaction of copper(i) iodide with N-phenyl-imidazolidine-2-thione (l-Ph) in 1 : 1 molar ratio yielded a polymer, [-Cu(μ-I) 2 Cu(μ-S-l-Ph) 2 Cu-] n 2, with alternate Cu 2 I 2 and Cu 2 S 2 cores. Further, a series of reactions of copper(i) halides with N-substituted imidazolidine-2-thiones, namely, l-R in 1 : 2 metal to ligand molar ratio (M : L) in acetonitrile have yielded different type of complexes: trigonal planar {CuX(κ 1 -S-l-R) 2 , R, X : Et, I, 4; Me, I, 5; Bu n , I,6; Me, Br,7; Bu n , Br, 8; Me, Cl, 9; Pr n , Cl, 10; Ph, Cl, 11}, dinuclear [Cu 2 Br 2 (μ-S-l-Ph) 2 (κ 1 -S-l-Ph) 2 ] 12, tetranuclear, [Cu 4 I 2 (μ-I) 2 (μ-S-l-Ph) 4 (κ 1 -S-l-Ph) 2 ] 3 and hexanuclear [Cu 6 Cl 6 (μ-S-l-Bu n ) 6 ] 13. All these complexes have been characterized using analytical data, IR and proton NMR spectroscopy, ESI-mass studies and single crystal X-ray crystallography. The antimicrobial activity of these complexes has been investigated against Gram positive bacteria, namely, Staphylococcus aureus (MTCC740), methicillin resistant Staphylococcus aureus (MRSA), Gram negative bacteria, Klebsiella pneumoniae (MTCC109), Salmonella typhimurium (MTCC741) and Candida albicans (MTCC227)- a yeast. It is significant to add that among various complexes tested for cytotoxicity toward living cells, 4, 5, 8, 9 and 10 complexes were toxic, while complex 12 was non-toxic.

The syntheses and crystal structure of 3-chloro-3-methyl- r -2, c -6-di-phenyl-piperidin-4-one, C 18 H 18 ClNO, (I), 3-chloro-3-methyl- r -2, c -6-di- p -tolyl-piperidin-4-one, C 20 H 22 ClNO, (II), and 3-chloro-3-methyl- r -2, c -6-bis-(4-chloro-phen-yl)piperidin-4-one, C 18 H 16 Cl 3 NO, (III), are described. In each structure, the piperidine ring adopts a chair conformation and dihedral angles between the mean planes of the phenyl rings are 58.4 (2), 73.5 (5) and 78.6 (2)° in (I), (II) and (III), respectively. In the crystals, mol-ecules are linked into C (6) chains by weak N-H⋯O hydrogen bonds and C-H⋯π inter-actions are also observed.

The lattice of 5,7,12,14-tetra-hydro-5,14:7,12-bis-([1,2]benzeno)-penta-cene-6,13-dione, C 34 H 20 O 2 , at 173 K has triclinic ( P -1) symmetry and crystallizes with four independent half-mol-ecules in the asymmetric unit. Each mol-ecule is generated from a C 17 H 10 O substructure through an inversion center at the centroid of the central quinone ring, generating a wide H-shaped mol-ecule, with a dihedral angle between the mean planes of the terminal benzene rings in each of the two symmetry-related pairs over the four mol-ecules of 68.6 (1) ( A ), 65.5 (4) ( B ), 62.3 (9) ( C ), and 65.8 (8)° ( D ), an average of 65.6 (1)°. This compound has applications in gas-separation membranes constructed from polymers of intrinsic microporosity (PIM). The title compound is a product of a double Diels-Alder reaction between anthracene and p -benzo-quinone followed by de-hydrogenation. It has also been characterized by cyclic voltammetry and rotating disc electrode polarography, FT-IR, high resolution mass spectrometry, elemental analysis, and 1 H NMR.

The one-pot [3 + 2] cycloaddition of an azomethine ylide with a maleimide followed by another [3 + 2] cycloaddition of an azide with the second maleimide gives a 1,5-diamino intermediate which is used for a sequential aminomethylation reaction with formaldehyde through [5 + 1] annulation to afford a novel polycyclic scaffold bearing tetrahydroquinazoline, pyrrolidine, pyrrolidinedione, and N -substituted maleimide in stereoselective fashion.

Hydrazone derivatives exhibit a wide range of biological activities, while pyrazolo[3,4-b]quinoline derivatives, on the other hand, exhibit both antimicrobial and antiviral activity, so that all new derivatives in these chemical classes are potentially of value. Dry grinding of a mixture of 2-chloroquinoline-3-carbaldehyde and 4-methylphenylhydrazinium chloride gives (E)-1-[(2-chloroquinolin-3-yl)methylidene]-2-(4-methylphenyl)hydrazine, C17H14ClN3, (I), while the same regents in methanol in the presence of sodium cyanoborohydride give 1-(4-methylphenyl)-4,9-dihydro-1H-pyrazolo[3,4-b]quinoline, C17H15N3, (II). The reactions between phenylhydrazinium chloride and either 2-chloroquinoline-3-carbaldehyde or 2-chloro-6-methylquinoline-3-carbaldehyde give, respectively, 1-phenyl-1H-pyrazolo[3,4-b]quinoline, C16H11N3, (III), which crystallizes in the space group Pbcn as a nonmerohedral twin having Z' = 3, or 6-methyl-1-phenyl-1H-pyrazolo[3,4-b]quinoline, C17H13N3, (IV), which crystallizes in the space group R\overline{3}. The molecules of compound (I) are linked into sheets by a combination of N-H...N and C-H...π(arene) hydrogen bonds, and the molecules of compound (II) are linked by a combination of N-H...N and C-H...π(arene) hydrogen bonds to form a chain of rings. In the structure of compound (III), one of the three independent molecules forms chains generated by C-H...π(arene) hydrogen bonds, with a second type of molecule linked to the chains by a second C-H...π(arene) hydrogen bond and the third type of molecule linked to the chain by multiple π-π stacking interactions. A single C-H...π(arene) hydrogen bond links the molecules of compound (IV) into cyclic centrosymmetric hexamers having \overline{3} (S6) symmetry, which are themselves linked into a three-dimensional array by π-π stacking interactions.

Pyrazole and isoxazole rings differ only in the notional replacement of a potential hydrogen-bond-donor NH unit in pyrazole by a potential hydrogen-bond-acceptor O atom in isoxazole. It is thus of interest to compare the hydrogen-bonding characteristics of these rings. (4-Fluorophenyl)pyrazole undergoes protonation in the presence of 2,4,6-trinitrophenol to yield the salt 3-(4-fluorophenyl)-1H-pyrazolium 2,4,6-trinitrophenolate, C9H8FN2(+)·C6H2N3O7(-), (I), whereas there is no proton transfer between 4-amino-N-(3,4-dimethyl-1,2-oxazol-5-yl)benzenesulfonamide and 3,5-dinitrobenzoic acid, whose reaction gives the 1:1 cocrystal, C11H13N3O3S·C7H4N2O6, (II). The bond lengths in salt (I) provide evidence for aromatic-type delocalization in the pyrazolium ring and for extensive delocalization of the negative charge into the ring of the trinitrophenolate anion. The O atoms of one of the nitro groups in the trinitrophenolate anion are disordered over two sets of atomic sites having occupancies of 0.571 (6) and 0.429 (6), but all of the other substituents on the carbocyclic rings are fully ordered. The ions in salt (I) are linked by an extensive series of N-H...O hydrogen bonds to form a three-dimensional framework structure, and in cocrystal (II), the molecular components are linked by a combination of O-H...N and N-H...O hydrogen bonds to form complex bilayers. Comparisons are made with some related compounds.

In the crystal of compound (I), C14H11ClOS, mol-ecules are linked by C-H⋯O hydrogen bonds to form simple C(5) chains. Compound (II), C26H22O, crystallizes with Z' = 2 in space group P-1; one of the mol-ecules is fully ordered but the other is disordered over two sets of atomic sites having occupancies 0.644 (3) and 0.356 (3). The two disordered components differ from one another in the orientation of the isopropyl substituents, and both differ from the ordered mol-ecules in the arrangement of the central propenone spacer unit, so that the crystal of (II) contains three distinct conformers. The ordered and disordered conformers each form a C(8) chain built from a single type of C-H⋯O hydrogen bond but those formed by the disordered conformers differ from that formed by the ordered form.

In the title compound, C21H17N3O3S, the non-H atoms, apart from those in the benzoyl group, are almost coplanar (r.m.s. deviation = 0.049 Å) and the benzoyl group is almost orthogonal to the plane of the rest of the mol-ecule [dihedral angle = 80.34 (6)°]. In the crystal, a combination of N-H⋯O and asymmetric bifurcated O-H⋯(N,O) hydrogen bonds link the mol-ecules into a three-dimensional network. Weak C-H⋯O inter-actions are also observed.

The first asymmetric synthesis of spiro-γ-lactam oxindoles bearing three stereocenters is reported. One-pot thiol-Michael/Mannich/lactamization reactions promoted by a recyclable fluorous bifunctional cinchona alkaloid/thiourea organocatalyst afford products in moderate to good yields with up to 95% ee and 6:1 dr.