Synthesis and monoamine oxidase A/B inhibitory evaluation of new benzothiazole-thiazolylhydrazine derivatives

Abstract

In this study, a novel series of benzothiazole-thiazolylhydrazine (3a–3i) was synthesized and their structures were characterized by ¹H-NMR, ¹³C-NMR spectrometry, and mass spectroscopy. These compounds were evaluated as inhibitors of type A and type B monoamine oxidase (MAO) enzymes. The most active compound 3b (2-((2-(2-(4-(4-Nitrophenyl)thiazol-2-yl)hydrazineylidene)-2-phenylethyl)thio)benzothiazole) showed strong inhibitory activity at hMAO-A (IC₅₀ of 0.095?±?0.004?µM). Furthermore, compound 3i (2-((2-(2-(4-(2,4-dichlorophenyl)thiazol-2-yl)hydrazineylidene)-2-phenylethyl)thio)benzothiazole) showed significant inhibition profile on hMAO-A with the IC₅₀ values 0.141?±?0.006?µM.     

Synthesis,characterization, and magnetochemical properties of two Mn4 clusters derived from 2-pyridinecarboxaldehyde Schiff base ligands

Two tetranuclear manganese complexes, [Mn₄(L¹)₆](ClO₄)₂?2.75H₂O (1) [HL¹ = 4-methyl-2-((pyridin-2-ylmethylene)amino)phenol] and [Mn₄(L²)₄(NO₃)₃(OH)]?pz?3H₂O (2) [HL² = (1H-pyrazol-1-yl)(pyridin-2-yl)methanol, pz = pyrazole], have been synthesized and characterized by IR spectroscopy, elemental analysis, single-crystal X-ray diffraction, and magnetic measurements. The structural analysis revealed that the central manganese ion is linked with three apical manganese ions through six phenoxo-bridges creating a Mn₄O₆ core for 1; 2 has a cubane-like topology with the Mn(II) ions and the deprotonated oxygens from L² alternatively occupying vertices. The magnetic studies indicated a weak ferromagnetic coupling interaction (J = 0.48 ± 0.087 cm^?1, g = 2.00, θ = ?0.78 K) for 1 and a weak antiferromagnetic spin-exchange interaction (J₁ = ?0.50 ± 0.075 cm^?1, J₂ = ?0.13 ± 0.082 cm^?1, g = 1.98) between Mn(II) ions for 2. The magnetostructural correlations of the two Mn₄ clusters have been discussed tentatively.     

Syntheses,urease inhibition activities,and fluorescent properties of transition metal complexes

Four transition metal complexes with Schiff base and 1,10-phenanthroline, [Cu(L)(phen)]₂·C₂H₅OH (1), [Zn(L)(phen)]₂·C₂H₅OH (2), [Ni(L)(phen)]₂·C₂H₅OH (3), and [Co(L)(phen)]₂·C₂H₅OH (4) (H₂L?=?1-((2-hydroxynaphthalen-1-yl)methylene)thiosemicarbazide; phen?=?1,10-phenanthroline) were synthesized and characterized by physico-chemical methods. The crystal structure of 1 was determined by X-ray single-crystal diffraction analysis. 1 crystallizes in the orthorhombic space group Pbca with a?=?15.008(9), b?=?16.100(10), c?=?37.54(2)?Å, V?=?9070(10)?ų, Z?=?8, GOOF?=?1.002, R ₁?=?0.0626, and wR ₂?=?0.0912. The fluorescence and urease inhibitory activities of the compounds were tested. The enzymatic activity study indicated that 3 possessed potent inhibition against jack bean urease, with IC₅₀?=?1.2?±?0.1?μM, and about 35 times more than 42.1?±?0.4 acetohydroxamic acid as positive reference. This suggests that inhibitory efficiency of these complexes can be strongly influenced by different transition metal ions.     

The structure and thermochemistry of 3:4,5:6-dibenzo-2-hydroxymethylene-cyclohepta-3,5-dienenone (1) and some related compounds

Condensed and gas phase enthalpies of formation of 3:4,5:6-dibenzo-2-hydroxymethylene-cyclohepta-3,5-dienenone (1, (−199.1 ± 16.4), (−70.5 ± 20.5) kJ mol⁻¹, respectively) and 3,4,6,7-dibenzobicyclo[3.2.1]nona-3,6-dien-2-one (2, (−79.7 ± 22.9), (20.1 ± 23.1) kJ mol⁻¹) are reported. Sublimation enthalpies at T=298.15 K for these compounds were evaluated by combining the fusion enthalpies at T = 298.15 K (1, (12.5 ± 1.8); 2, (5.3 ± 1.7) kJ mol⁻¹) adjusted from DSC measurements at the melting temperature (1, (T _fus, 357.7 K, 16.9 ± 1.3 kJ mol⁻¹)); 2, (T _fus, 383.3 K, 10.9 ± 0.1) kJ mol⁻¹) with the vaporization enthalpies at T = 298.15 K (1, (116.1 ± 12.1); 2, (94.5 ± 2.2) kJ mol⁻¹) measured by correlation-gas chromatography. The vaporization enthalpies of benzoin ((98.5 ± 12.5) kJ mol⁻¹) and 7-heptadecanone ((94.5 ± 1.8) kJ mol⁻¹) at T = 298.15 K and the fusion enthalpy of phenyl salicylate (T _fus, 312.7 K, 18.4 ± 0.5) kJ mol⁻¹) were also determined for the correlations. The crystal structure of 1 was determined by X-ray crystallography. Compound 1 exists entirely in the enol form and resembles the crystal structure found for benzoylacetone.     

Cytotoxicity,apoptosis, interaction with DNA,cellular uptake,and cell cycle arrest of ruthenium(II) polypyridyl complexes containing 4,4′-dimethyl-2,2′-bipyridine as ancillary ligand

Two new ruthenium(II) polypyridyl complexes, [Ru(dmb)₂(DNPIP)](ClO₄)₂ (1) (DNPIP?=?2-(2,4-dinitrophenyl)imidazo[4,5-f][1,10]phenanthroline, dmb?=?4,4′-dimethyl-2,2′-bipyridine) and [Ru(dmb)₂(DAPIP)](ClO₄)₂ (2) (DAPIP?=?2-(2,4-diaminophenyl)imidazo[4,5f][1,10]phenanthroline), were synthesized and characterized. The DNA-binding behaviors of these complexes have been studied by UV-Vis absorption titration, viscosity measurements, and photocleavage. The DNA-binding constants are 7.39 (±0.16)?×?10⁴ (s?=?2.68) and 2.73 (±0.16)?×?10^4?(mol?L^?1)^?1 (s?=?0.64) for 1 and 2, respectively. Their evaluation as cytotoxic agents on different cancer cell lines was investigated with IC₅₀ values of 59.5, 51.3, and 70.3?µmol?L^?1 for 1, >100, 87.9, and 77.9?µmol?L^?1 for 2 against BEL-7402, HepG-2, and MCF-7 cells, respectively. Complex 1 is more active than 2 against selected cancer cell lines. The apoptosis induced by these complexes was studied. Cellular uptake showed that these complexes could enter into the cytoplasm and accumulate in the nuclei. The cell cycle arrest and antioxidant activity against hydroxyl radicals were also investigated.     

Synthesis,structural, electrochemical,and spectroscopic studies of some (diimine)ruthenium nitrile complexes

The syntheses of cationic ruthenium(II) complexes [Ru(Me₂-bpy)(PPh₃)₂RR?][PF₆]_x {Me₂-bpy = 4,4?-dimethyl-2,2?-bipyridine, (3) R = Cl, R? = N≡CMe, x = 1, (4) R = Cl, R? = N≡CPh, x = 1, (5) R = R? = N≡CMe, x = 2} and [Ru(Me₂-bpy)(κ²-dppf)RR?][PF₆]_x {dppf = 1,1?-bis(diphenylphosphino)ferrocene, (6) R = Cl, R? = N≡CMe, x = 1, (7) R = Cl, R? = N≡CPh, x = 1, (8) R = R? = N≡CMe, x = 2} are reported, together with their structural confirmation by NMR (³¹P, ¹H) and IR spectroscopy and elemental analysis, and, in the case of trans-[Ru(Me₂-bpy)(PPh₃)₂(N≡CCH₃)Cl][PF₆] (3), by X-ray crystallography. Electronic absorption and emission spectra of the complexes reveal that all complexes except 4 and 6 are emissive in the range 370–400 nm with 8 exhibiting an emission in the blue. Cyclic voltammetry studies of 3–8 show reversible or quasi-reversible redox processes at ca. 1 V, assigned to the Ru(II/III) couple.     

PtII Coordination to N1 of 9‐Methylguanine: Why it Facilitates Binding of Additional Metal Ions to the Purine Ring

The preparation and X‐ray crystal structure analysis of {trans‐[Pt(MeNH₂)₂(9‐MeG‐N1)₂]} ? {3 K₂[Pt(CN)₄]} ? 6 H₂O ( 3 a ) (with 9‐MeG being the anion of 9‐methylguanine, 9‐MeGH) are reported. The title compound was obtained by treating [Pt(dien)(9‐MeGH‐N7)]²⁺ ( 1 ; dien=diethylenetriamine) with trans‐[Pt(MeNH₂)₂(H₂O)₂]²⁺ at pH 9.6, 60 °C, and subsequent removal of the [(dien)Pt^II] entities by treatment with an excess amount of KCN, which converts the latter to [Pt(CN)₄]^2?. Cocrystallization of K₂[Pt(CN)₄] with trans‐[Pt(MeNH₂)₂(9‐MeG‐N1)₂] is a consequence of the increase in basicity of the guanine ligand following its deprotonation and Pt coordination at N1. This increase in basicity is reflected in the pK_a values of trans‐[Pt(MeNH₂)₂(9‐MeGH‐N1)₂]²⁺ (4.4±0.1 and 3.3±0.4). The crystal structure of 3 a reveals rare (N7,O6 chelate) and unconventional (N2,C2,N3) binding patterns of K⁺ to the guaninato ligands. DFT calculations confirm that K⁺ binding to the sugar edge of guanine for a N1‐platinated guanine anion is a realistic option, thus ruling against a simple packing effect in the solid‐state structure of 3 a . The linkage isomer of 3 a , trans‐[Pt(MeNH₂)₂(9‐MeG‐N7)₂] ( 6 a ) has likewise been isolated, and its acid–base properties determined. Compound 6 a is more basic than 3 a by more than 4 log units. Binding of metal entities to the N7 positions of 9‐MeG in 3 a has been studied in detail for [(NH₃)₃Pt^II], trans‐[(NH₃)₂Pt^II], and [(en)Pd^II] (en=ethylenediamine) by using ¹H NMR spectroscopy. Without exception, binding of the second metal takes place at N7, but formation of a molecular guanine square with trans‐[(Me₂NH₂)Pt^II] cross‐linking N1 positions and trans‐[(NH₃)₂Pt^II] cross‐linking N7 positions could not be confirmed unambiguously, despite the fact that calculations are fully consistent with its existence.     

Struktur des Zwischenproduktes einer (i-PrO)2 TiMe2-Methylierung: NMR-Untersuchungen und Konformationsanalyse

Structure of the Intermediate of a Methylation with (i-PrO)₂TiMe₂: NMR Investigations and Conformational Analysis The intermediate of the reaction of 3-(1-nitro-2-oxocyclohexyl)propanal ((±)- 1 ) with (i-PrO)₂TiMe₂ was shown to be a titanium salt of 6-(hydroxynitroryl)decano-9-lactone. ¹H-, ¹³C-, HSQC-, ¹H,¹H-TOCSY- and long-range HMBC-NMR spectra of this intermediate indicate a complexation of the carbonyl O-atom and an O-atom of the hydroxynitroryl group to the same Ti-atom. The product of the reaction (t-3-methyl-c-6-nitro-2-oxabicyclo[4.4.0]decan-r-1-ol, (±)- 2 ) was reacted with several titanium reagents to give also titanium salts of the 6-(hydroxynitroryl)decano-9-lactone. Monte Carlo studies and MM3^* force-field calculations of the anion of 6-(hydroxynitroryl)decano-9-lactone, 3′ , resulted in a conformation of the ten-membered ring (only 9.57 kJ/mol higher in energy than the global minimum), which allows the Ti-atom to coordinate to the O-atom of the N(O)OH and C?O group at the same time. With the suggested structure of 3′ · TiR_n, we are able to explain the selectivity of the reaction.     

Photocurrent kinetics at the electron emission from a metal into electrolyte solution: Part II. Solutions without acceptors and solutions of N2O,NO2−, NO3−

A method of measuring the kinetics of currents arising at the electron photoemission from a metal into electrolyte solution when affected by the u.v. laser pulses for 10^?8 s at the frequency of repetitions 10–25 Hz is described. Measurements have been taken in solutions without acceptors and in those containing N₂O and NO₂^?, NO₃^? ions as electron acceptors. The rate constants of capture of the solvated electrons by N₂O ((6±1)×0⁹ mol^?1 s^?1) and NO₂^? ((4.5±1)×10⁹ mol^?1 s^?1) and the diffusion coefficients of OH-radicals ((1.0±0.3)×10^?5 cm² s^?1) and of NO ((1.2±0.3)×10^?5 cm² s^?1) are found. The oxidation rate of NO₃^2? has been shown to decrease from 40 cm s^?1 in the range of potentials ?0.55 to ?1.0 V. The rate constant of bimolecular recombination of the solvated electrons ((1.3±0.4)×10¹⁰ mol^?1 s^?1) has been found from the dependence of the emitted charge on the light intensity.     

Synthesis,structure, spectroscopic,and DNA binding properties of Co(III) and Ni(II) complexes with ((E)-2-(amino((pyridin-2-ylmethylene)amino)methylene)maleonitrile)

Two new complexes, [Co(L)₂]Cl·(MeOH)₂ (1) and [Ni(L)₂]₄·EtOH (2) (L?=?(E)-2-(amino((pyridin-2-ylmethylene)amino)methylene)maleonitrile), were synthesized and characterized by X-ray crystallography, IR, UV, and fluorescence spectroscopy. According to X-ray crystallographic studies, each metal was six-coordinate with six nitrogens from two ligands. Both complexes form two-dimensional supramolecular networks via hydrogen bonding and π–π interactions. Ultraviolet and visible spectra showed that absorptions arise from π–π ^?, MLCT, and d–d electron transitions. Fluorescence spectroscopy revealed moderate intercalative binding of these two complexes with EB–DNA, with apparent binding constant (K _app) values of 9.14?×?10⁵ and 3.20?×?10^5?M^?1 for Co(III) and Ni(II) complexes, respectively. UV–visible absorption spectra showed that the absorption of DNA at 260?nm was quenched for 2 but quenched then improved for 1 with addition of complexes, tentatively attributed to the effect of the combined intercalative binding and electrostatic interaction for 1.     

Kinetics of oxidation of phenylhydrazine by a μ-oxo diiron(III,III) complex in acidic aqueous media

Phenylhydrazine (R) quantitatively reduces [Fe₂(μ-O)(phen)₄(H₂O)₂]⁴⁺ (1) (phen?=?1,10-phenanthroline) and its conjugate base [Fe₂(μ-O)(phen)₄(H₂O)(OH)]³⁺ (2) to [Fe(phen)₃]²⁺ in presence of excess 1,10-phenanthroline in the pH range 4.12–5.55. Oxidation products of phenylhydrazine are dinitrogen and phenol. The reaction proceeds through two parallel paths: 1?+?R?→?products (k ₁), 2?+?R?→?products (k ₂); neither RH⁺ nor the doubly deprotonated conjugate base of the oxidant, [Fe₂(μ-O)(phen)₄(OH)₂]²⁺ (3) is kinetically reactive though both are present in the reaction media. At 25.0°C, I?=?1.0?M (NaNO₃), the rate constants are k ₁?=?425?±?10?M^?1?s^?1 and k ₂?=?103?±?5?M^?1?s^?1. An inner-sphere, one-electron, rate-limiting step is proposed.     

Ruthenium(II) complexes: synthesis,cytotoxicity in vitro,apoptosis, DNA-binding,photocleavage, and antioxidant activity studies

Two new ruthenium(II) complexes, [Ru(dmp)₂(APIP)](ClO₄)₂ (1) (APIP?=?2-(2-aminophenylimidazo[4,5-f][1,10]phenanthroline), dmp?=?2,9-dimethyl-1,10-phenanthroline) and [Ru(dmp)₂(HAPIP)](ClO₄)₂ (2) (HAPIP?=?2-(2-hydroxyl-5-aminophenyl)imidazo[4,5-f][1,10]phenanthroline), were synthesized and characterized. The DNA-binding properties of these complexes were investigated by absorption titration, viscosity measurements, and photoactivated cleavage. The DNA-binding constants for 1 and 2 have been determined to be 2.3 (±?0.3)?×?10⁴ (mol?L^?1)^?1 and 3.3 (±?0.4)?×?10⁴ (mol?L^?1)^?1. The results indicate that 1 and 2 interact with DNA through intercalative mode. The cytotoxicities of 1 and 2 were assessed against BEL-7402, HepG-2 and MCF-7 cell lines using standard MTT assay. The apoptosis induced by these complexes was studied with the acridine orange/ethidium bromide staining method. The antioxidant activity on hydroxyl radical was also investigated.     

Syntheses and structural determination of binuclear nine-coordinate (NH4)4[SmIII2(Httha)2]·16H2O and 2-D ladder-like binuclear nine-coordinate (NH4)4[SmIII2(dtpa)2]·10H2O

Two rare-earth metal coordination compounds, (NH₄)₄[Sm^III₂(Httha)₂]·16H₂O (1) (H₆ttha?=?triethylenetetramine-N,N,N′,N′′,N′′′,N′′′-hexaacetic acid) and (NH₄)₄[Sm^III₂(dtpa)₂]·10H₂O (2) (H₅dtpa?=?diethylenetriamine-N,N,N′,N′′,N′′-pentaacetic acid), have been synthesized through reflux and characterized by FT-IR spectroscopy, thermal analysis, and single-crystal X-ray diffraction techniques. Sm^III of (NH₄)₄[Sm^III₂(Httha)₂]·16H₂O (1) is nine-coordinate, forming tricapped trigonal prismatic coordination with three amine nitrogens and six oxygens, in which four oxygens are from one ttha and two from the other ttha. (NH₄)₄[Sm^III₂(Httha)₂]·16H₂O (1) crystallizes in the monoclinic crystal system with P2(1)/c space group. The crystal data are: a?=?13.9340(13) Å, b?=?22.890(3) Å, c?=?20.708(2) (14) Å, β?=?99.521(2)°, and V?=?6513.7(13) ų. There are two –NH⁺– groups in the [Sm^III₂(Httha)₂]^4?. The polymeric (NH₄)₄[Sm^III₂(dtpa)₂]·10H₂O (2) also is nine-coordinate with tricapped trigonal prismatic conformation and crystallizes in the triclinic crystal system with P–1 space group. The cell dimensions are: a?=?9.8240(8) Å, b?=?10.0329(9) Å, c?=?13.0941(11) Å, β?=?77.1640(10)°, and V?=?1227.30(18) ų. In (NH₄)₄[Sm^III₂(dtpa)₂]·10H₂O, there are two types of ammonium cations, which connect [Sm^III₂(dtpa)₂]^4? and lattice water through hydrogen bonds, leading to a 2-D ladder-like layer structure.     

Synthesis,spectral, catalytic,and thermal studies of vanadium complexes with quadridentate schiff bases

The paper reports the synthesis and characterization of vanadium complexes of N,N′-(±)-trans-bis(2,4-dihydroxyacetophenone)-1,2-cyclohexanediamine (H₂L¹) and N,N′-(±)-trans-bis(2,4-dihyroxy-5-nitroacetophenone)-1,2-chyclohexanediamine (H₂L²). All the complexes were characterized by elemental analysis, magnetic susceptibility measurements, infrared and electronic spectra, and thermogravimetric analysis. The X-ray patterns of the [VO(L¹)] · H₂O (I) and [VO(L²)] · H₂O (II) complexes show the monoclinic system with the unit cell parameters a = 26.1352, b = 11.7149, c = 6.0401 β = 115.38° and a = 29.3787, b = 12.9398, c = 5.9175 β = 96.84°, respectively. The complexes I and II catalyze the oxidation of styrene in the presence of hydrogen peroxide.     

Two spin systems based on [Ni(dmit)2]− building blocks exhibiting 1-D chain and 2-D sheet structures: crystal structures and magnetic properties

The crystal structures and magnetic properties for two ion-pair complexes, [MG][Ni(dmit)₂] (1) and [RhB][Ni(dmit)₂] (2) (MG⁺ = N-(4-((4-(dimethylamino)phenyl)(phenyl)methylene)cyclohexa-2,5-dienylidene)-N-methylmethanaminium, RhB⁺ = 9-(2-carboxyphenyl)-3,6-bis(diethylamino)xanthylium; dmit^2? = 1,3-dithiole-2-thione-4,5-dithiolate), have been investigated. Complex 1 crystallizes in the monoclinic space group P2₁/c, the stacking interactions between the GM⁺ and [Ni(dmit)₂]^? lead to the anion exhibiting a banana-shaped molecular geometry; the neighboring anions form a 1-D alternating chain along the crystallographic [1 1 0] direction via intermolecular lateral-to-lateral and head-to-head S ··· S contacts. The temperature dependence of magnetic susceptibility from 2–350 K does not display the magnetic character of a 1-D chain; the magnetic susceptibility data were fit to the Curie–Weiss equation to give C = 0.351(15) emu K mol^?1, θ = ?3.51(28) K, and χ ₀ = 8.00(3) × 10^?5 emu mol^?1. Complex 2 belongs to the triclinic space group P-1 with two crystallographic inequivalent [Ni(dmit)₂]^? anions, which exhibit perfect planar geometry. Two ethyl groups of RhB⁺ are disordered over two positions at 296 K, and one becomes ordered at 150 K. The [Ni(dmit)₂]^? anions form a 2-D molecular layer via intermolecular lateral-to-lateral and head-to-lateral S ··· S interactions with the anionic layer parallel to the crystallographic (0 1 ?1) plane. The temperature variation of magnetic susceptibility from 2 to 350 K shows that antiferromagnetic coupling dominates in the anionic layer, and the disorder–order changes of cationic structure are not coupled to magnetic property.     

Self-assembly of copper(II) complexes with substituted aroylhydrazones and monodentate N-heterocycles: synthesis,structure and properties

Two ternary copper(II) complexes [Cu(L¹)(py)] (1) and [Cu(L²)(Himdz]?·?CH₃OH (2) with substituted aroylhydrazones, 5-bromo-salicylaldehyde-3,5-dimethoxy-benzoylhydrazone (H₂L¹) and 5-bromo-salicylaldehyde-p-methyl-benzoylhydrazone (H₂L²), pyridine (py) and imidazole (Himdz), have been synthesized. Their crystal structures and spectroscopic properties have been studied. In each complex, the metal is in a square-planar N₂O₂ coordination formed by the phenolate-O, the imine-N and the deprotonated amide-O atoms of L^2?, and the sp²?N atom of the neutral heterocycle. In the solid state, 1 exists as a centrosymmetric dimer due to very weak apical coordination of the metal bound phenolate-O. Complex 2 has no such apical coordination and exists as a monomer. Self-assembly via C–H?···?O, N–H?···?O and O–H?···?N interaction leads to a one-dimensional chain arrangement; other non-covalent interactions such as C–H?···?π and π?···?π are not involved.     

Synthesis and antitumor activity of novel pyridazinone derivatives containing 1,3,4-thiadiazole moiety

Abstract

A series of novel pyridazinone derivatives containing the 1,3,4-thiadiazole moiety were synthesized and characterized by ¹H NMR, 13C NMR, spectroscopies HRMS and IR. Among them, the structure of compound 5c (2-(Tert-butyl)?4-chloro-5-((5-((2-ethylphenyl)amino)?1,3,4-thiadiazol-2-yl)thio)pyridazin-3(2H)-One) was unambiguously confirmed via single crystal X-ray diffraction analysis. The inhibitory activity of all the target compounds against MGC-803 and Bcap-37 was determined by MTT assay, with doxorubicin (the inhibition rates were 95.5?±?0.4% and 95.7?±?1.0% respectively) as a control. The preliminary results showed that the inhibitory activity of compound 5n (2-(Tert-butyl)?4-chloro-5-((5-((3-fluorophenyl)amino)?1,3,4-thiadiazol-2-yl)thio)pyridazin-3(2H)-One) was superior to the others. The inhibition rates of MGC-803 and Bcap-37 cells were 86.3?±?2.2% and 92.3?±?0.6% at a concentration of 10?μmol/L, respectively. The preliminary structure-activity relationship showed that when the 2-position of the benzene ring was substituted by a methyl group, such as compound 5j (2-(Tert-butyl)?4-chloro-5-((5-((2,3-dimethylphenyl)amino)?1,3,4-thiadiazol-2-yl)thio)pyridazin-3(2H)-One), it exhibited good anticancer activity on MGC-803 cells. Besides, introducing fluorine, chlorine, or trifluoromethyl group onto the benzene ring, such as compound 5?m (2-(Tert-butyl)?4-chloro-5-((5-((4-(trifluoromethoxy)phenyl)amino)?1,3,4-thiadiazol-2-yl)thio)pyridazin-3(2H)-One), displayed good anticancer activity on MGC-803 and Bcap-37 cells.     

Hydrogen bonded networks based on Ni(II)-tetraazamacrocycle (tet-b) complexes: synthesis,isolation and structural characterization of α -[Ni(tet-b)(Cl)](ClO4) and α -[Ni(tet-b)(en)](ClO4)2

Five- and six-coordinate, α-[Ni(tet-b)(Cl)](ClO₄) (1) and α-[Ni(tet-b)(en)](ClO₄)₂ (2) (tet-b?= C-racemic-5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane) complexes have been synthesized and isolated from the reactions of α-[Ni(tet-b)](ClO₄)₂, which has trans-V (1R,4R,8R,11R,7S,14S or 1S,4S,8S,11S,7R,14R) conformation, with t-Bu₄NCl and ethylenediamine (en), respectively. The complexes have been characterized by X-ray crystallography. The crystal structure of 1 shows a distorted trigonal bipyramidal (TBP) coordination geometry composed of four nitrogen atoms from tet-b and a chloro group with an N₄Cl chromophore about the nickel(II) ion. The complex cations of 1 are assembled by the perchlorate ions via N–H?···?O hydrogen bonding to form 1-D zigzag chains along the [001] direction. The chains are linked through intermolecular hydrogen bonding where the coordinated chloro group of the complex cation forms two-center double hydrogen bonds with the adjacent N–H groups of the macrocyclic ligand along the [100] direction, resulting in a two-dimensional α-network. The crystal structure of 2 shows a distorted octahedral coordination environment consisting of four nitrogen atoms from tet-b and two from en with an N₆ chromophore about nickel(II) ion. The crystal packing analysis shows that the complex cations, α-[Ni(tet-b)(en)]²⁺ are interconnected by perchlorate ions through conventional two-center (N)H?···?O, and bifurcated (N)H?···?O?···?H(N) hydrogen bonding.     

Syntheses,spectroscopy, and X-ray structures of 3-{(R)-(Ar)-ethylimino}-1,3-dihydro-indol-2-one (Ar = Ph,MeOC6H4, BrC6H4, 1-naphthyl) and [Rh(η4-cod){3-((R)-(Ar)-ethylimino)-3H-indol-2-olato}]

Condensation of 1H-indole-2,3-dione (isatin) with (R)-(Ar)-ethylamines gives enantiopure Schiff bases, 3-{(R)-(Ar)-ethylimino}-1,3-dihydro-indol-2-one (HL) {Ar?=?Ph (HL1), 2-MeOC₆H₄ (HL2), 4-MeOC₆H₄ (HL3), 4-BrC₆H₄ (HL4), and 1-naphthyl (HL5)}. The Schiff bases readily coordinate to [Rh(μ-O₂CMe)(η⁴-cod)]₂ (cod?=?1,5-cyclooctadiene) to give mononuclear [Rh(η⁴-cod){3-((R)-(Ar)-ethylimino)-3H-indol-2-olato}] {Ar?=?Ph (1), 4-MeOC₆H₄ (2), and 4-BrC₆H₄ (3)}, respectively. The Schiff bases and complexes have been fully characterized by IR, UV-Vis, ¹H-NMR, mass, and circular dichroism (CD) spectrometry. Polarimetry and CD measurements show the enantiopurity of the Schiff bases as well as the complexes. ¹H NMR measurements reveal slow conversion of the lactam to the enol form of the Schiff bases in solution. In the solid state the lactam form dominates as shown by crystal structures of HL1 and HL4. While gross structural features of both are similar, the molecules differ significantly in the relative orientations of the aryl and lactam rings. The difference is mostly rotation about the N2–C9 bond with different C8–N2–C9–C11 torsion angle of +89.77(12)° for HL1 and C2–N2–C9–C11 of +106.8(3)° for HL4.     

Synthesis and X-ray crystal structures of N,N,N′,N′-tetraalkylpyridine-2,6-dithiocarboxamides (S-dapt) complexes of cobalt(II) and nickel(II)

Reactions of anhydrous CoX₂ (X?=?Br^?, SCN^?) and Ni(ClO₄)₂ with N,N,N′,N′-tetraisobutylpyridine-2,6-dithiocarboxamides (S-dbpt), N,N,N′,N′-tetraisopropyl pyridine-2,6-dithiocarboxamides (S-dppt), and N,N,N′,N′-tetraethylpyridine-2,6-dithiocarboxamides (S-dept) lead to the formation of [Co(S-dbpt)Br₂] (1), [Co(S-dppt)(SCN)₂] (2), and [Ni(S-dept)₂]·(ClO₄)₂·H₂O (3), respectively. The X-ray crystal structures of the three S-dapt ligands and three complexes along with spectroscopic analyzes are presented. The molecular structure investigations of the S-dapt ligands show that the thiamide planes are twisted with respect to the pyridine ring, which is more in the case of phenyl groups. The structures of the Co(II) complexes reveal that an increase in steric crowding on the amide side arms of the ligands has no substantial effect on the geometry adopted by the corresponding complexes. The Co(II) gives only 1?:?1 five-coordinate, ion-paired complexes with a distorted square pyramidal geometry. Ni(II), on the other hand, prefers an octahedral geometry with 1?:?2 metal–ligand ratio. The coordination behavior of S-dapt has been compared to the analogous oxo(O-daap) ligands. Lesser propensity of S atom to get involved in H-bonding interactions ensures an S-N-S type of tridentate coordination by S-dapt.