Experimental and theoretical vibrational study of isatin, its 5-(NO2, F, Cl, Br, I, CH3) analogues and the isatinato anion

Synthetic beidellite clay as nanocarrier for delivery of antitumor oxindolimine-metal complexes

Studies on the immobilization of oxindolimine‑copper(II) or zinc(II) complexes [ML] in synthetic beidellite (BDL) clay were developed to obtain a suitable inorganic carrier capable of promoting the modified-release of metallopharmaceuticals. Previous investigations have shown that the studied metal complexes are promising antitumor agents, targeting DNA, mitochondria, and some proteins. They can bind to DNA, causing oxidative damage via formation of reactive oxygen species (ROS). In mitochondria they lead to a decrease in membrane potential, acting as decoupling agents, and therefore efficiently inducing apoptosis. Additionally, they inhibit human topoisomerase IB and cyclin dependent kinases, proteins involved in the cell cycle. BDL clays in the sodium form were synthesized under hydrothermal conditions and characterized by a set of physicochemical techniques while the BDL-[ML] hybrid materials were prepared by ion exchange method. The characterization of pristine clay and the obtained hybrids were performed by Infrared, Raman, electron paramagnetic resonance and energy dispersive X-ray spectroscopies, thermogravimetric analysis, scanning electron microscopy, X-ray powder diffraction, specific surface area, zeta potential and surface ionic charge measurements. The [ML] release assays under the same cell incubation conditions were performed monitoring metals by X-ray fluorescence. The BDL-[CuL] hybrid materials were stable and able to derail tumor HeLa cells, with corresponding IC₅₀ values in the 0.11-0.41 mg mL^-1 range. By contrast, the analogous hybrid samples of zinc(II) and the pristine BDL proved to be non-toxic facing the same cells. These results indicate a promising possibility of using synthetic beidellite as a carrier of such antitumor metal complexes.

Exploring the Effects of Water on the Mechanism of the Catalyst-Free Reaction between Isatin and 3-Methyl-2-pyrazolin-5-one from the Mixed Implicit/Explicit Multiple Types of Water Clusters

Density functional theory calculations with implicit/explicit water cluster models were conducted to pursue deeper understandings about the mechanism and the water effects in the reaction of isatin with 3-methyl-2-pyrazolin-5-one. The proposed preferential mechanistic scenario here undergoes three major steps: first, 3-methyl-2-pyrazolin-5-one converts to its enol form and then, the aldol addition reaction takes place between isatin and enol to generate the intermediate INT2, followed finally by the tautomerization of INT2 to become the product 3-pyrazolone. The computed results indicate that the direct aldol reaction without the water auxiliary is feasible in the second step and the remaining tautomerization steps (steps 1, 3, and 4) assisted by tri-, tri-, and six-water cluster models, respectively, are the most favorable cases. It is further noted that more hydrogen bonding interactions in the tri-water auxiliary reaction are essential for the reduction of the free energy barrier ΔG^⧧ in the proton transfer largely than those assisted by the other types of water cluster models. The origin of the more stable transition state in the rate-determining step of the tri-water cluster model is ascribed to smaller cyclic strain and more global electron density transfer associated to its structure than the other types of water cluster models.

Single-crystal X-ray structural characterization, Hirshfeld surface analysis, electronic properties, NBO, and NLO calculations and vibrational analysis of the monomeric and dimeric forms of 5-nitro-2-oxindole

The information of interactions is given by RDG versus sign(λ₂)ρ product of the sign of the second largest eigenvalue of electron density Hessian matrix and electron density) investigated by RDG surface analysis.

Structure and catalytic properties of novel copper isatin Schiff base complexes

Isatin Schiff bases in combination with copper ions act as non-innocent ligands amplifying the alcohol oxidation process.

Effect of Structure on Charge Distribution in the Isatin Anions in Aprotic Environment: Spectral Study

Five isatin anions were prepared by deprotonation of initial isatins in aprotic solvents using basic fluoride and acetate anions (F⁻ and CH₃COO⁻). The F⁻ basicity is sufficient to deprotonate isatin NH hydrogen from all the studied compounds. This process is reversible. In the presence of proton donor solvents, the anions form the corresponding isatins. The isatin hydrogen acidity depends on the overall structure of the isatin derivatives. The anions were characterized by ultraviolet–visible (UV–Vis), Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopy. Interestingly, the anions form aggregates at concentrations above 10⁻³ mol·dm⁻³. Further, the effect of cations on the UV–Vis spectra of the studied anions was studied. Charge transfer and its distribution in the anion depends on the radius and the cation electron configuration. The alkali metal cations, tetrabutylammonium (TBA⁺), Mg²⁺ and Ag⁺, interact with the C-2 carbonyl oxygen of the isatin anion. The interaction has a coulombic character. On the other hand, Cd²⁺, Zn²⁺, Hg²⁺, Co²⁺, and Cu⁺ cations form a coordinate bond with the isatin nitrogen.

Pharmacophore hybrid approach of new modulated bis-diimine Cu(II)/Zn(II) complexes based on 5-chloro Isatin Schiff base derivatives: Synthesis, spectral studies and comparative biological assessment

Novel bioactive 5-chloro isatin based Schiff base ligands, (N,N'E,N,N'Z)-N,N'-(5-chloroindoline-2,3-diylidene)bis(5-nitrobenzo [d]thiazol-2-amine), L(1) and (N,N'E,N,N'Z)-N,N'-(5-chloroindoline-2,3-diylidene)bis(5-nitrothiazol-2-amine), L(2) derived from 2-amino 5-nitrobenzothiazole and 2-amino 5-nitrothiazole and their metal complexes, [Cu(L(1))2]Cl2;1, [Zn(L(1))2(H2O)2]Cl2;2, [Cu(L(2))2]Cl2;3 and [Zn(L(2))2(H2O)2]Cl2;4 have been synthesized. The composition, stoichiometry and geometry of the proposed ligands and their complexes have been envisaged by the results of elemental analyses and spectroscopic data (FT-IR, (1)H NMR and (13)C NMR, Mass and EPR). The molar conductivity values of the metal complexes revealed their ionic nature. The thermal stability of metal complexes was demonstrated by TGA/DTA studies while the crystalline nature of the complexes has been ascertained by XRD. Furthermore, a comparative account of in vitro antibacterial study against different bacterial strains with respect to standard antibiotic and scavenging activity against standard control at different concenterations unfolded pronounced antibacterial and radical scavenging potencies of the metal complexes as compared to free ligands. In addition, in vitro cytotoxicity of ligands and its metal complexes was also screened on MCF7 (Human breast adenocarcinoma), HeLa (Human cervical carcinoma) and HepG2 (Human Hepatocellular carcinoma), cell lines and normal cells (PBMC). The antiproliferative outcomes revealed that metal complexes exhibit superior activity in general as compared to free ligands (L(1) and L(2)) where metal complexes (1 and 2) of 5-chloro isatin linked benzothiazole motif (L(1)) are found to have better prospect of acting as chemotherapeutic agents which can be explained in terms of greater biopotency, planarity and conjugation against all the tested cancer cell lines with IC50<2.80 μM.

Ab initio and density functional theory studies on vibrational spectra of 3-hydroxy-3-(2-methyl-1H-indol-3-yl)indolin-2-one

Computational studies have been carried out on 3-hydroxy-3-(2-methyl-1H-indol-3-yl) indolin-2-one (HMI) using both the DFT-B3LYP/6-311+G and HF/6-311+G methods. The optimized geometry of HMI and its bonding parameters as well as IR spectra have been calculated and analyzed. It can be seen that the calculated bond lengths are in good agreement with the reported bond lengths of indole and isatins. The calculated spectra have been compared with the available experimental FT-IR spectra. From vibrational frequency analysis, it can be seen that the vibrational frequencies obtained from B3LYP method are in good agreement with the experiment, when compared to HF method and there is an excellent correlation with the 0.999 regression coefficient between the experimental and calculated vibrations for HMI. The geometrical parameters, non-linear optical properties and thermodynamic properties are calculated and reported.

Synthesis and Toxicity Evaluation of Some N4-Aryl Substituted 5-Trifluoromethoxyisatin-3-thiosemicarbazones

A series of twenty one N4-aryl substituted 5-trifluoromethoxyisatin-3-thiosemicarbazones 3a-3u was synthesized by the reaction of trifluoromethoxyisatin 1 with different arylthiosemicarbazides 2 in aqueous ethanol (50%), containing a few drops of acetic acid. Their structures were established on the basis of analytical (CHN) and spectral (IR, 1H-NMR, EIMS) data. All the synthesized compounds were evaluated for their toxicity potential by a brine shrimp lethality bioassay. Ten compounds i.e., 3a, 3e, 3i-3l and 3n-3q proved to be active in this assay, displaying promising toxicity (LD50 = 1.11 × 10-5 M - 1.80 × 10-4 M). Amongst these, 3k, 3n and 3o were found to be the most active ones (LD50 = 1.11 × 10-5 M - 1.43 × 10-5 M). Compound 3k showed the highest activity with a LD50 value of 1.11 × 10-5 M and can, therefore, be used as a lead for further studies. Structure-activity relationship (SAR) studies revealed that the presence of strong inductively electron-attracting trifluoromethoxy substituent at position-5 of the isatin moiety played an important role in inducing or enhancing toxic potentiality of some of the synthesized compounds.

Synthesis and primary cytotoxicity evaluation of new 5-nitroindole-2,3-dione derivatives

A new series of 5-nitro-1H-indole-2,3-dione-3-thiosemicarbazones (3a-k) obtained by condensation of 5-nitro-1H-indole-2,3-dione (1) with N-substituted-thiosemicarbazides (2a-k) were treated with morpholine or piperidine and formaldehyde to yield 1-morpholino/piperidinomethyl-5-nitroindole-2,3-dione-3-thiosemicarbazones (4a-m). The structures of all the compounds were determined by analytical and spectral (IR, 1H-NMR, EIMS) methods. Compounds 3b, 3c, 3f, 3k, 4a, 4c, 4f and 4l chosen as prototypes were evaluated in the National Cancer Institute's 3-cell line, one dose in vitro primary cytotoxicity assay. All the compounds that passed the criteria for activity in this assay were scheduled automatically for evaluation against the full panel of 60 human tumour cell lines at a minimum of five concentrations at 10-fold dilutions. Sulphorhodamine B (SRB) protein assay was used to estimate cell stability or growth. The most active compound was found to be 1-morpholinomethyl-5-nitroindole-2,3-dione-3-N-(chlorophenyl)thiosemicarbazone (4l). This compound demonstrated the most marked effects in the National Cancer Institute's 60 human tumour cell line in vitro screen on a non-small cell lung cancer cell line (HOP-62, log(10)GI(50) value <-8.00) and on leukaemia cell lines (HL-60(TB), log(10)GI(50) value -6.30; MOLT-4, log(10)GI(50) value -6.18).