Azaindoles: Suitable ligands of cytotoxic transition metal complexes

Vibrational and DFT Studies and Anticancer Activity of Novel Pd(II) and Pt(II) Complexes with Chloro Derivatives of 7-Azaindole-3-Carbaldehyde

This study investigates the structural, vibrational, and biological properties of novel palladium(II) and platinum(II) complexes with 5-chloro-7-azaindole-3-carbaldehyde (5ClL) and 4-chloro-7-azaindole-3-carbaldehyde (4ClL) ligands. Infrared and Raman spectroscopy, combined with DFT (ωB97X-D) calculations, provided valuable information about metal-ligand interactions, the cis or trans conformation of the aldehyde group in the ligands, and the presence of trans isomers in the metal complexes obtained in the solid state. In vitro tests were used to evaluate the antiproliferative activity of the novel complexes against several cancer cell lines, including ovarian cancer (A2780), cisplatin-resistant ovarian cancer (A2780cis), colon cancer (HT-29), and triple-negative breast cancer (MDA-MB-231), as well as normal mouse fibroblasts (BALB/3T3). The platinum complex, trans-[PtCl2(5ClL)2], exhibited superior activity against A2780cis (IC50 = 4.96 ± 0.49 µM) and MDA-MB-231 (IC50 = 4.83 ± 0.38 µM) compared to cisplatin, while the palladium complexes (trans-[PdCl2(4ClL)2] and trans-[PdCl2(5ClL)2]) demonstrated enhanced selectivity with reduced toxicity to normal fibroblasts (IC50 = 11.29 ± 6.65 µM and 14.98 ± 5.59 µM, respectively).

Discovery of Novel Fluorescent Azaindoles with Cytotoxic Action in A2780 Ovarian Carcinoma Cells

Azaindole scaffold is a privileged structure in medicinal chemistry and some derivatives have demonstrated to be potential anticancer drugs. Herein, a set of novel azaindoles, comprising the four regioisomers, bearing a morpholine (azaindoles 3 a-d) and N-methyl-N-benzylamine (azaindoles 4 a-d) groups were prepared. Among these compounds, azaindoles 4 exhibited higher cytotoxicity against the ovarian cancer cell line A2780 and normal dermal fibroblasts compared to azaindoles 3. Furthermore, azaindoles 4 b and 4 c promoted a delay in the cell cycle of the cancer cell line, inspiring an investigation into the intracellular localization of these derivatives.

Laser spectroscopic characterization of supersonic jet cooled 2,7-diazaindole

We report the first gas phase comprehensive study of the electronic spectroscopy of 2,7-diazaindole molecule in the ground and excited states. Single vibronic level fluorescence spectroscopy (SVLF) was performed to determine the ground state vibrations of the molecule, which depicted a large Franck-Condon activity beyond 2600 cm-1. For the excited state characterization, laser-induced fluorescence (LIF) and two-color resonant two-photon ionization spectroscopy (2C-R2PI) were performed. The band origin (000) for S1 ← S0 transition appeared at 33910 ± 1 cm-1 which was red shifted by 718 cm-1 and 1322 cm-1 compared to that of 7-azaindole and indole respectively. The Franck-Condon active vibrational modes in the spectra were seen till the (000) + 1600 cm-1 region. The IR-UV hole burning spectroscopy confirmed the absence of any other isomeric species in the molecular beam. The ionization energy (IE) of the molecule was measured as 8.921 ± 0.001 eV, recorded using photoionization efficiency spectroscopy. The above IE value was significantly higher than that of the related indole derivatives, suggesting the higher photostability of the 27DAI molecule due to N(2) insertion. The ground and excited state N-H stretching frequencies of the molecule were determined using fluorescence-dip infrared spectroscopy (FDIR) and resonant ion-dip infrared spectroscopy (IDIR), and the values are 3523 and 3467 cm-1, respectively. The lower value of νNH in the electronic excited state implied the increased photoacidity of the group. A comparative analysis of the experimental LIF/2C-R2PI spectra was done against Franck-Condon simulated spectra at three different levels of theory. The vibrational frequencies calculated at B3LYP-D4/def2-TZVPP showed the most accurate prediction in comparison with the experimentally detected symmetric modes in the ground state. However, in the excited state, the lower energy asymmetric modes simulated at the B3LYP/def-SVP level of theory provided the best agreement with the experiment. This is most probably due to the distortion observed at the pyrazolyl ring leading to the appearance of asymmetric vibrational modes. The above study highlights the possibility to appropriately tune the excitation wavelengths as well as alter the photostability of the organic chromophores via additional N-insertion in the molecular systems.

The Application of Microwaves, Ultrasounds, and Their Combination in the Synthesis of Nitrogen-Containing Bicyclic Heterocycles

The use of alternative energy sources, such as microwaves (MW) or ultrasounds (US), and their mutual cross-combination have been widely described in the literature in the development of new synthetic methodologies in organic and medicinal chemistry. In this review, our attention is focused on representative examples, reported in the literature in the year range 2013-2023 of selected N-containing bicyclic heterocycles, with the aim to highlight the advantages of microwave- and ultrasound-assisted organic synthesis.

Fluorescence, DNA Interaction and Cytotoxicity Studies of 4,5-Dihydro-1H-Pyrazol-1-Yl Moiety Based Os(IV) Compounds: Synthesis, Characterization and Biological Evaluation

Osmium(IV) pyrazole compounds and ligands were synthesized and well characterised. Ligands were characterized by heteronuclear NMR spectroscopy (¹H & ¹³C), elemental analysis, IR spectroscopy and liquid crystal mass spectroscopy. Os(IV) complexes were characterized by ESI-MS, ICP-OES, IR spectroscopy, conductance measurements, magnetic measurements and electronic spectroscopy. Binding of compounds with HS-DNA were evaluated using viscosity measurements, absorption titration, fluorescence quenching, and molecular docking, which show effective intercalation mode exhibited by compounds. Binding constant of Os(IV) complexes are found to be 8.1 to 9.2 × 10⁴ M^-1. Bacteriostatic and cytotoxic activities were carried out to evaluate MIC, LC₅₀, and IC₅₀. The compounds have been undergone bacteriostatic screening using three sets of Gram^+ve and two sets of Gram^-ve bacteria. MIC of complexes are found to be 72.5-100 μM, whereas that of ligands fall at about 122.5-150 μM.. LC₅₀ count of ligands fall in the range of 16.22-17.28 μg/mL whereas that of complexes of Os(IV) fall in the range of 4.87-5.87 μg/mL. IC₅₀ of osmium compounds were evaluated using HCT-116 cell line. All the Os(IV) compounds show moderate IC₅₀.

An unexpected in-solution instability of diiodido analogue of picoplatin complicates its biological characterization

Complex cis-[PtI2(NH3)(pic)] (1; pic = 2-methylpyridine), a diiodido analogue of clinically studied picoplatin (2), is unstable in solution, which is intriguingly connected with the release of its pic ligand. This observation complicates the biological testing of e.g. cytotoxicity in human cancer cells for 1.