Supramolecular spectroscopic and thermal studies of azodye complexes

Application of Novel Ruthenium (II) Polypyridyl Complexes as Robust DNA Probes, Optical Material and Antimicrobials-An Experimental and DFT Approach

The nature of the interaction of DNA with heteroleptic Ruthenium (II) Polypyridyl complexes of the type [Ru (A)2TPIP]2+, where TPIP = 2-(1-p-tolyl-1H pyrazol-4 -yl)-1H-imidazo [4, 5-f[1. 10] phenanthroline and A = 1,10 phenanthroline (1),4,4'-dimethyl-1,10-ortho Phenanthroline (2), 2,2' - bipyridine (3) and 4, 4' dimethyl 2, 2'- bipyridine (4), has been investigated by experimentaland molecular docking approaches. The order of the DNA binding affinities of the synthesised complexes is 1 > 2 > 3 > 4. The findings imply that the unsubstituted complex has a better affinity to bind with DNA than the substituted (dmp and dmb) emphasizing the significance of the auxiliary ligand. Additionally, as the medium's ionic strength drops, the DNA/Ru ratio rises, or when water is displaced by glycerol, the intercalation of complexes into DNA increases. DFT calculations at the B3LYP/LANL2MB level was used for molecular geometry (Ground State) and electronic characteristic calculations. The HOMO-LUMO gap of the Ru [II] complex is less than the intercalator and hence kinetically labile. Among the complexes, the bpy complex has shown utmost non-linear optical properties (α = -153.9099 10-24esu and β = 3.8498 10-30esu). The docking study shows the significance of the Metal-intercalator's shorter length may increase DNA binding affinity. This study divulges that the Ruthenium (II) polypyridyl complexes bind to DNA preponderantly by intercalation supporting Viscosity studies. All the complexes have a considerable attraction for guanine. The standard disk diffusion method reveals that complexes (1, 2, 3 and 4) have good antibacterial activity.

TD-DFT calculations, dipole moments, and solvatochromic properties of 2-aminochromone-3-carboxaldehyde and its hydrazone derivatives

2-Aminochromone-3-carboxaldehyde (ACC) and its hydrazones (ACMHCA and ACMNPHTCA) with semicarbazide hydrochloride and N-phenylthiosemicarbazide were synthesized and characterized by elemental analysis and spectral studies. The solvatochromic behavior of the title compounds in various solvents showed distinct bathochromic shifts on going from nonpolar to polar solvents, suggesting intramolecular-charge-transfer (ICT) solute-solvent interactions. The ground and excited state dipole moments of ACC, ACMHCA, and ACMNPHTCA were determined experimentally by the solvatochromic shift method using the Bilot-Kawski, Lippert-Mataga, Bakhshiev, Kawski-Chamma-Viallet functions, and a microscopic Reichardt's solvent polarity parameter (ENT). All the investigated molecules showed a substantial increase in the dipole moment upon excitation to the emitting state. The experimental results were generally consistent with the values obtained by the TD-DFT, B3LYP/6-311G++(d,p) method. Molecular electrostatic potential (MEP) mapping and natural charge and natural bonding orbital (NBO) analysis were performed and the results were discussed. The 1H NMR chemical shifts of the prepared compounds were simulated by the gage independent atomic orbital (GIAO) method and compared with their experimental chemical shift values. The biological activity data were correlated with the frontier molecular orbitals. The photovoltaic behavior of the title compounds showed there was sufficient electron injection.

Novel Fluorescent Benzothiazolyl-Coumarin Hybrids as Anti-SARS-COVID-2 Agents Supported by Molecular Docking Studies: Design, Synthesis, X-ray Crystal Structures, DFT, and TD-DFT/PCM Calculations

This study revealed the design and preparation of new 3-(benzo[d]thiazol-2-yl)-2H-chromen-2-one derivatives 9a-h. The structures of the synthesized products were elucidated by their spectroscopic data and X-ray crystallography for compounds 9a and 9d. The prepared new compounds were measured for their fluorescence, and a good result indicated that the emission efficiency was decreased by increasing the electron-withdrawing groups from the unsubstituted compound 9a to the highly substituted derivative 9h (2 Br heavy atoms). On the other hand, the B3LYP/6-311G** theoretical level of theory was used to optimize the quantum mechanical calculations of the geometrical characteristics and energy of the novel compounds 9a-h under study. The electronic transition was investigated using the TD-DFT/PCM B3LYP approach, which uses time-dependent density functional calculations. Moreover, the compounds exhibited nonlinear optical properties (NLO) and a small HOMO-LUMO energy gap, which makes them easy to polarize. Furthermore, the acquired infrared spectra were compared with the expected harmonic vibrations of the substances 9a-h. On the other hand, binding energy analyses of compounds 9a-h with human corona virus nucleocapsid protein Nl63 (PDB ID: 5epw) were predicted using molecular docking and virtual screening tools. The results showed a promising binding and how these potent compounds were inhibiting the COVID-19 virus. Compound 9h was the most active anti-COVID-19 agent among all the synthesized benzothiazolyl-coumarin derivatives, as it forms five bonds. The presence of the two bromine atoms in its structure was responsible for the potent activity.

Experimental and theoretical studies of linear and non-linear optical properties of novel fused-triazine derivatives for advanced technological applications

Controlling photophysical properties is critical for the continued development of electroluminescent devices and luminescent materials. The preparation and study of novel molecules suitable as luminescent for the development of optoelectrical devices have recently received a lot of attention. Even though the as-triazine unit is a good building block for organic active substances, it is rarely used in this context. We created here novel bis-triazine derivative dyes in the far UV–Vis range by alkylation of triazine-thione derivatives with appropriate dibromo compounds. At the B3LYP/6-311**G(d,p) basis set, their optimal molecular structures were obtained. DFT technique confirmed that the new triazine derivatives are in noncoplanar with one of the two phenyl rings and the triazine plane rotating out by 102.09. Also, depending on the energy gap difference between HOMO and LUMO, some important parameters including chemical potential (π), electronegativity (χ), and chemical hardness (η) were calculated. The compounds may be readily polarized and have significant NLO characteristics, as seen by the tiny HOMO–LUMO energy gap. The calculated values for the polarizability (α) of the two new triazine derivatives have the range 6.09–10.75 × 10^–24 (esu). The emission peaks seemed to move to the long-wavelength (redshift), with a rise in the fluorescence band, suggesting that the singlet excited state is more polar than the ground state. The influence of solvent polarity and the intermolecular charge transfer (ICT) processes are reflected in the photophysical properties of new fused triazine derivatives. These properties such as extinction coefficient, absorption and emission cross-sections, fluorescence quantum yield, fluorescence lifetime, oscillator strength, the dipole moment, radiative decay rate constant, the energy yield of fluorescence, and the attenuation length were assessed and discussed.

An Aluminum-Based Metal-Organic Cage for Cesium Capture

Metal-organic cages are a class of supramolecular structures that often require the careful selection of organic linkers and metal nodes. Of this class, few examples of metal-organic cages exist where the nodes are composed of main group metals. Herein, we have prepared an aluminum-based metal-organic cage, H₈[Al₈(pdc)₈(OAc)₈O₄] (Al-pdc-AA), using inexpensive and commercially available materials. The cage formation was achieved via solvothermal self-assembly of solvated aluminum and pyridine-dicarboxylic linkers in the presence of a capping agent, acetic acid. The obtained supramolecular structure was characterized by single-crystal X-ray diffraction (SCXRD), thermogravimetric analysis, and NMR spectroscopy. Based on crystal structure and computational analyses, the cage has a 3.7 Å diameter electron-rich cavity suitable for the binding of cations such as cesium (ionic radius of 1.69 Å). The host-guest interactions were probed with ¹H and ¹³³Cs NMR spectroscopy in DMSO, where at low concentrations, Cs⁺ binds to Al-pdc-AA in a 1:1 ratio. The binding site was identified from the crystal structure of CsH₇[Al₈(pdc)₈(OAc)₈O₄] (Cs⁺⊂Al-pdc-AA), and a binding affinity of ∼10⁶-10⁷ M^-1 was determined from NMR titration experiments. The Al-pdc-AA showed improved selectivity for cesium binding over alkali metal cations (Cs⁺ > Rb⁺ > K⁺ ≫ Na⁺ ∼ Li⁺). Collectively, the study reports a novel aluminum cage that can serve as a promising host for efficient and selective cesium removal.

A Biophysical Study of Ru(II) Polypyridyl Complex, Properties and its Interaction with DNA

Mononuclear Ru(II)Polypyridyl complexes of type [Ru(A)₂BPIIP] (ClO₄)₂.2H₂O, where BPIIP = 2-(3-(4-bromophenyl)isoxazole-5-yl)-1 H-imidazo [4,5-f] [1, 10] phenanthroline and A = bpy = bipyridyl (1), phen = 1,10 Phenanthroline (2), dmb = 4, 4' -dimethyl 2, 2'- bipyridine (3) & dmp = 4,4'-dimethyl-1,10 -Ortho Phenanthroline (4), were synthesized and their antibacterial activity were examined. The synthesized complexes were characterized and their interaction with DNA was studied using Computational and Biophysical methods (Absorption, emission methods, and viscosity). Molecular modelling studies were carried out for molecular geometry and electronic properties (Frontier molecular orbital HOMO-LUMO). The electrostatic potential surface contours for the complexes were analysed to give their nucleophilic level of sensitivity. The study reveals that the Ru(II) Polypyridyl complexes bind to DNA preponderantly by intercalation. The results recommend that the phen and dmp complex have more effective binding ability than the bpy and dmb, indicating the role of the ancillary ligand in determining their specificity for DNA binding. Further molecular docking studies suggested an octahedral geometry and bind to DNA by preferential binding to Guanine. The docking study additionally sustains the binding constant data acquired with the absorption and emission techniques.The results reveal that the nature of the ancillary Ligand plays a considerable role for the intercalation of the Ru(II) polypyridyl complex to DNA, which subsequently influences the antibacterial activity. Biological studies conducted on Gram-Negative (E.coli and K.pneumonia) and Gram-Positive (S. aureus and E. faecalis) bacteria establish that complex 1 and 2 were considerably active against S. aureus and E. coli.

A novel palladium(II) antitumor agent: Synthesis, characterization, DFT perspective, CT-DNA and BSA interaction studies via in-vitro and in-silico approaches

Since numerous people annually pass away due to cancer, research in this field is essential. Thus a newly made and water like palladium(II) complex of formula [Pd(phen)(acac)]NO₃, where phen is 1,10-phenanthroline and acac is acetylacetonato ligand, has been synthesized by the reaction between [Pd(phen)(H₂O)₂](NO₃)₂ and sodium salt of acetylacetone in the molar ratio of 1:1. It has been structurally characterized via the methods such as conductivity measurement, elemental analysis and spectroscopic methods (FT-IR, UV-Vis and ¹H NMR). The geometry optimization of this complex at the DFT level of theory reveals that Pd(II) atom is situated in a square-planar geometry. The complex has been screened for its antitumor activity against K562 cancer cells which demonstrated efficacious activity. The interaction of above palladium(II) complex with CT-DNA as a target molecule for antitumor agents and BSA as a transport protein was studies by a variety of techniques. The results of UV-Vis absorption and fluorescence emission indicated that the Pd(II) complex interacts with EB + CT-DNA through hydrophobic and with BSA by hydrogen bonding and van der Waals forces at very low concentrations. In these processes, the fluorescence quenching mechanism of both the macromolecules seems to be the combined dynamic and static. The interaction was further supported for CT-DNA by carrying out the gel electrophoresis and viscosity measurement and for BSA by the circular dichroism and Förster resonance energy transfer experiments. Furthermore, results of partition coefficient determination showed that the [Pd(phen)(acac)]NO₃ complex is more lipophilic than that of cisplatin. Moreover, molecular docking simulation confirms the obtained results from experimental tests and reveals that the complex tends to be located at the intercalation site of DNA and Sudlow's site I of BSA.

The synthesis, spectroscopic characterization, DFT/TD-DFT/PCM calculations of the molecular structure and NBO of the novel charge-transfer complexes of pyrazine Schiff base derivatives with aromatic nitro compounds

Novel charge-transfer complexes of pyrazine Schiff bases derived from 2-aminopyrazine with benzaldehyde and N-4-dimethylaminobenzaldehyde with some aromatic nitro compounds have been synthesized and characterizes experimentally and confirmed theoretically.

A coumarin Schiff base and its Ag(i) and Cu(ii) complexes: synthesis, characterization, DFT calculations and biological applications

Synthesis, characterization and DFT calculations of coumarin Schiff base and its complexes.

Allyl rhodanine azo dye derivatives: Potential antimicrobials target d-alanyl carrier protein ligase and nucleoside diphosphate kinase

3-Allyl-5-(4-arylazo)-2-thioxothiazolidine-4-one (HL_n ) ligands (where n = 1 to 3) were hypothesized to have antimicrobial activities mediated through inhibition of new antimicrobial targets. The ligands (HL_n ) were synthesized and characterized by infrared (IR) and ¹ H nuclear magnetic resonance (¹ H NMR) spectra. The ligands (HL_n ) were in silico screened to their potential inhibition to models of d-alanyl carrier protein ligase (DltA) (from Bacillus cereus, PDB code 3FCE) and nucleoside diphosphate kinase (NDK) (from Staphylococcus aureus; PDB code 3Q8U). HL₃ ligand has the best energy and mode of binding to both NDK and DltA, even though its binding to DltA was stronger than that to NDK. In antimicrobial activity of HL₃ ligand, morphological and cytological changes in HL₃ -treated bacteria agreed with the in silico results. The HL₃ ligand showed significant antimicrobial activity against B. cereus, S. aureus, and Fusarium oxysporium. The HL₃ -treated bacterial cells appeared malformed and incompletely separated. Its cell walls appeared electron-lucent and ruptured. They contained more mesosomes than normal cells. It was found that the HL₃ ligand represented as a bactericide against B. cereus and S. aureusby blocking target DltA, and may target NDK.

Combined experimental, DFT theoretical calculations and biological activity of sulfaclozine azo dye with 1-hydroxy-2-naphthoic acid and its complexes with some metal ions

Sulfaclozine-1-hydroxy-2-naphthoic acid azo dye (Scna) and its metal complexes with Ni(ii) Cu(ii), Zn(ii) and Pd(ii) metal ions have been prepared and characterized using different techniques.

Tautomeric transformations and electronic structures of azopyrazolone dyes and their metal complexes

The features of molecular and electronic structures of complex compounds derived from azopyrazolone derivatives are reviewed. Despite the wide use of metal-containing azopyrazolone dyes for more than 1.5 centuries, little information on their molecular structure is found. Our recent researches allowed the introduction of new coordination modes of azopyrazolone derivatives at complexation with metals. Together with traditional bi- and tridentate coordination, the possibility of an N pyrazolone atom to be involved in coordination was also found. As a result, polymeric or polynuclear complexes were isolated and described by X-ray analysis, NMR, EPR, IR, and UV spectroscopy. The analysis of the interatomic distances in the organic anions indicated that azopyrazolone derivatives do not undergo significant azo-hydrazo tautomeric transformations at ionization and complexation despite strong shifts of the absorption bands in their IR and UV-VIS spectra.

Copper-metformin ternary complexes: Thermal, photochemosensitivity and molecular docking studies

The copper(II) complexes [Cu(Cl)₂(met)(o-phen)] (1), [Cu(Cl)₂(met)(en)] (2) and [Cu(Cl)₂(met)(opda)] (3) (met = metformin, o-phen = ortho-phenanthroline, en = ethylenediamine, opda = ortho-phenylenediamine) were synthesized and characterized by LC-MS, elemental analysis, molar conductance, thermal analysis, infrared spectra, magnetic moment, electronic spectra and XRD studies. The metal center was found in an octahedral geometry. The activation thermodynamic properties were calculated using Coats-Redfern method. Thermal decomposition processes of complexes 1, 2, 3 are non-spontaneous, i.e., the complexes are thermally stable. The positive value of Gibbs free energy of decomposition (ΔG^⁎) for the Cu(II) complexes is non-spontaneous processes. UV-Visible absorption, fluorescence, and viscosity measurements have been conducted to assess the interaction of the complexes with CT DNA. The complexes showed absorption hyperchromism in its UV-Vis spectrum with DNA. The binding constants K_b from UV-Vis absorption studies were 4.6 × 10⁵, 1.48 × 10⁵, 2.09 × 10⁵ M^-1 for 1, 2, 3 respectively and Stern-Volmer quenching constants (K_sq) from fluorescence studies were 0.636, 0.293, 0.487 for 1, 2, 3 respectively. Finally, viscosity measurements revealed that the binding of the complexes with CT-DNA could be surface binding, mainly due to groove binding. The activity of complexes towards DNA cleavage decreases in the order of 1 > 3 > 2. The complexes were docked in to B-DNA sequence, 5'(D*AP*CP*CP*GP*AP*CP*GP*TP*CP*GP*GP*T)-3' retrieved from protein data bank (PDB ID: 423D), using Discovery Studio 2.1 software.