Pyridine appended pyrimidine bis hydrazone: Zn2+/ATP detection, bioimaging and functional properties of its dinuclear Zn(II) complex.

A pyridine functionalized pyrimidine-based system, H2P was successfully synthesized, characterized, and evaluated for its remarkable selective characteristics towards Zn2+ and ATP ions. The chemical sensing capabilities of H2P were demonstrated through absorption, fluorescence, and NMR spectroscopic techniques. The probe exhibited outstanding sensitivity when interacting with the ions, demonstrating relatively strong association constants and impressively low detection limits. The comprehensive binding mechanism of H2P with respect to Zn2+ and ATP ions was investigated using a combination of analytical methods, including Job's plot, NMR spectroscopy, mass spectrometry, and density functional theory (DFT) experiments. The interesting sensing ability of H2P for Zn2+/ATP ions was harnessed for live cell bioimaging and other diverse on-site detection purposes, including paper strips, cotton swabs, and applications involving mung bean sprouts. Further, the fluorescent probe demonstrated its effectiveness in detecting Zn2+ and ATP within live cells, indicating its significant potential in the realm of biological imaging applications. Moreover, the molecular configuration of the zinc complex (H2P-Zn2Cl4), derived from H2P, was elucidated using X-ray crystallography. This complex exhibited intriguing multifunctional attributes, encompassing its capability for detecting picric acid and for reversible acid/base sensing responses. The enhanced conducting behavior of the complex as well as its resistance properties were investigated by performing I-V characteristics and electrochemical impedance spectroscopic (EIS) experiments respectively.

Diethylaminophenol appended pyrimidine bis hydrazone for the sequential detection of Al3+ and PPi ions.

In this study, a novel easy-to-prepare diethylaminophenol appended pyrimidine bis hydrazone (HD) has been designed and developed. The probe exhibits excellent sequential sensing characteristics towards Al3+ and PPi ions. The emission studies, various spectroscopic techniques and lifetime results have been utilized to understand the binding mechanism of HD with Al3+ ions and, to discover the specificity as well as the efficacy of the probe in sensing Al3+ ions. The good association constant in addition to the lower detection limit values makes the probe effective for the detection of Al3+. The in-situ produced HD-Al3+ ensemble could consecutively detect PPi via a turn-off fluorescence response and the selectivity and sensitivity characteristics of the generated ensemble towards PPi were described based on the demetallation approach. The overall sensing property of HD was perfectly employed for constructing logic gates, real water, and tablet applications. Paper strips, as well as cotton-swab experiments, were also conducted inorder to check the practical utility of the synthesized probe.

Intramolecular interactions (O-H∙∙∙O, C-H∙∙∙N, N-H∙∙∙π) in isomers of neutral, cation, and anion dopamine molecules: A DFT study on the influence of solvents (water and ethanol).

CONTEXT: Dopamine (DA) is one of the most important neurotransmitters associated with numerous neural disorders. This investigation reports the intramolecular interactions present in the isomers of neutral (DA0), anionic (DA-), and cationic (DA+) dopamine isomers in gas, water, and ethanol mediums. Neutral and anion isomers have O-H∙∙∙O, C-H∙∙∙N intramolecular hydrogen bonds and N-H∙∙∙π interactions. All the interactions are electrostatic in nature. Isomers of cation dopamine show no intramolecular interactions in the solvent. Natural charges from natural bond orbital (NBO) analysis show that O-H∙∙∙O bonds and the N-H∙∙∙π interactions are the most and least polar, respectively. 1H NMR study reveals the inverse linear correlation between shielding constant and electron density in a solvent medium. HOMO-LUMO energy gap indicates higher stability for neutral and cationic forms of dopamine isomers in water and ethanol medium. METHODS: We have optimized all the structural forms of dopamine molecule using the Becke three hybrid exchange and Lee-Yang-Parr correlation functional with Grimme's dispersion correction, B3LYP-D3(BJ), and aug-cc-pVTZ basis set using the Gaussian16 software. Vibrational frequency analysis with no imaginary frequencies confirms the nature of global minima. The solvent studies (water and ethanol) were carried out using the SCRF keyword and the polarisable continuum model (PCM) of Miertus and Tomasi. NBO analysis and NMR studies were also performed for all conformers. Topology analysis was explored using the software Multiwfn.

Green synthesis of benzimidazole derivatives by using zinc boron nitride catalyst and their application from DFT (B3LYP) study.

A new zinc-based boron nitride (Zn-BNT) material was synthesized from boron nitride and zinc acetate in 95% yield. The morphological and spectroscopic properties of Zn-BNT were elucidated by SEM, XRD, BET, DSC-TGA, and FT-IR. Zn-BNT catalyzed the synthesis of benzimidazoles (3a-3h) through a reaction between o-phenylenediamine and different aromatic aldehydes under microwave conditions for 15 min. The compounds were purified by silica-gel chromatography. The synthesized compounds were characterized by FT-IR, 1H-NMR, 13C-NMR, and elemental analysis. Zn-BNT was reused eight times with only a 5% loss of catalytic activity. Furthermore, 2-(4-fluorophenyl)-1H-benzo[d]imidazole (3f) was selected for a computational study of the IR and NMR spectrum, which matched the experimentally generated spectra. The HOMO-LUMO gap was 4.48, and the Fukui function analysis showed high activity in the reactive sites.

Cation-Anion Interactions, Stability, and IR Spectra of Dicationic Amino Acid-Based Ionic Liquids Probed Using Density Functional Theory.

In this work, we have theoretically studied the dicationic ionic liquids (DILs) constructed from geminal methylimidazolium dication with varying amino acid anions and spacers using density functional theory. Amino acid-based DILs form via strong C-H···O hydrogen bonds. These hydrogen bonds have a significant role in stabilizing the DILs. The higher cation-anion interaction energy in the order of covalent bond energy and liquid density of DILs imply higher thermal stability than their mono analogues. The C-H stretching frequencies are above 3100 cm-1 in all complexes and form a signature for DILs. Interestingly, aliphatic and aromatic amino acid anions show similar molecular properties. Overall, the DILs formed from amino acids exhibit high stability and large surface tension and are chemically non-toxic; hence, they can replace inorganic DILs.

Molecular properties of metal difluorides and their interactions with CO2 and H2O molecules: a DFT investigation.

A computational study of metal difluorides (MF2; M = Ca to Zn) and their interactions with carbon dioxide and water molecules was performed. The structural parameter values obtained and the results of AIM analysis and energy decomposition analysis indicated that the Ca-F bond is weaker and less ionic than the bonds in the transition metal difluorides. A deformation density plot revealed the stablizing influence of the Jahn-Teller effect in nonlinear MF2 molecules (e.g., where M= Sc, Ti, Cr). An anaysis of the metal K-edge peaks of the difluorides showed that shifts in the edge energy were due to the combined effects of the ionicity, effective nuclear charge, and the spin state of the metal. The interactions of CO2 with ScF2 (Scc3 geometry) and TiF2 (Tic2 geometry) caused CO2 to shift from its usual linear geometry to a bent geometry (η2(C=O) binding mode), while it retained its linear geometry (η1(O) binding mode) when it interacted with the other metal difluorides. Energy decomposition analysis showed that, among the various geometries considered, the Scc3 and Tic2 geometries possessed the highest interaction energies and orbital interaction energies. Heavier transition metal difluorides showed stronger affinities for H2O, whereas the lighter transition metal (Sc and Ti) difluorides preferred CO2. Overall, the results of this study suggest that fluorides of lighter transition metals with partially filled d orbitals (e.g., Sc and Ti) could be used for CO2 capture under moist conditions. Graphical abstract Interaction of metal difluorides with carbon dioxide and water.

Gas adsorption efficacy of graphene sheets functionalised with carboxyl, hydroxyl and epoxy groups in conjunction with Stone-Thrower-Wales (STW) and inverse Stone-Thrower-Wales (ISTW) defects.

The complete reduction of graphene oxide is difficult to achieve, and hence oxygen-containing functional groups do exist in graphene, along with structural defects. On the other hand, efficient gas sensor materials have been a subject of relentless interest. This instigates the need to explore the gas adsorption on STW and ISTW defective graphene sheets functionalised by -COOH, -OH and C-O-C groups, using density functional theory calculations. Both defects are experimentally feasible as evident through their formation energies. Furthermore mono-functionalisation induces significant buckling of the sheet; in contrast, bi-functionalisation of the sheet restores the planarity of the sheet. We found that the ISTW defective sheet is more reactive than the STW defective sheet to all the functional groups considered, and in particular -COOH is the most adsorptive group to both the defects, while epoxy has consistent adsorptivity towards the defects. Gas molecules such as CO2, H2, N2, CH4 and O2 are physisorbed, whereas HF and H2O are chemisorbed on the functionalised sheets. The sensitivity of the gas molecules towards the functionalised sheets is obtained by ΔEg, which is pronounced for pristine + OH and STW + epoxy and bare ISTW defective sheets. However, the functionalised sheets exhibit improved sensing properties for O2; specifically, mono-epoxy functionalised and bi-carboxylated defective sheets show high sensitivity towards O2. Furthermore, the surface functionalisation enhances the selectivity of the sensor. From the TDOS plot, the functionalised sheet exhibits p-type behaviour. Thus, the results of this study reveal that the functionalised defective sheets can be utilized as O2 sensors.

Hydrogen bonds in Zif268 proteins - a theoretical perspective.

The aim of the work was to elucidate the presence of different hydrogen bond (H-bond) in five Zif268 proteins (1A1F, 1A1G, 1A1H, 1A1I and 1A1K). For this purpose, we have performed the QM/MM and molecular dynamics (MD) studies, the results of which reveal that H-bonds depend on the amino acid sequence and orientation of the H-bond donor atoms. Further, high specificity of Arg and Asn is observed for guanine and adenine, respectively. Furthermore, both conventional and non-conventional hydrogen bond also exists in the proteins, among them N-H⋯O H-bonds are the strongest. Besides, the non-conventional bonds play a role in the protein folding and DNA stacking. From the QSAR properties, amino acids such as asparagine and aspartic acids are the major reactive sites in the Zif268 protein. The electron affinities of Zif268 proteins are high, so the charge transfer occurs from the DNA to the protein molecules. NBO analysis indicates the majority of charge transfer occurs from DNA to the corresponding anti-bonding orbital of the peptides. Root mean square deviation and Rg (radius of gyration) show that 1A1F is more compact and in native state during MD simulation. The minimum Rg leads to the large number of hydrogen bonds formation in 1A1F. Higher solvent accessible surface area in 1A1I indicates that the cavity inside the protein is large.