FT-IR, FT-Raman spectra and ab initio HF and DFT calculations of 4-N,N'-dimethylamino pyridine

Synthesis, characterization, DNA binding interactions, DFT calculations, and Covid-19 molecular docking of novel bioactive copper(I) complexes developed via unexpected reduction of azo-hydrazo ligands

In this work, we focused on the 3rd goal of the sustainable development plan: achieving good health and supporting well-being. Two redox-active hydrazo ligands namely, phenylcarbonohydrazonoyldicyanide (PCHD) and pyridin-4-ylcarbonohydrazonoyl-dicyanide (PyCHD), and their copper(I) complexes have been synthesized and characterized. The analytical data indicates the formation of copper(I) complexes despite starting with copper(II) perchlorate salt. The 1H-NMR and UV-visible spectral studies in DMSO revealed that PyCHD mainly exists in its azo-form, while PCHD exists in azo ↔ hydrazo equilibrium form, and confirmed the copper(I) oxidation state. XPS, spectral and electrochemistry data indicated the existence of copper(I) valence of both complexes. Cyclic voltammetry of PCHD and its copper(I) complex supported the reduction power of the ligand. The antimicrobial activity, cytotoxicity against the mammalian breast carcinoma cell line (MCF7), and DNA interaction of the compounds are investigated. All compounds showed high antimicrobial, and cytotoxic activities, relative to the standard drugs. Upon studying the wheat DNA binding, PCHD and PyCHD were found to bind through external contacts, while both [Cu(PCHD)2]ClO4.H2O and [Cu(PyCHD)2]ClO4.H2O were intercalated binding. In-silico molecular docking simulations against Estrogen Receptor Alpha Ligand Binding Domain (ID: 6CBZ) were performed on all produced compounds and confirmed the invitro experimentally best anticancer activity of [Cu(PyCHD)2]ClO4.H2O. The molecular docking tests against SARS-CoV-2 main protease (ID: 6 WTT) showed promising activity in the order of total binding energy values: [Cu(PCHD)2]ClO4.H2O > [Cu(PyCHD)2]ClO4.H2O > PCHD > PyCHD.

Mesoporous One-Component Gold Microshells as 3D SERS Substrates

Surface-enhanced Raman scattering (SERS) is a powerful analytical tool for label-free analysis that has found a broad spectrum of applications in material, chemical, and biomedical sciences. In recent years, a great interest has been witnessed in the rational design of SERS substrates to amplify Raman signals and optionally allow for the selective detection of analytes, which is especially essential and challenging for biomedical applications. In this study, hard templating of noble metals is proposed as a novel approach for the design of one-component tailor-made SERS platforms. Porous Au microparticles were fabricated via dual ex situ adsorption of Au nanoparticles and in situ reduction of HAuCl₄ on mesoporous sacrificial microcrystals of vaterite CaCO₃. Elimination of the microcrystals at mild conditions resulted in the formation of stable mesoporous one-component Au microshells. SERS performance of the microshells at very low 0.4 µW laser power was probed using rhodamine B and bovine serum albumin showing enhancement factors of 2 × 10⁸ and 8 × 10⁸, respectively. The proposed strategy opens broad avenues for the design and scalable fabrication of one-component porous metal particles that can serve as superior SERS platforms possessing both excellent plasmonic properties and the possibility of selective inclusion of analyte molecules and/or SERS nanotags for highly specific SERS analysis.

Distinct chemical fixation of CO2 enabled by exotic gold nanoclusters

Atomically precise metal nanoclusters, especially the metal nanoclusters with an exotic core structure, have given rise to a great deal of interest in catalysis, attributing to their well-defined structures at the atomic level and consequently unique electronic properties. Herein, the catalytic performances of three gold nanoclusters, such as Au₃₈S₂(S-Adm)₂₀ with a body-centered cubic (bcc) kernel structure, Au₃₀(S-Adm)₁₈ with a hexagonal close-packed (hcp) core structure, and Au₂₁(S-Adm)₁₅ with a face-centered cubic (fcc) kernel structure, were attempted for the CO₂ cycloaddition with epoxides toward cyclic carbonates. Due to the excess positive charge with a strong Lewis acidity and large chemical adsorption capacity, the bcc-Au₃₈S₂(S-Adm)₂₀ nanocluster outperformed the hcp-Au₃₀(S-Adm)₁₈ and fcc-Au₂₁(S-Adm)₁₅ nanoclusters. Additionally, the synergistic effect between the gold nanocluster and co-catalyst played a crucial role in CO₂ cycloaddition.

Bioinspired Adenosine Triphosphate as an "All-In-One" Green Flame Retardant via Extremely Intumescent Char Formation

The development of eco-friendly flame retardants is crucial due to the hazardous properties of most conventional flame retardants. Herein, adenosine triphosphate (ATP) is reported to be a highly efficient "all-in-one" green flame retardant as it consists of three essential groups, which lead to the formation of char with extreme intumescence, namely, three phosphate groups, providing an acid source; one ribose sugar, working as a char source; and one adenine, acting as a blowing agent. Polyurethane foam was used as a model flammable material to demonstrate the exceptional flame retardancy of ATP. The direct flammability tests have clearly shown that the ATP-coated polyurethane (PU) foam almost did not burn upon exposure to the torch flame. Importantly, ATP exhibits an extreme volume increase, whereas general phosphorus-based flame retardants show a negligible increase in volume. The PU foam coated with 30 wt % of ATP (PU-ATP 30 wt %) exhibits a significant reduction in the peak heat release rate (94.3%) with a significant increase in the ignition time, compared to bare PU. In addition, PU-ATP 30 wt % exhibits a high limiting oxygen index (LOI) value of 31% and HF-1 rating in the UL94 horizontal burning foamed material test. Additionally, we demonstrated that ATP's flame retardancy is sufficient for other types of matrices such as cotton, as confirmed from the results of the standardized ASTM D6413 test; cotton-ATP 30 wt % exhibits an LOI value of 32% and passes the vertical flame test. These results strongly suggest that ATP has great potential to be used as an "all-in-one" green flame retardant.

Adsorption of Mono- and Divalent 4-(Dimethylamino)pyridines on Gold Surfaces: Studies by Surface-Enhanced Raman Scattering and Density Functional Theory

The adsorption thermodynamics of 4-(dimethylamino)pyridine (DMAP) and its five divalent derivatives di-DMAP- n (2 ≤ n ≤ 6) with gradually increasing methylene-spacer lengths n binding to planar gold surfaces has been studied by surface-enhanced Raman spectroscopy (SERS) and density functional theory (DFT). SERS intensities of the totally symmetrical breathing mode of the pyridine ring at approximately 1007 cm^-1 are used to monitor the surface coverage of the DMAP and di-DMAP- n ligands on gold surfaces at different concentrations. The equilibrium constant as a measure of the binding affinity is obtained from these measurements by using a modified Langmuir isotherm. Due to multivalent binding to the gold substrate, a characteristic enhancement of the binding affinity of di-DMAP- n compared to the monovalent DMAP is observed for all divalent species. First principles calculations of the di-DMAP- n ligands on an ideal Au(111) surface model as well as step terrace models have been performed to understand the adsorption structures and the multivalent binding enhancements. Furthermore, Raman spectra of the adsorbed molecules have been studied by first principles calculations to correlate the binding affinities to experimentally determined adsorption constants. The joint experimental and theoretical investigation of an oscillatory behavior of the binding affinity as a function of the methylene-spacer length in mono- and divalent 4-(dimethylamino)pyridines reveals that the molecular architecture plays an important role for the structure-function interplay of multivalently bound adsorbates.

A one-dimensional supramolecular chain based on [H2V10O28]4− units decorated with 4-dimethylaminopyridinium ions: an experimental and theoretical characterization

One-dimensional supramolecular structure with [H₂V₁₀O₂₈]⁴⁻ units was synthesized and experimental-theoretical characterized as potential releasing prodrug of the decavanadate ion.

Versatility of CoPcS in CoPcS/TiO2 for MB degradation: photosensitization, charge separation and oxygen activation

In this report, a composite photocatalyst consisting of cobalt phthalocyanine sulfate (CoPcS) and TiO₂ was prepared by a facile synthesis. Careful characterizations and measurements indicate a covalent grafting of CoPcS onto TiO₂ through Ti–O–S linkages, acquiring an intimate heterojunction between TiO₂ and CoPcS. The obtained composite was evaluated for its photocatalytic activity toward the degradation of methyl blue (MB) under visible light irradiation. The evaluation showed a significantly enhanced degradation rate of MB by CoPcS/TiO₂. The improved photocatalytic performance of CoPcS/TiO₂ was attributed to the photosensitization of TiO₂ by CoPcS, charge separation by electron transfer at the interface of the heterojunction formed between CoPcS and TiO₂, and oxygen activation via CoPcS. A synergetic mechanism in improving the photocatalytic performance of TiO₂ by CoPcS was investigated.

In this report, a composite photocatalyst consisting of cobalt phthalocyanine sulfate (CoPcS) and TiO₂ was prepared by a facile synthesis.

Experimental and theoretical spectroscopic studies in relation to molecular structure investigation of para chloro, para fluoro and para nitro maleanilinic acids

In the present work novel para chloro, para fluoro and para nitro maleanilic acid derivatives were prepared and investigated using FT-IR, thermal analyses (TA) measurements (TGA/DTG and DTA) in comparison with mass spectral (MS) fragmentation at 70 eV. The crystallographic structures of studied compounds were investigated by X-ray diffraction (XRD). The vibrational frequencies and the corresponding normal modes were evaluated at the optimized geometry. Vibrational modes were analyzed using GAUSSVIEW software. Experimental FT-IR and Raman spectra of the three newly prepared derivatives, namely, (E) - oxo -4- ((4- nitro phenyl) amino)-4- oxobut-2-enoic acid (p-NMA), (E) -4- ((4- chloro phenyl)amino)-4- oxobut -2- enoic acid (p-ClMA), (E) -4- ((4- fluoro phenyl) amino)- 4- oxobut -2- enoic acid (p-FMA) were compared with the theoretically calculated one. FT-IR and the observed vibrational frequencies were assigned; thermal analysis and mass spectrum measurements of the maleanilic acid derivatives were recorded and discussed. The computational calculations were carried out by DFT - B3LYP method with 6-311++G(d,p) basis sets and the corresponding results were tabulated. The alternations of structures of p-FMA, p-ClMA and p-NMA due to the subsequent substitutions were investigated. This correlation between experimental and theoretical calculations provided a good confirmation of the proposed structures of the newly prepared compounds. The derivatives were found to be highly effective against Hepatocellular carcinoma cells > Breast carcinoma cells > colon carcinoma cells. It was recognized, that cancer cells over expression promotes tumorigenic functions; can be suppressed by p-NMA > p-FMA > p-ClMA inhibitors.

Surface Separation and in Situ Structural Regulation of Photosensitive Oligomer in a Flexible Template

Surface-selective adsorption and separation are very important for the application of surface functional materials. In this study, a photosensitive diazo-macrocycle has been synthesized by the solvent method with a very low yield, which can adsorb onto the substrate surface modified with a template molecule. By using this flexible template on the graphite surface, a simple separation strategy for the macrocyclic molecule with specific shape and size from reaction mixtures was developed. Additionally, one of the two azo units in this trapped photosensitive macrocycle could convert from trans to cis conformation under UV irradiation due to the steric effect. Our results provide a new way to construct functional nanodevices using a surface flexible template as the separation and regulation medium.

Reductive nitrosylation of nickel(ii) complex by nitric oxide followed by nitrous oxide release

Ni(ii) complex of ligand ( = bis(2-ethyl-4-methylimidazol-5-yl)methane) in methanol solution reacts with an equivalent amount of NO resulting in a corresponding Ni(i) complex. Adding further NO equivalent affords a Ni(i)-nitrosyl intermediate with the {NiNO}(10) configuration. This nitrosyl intermediate upon subsequent reaction with additional NO results in the release of N2O and formation of a Ni(ii)-nitrito complex. Crystallographic characterization of the nitrito complex revealed a symmetric η(2)-O,O-nitrito bonding to the metal ion. This study demonstrates the reductive nitrosylation of a Ni(ii) center followed by N2O release in the presence of excess NO.

Varying structural motifs, unusual X-band electron paramagnetic spectra, DFT studies and superoxide dismutase enzymatic activity of copper(ii) complexes with N′-[(E)-phenyl(pyridin-2-yl)methylidene]benzohydrazide

A diverse set of new copper(ii) complexes synthesized as possible models for antioxidant superoxide dismutase mimics.

Synthesis and spectral characterization of bis(4-amino-5-mercapto-1,2,4-triazol-3-yl)propane

Bis(4-amino-5-mercapto-1,2,4-triazol-3-yl)propane (BAMTP) was synthesized and characterized by FT-IR and FT-Raman spectra. Gas phase structure of BAMTP was examined under density functional theory B3LYP/6-311++G(d, p) level of basis set, wherein the molecule was subjected to conformational analysis. Thus the identified stable structure utilized for the calculations such as geometry optimization, vibrational behavior, hyperpolarizability analysis, natural bond orbital analysis, band gap, chemical hard/softness and stability. Geometry of BAMTP has been discussed elaborately with related crystal data. The results found from experimental and theoretical methods were reported herewith.

Unprecedented copper(ii) mediated in situ formation of gem-diol binuclear complexes: a combined experimental and computational study

The two alkoxo bridged complexes [Cu₂(L¹)₂(HL²)₂(H₂O)](NO₃)₂·2H₂O 1 and [Cu₂(L¹)₂(HL²)₂](NO₃)₂·H₂O 2 have been synthesized by metal assisted hydrolysis with two Schiff bases, where L¹ is 2-benzoylpyridine and HL² is phenyl(pyridin-2-yl)methanediol.