Three novel Cu(II), Cd(II) and Cr(III) complexes of 6−Methylpyridine−2−carboxylic acid with thiocyanate: Synthesis,crystal structures,DFT calculations,molecular docking and α-Glucosidase inhibition studies

Novel complexes of 6?methylpyridine?2?carboxylic acid and thiocyanate {[Cu(NCS)(6-mpa)₂], (1); [Cd(NCS)(6-mpa)]_n, (2); [Cr(NCS)(6-mpa)₂·H₂O], (3)} were synthesized, and their structures were characterized by XRD analysis, FT–IR and UV–Vis spectroscopic techniques. The inhibitory activities of the synthesized complexes (1–3) on α-glucosidase were determined by using genistein reference compound. Furthermore, the optimized geometry and vibrational harmonic frequencies for the complexes 1–3 were obtained by DFT/HSEh1PBE/6–311G(d,p)/LanL2DZ level. Electronic spectral properties were examined by using TD-DFT/HSEh1PBE/6–311G(d,p)/LanL2DZ level with CPCM model. Additionally, major contributions to the electronic transitions were determined via Swizard program. The refractive index, linear optical and non?nonlinear optical parameters of the complexes 1–3 were investigated at HSEh1PBE/6–311G(d,p) level. The docking studies of the complexes 1–3 to the binding site of the target protein (the template structure S. cerevisiae isomaltase are fulfilled. Lastly, natural bond orbital analysis was used to investigate inter- and intra-molecular bonding and interaction among bonds.     

High chemical and solvent resistant,branched terpene methacrylate polymers—Preparation,thermal properties,and decomposition mechanism

Branched terpene methacrylate polymers under UV‐polymerization process of methacrylates prepared based on naturally occurring terpene alcohols such as geraniol, nerol, and citronellol have been obtained. Amine catalysed reaction of geraniol, nerol, or citronellol with methacryloyl chloride allowed obtaining terpene methacrylate monomers with high yield. Their structure was confirmed by spectroscopic methods (¹HNMR, ¹³CNMR, ATR‐FTIR). The structure of the resulting polymers was evaluated by applying the ¹³C/CP MAS and ATR‐FTIR. The chosen physicochemical properties such as chemical resistance, solvent resistance, and thermal properties in inert and oxidative atmospheres have been studied. In addition, the detailed pyrolysis and oxidative degradation mechanism by applying the TG/DSC/FTIR/QMS‐coupled method was evaluated. The results indicated the potential application of novel, branched terpene methacrylate polymers for manufacturing products which could be utilized under corrosive conditions, due to their high resistance in both acidic and basic environments and different polarity solvents, as well as satisfactory thermal resistance.     

Fourier Transform Surface Plasmon Resonance (FTSPR) with Gyromagnetic Plasmonic Nanorods

An unprecedented active and dynamic sensing platform based on a LSPR configuration that is modulated by using an external magnetic field is reported. Electrochemically synthesized Au/Fe/Au nanorods exhibited plasmonically active behavior through plasmonic coupling, and the middle ferromagnetic Fe block responded to a magnetic impetus, allowing the nanorods to be modulated. The shear force variation induced by the specific binding events between antigens and antibodies on the nanorod surface is used to enhance the sensitivity of detection of antigens in the plasmonics‐based sensor application. As a proof‐of‐concept, influenza A virus (HA1) was used as a target protein. The limit of detection was enhanced by two orders of magnitude compared to that of traditional LSPR sensing.     

Accurate prediction of vertical electronic transitions of Ni(II) coordination compounds via time dependent density functional theory

Time dependent density functional theory calculations are completed for five Ni(II) complexes formed by polydentate peptides to predict the electronic absorption spectrum. The ligands examined were glycyl‐glycyl‐glycine (GGG), glycyl‐glycyl‐glycyl‐glycine (GGGG), glycyl‐glycyl‐histidine (GGH), glycyl‐glycyl‐cysteine (GGC), and triethylenetetramine (trien). Fifteen functionals and two basis sets were tested. On the basis of the mean absolute percent deviation (MAPD), the ranking among the functionals is: HSE06 ∼ MPW1PW91 ∼ PBE0 > ω‐B97x‐D ∼ B3P86 ∼ B3LYP ∼ CAM‐B3LYP > PBE ∼ BLYP ∼ BP86 > TPSS > TPSSh > BHandHLYP > M06 ≫ M06‐2X. Concerning the basis sets, the triple‐ζ def2‐TZVP performs better than the double‐ζ LANL2DZ. With the functional HSE06 and basis set def2‐TZVP the MAPD with respect to the experimental λ_max is 1.65% with a standard deviation of 1.26%. The absorption electronic spectra were interpreted in terms of vertical excitations between occupied and virtual MOs based on Ni‐d atomic orbitals. The electronic structure of the Ni(II) species is also discussed.     

Effect of urea on the structure and functional activity of proteins. Chymotrypsinogen A and α-chymotrypsin

The effect of urea on the structural stability and functional activity of globular proteins,viz., chymotrypsinogen A (ChtG) and -chymotrypsin (Cht), was studied over a wide range of concentrations (0.5–6 rnol L-1), and the existence of two different mechanisms of the action of urea on these proteins was demonstrated. No changes in the spatial structure of ChtG were observed in the concentration range from 0,5 to 3 mol L^–1 (region 1). Differential UV spectroscopy shows tile redistribution of aromatic groups between the inner volume and the outer surface of a protein molecule (protein denaturation) at concentrations >3 mol L^–1 (regionII), In regionI, urea changes the kinetic parameters of enzymatic reactions involving Cht, which is explained on the basis of millimeter spectroscopy data by its action on the structure and nucleophilic reactivity of water.Deceased.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 998–1002, April, 1996.     

Isolation and characterization of an iodide bridged dimeric palladium complex in carbonylation of methanol

Palladium-catalyzed carbonylation of methanol in presence of iodide promoters was investigated. Iodide bridged palladium dimeric complex, [PPh₃CH₃]₂[Pd₂I₆] was isolated from the carbonylation reaction mixture and characterized using X-ray crystallography. Reaction mechanism was proposed based on IR and UV spectroscopic characterizations of catalytic species involved in the catalytic cycle. The isolated dimeric palladium species, [Pd₂I₆]²⁻ underwent carbonylation to give monomeric species [PdI₃CO]⁻ at atmospheric pressure of carbon monoxide. It was also observed that PPh₃ plays an important role to avoid catalyst deactivation at higher temperatures. Turnover frequency (TOF) of 1052 h⁻¹ was achieved using Pd(OAc)₂-HI-PPh₃ catalyst system at 175 °C.     

Hydrogen Bonding of Carboxylic Acids in Aqueous Solutions—UV Spectroscopy, Viscosity, and Molecular Simulation of Acetic Acid

The UV spectra of aqueous acetic acid solutions up to 2M were investigated. At these wavelengths, the carboxylic acids exhibit an absorption peak, attributed to the C=O group, which shifts when hydrogen bonds are formed.. The measured spectra were best fitted to several bands, either of Gaussian or Lorentzian shape, which can be explained as several types of structural units formed by hydrogen bonds established between acetic acid and water molecules and between acetic acid molecules themselves. Molecular dynamics simulation of these mixtures was also performed, confirming the occurrence of several types of hydrogen bonds and showing the presence of dimers at higher concentrations. The viscosity and density of these solutions were also measured at different concentrations and temperatures. These results give a more complete picture of the hydrogen bond network of the system.     

A validated HPLC determination of the flavone aglycone diosmetin in human plasma

Diosmetin, 3',5,7-trihydroxy-4'-methoxy flavone, is the aglycone of the flavonoid glycoside diosmin that occurs naturally in foods of plant origin. Diosmin exhibits antioxidant and anti-inflammatory activities, improves venous tone and it is used for the treatment of chronic venous insufficiency. Diosmin is hydrolyzed by enzymes of intestinal micro flora before absorption of its aglycone diosmetin. A specific, sensitive, precise, accurate and robust HPLC assay for the determination of diosmetin in human plasma was developed and validated. Diosmetin and the internal standard 7-ethoxycoumarin were isolated from plasma by liquid-liquid extraction and separated on a C8 reversed-phase column with methanol-water-acetic acid (55:43:2, v/v/v) as the mobile phase at 43 degrees C. Peaks were monitored at 344 nm. The method was linear in the 10-300 ng/mL concentration range (r > 0.999). Recovery for diosmetin and internal standard was greater than 89.7 and 86.8%, respectively. Intra-day and inter-day precision for diosmetin ranged from 1.6 to 4.6 and from 2.2 to 5.3%, respectively, and accuracy was better than 97.9%.     

Synthesis, spectroscopic, and electrochemical studies of 1,2-naphthalene-ring-fused tetraazachlorins, -bacteriochlorins, and -isobacteriochlorins: the separation and characterization of structural isomers

1,2-Naphthalene-ring-expanded tetraazachlorins (TACs), tetraazabacteriochlorins (TABCs), and tetraazaisobacteriochlorins (TAiBCs) have been synthesized. Procedures for the synthesis of the starting materials, that is, derivatives of 1,2-naphthalenedicarboxylic acid, have been reinvestigated and improved. Nine possible derivatives, including four, two, and three structural isomers of TACs, TABCs, and TAiBCs, respectively, were separated by using thin-layer chromatography (TLC) or high-performance liquid chromatography (HPLC), and the structure of each isomer was determined by (1)H NMR spectroscopy combined with the NOE technique. The formation ratio of each isomer was rationalized in terms of the intramolecular steric repulsion effect, which was predicted by geometry optimizations at the DFT level. The derived compounds were characterized by using IR, electronic, and magnetic circular dichroism (MCD) spectroscopy, and by electrochemical methods. Frequency calculations at the DFT level correctly reproduced the experimental IR spectra and, in particular, distinguished between the three isomers of the TAiBCs. In the electronic absorption and MCD spectra of the TAC and TABC species, the Q-band splits into two intense components similarly to the 2,3-naphthalene-fused derivatives described in our preceding paper, although no significant spectral differences were observed from species to species. On the other hand, the spectra of the TAiBCs showed moderate differences depending on the structure of the isomer. The spectroscopic properties as well as the electrochemical behavior of these chlorins resemble those of the corresponding benzene-fused derivatives rather than the 2,3-naphthalene-fused derivatives. Molecular-orbital and configuration-interaction calculations within the framework of the ZINDO/S method were helpful in the discussions of the above observations.     

On the Synthesis and Basicity of 1,3-Diaminoisoquinolines

Summary.  A series of 6- and 7-substituted derivatives of 1,3-diaminoisoquinoline were synthesized by the reaction of N,N-diethylarylacetamides with POCl₃ and then with N,N-dimethylcyanamide. The products were identified by means of spectroscopic methods and their pK _a dissociation constants were determined. Corresponding author. E-mail: kudelkoa@zeus.polsl.gliwice.pl Received July 7, 2002; accepted July 22, 2002