Palladium(II) complexes with R2edda-derived ligands. Part V. Reaction of O,O′-diethyl-(S,S)-ethylenediamine-N,N′-di-2-(3-methyl)butanoate with K2[PdCl4]

The reaction of K₂[PdCl₄] with [(S,S)-H₂(Et)₂eddv]Cl₂ diester (O,O′-diethyl-(S,S)-ethylenediamine-N,N′-di-2-(3-methyl)butanoate) (1) resulted in [PdCl₂{(S,S)-(Et)eddv-κ² N,N′,κO}] (2) complex with one hydrolyzed ester group. The compound was characterized by spectroscopic methods and it was found that the reaction is diastereoselective (¹H and ¹³C NMR; one diastereoisomer of four possible). In addition, the structure of 2 was confirmed by X-ray diffraction analysis, indicating that the product is the (R,R)–N,N′-configured isomer. DFT calculations support the formation of one diastereoisomer of 2.     

Revised mechanism of Boyland-Sims oxidation

New computational insights into the mechanism of the Boyland-Sims oxidation of arylamines with peroxydisulfate (S(2)O(8)(2-)) in an alkaline aqueous solution are presented. The key role of arylnitrenium cations, in the case of primary and secondary arylamines, and arylamine dications and immonium cations, in the case of tertiary arylamines, in the formation of corresponding o-aminoaryl sulfates, as prevalent soluble products, and oligoarylamines, as prevalent insoluble products, is proposed on the basis of the AM1 and RM1 computational study of the Boyland-Sims oxidation of aniline, ring-substituted (2-methylaniline, 3-methylaniline, 4-methylaniline, 2,6-dimethylaniline, anthranilic acid, 4-aminobenzoic acid, sulfanilic acid, sulfanilamide, 4-phenylaniline, 4-bromoaniline, 3-chloroaniline, and 2-nitroaniline) and N-substituted anilines (N-methylaniline, diphenylamine, and N,N-dimethylaniline). Arylnitrenium cations and sulfate anions (SO(4)(2-)) are generated by rate-determining two-electron oxidation of primary and secondary arylamines with S(2)O(8)(2-), while arylamine dications/immonium cations and SO(4)(2-) are initially formed by two-electron oxidation of tertiary arylamines with S(2)O(8)(2-). The subsequent regioselectivity-determining reaction of arylnitrenium cations/arylamine dications/immonium cations and SO(4)(2-), within the solvent cage, is computationally found to lead to the prevalent formation of o-aminoaryl sulfates. The formation of insoluble precipitates during the Boyland-Sims oxidation of arylamines was also computationally studied.     

Thermal behavior of modified urea–formaldehyde resins

The thermal stability of pure urea–formaldehyde resin (PR) and modified urea–formaldehyde (UF) resins with hexamethylenetetramine-HMTA (Resin 1), melamine-M (Resin 2), and ethylene urea (EU, Resin 3) including nano-SiO₂ was investigated by non-isothermal thermo-gravimetric analysis (TG), differential thermal gravimetry (DTG), and differential thermal analysis (DTA) supported by data from IR spectroscopy. Possibility of combining inorganic filler in a form of silicon dioxide with UF resins was found investigated and percentage of free formaldehyde was determined. The shift of DTG peaks to a high temperature indicates the increase of thermal stability of modified UF resin with EU (Resin 3) which is confirmed by data obtained from the FTIR study. The minimum percentage (6%) of free formaldehyde was obtained in Resin 3.     

Breaking Barriers in Emerging Biomedical Applications

The recent global COVID-19 pandemic has revealed that the current healthcare system in modern society can hardly cope with the increased number of patients. Part of the load can be alleviated by incorporating smart healthcare infrastructure in the current system to enable patient’s remote monitoring and personalized treatment. Technological advances in communications and sensing devices have enabled the development of new, portable, and more power-efficient biomedical sensors, as well as innovative healthcare applications. Nevertheless, such applications require reliable, resilient, and secure networks. This paper aims to identify the communication requirements for mass deployment of such smart healthcare sensors by providing the overview of underlying Internet of Things (IoT) technologies. Moreover, it highlights the importance of information theory in understanding the limits and barriers in this emerging field. With this motivation, the paper indicates how data compression and entropy used in security algorithms may pave the way towards mass deployment of such IoT healthcare devices. Future medical practices and paradigms are also discussed.     

Di­iodo(3,4,5,6‐tetrahydropyrimidin­ium‐2‐thiol­ato‐S)­mercury(II)

The reaction of 3,4,5,6‐tetrahydropyrimidine‐2‐thione (H₄py­mtH) with mercury(II) iodide in methanol in a 1:1 molar ratio resulted in the formation of single crystals of the title compound, [Hg(C₄H₈N₂S)I₂]. The Hg atom is coordinated by one S atom from H₄pymtH at 2.456 (2) Å and by two I atoms at distances of 2.6872 (7) and 2.7044 (6) Å, and has a characteristic deformed trigonal coordination geometry. The molecule has crystallographic m symmetry but the Hg atom is disordered above and below the mirror plane.     

Right-veering diffeomorphisms of compact surfaces with boundary

We initiate the study of the monoid of right-veering diffeomorphisms on a compact oriented surface with nonempty boundary. The monoid strictly contains the monoid of products of positive Dehn twists. We explain the relationship to tight contact structures and open book decompositions. Mathematics Subject Classification (1991) Primary 57M50, secondary 53C15     

Polymerization of aniline on polyaniline membranes

When solutions of aniline hydrochloride and ammonium peroxydisulfate were separated by a semipermeable cellulose membrane, the reactants met at the membrane and produced a polyaniline (PANI) membrane at the interface. The oxidative polymerization of aniline then proceeded in situ on the PANI-cellulose composite membrane. PANI was produced entirely at the monomer side of the membrane; about 80% conversion of aniline to PANI was observed after 24 h. The oxidation of aniline with peroxydisulfate consists in the transfer of electrons from aniline to the oxidant; it is proposed that electrons pass through the PANI membrane, which is conducting, and electroneutrality is maintained by the simultaneous transfer of protons. The reaction between aniline and peroxydisulfate thus takes place without the need for both reactant molecules to be in physical contact. The residual aniline is located only at its original side of the membrane, but the product of ammonium peroxydisulfate conversion, ammonium hydrogen sulfate, was found on both sides of the membrane. Fourier-transform infrared spectroscopy has been used to analyze PANI, the reaction residues and byproducts, and to prove that PANI is protonated with counter-ions of the sulfate type. Using this technique, we have detected only small differences in the molecular structure of PANI prepared with the membrane-separated reactants and in the polymerization when reactants were mixed; also, the molecular weights differed only marginally. The conductivity of both types of PANI was about the same. The repeated polymerization of aniline on the earlier prepared PANI-cellulose membrane yielded similar results, thus confirming the proposed concept of coupled electron- and proton-transfer through the PANI membrane.     

Spectroscopic characterization, crystal structure determination and interaction with DNA of novel cyano substituted benzimidazole derivative

Novel cyano-substituted benzimidazole derivatives 3 and 4 were synthesized from 4-N,N-dimethylamino-benzaldehyde and 2-cyanomethyl-benzimidazole. 2-(1H-benzimidazol-2-yl)-3-(4-N,N-dimethylamino-phenyl)-acrylonitrile hydrochloride monohydrate 4 has been studied by ¹H and ¹³C NMR, IR, MS, UV/Vis and fluorescence spectroscopy and confirmed by X-ray crystal structure analysis. The interaction of 4 with ct-DNA has also been investigated by fluorescence spectroscopy and melting temperature determination experiment. According to the emission spectra recorded in the absence and presence of ct-DNA at different ratios r ([compound]/[polynucleotide]), 4 showed marked decrease in the fluorescence intensity and very strong hypochromic effect. Melting temperature experiment showed weak stabilization of double helix. To determine binding mode of 4, other additional experiments are necessary. The molecules of 4 are almost planar with the dihedral angle between benzimidazole and phenyl rings of 6.99(6)°. The protonation of nitrogen atom of benzimidazole ring is followed by π-electrons delocalization in the region resulting in C–N bond distances equality [1.341(2) and 1.337(2) Å]. Both NH groups of benzimidazole ring form intermolecular hydrogen bonds, one with the oxygen atom of water molecule [N···O 2.689(2) Å] and the other with Cl^? ion (N···Cl^? 3.051(1) Å). Except proton acceptor, water molecule acts as double proton donor in the formation of intermolecular hydrogen bonds with Cl^? ion [O···Cl^? 3.126(2) and 3.169(2) Å]. In that way, infinite chains along [110] direction are formed.     

Synthesis and characterization of mercury(II) complexes with 2-styryl-1,3-benzothiazole (sb). Presence of two differently coordinated Hg(II) ions in the dinuclear complex Hg2Cl4(sb)3. Structural characterization of 2-styryl-1,3-benzothiazole and some of its derivatives

The molecular and crystal structures of the following compounds 2-styryl-1,3-benzothiazole, sb, (1), Hg₂Cl₄(sb)₃ (2), 1,3-bis(1,3-benzothiazol-2-yl)-2,4-diphenylcyclobutane (3) 1,3-bis(1,3-benzothiazol-2-yl)-2,4-bis(4-chlorophenyl)cyclobutane (4) and HgBr₂(sb)₂ (5) were determined by single-crystal X-ray diffractometry. The crystal structure of 1 consists of discrete sb molecules which are essentially planar. The dimeric molecules of 3 and 4 are characterized by a cyclobutane ring. In both isolated complexes 2 and 5, sb acts as a neutral monodentate ligand coordinated to the mercury atom through the thiazolyl nitrogen atom. The dinuclear complex 2 is characterized by the unique example of two differently coordinated Hg(II) ions bridged via a non-symmetrical linear Cl⁻ bridge. The first one is coordinated by one terminal and one bridging Cl⁻ ion and two thiazolyl nitrogen atoms in the form of distorted tetrahedron. The second one is bonded to two terminal Cl⁻ ions and the bridging Cl⁻ ion and one thiazolyl nitrogen atom in a 2+2 manner. In complex 5 the Hg(II) ion, which is situated on a crystallographic twofold axis, is tetrahedrally coordinated by two Br⁻ ions and two thiazolyl nitrogen atoms. Both complexes are characterized by stronger mercury-to-halide covalent bonds than mercury-to-nitrogen bonds, which are regarded as contacts shorter than the van der Waals radii sum of the corresponding atoms. The geometry of the sb ligand in both complexes 2 and 5 has not been changed remarkably from that one in the uncoordinated state due to not so strong bonds formation with the Hg(II) ion.