1,2-Metallobridging and the Antiperiplanar Effect. Thermodynamic Preference for the Z-Configuration in Imidoyl(Alkali Metals) and their Phosphorus Analogs

We showed that imidoyl- and phosphaethenyl(alkali metals) would thermodynamically prefer the Z-configuration. The bond model analysis of the electronic structures showed that the Z-preference should originate from 1,2-metallobridging by the delocalization of lone pairs on N or P to vacant p-orbitals of the alkali metals and from the antiperiplanar effect of the delocalization from σ _C—M to σ? _{N(P)—R ²} and from n _N(P) to the C—R¹. The Z-preference increases by more electron-withdrawing groups at the carbon atom of the double bond. However, substitution at the nitrogen/phosphorus results in E-preference because of 1,4-chelation of the lone pair of the substituents to alkali metals. Most of halogen derivatives were not stable and eliminate metal halides.     

Synthesis and In Vitro Anti-HIV Activity of Some New Schiff Base Ligands Derived from 5-Amino-4-phenyl-4H-1,2,4-triazole-3-thiol and Their Metal Complexes

New Schiff base ligands (6–9) derived from 5-amino-4-phenyl-4H-1,2,4-triazole-3-thiol 1 and substituted benzaldehydes (2–5) as well as their metal complexes with Cu(II), Fe(II), Au(III), and Mn(II) (12–17) have been synthesized. A new benzothiazole derivative (11) was prepared from coupling of 7 with N-(benzothiazol-2-yl)-2-chloroacetamide 10. Their spectral properties were investigated. The newly designed and synthesized Schiff base ligands and the metal complexes were assayed for anti-HIV-1 and HIV-2 activity by examination of their inhibition of HIV-induced cytopathogenicity in MT-4 cells. Compounds 11 and 16 were found to be the most active inhibitors in cell culture (EC₅₀ = 12.2 μg/mL (SI = 4) and > 2.11 μg/mL (SI = > 1), respectively) against HIV-1, whereas 11 showed inhibition against HIV-2 of EC₅₀ > 10.2 μg/mL with SI = 9, which provided a good lead for further optimization.     

Phenol-formaldehyde resin route to the synthesis of several iron group transition metal phosphides

Abstract

A series of iron, cobalt and nickel metal phosphides of chemical formula Fe_xP, Co₂P and Ni₂P with high specific surface areas of 331.1, 294.2 and 228.0 m² g^?1, respectively, was firstly synthesized by phenol-formaldehyde resin route. It was found that the as-prepared Co₂P and Ni₂P samples synthesized using phenol-formaldehyde resin as a carbon source showed much higher BET surface areas than those prepared using other carbon sources reported before, including cinnamic strong alkali anion exchange resin, p-phenylenediamine and hexamethylenetetramine. This phenol-formaldehyde resin route was proved to be as universal as traditional H₂ reduction method.     

New Organotin Compounds Including a Tin–Zinc Bond

Abstract

The reaction of dialkyltinhydrides with dialkylzinc results in a tin metal bond formation. Crystal structures of 1,1,1,2,3,3,3-hepta-phenyl-2-(ethylzincio)tristannane *TMEDA 1, 1,1,2,2,3,3,4,4-octaphenyl-1,4-(ethylzincio)tetrastannane*2TMEDA 2, and triphenyl(phenylzincio)stannane*TMEDA 3 could be obtained.

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GRAPHICAL ABSTRACT     

Polymers Derived from 4-Substituted Salicylic Acids as Antifungal Agents

4-Amino-, chloro-, and bromo-substituted salicylic acid-formaldehyde polymers and their metal chelates were screened for their antifungal activity. Various copolymers prepared from 4-chloro-(bromo)salicylic acid, formaldehyde, and other comonomers were also screened for their antifungal activity. All these polymers, copolymers, and polychelates were found active against several fungi Their fungicidal activities are compared with those of the corresponding monomers and monomeric chelates.     

Crystallization Behavior of the System Poly(L-lactic Acid) and Pentaerythrityl Tetrabromide

Differential scanning calorimetry has been used to study the thermal crystallization of poly(L-lactic acid) (PLLA) and pentaerythrityl tetrabromide mixtures at different compositions. The melting temperature-composition phase diagram of the system reveals that PLLA forms a simple eutectic with pentaerythrityl tetrabromide, with a eutectic composition of 46% (w/w) of PLLA and a eutectic temperature of 422 K. Investigation of the microstructures obtained after removal of the diluent from the eutectic using scanning electron microscopy shows that the simultaneous crystallization of PLLA and the diluent proceeded in such a way that the diluent rods are the leading phases.     

Synthesis of a Calix[4]crown‐6 Cone Conformer‐Based Oligomer and its Metal Cation Extraction Abilities

A new calixcrown‐6 oligomer 5 was synthesized by reacting a 1,3‐distal di‐amino derivative of cone p‐tert‐butylcalix[4]crown‐6 with malonyl dichloride. Extraction studies with precursor monomers 2 and 3 and oligomer 5 showed differences in their metal cation extraction behavior and selectivity. Precursors monomers 2 and 3 were selective for Hg²⁺; whereas, oligomer 5 showed high affinity towards both alkali (Li⁺, Na⁺, K⁺, and Cs⁺) and heavy metal cations (Cu²⁺, Cd²⁺, Hg²⁺ and Pb²⁺).     

pH-Responsive Nanocomposites From Methylcellulose and Attapulgite Nanorods: Synthesis,Swelling and Absorption Performance on Heavy Metal Ions

A pH-responsive methylcellulose-g-poly(sodium acrylate)/attapulgite (MC-g-PNaA/APT) nanocomposite superabsorbent was prepared by the free-radical solution polymerization of methylcellulose (MC), sodium acrylate (NaA) and nanoscale attapulgite (APT) in the presence of the crosslinker N,N′-methylene-bis-acrylamide (MBA). The structure and morphology of the nanocomposite were characterized by FTIR, FESEM, TEM, XRD and EDS techniques, and the effects of the amount of MBA, MC and APT nanorods on swelling behaviors were also evaluated. Results indicate that NaA has been grafted onto MC macromolecular chains and APT nanorods participated in polymerization by its active silanol groups, and APT led to a better dispersion in the MC-g-PNaA matrix. The incorporation of APT clearly enhanced the swelling capacity and rate of the superabsorbent. In addition, the nanocomposite exhibited excellent absorption capacity on heavy metal ions, and its absorption amounts on Ni²⁺, Cu²⁺ and Zn²⁺ ions reached 9.86, 7.66 and 21.86 times greater than active carbon (AC). The biopolymer-based nanocomposite superabsorbents can be used as a potential water-saving material and candidate of AC for heavy metal ion absorption.     

Preparation of Iminoacetic Acid-type Composite Chelating Material IAA-PEI/SiO2 and Preliminary Studies on Chelating Adsorption Property towards Heavy Metal Ions

Polyamine polyethyleneimine (PEI) was first grafted on the surfaces of micro-sized silica gel particles in the manner of the coupling graft (the manner of “grafting to”), forming the grafting particles PEI/SiO₂. Subsequently, via a polymer reaction, the nucleophilic substitution reaction between the primary and secondary amino groups of the grafted PEI macromolecule and chloroactic acid (CAA), iminoacetic acid groups were bonded onto the grafted PEI chains, and an iminoacetic acid (IAA)-type composite chelating material, IAA-PEI/SiO₂, was formed. In this work, the preparation process of IAA-PEI/SiO₂ particles was mainly researched, and the effects of the main factors on the polymer reaction, i.e., the nucleophilic substitution reaction, were examined emphatically. The adsorption behavior of IAA-PEI/SiO₂ particles towards several kinds of heavy metal ions was preliminarily evaluated. The experiments results show that it is feasible to introduce IAA groups onto PEI/SiO₂ particles via the substitution reaction between CAA and the amino groups of the grafted PEI. The reaction rate is affected greatly by the feed ratio of the amino group of PEI to CAA, so the substitution reaction between CAA and the amino groups of the grafted PEI is a bimolecular nucleophilic substitution reaction (S_N2). The reaction temperature and the used amount of acid-acceptor NaHCO₃ affect the bonding rate of IAA groups greatly. The fitting temperature was 60°C, and 1:1 of the molar ratio of NaHCO₃ to CAA was an appropriate amount of acid-acceptor NaHCO₃. Under the above optimal reaction conditions and with 3:1 molar ratio of amino group of PEI to CAA, 72% of the IAA group bonding rate (it is based on the hydrogen atoms in the primary and secondary amino groups of the grafted PEI) in 8 h can be reached. The composite chelating material IAA-PEI/SiO₂ possesses a strong chelating adsorption ability for heavy metal ions because of the increase of the ligands and formation of stable five-membered chelate rings.