Synthesis of the Bacteriostatic Poly(L-Lactide) by Using Zinc (II)[(acac)(L)H2O] (L = Aminoacid-Based Chelate Ligands) as an Effective ROP Initiator

The paper presents a synthesis of poly(l-lactide) with bacteriostatic properties. This polymer was obtained by ring-opening polymerization of the lactide initiated by selected low-toxic zinc complexes, Zn[(acac)(L)H2O], where L represents N-(pyridin-4-ylmethylene) tryptophan or N-(2-pyridin-4-ylethylidene) phenylalanine. These complexes were obtained by reaction of Zn[(acac)2 H2O] and Schiff bases, , the products of the condensation of amino acids and 4-pyridinecarboxaldehyde. The composition, structure, and geometry of the synthesized complexes were determined by NMR and FTIR spectroscopy, elemental analysis, and molecular modeling. Both complexes showed the geometry of a distorted trigonal bipyramid. The antibacterial and antifungal activities of both complexes were found to be much stronger than those of the primary Schiff bases. The present study showed a higher efficiency of polymerization when initiated by the obtained zinc complexes than when initiated by the zinc(II) acetylacetonate complex. The synthesized polylactide showed antibacterial properties, especially the product obtained by polymerization initiated by a zinc(II) complex with a ligand based on l-phenylalanine. The polylactide showed a particularly strong antimicrobial effect against Pseudomonas aeruginosa, Staphylococcus aureus, and Aspergillus brasiliensis. At the same time, this polymer does not exhibit fibroblast cytotoxicity.

Metal-involving halogen bond Ar–I⋯[dz2PtII] in a platinum acetylacetonate complex

The observed and confirmed theoretically metal-involving halogen bond Ar–I⋯[dz2PtII] provides experimental evidence favoring a XB formation step upon oxidative addition of ArI to PtII.

Discovery of face-centred cubic Os nanoparticles

The first example of the crystal structure control of Os is reported. The fcc-structured Os nanoparticles were synthesized using an Os acetylacetonate complex as a precursor although the fcc structure does not exist in the bulk state.

SYNTHESIS AND STUDY OF THE HETERONUCLEAR ACETYLACETONATE Nd(III) AND Ni(II) COMPLEX AS A PRECURSOR FOR OBTAINING COMPLEX-OXIDE STRUCTURES

The heterometallic acetylacetonate complex NdNi(АА)5·6Н2О has been synthesized to obtain nickel-neodymium-containing complex oxide materials. The properties of the complex have been investigated by physico-chemical methods of analysis (elemental analysis, differential thermal analysis, IR spectroscopy, X-ray powder diffraction). The data of X-ray powder diffraction and IR spectroscopy of NdNi(АА)5·6Н2О confirmed the formation of a new heterometallic single-phase compound. In the IR spectrum of NdNi(АА)5·6Н2О, a change is observed in the amount and position of the bands in the region of stretching vibrations of the М-О, CС, CО bonds, as compared to the IR spectra of the monometallic complexes Ni(AA)2·2Н2О and Nd(AA)3·3Н2О. An assessment of the thermal stability of the complex has been performed. It was shown that the synthesized heterometallic complex NdNi(АА)5·6Н2О is thermally more stable than monometallic acetylacetonates of Ni(II) and Nd(III). The heterocomplex can be used as a precursor to obtain heterometallic oxide structures. The pyrolysis of the NdNi(АА)5·6Н2О complex and, for comparison, the pyrolysis of the monocomplexes Ni(AA)2·2Н2О and Nd(AA)3·3Н2О were carried out with changing the thermolysis conditions — change of heating rate (from 5 °C/min to 20 °C/min), change of the final heating temperature (to 500 °C and to 800 °C), change of the exposure time at the final temperature (from 1 hour to 5 hours). It has been established that a change in the temperature conditions of the pyrolysis process affects the characteristics of the materials obtained (degree of amorphism, phase composition, the presence of impurities). The study of the composition of the pyrolysis products of the heterocomplex and the mixture of monometallic acetylacetonates of Ni(II) and Nd(III), obtained under heating to 800°C and holding at this temperature for 3 hours, showed the formation of a complex oxide Nd2NiO4, as well as other phases NiO, Nd6O11, Nd-Ni-O. However, their amount is noticeably smaller in the case of using a heterocomplex. It is shown that the temperature of heat treatment of the heterometallic complex and the time of its pyrolysis are much less in comparison with solid-phase synthesis methods.