Provider: - Institution: - Data provided by Europeana Collections- Reakcijom srebrova(I) nitrata s mono- i dihalogen derivatima piridina u molarnom omjeru 1 : 2 u smjesi vode i alkohola priređeno je ...12 novih kompleksa srebra(I) opće formule Ag(NO3)(Xnpy)2, X = Cl, Br, I; n = 1 – 2. Pripravljeni kompleksni spojevi identificirani su pomoću elementne analize, dok je njihova struktura u otopini okarakterizirana tehnikama višenuklearne spektroskopije NMR (1H, 13C, 15N, 109Ag) i spektrometrije masa. Kompleksi su u čvrstom stanju okarakterizirani spektroskopijom IR, a kristalna i molekulska struktura im je određena metodama rentgenske strukturne analize.
Molekule liganda su u svim kompleksima na srebrov(I) ion vezane preko atoma dušika piridinskog prstena. U koordinacijskoj sferi srebra(I) dokazan je i nitratni ion koji ovisno o načinu koordiniranja na srebro omogućava stvaranje koordinacijskih polimera ili supramolekulskih struktura. Koordinacijski broj srebra kod sintetiziranih spojeva varira između tri, četiri, pet ili šest i to čak ponegdje i unutar istog spoja. Pored kovalentnih veza, Ag–N i Ag–O, u strukturama su pronađene i nekovalentne interakcije (vodikove i halogenske veze te π···π interakcije) koje pridonose konačnoj dimenzionalnosti spoja. Slaba veza Ag–Ag otkrivena je u kompleksu s 3-Ipy kao ligandom. Priređeni spojevi pokazuju bolju antibakterijsku aktivnost u uvjetima in vitro spram Gram-negativnih nego spram Gram-pozitivnih bakterijskih vrsta.- Twelve 1:2 complexes of silver(I) nitrate with mono- and dihalopyridine of the general formula Ag(NO3)(Xnpy)2, X = Cl, Br, I; n = 1–2, were prepared by reaction of AgNO3 and corresponding pyridine derivative in water-alcohol solution. All synthesized complexes were identified by elemental analysis and characterized in solution by multinuclear NMR spectroscopy (1H, 13C, 15N, 109Ag) and mass spectrometry. In solid state the complexes were characterized by IR spectroscopy, while their crystal and molecular structures were revealed by single crystal X-ray analysis.
It was established that in all complexes, besides pyridine nitrogen atoms, the oxygen atoms belonging to nitrate ion are also coordinated to silver ion thus providing not only different coordination numbers of Ag(I) which vary from three, four, five and six but also a formation of coordination polymers or supramolecular structures. It is interesting that in the molecule of one complex, which is dinuclear, there are even two differently coordinated silver ions (3, 4). Beside covalent Ag–N and Ag–O bonds present in complex molecules, there are various non-covalent interactions such as hydrogen bonding, halogen bonds and halogen-halogen interactions thus contributing to final dimensionality. Moreover, a weak Ag–Ag bonding was determined in complex with 3-Ipy as a ligand. In vitro tests of all complexes gave better antibacterial activity against Gram-negative than Gram-positive strains.- All metadata published by Europeana are available free of restriction under the Creative Commons CC0 1.0 Universal Public Domain Dedication. However, Europeana requests that you actively acknowledge and give attribution to all metadata sources including Europeana
Provider: - Institution: - Data provided by Europeana Collections- Izvršena su strukturna istraživanja uzoraka AMn2O4 (A= Co, Zn, Ni, Cd, Cu) s ciljem određivanja utjecaja uvjeta sinteze na ...specifične značajke spinelnih struktura. Nađeno je da svi uzorci spinelne strukture pri čemu CoMn2O4, ZnMn2O4 i CdMn2O4 kristaliziraju u tetragonskom, a NiMn2O4 i CuMn2O4 u kubnom sustavu. Parametri inverzije za CoMn2O4 i CdMn2O4 rastu s porastom temperature termičke obrade (25500 oC). Parametar inverzije ZnMn2O4 povećava se s porastom temperature do 300 oC nakon čega se inverzija smanjuje. Struktura NiMn2O4 ne ovisi o temperaturi termičke obrade. Spoj CuMn2O4 nije moguće prirediti bez prisutstva nečistoća neovisno o temperaturi termičke obrade. Provedena su i elektrokemijska mjerenja; ustanovljeno je da najbolje ponašanje pokazuje CoMn2O4. Porast temperature termičke obrade uzrokovao je i rast čestica. Uzorak s najvećom veličinom čestica koji pokazuje najviši specifični kapaciteta, najbolje elektrokemijsko ponašanje te izrazito visoku održivost kapaciteta od 104 % nakon 1000 ciklusa punjenja i pražnjenja.- Structural studies on AMn2O4 (A = Co, Zn, Ni, Cd, Cu) have been performed in order to determine the influence of the synthesis conditions on the specific features of spinel structure, primarily on the inversion parameter. It was found that all samples belong to the spinel structure type; CoMn2O4, ZnMn2O4 and CdMn2O4 are tetragonal while NiMn2O4 and CuMn2O4 crystallize in the cubic system. The inversion parameter of CoMn2O4 and CdMn2O4 increases with increasing temperature (25500 C) while inversion in ZnMn2O4 increases with increase of temperature up to 300 C and decreases afterwards. Structure of NiMn2O4 does not depend on the heat treatment. Phase purity for CuMn2O4 was not achieved regardless of the temperature of the heat treatment. Electrochemical measurements were carried out for all samples; CoMn2O4 showed the best electrochemical performance. The increase in heat treatment caused pronounced particle growth. The sample with the largest particle size showed the highest specific capacity, best electrochemical cycling and extremely high capacity retention (104 % after 1000 cycles).- All metadata published by Europeana are available free of restriction under the Creative Commons CC0 1.0 Universal Public Domain Dedication. However, Europeana requests that you actively acknowledge and give attribution to all metadata sources including Europeana
