SINTEZA, STRUKTURA I SVOJSTVA DVOFAZNOG Mn(II)/Zn(II) MATERIJALA

Abstract

Reakcijom izmene liganada sintetisan je dvofazni materijal I izgrađen od kompleksa [Mn(dipya)(H2O)4](tpht) i {[Zn(dipya)(tpht)]·H2O}n(tpht = anjon tereftalne kiseline, dipya = 2,2’-dipiridilamin) i okarakterisan je rendgenskom difrakcijom praha (XRPD), elementarnom analizom i IC-spektroskopijom. Ritveldovom metodom utvrđena je struktura obe faze na osnovu poznatih kristalnih struktura kompleksa [Mn(dipya)(H2O)4](tpht) (monokliničan sistem, prostorna grupa P21/c, a = 7,62769(7), b = 23,8578(2), c = 11,09364(20) Å, β = 102,2997(10) °) i {[Zn(dipya)(tpht)]·H2O}n (monokliničan sistem, prostorna grupa P21/n, a = 9,83498(12), b = 14,40421(15), c = 12,27228(16) Å, β = 95,7954(9) °), koje su određene rendgenskom strukturnom analizom [1, 2]. Odnos faza [Mn(dipya)(H2O)4](tpht) i {[Zn(dipya)(tpht)]·H2O}n u I iznosio je 31:69 mas. %. Rezultati utačnjavanja Ritveldovom metodom u dobroj su saglasnosti, sa neznatnim odstupanjem od strukturnih parametara originalnih struktura: Rp: 4,28, Rwp: 5,60, Rexp: 4,42, χ 2 : 1,60, RB: 2,39, Rf: 1,99 za Mn(II)-fazu i RB: 3,15, Rf: 3,13 za Zn(II)-fazu. Mn(II)-fazu obrazuju diskretne kompleksne jedinke [Mn(dipya)(H2O)4](tpht) u kojima tpht ima ulogu jona suprotnog naelektrisanja sa deformisano-oktaedarskom geometrijom Mn(II)-jona. Zn(II)-faza izgrađena je od cikcak lanaca {[Zn(dipya)(tpht)]·H2O}n, sa dva kristalografski različita mostovna tphtliganda: bis-helatnim i bis-monodentatnim. Zn(II)-jon se nalazi u deformisanom kvadratno-piramidalnom okruženju. Termičko ponašanje I ispitano je simultanom TG/DSC-analizom u atmosferi vazduha i azota. XRPD identifikacija čvrstog ostatka nakon analize u atmosferi vazduha pokazala je prisustvo dve faze: ZnO (ICDD PDF 36- 1451) i ZnMn2O4 (ICDD PDF 24-1123), čija je morfologija ispitana skenirajućom elektronskom mikroskopijom (SEM). Merenjem magnetne susceptibilnosti na niskim temperaturama utvrđene su magnetne interakcije u I i analizirana su fotoluminescentna svojstva na sobnoj temperaturi.

A biphasic material I that is composed of complexes [Mn(dipya)(H2O)4](tpht) and {[Zn(dipya)(tpht)]·H2O}n(tpht = anion of terephthalic acid, dipya = 2,2’-dipyridylamine) has been synthesized by the ligand exchange reaction and characterized by X-ray powder diffraction (XRPD), elemental analysis and IR spectroscopy. The structural characterization of each phase was performed by Rietveld method according to the known crystal structures of [Mn(dipya)(H2O)4](tpht) (monoclinic, space group P21/c, a = 7,62769(7), b = 23,8578(2), c = 11,09364(20) Å, β = 102,2997(10) °) and {[Zn(dipya)(tpht)]·H2O}n (monoclinic, space group P21/n, a = 9,83498(12), b = 14,40421(15), c = 12,27228(16) Å, β = 95,7954(9) °) determined from single crystal data [1, 2]. [Mn(dipya)(H2O)4](tpht) to {[Zn(dipya)(tpht)]·H2O}n phase-ratio in I was 31:69 wt. %. The Rietveld refinement results were in a good agreement with a minor deviation of the final structural parameters from the original structures: Rp: 4.28, Rwp: 5.60, Rexp: 4.42, χ 2 : 1.60, RB: 2.39, Rf: 1.99 for the Mn(II)-phase, and RB: 3.15, Rf: 3.13 for the Zn(II)-phase. The Mn(II)-phase consists of discrete complex units [Mn(dipya)(H2O)4](tpht) in which the tpht is counter anion and with distorted octahedral geometry of Mn(II) ion. The Zn(II)-phase is comprised of zigzag chains of {[Zn(dipya)(tpht)]·H2O}n, with two crystallographically different tpht bridges: bischelate and bis-monodentate and Zn(II) ion in a distorted square pyramidal environment. The thermal behavior of I was studied by simultaneous TG/DSC analysis in both air and N2 atmospheres. XRPD identification of the solid residue after analysis in air atmosphere confirmed the presence of two phases: ZnO (ICDD PDF 36-1451) and ZnMn2O4 (ICDD PDF 24-1123), whose morphologies were analyzed using scanning electron microscopy (SEM). The magnetic susceptibility measurements at low temperatures of I were performed in order to examine the magnetic interactions and photoluminescence properties at room temperature have been investigated.