Naslov
Magnetic exchange interactions of CrIII ions through diamagnetic –O–NbV–O– bridges: synthesis and structural characterization of new [CrIIINbV] compounds

Autori
Jurić, Marijana ; Androš Dubraja, Lidija ; Pajić, Damir ; Torić, Filip ; Vito, Despoja

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
6th EuCheMS Chemistry Congress, Congress Program / - , 2016

Skup
6th EuCheMS Chemistry Congress

Mjesto i datum
Sevilla, Španjolska, 11.09.2016. - 15.09.2016

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
Transition Metals ; Oxo Bridges ; Oxalate ; Crystal Structure ; Magnetization

Sažetak
The area of heteropolynuclear metal complexes has attracted considerable interest not only due to their different architectures and topologies, but also for their potential applications in various fields from heterogeneous catalysis, gas storage and separation to supramolecular magnetism. Although the most used metals for the preparation of these complexes are the 3d first row transition, there are also many systems containing two or more different 3d and 4d metal ions. Diamagnetic ions such as Cl−, O2−, due to their small size, or closed-shell metal ions are usually good spin linkers, and generally cause considerable delocalization between magnetic centres. Nevertheless, the degree of delocalization depends strongly on the overlap between the magnetic orbitals on the metal and valence orbitals of ligands. Molecular ions such as oxalate, acetate, azide, etc., and conjugated bridges display low-lying excited valence states and produce larger spin and charge polarization effects. In the search for suitable synthetic routes leading to novel and more diversified polynuclear species, we have introduced the tris(oxalato)oxoniobate(V) anion, [NbO(C2O4)3]3− as new building block toward different metal centres. Special feature of this anion is that it can form heterometallic complexes through the bridging oxo (μ-O) or oxalate group (μ-C2O4). A novel heterotetranuclear oxo-bridged compound [Cr2(bpy)4(μ-O)4Nb2(C2O4)4]·3H2O (1) (bpy = 2, 2′-bipyridine) has been prepared and, in addition to the single-crystal X-ray study, characterized by magnetization measurements supported by DFT calculation. Compound 1 containing a square shaped {; ; ; ; Cr2(μ-O)4Nb2}; ; ; ; core exhibits relatively strong antiferromagnetic coupling between two chromium(III) ions mediated by two triatomic –O–NbV–O– diamagnetic bridges. In many cases, the magnetic interaction in the polynuclear complexes, based on metal centres and bridging ligands can be predicted ; in compound 1 any significant exchange coupling has not expected due to long intramolecular distances of ~7.4 Å between CrIII centres bridged by three diamagnetic atoms. In order to examine the role that metal centres, coordination sphere and crystal packing plays in modulating the magnetic properties of compound 1, additional new systems [CrIIINbV] of similar topology containing other aromatic ligands as 1, 10-phenathroline (phen) or terpyridine (terpy) have been prepared and structurally investigated: [Cr2(phen)4(μ-O)4Nb2(C2O4)4]·2H2O (2) and [Cr2(terpy)2(C2O4)2(μ-O)2Nb(C2O4)2][Cr(terpy)(C2O4)(H2O)]·3H2O (3). Exchange interaction between paramagnetic metal centres bridged by diamagnetic metal ion are known but are very rare, so the full comprehension of how the unpaired electrons of the metal centres feel each other through diamagnetic transition metal atom is still challenge.

Izvorni jezik
Engleski

Znanstvena područja
Fizika, Kemija

POVEZANOST RADA