engleski

Homo- and heterometallic oxalato-bridged coordination polymers: structural, magnetic and electrical properties

Coordination polymers are extensively studied due to a large variety of topologies and structures giving rise to a plethora of physical and chemical properties, which are often related to their intrinsic porous character and rich host-guest chemistry, making them archetypes of multifunctional molecular materials. The oxalate group, C2O42, due to its various coordination modes towards the metal centres as well as its ability to mediate magnetic interactions between paramagnetic metal ions, certainly represents an excellent tailoring tool as evidenced by large number of oxalate-based transition-metal species of different nuclearity, connectivity and dimensionality. Furthermore, these systems are mostly negatively charged and therefore can be combined with functional molecular cations in order to afford complex salts combining cooperative magnetism with a second property of interest. Proton conductivity is recently regarded as a new functionality of the coordination polymers. The simplest method to introduce proton carriers is to include counterion such as hydronium (H3O+), ammonium [NH4+, (CH3)2NH2+, ...] or anion (SO42−), resulting in the charged compounds. The counterions form the H-bonding with the guest water or the framework, representing the continuous H-bond network with efficient proton conduction. In our research we focus on structural properties of novel homo- and heterometallic oxalate-bridged coordination polymers reflected on their magnetic and electrical behaviours: one- dimensional exhibiting antiferromagnetic spin chains of the host anions [FeIIICl2(C2O4)]nn−, whereas the alkyl ammonium counterions [(C2H5) (CH3)2NH+ or (C2H5)2(CH3)NH+] and the guest molecules give rise to high room-temperature proton conductivity, and two polymorphs containing two-dimensional honeycomb layers [FeII2(C2O4)3]n2n−, which are bridged by paramagnetic [Cu(H2O)(terpy)]2+ cations (terpy = 2, 2′:6′, 2″-terpyridine), ultimately giving three-dimensional network showing long-range magnetic order and strong dependence of electrical conductivity on the relative humidity revealing proton conduction mechanism.

Coordination Polymers ; Oxalate-Bridged ; Crystal Structure ; Magnetic Property ; Electrical Property

nije evidentirano