Design and characterization of metal-thiocyanate coordination polymers
This thesis focuses on exploring the synthesis and chemical reactivity of thiocyanate-based building blocks of the type [M(SCN)x]y- for the synthesis of coordination polymers. A series of potassium, ammonium, and tetraalkylammonium metal isothiocyanate salts of the type Qy[M(SCN)x] were synthesized and structurally characterized. Most of the salts were revealed to be isostructural and classic Werner complexes, but for (Et4N)3[Fe(NCS)6] and (n-Bu4N)3[Fe(NCS)6], a solid-state size-dependent change in colour from red to green was observed. This phenomenon was attributed to a Brillouin light scattering effect by analyzing the UV-Visible spectra of various samples with different sized crystals. Coordination polymers of the type [M(L)x][Pt(SCN)4] were prepared and structurally characterized using a variety of bi- or tri-dentate capping ligands (ethylenediamine, 2,2’-bipyridine, 2,2';6',2"-terpyridine, N,N,N′,N′-Tetramethylethane-1,2-diamine). Overall, structural correlations between the ligand, the metal centre, the coordinating mode of the [Pt(SCN)4]2- building block and the topologies of the coordination polymers were established. Similar systems were synthesized using the ligands N,N’-bis(methylpyridine)ethane-1,2-diamine (bmpeda) and N,N’-bis(methylpyridine)cyclohexane-1,2-diamine (bmpchda) and were revealed to be multidimensional coordination polymers by structural analysis. Five complexes of the type [Cu2(μ-OH)2(L)2][A]x•yH2O (where L = 1,10-Phenanthroline, tmeda and 2,2’-bipyridine) were prepared and have been characterized by spectroscopic and crystallographic structural analyzes and by SQUID magnetometry. Two complexes were revealed to be dinuclear molecular units capped with the SCN- ligand. The complexes involving the [Au(CN)4]- anion were structurally characterized as double salts involving the dinuclear Cu(II) unit with a varying degree of hydration. The complex [Cu2(μ-OH)2(tmeda)2Pt(SCN)4] was revealed to be a 1D coordination polymer with trans- bridging [Pt(SCN)4]2- units. The magnetic susceptibility versus temperature was measured and fitted for each system to obtain J-coupling values that were qualitatively compared to the previously published magnetostructural correlation for dinuclear hydroxide-bridged units. The birefringence and luminescent properties for four new complexes of the type [Pb(4’-R-terpy)(SCN)2] were measured. The complexes presented unique luminescence based on the presence of the SCN unit, whereas the birefringence of the complexes was compared to [Au(CN)2]- analogues and was correlated to the structural properties of the system.