Selective crystallization offers new opportunities for separating lanthanide elements, which have considerable importance in advanced materials. The first part is the second and third chapters, which investigated that the coordination chemistry and selective crystallization of Ln3+ cations with the water-soluble ligand, 5-(pyrimidyl)tetrazolate (pmtz−), dtp2− (H2dpt = 2,3-di-1H-tetrazol-5-ylpyrazine) and H2ibt− (H3ibt = 4,5-bis(tetrazole-5-yl)imidazole). In the second chapter, the wide range of coordination modes of pmtz allows for discrimination between Ln3+ cations, and five distinct compound types can be prepared that are dependent on the lanthanide employed, [La(pmtz)2(H2O)6]Cl (S1), [Ln(pmtz)3(H2O)3]·(3+n)H2O (Ce3+and Pr3+, S2). [(Ce(pmtz)2(H2O)3)2(μ-pmtz)]∙11H2O (S3), [(Ln(pmtz)2(H2O)3)2(μ-pmtz)]2(pmtz)2∙14H2O (Nd3+ and Sm3+, S4) and [Ln(H2O)8](pmtz)3·3H2O (Dy3+ to Lu3+, S5). This selective crystallization of Ln3+ cations based primarily on ionic radii provides a simple method for achieving group separations. The third chapter describes a series of lanthanides with two water-soluble tetrazolate-based ligands, dtp2− and H2ibt−. These ligands allow the separation of Nd3+ and Dy3+ through selective crystallization. The reactions of Ln3+ with the ligand Na2(dtp)·2H2O lead to two distinct phases, Na[Ln(dtp)(H2O)8](dtp)∙H2O (Lndtp1, Ln = La−Pr) and [Ln(H2O)8](Hdtp)(dtp)∙H2O (Lndtp2, Ln = Nd, Sm−Lu). Three structure types [Ln(H2ibt)2(H2O)6](H2ibt)·3(H2O) (Lnibt1, Ln = La, Ce), [Ln(H2ibt)((H2O)7](H2ibt)2·4(H2O) (Lnibt2, Ln = Pr, Nd), and [Ln(Hibt)(H2ibt)(H2O)4]·4+x(H2O) (Lnibt3, Ln = Sm−Lu) are obtained from reacting Ln3+ and Na(H2ibt)·3(H2O). Changing the pyrazine core in H2dtp to imidazole in H3ibt leads to different phases for Nd (Lnibt2) and Dy (Lnibt3), which allows for a crystallization-based separation of Nd/Dy in a short separation time.The second part is fourth, fifth, seventh chapters, which focus on the coordination of tetrazolate ligands with plutonium, reporting that the salt metathesis reaction of 5-(Pyrimidyl)Tetrazolate (pmtz‒), 2,3-di-1H-tetrazolate-5-ylpyrazine (dtp2‒), 5-(2-Pyridyl)-tetrazolate (pdtz‒) and 1,3-di(tetrazolate-5-yl)benzene (m-dtb2‒) with hydrated 239PuBr3 in an aqueous solution gives the mononuclear compound [239Pu(pmtz)3(H2O)3]·(3+n)H2O (n = ~8), dinuclear compound, [(Pu(pmtz)2(H2O)3)2(μ-pmtz)]2(pmtz)2∙14H2O, xxvi [239Pu(pdtz)3(H2O)3]·3.5(H2O), [Pu(m-dtbH)(H2O)8](m-dtb)·11(H2O) and [Pu(H2O)9](m-dtbH)3·9(H2O). All these plutonium compounds were synthesized and characterized by single-crystal X-ray diffraction, in addition to solid-phase and solution UV–vis–NIR absorption spectroscopy. The comparisons between these compounds and their lanthanide isostructural complexes demonstrate the bonding differences between lanthanide and actinide ions of identical ionic radii. The Laporte-forbidden 5f → 5f transitions are assigned in the UV-VIS-NIR spectra for these f-element-tetrazolate coordination compounds. The sixth chapter is about the synthesis and characterization of Am1, [Am(pdtz)3(H2O)3]·3.5(H2O) through single-crystal X-ray diffraction, solid-phase, solution UV–vis–NIR absorption spectroscopy and pressure study. The comparisons between Am1 and its lanthanide isostructural complexes demonstrate the bonding differences between lanthanide and actinide ions of identical ionic radii. The Laporte-forbidden 5f → 5f transitions are assigned in the UV-VIS-NIR spectra for Am1. Also, with the increasing of the pressure, the broad, split and blue shift of these transition from 8S7/2 are observed. The seventh chapter concludes the dissertation.
