Crystal engineering of MOF based on polypyridyl ligands and coordinatively unsatured NiII ions

The thesis reports on the synthesis, structural and spectroscopic characterization of coordination polymers obtained by reacting dithiophosphato [((RO)2PS2)2Ni] and dithiophosphonato [Ni(ROpdt)2] NiII complexes [ROpdt = (RO)(4-MeOC6H4)PS2; R = Me, Et] with a variety of polypyridyl donors prepared and characterized as a part of the PhD work, selected according to their rigidity, topology, number and position of donor atoms. Chapter 1 An introductory part is presented which reports the main concepts of supramolecular chemistry and crystal engineering. The objectives of the research are outlined and the square planar NiII phosphorodithioato complexes used as the building blocks in the building up of the polymers introduced. The tendency of these coordinatively unsaturated complexes to axially bound two additional donor molecules by reaching octahedral coordination geometry in a quite predicable way, is discussed. Chapter 2 A discussion of the results is presented mainly focused on structural description motifs and crystallographic datasets obtained through the deliberate construction of coordination polymers obtained by reacting NiII phosphorodithioato complexes with various bi-pyridyl donors. Three different typologies of ligands were prepared: bidentate rigid spacers such as the 1,4-bis(3-pyridyl)-butadiyne ligand; semi-rigid bidentate spacers such as the 2,5-bis(4-pyridyl)-4-thia-1,3-thiazolidine and 2,5-bis-(3-pyridyl)-4-thia-1,3-thiazolidine ligands, and a set of tridentate spacers such as 1 1,3,5-benzenetricarboxylic acid-1,3-bis-4-pyridyl ester. The ligands were synthesized following different synthetic routes here described. The self-assembly process is based on the capability of the coordinatively unsaturated NiII ion of the square-planar phosphorodithioato complexes to bind suitable bipyridyl and tripyridil-based spacers thus forming 1D and 2D coordination polymers with different geometrical and topological features. It has been demonstrated that the primary structural motif of the polymers depends mainly on the features of the pyridyl-based spacers such as length, rigidity, number and orientation of the donor atoms, whereas the substituents on the phosphorus atoms play a crucial role in determining the final network through secondary intermolecular interactions involving the polymeric chains. Chapter 3 The experimental procedures and spectroscopic characterizations are here reported along with all the materials, instruments, synthetic procedures, crystallization methods, and technical parameters used for the spectroscopic investigations. Chapter 4 The conclusions about this research work and new perspectives in coordination polymers building-up are here reported.