Electroactive Platinum (II) Thienyl complexes with N,N- or P,P- bridging ligands: Syntheses and characterization

Abstract

This thesis describes the syntheses, characterization and electrochemistry studies of some electroactive platinum(II) thienyl complexes with various N,N- or P,P- bridging ligands. It includes:a) Syntheses and characterization of platinum(II) thienyl complexes with various N,N- or P,P- bridging ligands under the assistance of ESMS; b) Syntheses and characterization of dppf-chelated platinum(II) thienyl complexes with various N,N- or P,P- bridging ligands under the assistance of ESMS;c) Electrochemistry studies of the complexes synthesized in parts a) and b). The complexes were characterized mainly by 1H, 31P NMR spectroscopy, ESMS, and X-ray single-crystal crystallography.ESMS provides us a soft yet powerful technique for the investigation of the reactivity of the precursors, complexes trans-[Pt(2-thienyl)(PPh3)2(MeCN)]BF4, 1, and [Pt2 (PPh3)2(m-C8H4S2)(MeCN)2](BF4)2, 10, with a range of N,N- or P,P- bridging ligands. The technique helps to develop a more predictive synthetic approach to bifunctional mono-, di-, and polymeric complexes. The nuclear-selectivity is conveniently controlled by the choice of the heterocyclic ligands or spacers.The complexes trans-PtBr(C4H3S)(PPh3)2 and trans, trans-Pt2Br2(I?-C8H4)(PPh3)4 undergo phosphine replacement with bis-1,1a??-(diphenylphosphino)ferrocene (dppf) to afford the corresponding cis- compounds. Dinuclear complexes [Pt2(2-thienyl)2(dppf)2(I?-BPE)](BF4)2, 16, [Pt2(2-thienyl)2(dppf)2(I?-dppf)](BF4)2, 18, could be obtained through the use of N,N- or P,P- bridging ligands, such as bipyridine, diphosphines. Polymeric and polynuclear materials could be obtained from the dinuclear precursor that has two functional sites. However, poor solubility of these complexes precludes further characterization in solution. Electroactive mono-, di- and tri-nuclear platinum(II) thienyl complexes show contrasting behaviour when examined by continuous cyclic voltammetry. For di- and tri-nuclear complexes, the electrochemical behavior is associated with the film formation on the electrode due to thienyl-thienyl coupling. In contrast, the mononuclear complexes and all the dppf analogues in this work do not show such behaviors. This work led to promising metal-containing thin films from electrocycling of di- and tri-nuclear complexes with thiophene at either end. The potential for film formation from structurally characterizable materials and the possibility for adjusting the film properties through the use of different spacers would add a new dimension in our current research.