Luminescent rhenium(I) and osmium(II) diimine complexes with anionic borate-containing ligands : design, synthesis, photophysics and applications

發光含硼陰離子配體錸(I)及鋨(II)二亞胺配合物 : 設計, 合成, 光物理與應用

Student thesis: Doctoral Thesis

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Author(s)

  • Wing Kin CHU

Detail(s)

Awarding Institution
Supervisors/Advisors
Award date15 Jul 2015

Abstract

Rhenium(I) tricarbonyl diimine complexes have been demonstrated to show interesting photophysical properties and rich photochemical properties associated with the long-lived MLCT excited state. With the suitable design either on diimine ligands or ancillary ligands of the complexes, their photophysical properties can be readily modified. In spite of the great versatility in the design of these luminescent rhenium(I) complexes for different applications such as chemosensors, photosensitizers and photocatalysts, their light-emitting device development is relatively much less explored. This is because many of the highly luminescent rhenium(I) tricarbonyl diimine complexes are positively charged and are not sublimable, and in addition most of the neutral rhenium(I) complexes commonly exhibit poor luminescent properties. To enhance the emission properties of the neutral rhenium(I) luminophores, a new class of strongly phosphorescent charge-neutral rhenium(I) diimine complexes with isocyanoborate ligands, [Re(CO)3(N-N)(CNBR3)] [N-N = bpy, 4,4'-Me2bpy, phen, 4,7-Me2phen, 2,9-Me2phen, 3,4,7,8-Me4phen; R = C6F5, C6H5, Cl, 4-ClC6H4, 3,5-(CF3)2C6H3] have been explored and described in Chapter 2. The X-ray crystal structures of eight of the target complexes have been determined. The photophysical and electrochemical properties of these complexes have been studied and detailed spectroscopic study revealed that these complexes exhibit green to yellow phosphorescence at room temperature and that the emission energy and quantum yield of some complexes are the highest among all neutral rhenium(I) tricarbonyl diimine complexes, and even comparable with most of the highly luminescent cationic rhenium(I) complexes. In view of the excellent emission properties and processability of these neutral complexes, electroluminescent devices using these complexes as emissive dopants have been demonstrated. Theoretical calculations on these complexes have also been carried out to elucidate the electronic structures and effect of metal-isocyanoborate interaction in these complexes. To have a better understanding and future exploitation of the intrinsic isocyanoborato complexes, a series of luminescent anionic bis(isocyanoborato) rhenate(I) complexes with general formula of [Re(CO)2(phen)(CNBR3)2] (R = C6F5, C6H5) have been designed and developed in Chapter 3. One of the target complexes has also been structurally determined by X-ray crystallography. The photophysics and electrochemistry of these complexes have been subjected to detailed investigation. The complex with the isocyanotriphenylborate ligand shows selective reactivity towards cyanide anions. The potential applications as selective luminescent chemosensor for cyanide anion in aqueous media have been explored. Extending our design concept for converting cationic triplet emitters to neutral phosphorescent materials with improved emission properties, rhenium(I) diimine complexes with other strong π-accepting anionic ligands, such as borate Lewis adducts of anionic carbene and phosphine ligands have been designed, synthesized and characterized (Chapter 4). The photophysics and electrochemistry of a new class of luminescent charge-neutral (carbene)borato or (phosphine)borato rhenium(I) phenanthroline complexes with the general formula of {Re(CO)3(phen)[CN(BR3)C6H4-2-O]} [R = C6F5, 3,5-(CF3)2C6H3] or {Re(CO)3(phen){P[B(C6F5)3]Ph2}} have been investigated. Through this study, the electronic nature and metal-ligand interaction of these unprecedented anionic ligands have also been evaluated. In addition, a validation of the design concepts with osmium(II) complexes, has also been made. In Chapter 5, the design, synthesis, photophysics and electrochemistry of a series of charge-neutral bis(isocyanoborato) bis(diimine) osmium(II) complexes, [Os(N-N)2 (CNBR3)2] (N-N = bpy, 4,4'-Me2bpy; R = C6F5, C6H5) with excellent luminescent properties have been reported. The stability and processablitiy of this new class of neutral osmium(II) luminophore have been examined to provide insights into the potential device applications.

    Research areas

  • Ligands (Biochemistry), Osmium compounds, Luminescent probes, Rhenium compounds