This dissertation, "Design and Synthesis of Luminescent Platinum(II) and Gold(III) Complexes With Tridentate Pincer-type Ligands: From Computational Study to Experiments and Application Studies" by Suk-hang, Lam, 林淑恒, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled DESIGN AND SYNTHESIS OF LUMINESCENT PLATINUM(II) AND GOLD(III) COMPLEXES WITH TRIDENTATE PINCER-TYPE LIGANDS - FROM COMPUTATIONAL STUDY TO EXPERIMENTS AND APPLICATION STUDIES Submitted by LAM Suk Hang for the degree of Doctor of Philosophy at The University of Hong Kong in June 2015 Square planar platinum(II) and gold(III) complexes possess unique spectroscopic and photophysical properties which enable them as promising candidates for many applications such as optoelectronic devices and biological sensors. The understanding of the intrinsic properties of these complexes is therefore essential to optimize their performance as well as provide guidance on the molecular design for specific applications. This thesis aims to provide useful insights for the molecular design strategies with the aid of computational studies to tune the electronic properties of these complexes and electroluminescence studies in the fabrication of organic light-emitting devices (OLEDs). Computational studies have been performed to inspect electronic structures and photophysical properties as well as their correlation with the nature of ancillary ligands in the platinum(II) complexes of 1,3-bis(N-alkylbenzimidazol-2′-yl)benzene, [Pt(bzimb)(C≡C-R)], 1,3-bis-hetero-azolylbenzenes, [Pt(N DEGREESC DEGREESN)(C≡C-R)], and pyridine-based N-heterocyclic carbene, [Pt(NHC)(C≡C-R)] . It was found that the emission of the arylalkynylplatinum(II) complexes with pyridine-based N-heterocyclic carbene ligand was originated from the triplet alkynyl-to-tridentate pincer ligand-to-ligand charge transfer excited state mixed with platinum-to-tridentate pincer metal-to-ligand charge transfer character, and the excited state energy was found to be red-shifted according to the increasing π electron-donating ability of the aryl group attached to the alkynyl ligand. On the other hand, the emission energies of the platinum(II) complexes of 1,3-bis(N-alkylbenzimidazol-2′-yl)benzene and 1,3-bis-hetero-azolylbenzenes were found to be dependent on the different electron-donating substituents on the pincer ligands. Calculations have also been performed on the representative alkynylplatinum(II) + + complexes [Pt(trpy)(C≡C-R)] (trpy = 2,2′ 6′,2′′-terpyridine), [Pt(bzimpy)(C≡C-R)] (bzimpy = 2,6-bis(N-alkylbenzimidazol-2′-yl)pyridine) and [Pt(bzimb)(C≡C-R)] as well as alkynylgold(III) complexes [Au(C DEGREESN DEGREESC)(C≡C-R)] (C DEGREESN DEGREESC = 2,6-diphenylpyridine), [Au{C(Np) DEGREESN DEGREESC(Np)}(C≡C-R)] (C(Np) DEGREESN DEGREESC(Np) = 2,6-di(2-naphthyl)pyridine) and [Au(N DEGREESN DEGREESN)(C≡C-R)] (N DEGREESN DEGREESN = 2,6-bis(1H-benzimidazol-2-yl)pyridine) in order to have a better understanding on their nature of the emissive origins as well as the radiative and nonradiative processes. In particular, factors governing the ordering of the triplet excited states and radiative decay rate constants of the emissive state ( ES) have been examined. Their potential energy profiles for the deactivation process from the ES via triplet metal-centered states have also been explored. This study revealed for the first time the potential energy profiles for the thermal deactivation pathway of square planar platinum(II) and gold(III) complexes. In addition to the computational