Light-emitting platinum (II) and gold (I) complexes containing cyclometalated and alkynyl ligands

by Lu, Wei

Abstract (Summary)

Submitted by Lu Wei

for the degree of Doctor of Philosophy at The University of Hong Kong

in July 2003

The syntheses, characterizations, spectroscopic properties and applications of light-emitting platinum(II) and gold(I) complexes containing cyclometalated and alkynylligands are described and five systems are explored in detail. The tuning of the photoluminescent properties of tridentate cyclometalated platinum(II) complexes bearing cr-alkynyl auxiliaries, namely [(CANAN)Pt(C=C)nR] [H(CANAN) = 62,2' -bipyridine; n = 1--4; R = aryl, alkyl or trimethylsilyl], through modifications of both the cyclometalating and acetylide ligands, is presented. These neutral Pt(II) materials exhibit enhanced stability during vacuum deposition. Organic light-emitting devices (OLEDs) based on these emitters display orange to red electrophosphorescence with low turn-on voltages (--4 V), maximum luminance approaching 10,000 cd m -2 and efficiencies up to 4.2 cd A-I. The crystal structures and photoluminescence of tethered trinuclear cyclometalated platinum(II) complexes, namely [{R(CANAN)hPt3(/l3-dpmp)]3+ (R denotes substituent(s) on the (CANAN) ligand, dpmp = bis( diphenylphosphinomethyl)phenylphosphine), were investigated and compared with their mono- and binuclear analogues to yield insight into the nature of their respective excited states. The emission energies were found to be

dependent on the substituents on the cyclometalating ligands and the oligophosphine ligands, and sensitive to d8-d8 and 1t-1t interactions. Intermolecular 1t-stacking interactions were found to affect the crystal packing, solid-state emission energy and vapochromic behavior of mono- and multinuclear dicyclometalated Pt(II) complexes, namely [Pt(C/\N/\C)L1] [HC/\N/\CH = 2,6-diphenylpyridine; L1 = pyridine, isocyanide, phosphine], [Ph(C/\N/\Ch(Il-L2)] [L2 = pyrazine, bidentate phosphine] and

[Pt3 (C/\N/\C)3 (1l3-dpmp )], and aromatic a-diimine Pt(II) complexes bearing functionalized cr-alkynyl auxiliaries, namely [(tBu2bpy)Pt(C=CArh] (tBu2bpy = 4,4'bis-tert-butyl-2,2'-bipyridine, Ar = 4-pyridyl, 3-pyridyl, 2-pyridyl, 4-ethynylpyridyl, 2-thienyl and pentafluorophenyl). The weak non-covalent interactions observed in the solvated crystal structures, such as 1t-1t, C-H .. ?t(C=C), C-H"'N(py), C-H"'P-C and CI .. ?I contacts, were invoked to rationalize the reversible VOC (volatile organic compound) sensing and signaling capabilities of these materials. The syntheses,

crystal structures and spectroscopic properties of several1t-conjugated carbon-rich scaffolds bearing [AU(PCY3)t (Cy = cyclohexyl) termini are described. The Vo-o of the acetylenic 3(1t1t*) emission for [(CY3P)Au(C=C)nAu(PCY3)] (n = (0) was estimated to occur at ~11000 cm-1 by extrapolation of the plot ofvo-o versus l/n. Prompt 1(1t1t*) fluorescence only was detected from the cross-conjugated species [TEE][Au(PCY3)]4 ([TEE]H4 = tetraethynylethene). A correlation between the solid-state emissions and crystal structures of the phosphorescent polymorphic complex [4- N02C6H4C=CAu(PCY3)] and their related complexes was observed, and a rationale based on excitonic coupling is proposed.

Bibliographical Information:


School:The University of Hong Kong

School Location:China - Hong Kong SAR

Source Type:Master's Thesis

Keywords:platinum gold complex compounds ligands


Date of Publication:01/01/2003

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