Photophysical Properties of Cyclometalated Pt(II) Complexes: Counterintuitive Blue Shift in Emission with an Expanded Ligand 蟺 System

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• 作者：Alberto Bossi ; Andreas F. Rausch ; Markus J. Leitl ; Rafa艂 Czerwieniec ; Matthew T. Whited ; Peter I. Djurovich ; Hartmut Yersin ; Mark E. Thompson
• 刊名：Inorganic Chemistry
• 出版年：2013
• 出版时间：November 4, 2013
• 年：2013
• 卷：52
• 期：21
• 页码：12403-12415
• 全文大小：566K
• 年卷期：v.52,no.21(November 4, 2013)
• ISSN：1520-510X

文摘

A detailed examination was performed on photophysical properties of phosphorescent cyclometalated (CN)Pt(OO) complexes (ppy)Pt(dpm) (1), (ppy)Pt(acac) (1鈥?, and (bzq)Pt(dpm) (2) and newly synthesized (dbq)Pt(dpm) (3) (CN = 2-phenylpyridine (ppy), benzo[h]quinoline (bzq), dibenzo[f,h]quinoline (dbq); OO = dipivolylmethanoate (dpm), acetylacetonate (acac)). Compounds 1, 1鈥? 2, and 3 were further characterized by single crystal X-ray diffraction. Structural changes brought about by cyclometalation were determined by comparison with X-ray data from model CN ligand precursors. The compounds emit from metal-perturbed, ligand-centered triplet states (E_0鈥? = 479 nm, 1; E_0鈥? = 495 nm, 2; E_0鈥? = 470 nm, 3) with disparate radiative rate constants (k_r = 1.4 脳 10⁵ s^鈥?, 1; k_r = 0.10 脳 10⁵ s^鈥?, 2; k_r = 2.6 脳 10⁵ s^鈥?, 3). Zero-field splittings of the triplet states (螖E_III鈥揑 = 11.5 cm^鈥?, 1鈥? 螖E_III鈥揑 < 2 cm^鈥?, 2; 螖E_III鈥揑 = 46.5 cm^鈥?, 3) were determined using high resolution spectra recorded in Shpol鈥檚kii matrices. The fact that the E_0鈥? energies do not correspond to the extent of 蟺-conjugation in the aromatic CN ligand is rationalized on the basis of structural distortions that occur upon cyclometalation using data from single crystal X-ray analyses of the complexes and ligand precursors along with the triplet state properties evaluated using theoretical calculations. The wide variation in the radiative rate constants and zero-field splittings is also explained on the basis of how changes in the electronic spin density in the CN ligands in the triplet state alter the spin鈥搊rbit coupling in the complexes.