Steady-state and Time-resolved Spectroscopic Studies on Gold(I) Complexes

本論文主要研究過渡金屬錯合物的光物理性質，包含一系列金(I)-銅(I)、純金錯合物與雙核金錯合物。d10是銅銀金的這一族，這一族特別受到重視是因為它會放很亮的磷光。原因是銅銀金可以有效的增強spin-orbit coupling使得ISC rate很高，進而得到相當高的磷光的量子產率。第一個部分是由不同的溶劑造成錯合物的排列變化，當我們把金銅錯合物暴露在不同的溶劑蒸氣中會有變色的效果，發現當金屬彼此的作用力越強，越增高了spin-orbit coupling，所以放光速率大大的提升。這種溶劑導致變色的光物理性質在金銅錯合物是前所未見的。 第二個部分是純金的錯合物。我們在合成d10complex喜歡使用乙烯作為線性的骨架並利用乙烯不飽和的特性可以跟金屬形成鍵結，但是很少人使用相同的芽基來組裝。通常相同芽基的金錯合物會形成聚合物材料，但我們使用有羥基的芽基，可以得到很亮的黃色的十核的錯合物，且產率很高。這個羥基可以幫助穩定結構, 而且在立體結構上也可以提供一個龐大的外圍取代基，所以即使在有氧的情形下，這些磷光仍然不會被氧氣經由碰撞的形式代謝掉能量。 第三部分我們研究雙核的金錯合物，主要探討此類錯合物特殊的同時放螢光和磷光的光物理性質。研究磷光的放光材料時常會探討heavy atom effect，主要是dπorbital有無參與到放光之中。如果有的話稱為internal heavy atom effect可以有效地增強spin-orbit coupling, 因為dπ到π*有角動量的變化，伴隨著電子的翻轉就可以做有效的偶合，所以ISC速率極快。相反的，若沒有dπ orbital貢獻到放光之中稱為external heavy metal effect。此系統仍然會有磷光的產生，但是重金屬不直接參與在躍遷的軌域之中，而是在放光基團的周圍增強spin-orbit coupling，這時spin-orbit coupling的強度是由金屬原子量以及金屬離放光基團的距離所決定。我們也展現此類錯合物上轉換的可行性。 Alkynyl gold complexes attract considerable attention due to their rich photoluminescent properties an pronounced tendency of the gold ions to form metal-metal (aurophilic) bonds, these compounds often aggregate in the solid state and in solution to give intriguing polynuclear assemblies of various structural types. We investigate a homoleptic Au−Cu alkynyl cluster that represents an unexplored class of luminescent materials with stimuli-responsive photophysical properties. We also synthesize high-yield self-assembly of homoleptic clusters (AuC2R)10 by treatment of Au(SC4H8)Cl with stoichiometric amount of hydroxyaliphatic alkyne in the presence of NEt3. The luminescence behavior of both AuI10 and AuI8 families has been studied, revealing efficient room-temperature phosphorescence in solution and in the solid state, with the maximum quantum yield approaching 100%. DFT computational studies showed that in both AuI10 and AuI8 clusters metal-centered Au→Au charge transfer transitions mixed with some π-alkynyl MLCT character play a dominant role in the observed phosphorescence. A series of newly synthesized diphosphine bimetallic Au(I) complexes exhibit remarkable ratiometric changes of intensity for phosphorescence versus fluorescence that are excitation wavelength dependent. This phenomenon is in stark contrast to what is commonly observed in condensed phase photophysics. The mechanism is rationalized by negligible metal d orbital contribution in the S1 state for the titled complexes. Conversely, significant ligand-to-metal charge transfer character in higher-lying excited states greatly enhances spin-orbit coupling and hence the ISC rate. The net result is to harvest high electronically excited energy toward triplet states, enhancing the phosphorescence. The above mechanism of harvesting triplet state may have numerous applications. For example, color-tunable OLED (organic light-emitting diode) devices for which the color of luminescence can be changed via altering the applied voltage may be fabricated. We also demonstrate the feasibility of transient upconversion in this type of au complexes. The triplet state can be considered as a reservoir of excited states for a subsequent energy transfer. We can pump the complex with “green” laser(532nm) and then obtain “blue” emission(430nm) which is of particular interest due to energy issue