雙金錯合物和二，六-雙雜氮吲哚的激發態性質

Abstract

本文的第一部份在探討雙金錯合物的激發態性質，這一系列的錯合物在受到光激發時可以同時發出螢光和磷光，並且透過不同的取代基去調控中心金屬的dpi軌域能量，達到調控螢光和磷光比例的效果，這個成功的例子帶給以後的化學家一個有效的依據。另外，我們還發現這一系列的錯合物在固態時有感測環境中氧氣的功能，這在金的錯合物研究裡是第一次發現到的案例。 第二部份在討論三-甲基-二,六-雙囃氮吲哚的在水中的激發態性質。我們現在這個化合物在水中會進行「激發態的三質子轉移」，反應速度約是8.3 * 108 s-1，並且在異構化之後會放出很強的螢光，可以用來研究蛋白質裡局部的環境中的水分子。我們也接著探討了「激發態的三質子轉移」的反應機制，質子總量(proton inventory) 的實驗結果認為是一個逐步的反應。動力學同位素效應也有在文中討論。這也是第一次發現在水中可以進行「激發態的三質子轉移」的案例。

Part 1 A series of gold(I) alkynyl-diphosphine complexes (XC6H4C2Au)PPh2–spacer–PPh2(AuC2C6H4X); spacer = –C2(C6H4)nC2– (A1, n = 2, X = CF3; A2, n = 2, X = OMe; A3, n = 3, X = CF3; A4, n = 3, X = OMe), –(C6H4)n– (B5, n = 3, X = OMe; B6, n = 4, X = OMe) were synthesized and their photophysical properties were investigated. The luminescence behaviour of the compounds is dominated by the diphosphine spacer, which serves as an emitting ππ* chromophore. The complexes exhibit dual emission, comprising low and high energy bands of triplet (phosphorescence) and singlet (fluorescence) origins, respectively. Different ancillary groups X, possessing either electron-donating or withdrawing, significantly affect the d orbitals energy, and hence affect the LLCT/MLCT contribution of both alkynyl ligand and the metal center into the lowest lying excited state. As a result, it substantially influences the rate of intersystem crossing kisc S1 → Tm (m ≥ 1) that allows for tuning the ratio fluorescence vs phosphorescence without alteration of the chromophore core. Solid state complexes A2 and B5, which exhibit dominating phosphorescence emission, for the first time for the unsupported gold luminophores were found as molecular oxygen sensors (max KSV1 = 63 atm-1). Part 2 3-Me-2,6-Diazaindole (2,6-DAI) has been strategically designed and synthesized to mimic the natural tryptophan. Upon UV (<320 nm) excitation 2,6-DAI are able to undergo excited state proton transfer in H2O (pH = 7.4) with great tautomer emission quantum yield of 0.1. Proton inventory experiments indicate that two water molecules and three protons are involved, undergoing a relay type of excited state triple proton transfer (ESTPT) with a stepwise manner. The rate constant (kpt) of the water-catalyzed ESTPT is slow and determined to be 8.3  108 s-1 in H2O and 4.5  108 s-1 in D2O, respectively. Computational approaches further affirm the thermodynamically favorable ESTPT in water. 2,6-DAI thus demonstrated for the first time water-catalyzed ESTPT in neutral water among Trp analogues. This, together with its high bio-compatibility and high Q.Y., makes (2,6-diaza)Trp unique to probe protein microsolvation in future.