芳杯分子、碳鏈及縮二醇醚上修飾三唑之螢光離子感測研究

Abstract

本論文的研究主題為：以三唑官能基作為金屬離子的錯合中心，分別鍵結於芳杯下緣、碳鍊或是縮二醇醚；再利用螢光基團（蒽或芘）的螢光強度增減、生命期的變化，來辨識金屬離子的錯合與否；最後藉由氫譜的滴定實驗，推測出較可能的金屬離子錯合模式。 第一部份的研究中，在芳杯的下緣修飾單－、雙－及四－「蒽基甲基三唑基團」的衍生物30□32（單取代）、33□35（雙取代）及36□37（四取代）。在溶劑為乙腈下，其中蒽基甲基三唑基團單取代化合物30□32對Cu2+、Hg2+及Cr3+有高度選擇性，由此可知，三唑基團對金屬離子即有錯合能力，且錯合後均是造成蒽基團的螢光放射減弱，推測可能是三唑基團與金屬離子錯合後，形成acceptor，激發蒽基團後，傳遞到三唑基團，所以觀測到螢光的淬熄，為reverse PET機制。蒽基甲基三唑基團雙取代化合物35除了對Cu2+、Hg2+及Cr3+仍有錯合能力外，更對Pb2+及Cd2+也有選擇性；與Pb2+錯合，造成螢光的淬熄，其機制仍屬reverse PET；而與Cd2+的錯合，造成螢光強度的增加，推測是因為錯合後，造成整個分子的構形較固定，所以螢光強度增加。蒽基甲基三唑基團四取代化合物37，對金屬離子有更佳的錯合能力，但是選擇性不佳，其對（a）Cu2+、Hg2+、Cr3+、Mg2+、Ni2+產生螢光淬熄；（b）Ag+、Ca2+、Cd2+、Li+、Pb2+、Zn2+螢光增強，不是一個好的感測器。

第二部份的研究中，在碳鍊或縮二醇醚上，修飾「三唑及芘」的雙取代官能基58□61及70□73。在乙腈為溶劑下，58□61對金屬離子的篩選中，發現碳鍊較短時，58□59僅對Cu2+、Hg2+及Cr3+有錯合能力，而增加鍊長時，60不僅對Cu2+、Hg2+及Cr3+有錯合能力，更對Pb2+也有選擇性；61更加對Cd2+及Zn2+有錯合能力。推測因為鍊長的增加，所以有較佳的柔軟性，故61對金屬離子有較佳的錯合能力。在乙腈為溶劑下，70□73對金屬離子的篩選中，沒有好的選擇性，均是對Cu2+、Hg2+、Cr3+、Pb2+、Cd2+及Zn2+有錯合的現象。但是將溶劑改為較高極性的甲醇，此系列化合物僅對Hg2+及Ag+，其錯合後均是造成螢光單體及激態雙體的放射減弱；再由氫譜的滴定實驗中證實，與Ag+的錯合，主要是利用三唑雙官能基上的氮與Ag+進行錯合，且因構形上的翻轉，使得縮二醇醚也對金屬離子提供錯合的能力。

第三部份的研究中，合成芳杯下緣含「三唑醯胺芘」雙取代80，其中三唑官能基為金屬離子的錯合中心，醯胺基團為陰離子的錯合中心，而芘基為訊號傳遞中心。發現，在乙腈為溶劑下，80的螢光放射在375及395 nm附近，且動態激態雙體放射在482 nm附近。80與F□、AcO□及H2PO4□混合後有螢光變化的現象。80與F□混合，造成醯胺基的去質子化，使得UV/vis有明顯的紅位移變化；螢光單體放射淬熄，且482 nm動態激態雙體放射消失，在472 nm附近新生成靜態激態雙體放射。80與AcO□產生錯合，UV/vis沒有顯著的變化；螢光放射淬熄，482 nm動態激態雙體放射消失，在472 nm附近新生成靜態激態雙體放射。80與H2PO4□產生錯合，UV/vis沒有顯著的變化；但螢光單體放射增加，動態激態雙體放射減弱，推測是H2PO4□離子半徑較大，所以錯合時造成芘基團相互遠離。在金屬離子篩選方面，80僅選擇性地對Cu2+、Hg2+及Cr3+有錯合能力；但與F□預混合，除了Cu2+、Hg2+及Cr3+外，更對Ag+有錯合的能力。

Triazole, as metal ions binding site, coupled with lower rim of calix[4]arene, methylenes, or polyoxyethylenes were prepared. The possible binding modes of hosts with guests were proposed based on results obtained from fluorescence, lifetime, and 1H-NMR titration experiments. A series of triazole-coupled calix[4]arene derivatives as fluorogenic sensors for metal ions are synthesized. The 1,3-dipolar cycloaddition reaction of mono-, bis-, and tetra-propargyl-coupled-calixarene with azide afforded triazole-coupled calixarene derivatives (30□37) as a class of selective receptors toward metal ions. The mono-triazole-coupled calixarene 30□31 are good sensors for Cu2+, Hg2+ and Cr3+; the bis-triazole 35 has excellent affinity toward Cu2+, Hg2+, Cr3+, Pb2+ and Cd2+. The tera-triazoles substituted calixarene 37 is not a good sensor, for it senses for too many metal ions.

Fluorescent chemosensors 58□61, with variable methylene chain length as spacers between the two triazole methyl ether units, have been synthesized under ‘Click’ condition, where the bistriazoles are used as the metal ion binding sites and the pyrenes as the fluorophores. Compound 61, having the longest methylene chain among 58□61, shows monomer and excimer fluorescence quenching in acetonitrile toward Ni2+, Pb2+, Cu2+, Hg2+, and Cr3+ ions, however, it shows an enhanced monomer but a decreased excimer emission when complexed with Cd2+ and Zn2+ ions. Fluorescent chemosensors 70□73, with variable polyoxyethylenes between the two triazole methyl ether units, have been synthesized under ‘click’ condition, where the bistriazoles and polyoxyethylenes are used as the metal ion binding sites and the pyrenes as the fluorophores. The fluorescence of chemosensors 70□73 in methanol solution was found to be selectively quenched by Hg2+ and Ag+ among 15 metal ions screened. Binding constants of 70□73 toward Ag+ increased as the chain length of the polyoxyethylenes increased. Finally, a very high selectivity of compound 9 toward Hg2+ in aqueous methanol solution was observed.

A new fluorescent chemosensor 25,27-bis{1’-N-(1-pyrenyl)-amino- carbonyl-methyl-1H-[1’,2’,3’]triazolyl-4’-methoxy}-26,28-dihydroxy- calix[4]arene, 80, for the selective recognition of anions as well as ion pairs in MeCN is presented. The calix[4]arene sensor 80 uses bis- triazoles as the metal ion binding ligands, bis-amides as the anion recognition site, and the pyrenes as the fluorophores. Among the eight anions screened, chemosensor 80 showed a dramatic fluorescence change only toward F□, H2PO4□, and AcO□ anions; however, it was found that 80 responded to each of the anions in a different way. In the presence of low equiv of F□, the dynamic excimer emission of compound 80 at □max 482 nm was completely quenched; however, a new emission at □max 472 nm appeared at high doses of F□. Contrary to the addition of fluoride anion, the addition of H2PO4□ to the solution of 80 showed an enhanced monomer but a decreased excimer emission (□max 482 nm). Upon adding AcO□ to 80, a systematic change from a dynamic excimer (□max □□□ nm) to a□max □□□ nm was observed but with little change in UV-vis spectra. Without pre-treated with anion, chemosensor 80 showed metal ion recognition only toward Cu2+, Hg2+, and Cr3+ ions; however, it became sensitive toward Ag+ ion when it was pre-complexed with fluoride anion.