含呋喃環之寡聚物與高分子:合成及光物理

Abstract

結合分流法 (divergent)/ 匯集法(convergent)，利用炔丙基硫縮酮單體和另一具有醛基的單體進行環化反應，可以迅速合成對位及間位取代苯環呋喃交錯寡聚物。利用此一策略，可以合成單一分子量的共軛寡聚分子並且不含重複基團，同時也探討這些對位及間位取代苯環呋喃交錯寡聚物的光電性質及分子摺疊現象。 我們也合成出一系列不同共軛長度的苯環呋喃交錯之硫醇寡聚物，利用反射式紅外線光譜儀以及STM觀察金表面，顯示此類分子以pi-pi堆疊方式，有緊密規則的晶格排列，且分子彼此之間的距離為0.51 nm。在測量單分子導電性方面，不同共軛長度的苯環呋喃交錯硫醇寡聚物的導電性，隨著分子共軛長度變長而降低。 另一方面，我們將連接降冰片烯骨架的基團，以一系列不同共軛長度的苯環呋喃交錯寡聚物取代。降冰片烯雙鍵經過開環歧化聚合反應產生的變化，導致聯結基團的呋喃寡聚體彼此聚集 (aggregation)，因而螢光放射強度減弱。當單體形成高分子後，其第一氧化電位皆一致的變小，並且是隨著呋喃寡聚體共軛長度增加，電位變化差距有愈大的趨勢。

A range of oligoaryls having alternating para- or meta-benzene-furan rings is synthesized by rapid convergent/divergent method from the annlation of a propargylic dithioacetal and an aldehyde having a propargylic dithioacetal moiety as the substituent. This route provides a useful procedure toward the synthesis of monodisperse oligoaryls without repetitive units. Systematic investigation on the photophysical properties and molecular folder phenomenon of these oligomers are also explored. A series of dithiolated alternating benzene-furan oligoaryls was synthesized. IRAS (infrared reflection-absorption spectroscopy) and STM (scanning tunneling microscopy) experiments revealed that single-component monolayers of these oligoaryls have lattice packing of crystalline by pi-pi interaction and each distance between two single molecules is about 0.51 nm. The conductance of single molecule was decreased with the conjugated length of alternating benzene-furan oligoaryls increased. In addition, a series of double stranded polymers by using furan-containing oligoaryls as linkers was synthesized. Conformational change of the norbornene moiety after ROMP (ring opening metathesis polymerization) lead chormophores aggregated and quenched the fluorescent intensity. The first oxidation potential of polymers were conformably lower than corresponding monomers, and the difference of first oxidation potential between monomer and polymer was increased with the conjugated length of chormophores increased.