含十六族（硒、碲）之過渡金屬（鐵、銅）聚合物對有機小分子的選擇性吸脫附及半導體性質之探討

Abstract

本研究以無機金屬團簇物 [EFe3(CO)9Cu2(MeCN)2] (E = Te, Se) 與 1.5 當量的對苯二甲腈 (para-dicyanobenzene, p-DCB) 進行反應，可獲得一維單−雙股 p-DCB 橋接 Z 字型的聚合物 [EFe3(CO)9Cu2(p-DCB)1.5]n (E = Te, 1a; Se, 1b)。過去研究發現聚合物 1a 及 1b 透過液體輔助研磨 (liquid-assisted grinding, LAG) 或只針對 1b 之純研磨 (neat grinding) 的方式吸附各種有機化合物，例如：C7−C10 之烷基芳香烴、多環芳香烴及雜環化合物，可獲得一系列主−客聚合物 [EFe3(CO)9Cu2(p-DCB)1.5(G)m]n (G = 客分子; E = Te, 1a·mG; Se, 1b·mG; m = 0.5 或 1)。特別的是，當 四氫呋喃 (THF) 嵌入 1a 會形成單−單股 p-DCB 橋接聚合物 [TeFe3(CO)9Cu2(p-DCB)(THF)]n (2a·THF)。本研究更進一步選用尺寸較大的多環芳香烴—芘 (pyrene)，可獲得新的環狀化合物 [{EFe3(CO)9Cu2}4(p-DCB)4(pyrene)3]·2pyrene (E = Te, 3a·5pyrene; Se, 3b·5pyrene)。由此系列的主−客聚合物以及環狀化合物之固態堆疊結構可知，p-DCB 配基與這些客分子之間具有 C−H‧‧‧π、π‧‧‧π 及 C−H‧‧‧E (E = O, S) 弱作用力。此外，主−客聚合物可藉由抽真空或結晶法的方式成功脫附客分子，達成有效回收聚合物 1a 及 1b 的目的。並透過 X 光電子能譜 (X-ray photoelectron spectroscopy, XPS) 與 X 光吸收近邊緣結構 (X-ray absorption near-edge structures, XANES) 光譜，研究這些聚合物的有效電子傳導能力，發現聚合物中銅原子的氧化態均低於 +1 價，並顯示無機金屬團簇物 [EFe3(CO)9]2- (E = Te, Se) 在聚合物的骨架中可作為電子提供配基的角色。重要的是，聚合物 1a、1b 及主−客聚合物表現出可調控之低能隙 (1.36−1.50 eV) 與電導率 ((1.21−6.55)×10-7 S∙cm–1)，顯示它們都具有良好的半導體特性且客分子在固態下可有效地調控電子傳輸的效能。One-dimensional singly-doubly para-dicyanobenzene-linked (p-DCB) zigzag chain polymers [EFe3(CO)9Cu2(p-DCB)1.5]n (E = Te, 1a; Se, 1b) were synthesized from reactions of clusters [EFe3(CO)9Cu2(MeCN)2] (E = Te, Se) with 1.5 equivalents of p-DCB. Polymers 1a and 1b were found to be able to encapsulate various organic compounds, such as alkyl-substituted C7−C10 aromatics, polycyclic aromatics hydrocarbon, and heterocyclic compounds, forming a series of host-guest polymers [EFe3(CO)9Cu2(p-DCB)1.5(G)m]n (G = guest molecules; E = Te, 1a·mG; Se, 1b·mG; m = 0.5 or 1) via liquid-assisted grinding (LAG) or neat grinding for the case of 1b. In particular, different guest molecule-intercalated product was found upon grinding 1a with THF, which gave rise to the 1D singly-singly p-DCB-linked polymer [TeFe3(CO)9Cu2(p-DCB)(THF)]n (2a·THF). If the larger polycyclic aromatic hydrocarbon−pyrene was employed, the new cyclic compounds [{EFe3(CO)9Cu2}4(p-DCB)4(pyrene)3]·2pyrene (E = Te, 3a·5pyrene; Se, 3b·5pyrene) were formed. Solid-state packing of the whole series of host-guest polymers and compounds revealed that numerous interactions, such as C−H‧‧‧π, π‧‧‧π, and C−H‧‧‧E (E = O, S) were observed between p-DCB linkers and the guest molecules. The desorption of host-guest polymers to give back the host polymers 1a and 1b could be achieved by vacuum or crystallization. The efficient electron transport of these polymers was also investigated by X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS), in which the oxidation state of the Cu atoms in these polymers was found to be lower than +1, showing clusters [EFe3(CO)9]2- (E = Te, Se) acting as electron donating ligands in these polymeric frameworks. Importantly, polymers 1a, 1b, and their host-guest polymers exhibited semiconducting behaviors possessing tunable energy gaps of 1.36‒1.50 eV with moderate electrical conductivities of (1.21‒6.55)×10-7 S∙cm–1. The role of the guest molecules in modulating the electron transport in the solid state was further investigated.