聯吡啶串接之含硫的過渡金屬 (鐵、銅) 聚合物: 合成、半導體特性及物性之探討

Abstract

1. 硫/鐵/銅系統 利用三組件 (three-component) 之固態溶劑輔助研磨 (liquid-assisted grinding, LAG) 或溶劑法，將 [Et4N]2[SFe3(CO)9] ([Et4N]2[1])、[Cu(MeCN)4][BF4] 及具共軛性之含氮吡啶 1,2-bis(4-pyridyl)ethylene (bpee) 以劑量比反應可獲得一系列具新穎構型之二維含 SFe3(CO)9−bpee混合銅聚合物 [SFe3(CO)9Cu2(bpee)x]n (x = 2, 1-bpee-2D-1; x = 3, 1-bpee-2D-2; x = 3.5, 1-bpee-2D-3)。此系列聚合物之結構轉換關係可藉由引入當量比之 bpee 或 [SFe3(CO)9]2−/[Cu(MeCN)4]+ 以溶劑輔助研磨 (LAG) 之方法成功完成，亦或是利用汞燈照射 1-bpee-2D-1‧MeCN 獲得由 Cu−N(bpee) 鍵斷裂重組之二維聚合物 [SFe3(CO)9Cu2(bpee)2]n (1-bpee-2D-1IR)。經由 X-ray 解析可知，這些含 bpee 與過去合成的其他具不同有機含氮吡啶 [4,4'-dipyridyl (dpy)、1,2-bis(4-pyridyl)ethane (bpea) 及 1,3-bis(4-pyridyl)propane (bpp)] 之含硫混合鐵銅聚合物可依 SFe3(CO)9 之角色而區分其鍵結模式為五大類，分別為團簇串聯 (cluster-linked)、團簇阻斷 (cluster-blocked)、團簇垂吊 (cluster-pendant)、團簇雙臂 (cluster-armed) 及團簇單臂 (cluster-one-armed)。此系列混合硫及鐵之銅聚合物具有低且可調控之光學能隙 (1.55 ~ 1.79 eV) 及平行趨勢之電導率值 (3.26×10–8 ~ 1.48×10–6 S/cm)，並進一步了解與其鍵結模式與半導體性質之關係。藉由 X-ray 結構解析、泛函密度理論計算 (DFT calculations)、X-ray 電子光譜 (X-ray Photoelectron spectroscopy, XPS) 和 X-ray 吸收近邊緣結構光譜 (X-ray absorption near-edge spectroscopy,XAS) 證明聚合物結構中具富電子之 SFe3(CO)9 可作為電子提供者，並利用聚合物骨架或羰基及含氮配基所產生之弱作用力達成有效電子傳輸。最後，此系列聚合物之固態電化學顯示其氧化還原峰值皆較 [Et4N]2[1] 往陰極偏移，表示錯合物引入無限延伸的銅−含氮配體結構能有效促進電子流通。2. 硒/鐵/銅系統 藉由三組件 (three-component) 之固態溶劑輔助研磨法 (liquid-assisted grinding, LAG)，將 [Et4N]2[SeFe3(CO)9] ([Et4N]2[1])、[Cu(MeCN)4][BF4] 及具共軛性之含氮吡啶4,4’-dipyridyl (dpy) 或 1,2-bis(4-pyridyl)ethylene (bpee)，或富彈性之 1,2-bis(4-pyridyl)ethane (bpea) 或 1,3-bis(4-pyridyl)propane (bpp) 以劑量比反應可獲得一系列具新穎構型之一維及二維含硒混合鐵銅有機−無機聚合物，其中包含團簇串聯 (cluster-linked) 二維聚合物 [SeFe3(CO)9Cu2(MeCN)(dpy)1.5]n (1-dpy-2D) 及 [SeFe3(CO)9Cu2(bpp)2]n (1-bpp-2D)、團簇垂吊 (cluster-pendant) 一維聚合物 [SeFe3(CO)9Cu2(dpy)3]n (1-dpy-1D) 及團簇阻斷 (cluster-blocked) 一維鏈 [SeFe3(CO)9Cu2(L)]n (1-L-1D, L = bpee, bpea)。此系列混合硒鐵之銅聚合物具有低且可調控之光學能隙 (1.49−1.72 eV)，並被發現其數值根據結構特性上升: 團簇串聯 1-dpy-2D 及 1-bpp-2D (1.49−1.58 eV)、團簇阻斷 1-bpea-1D 及 1-bpee-1D (1.59−1.62 eV)、 團簇垂吊 1-dpy-1D (1.72 eV)，證明引入 [SeFe3(CO)9] 的鍵結模式對於電子傳輸效率之重要性。此外，代表性聚合物1-bpp-2D、1-bpea-1D 及 1-dpy-1D 之電導率數值分別為 3.13×10–7、2.92×10–7 及 2.30×10–7 S/cm，與能隙之趨勢平行，顯示此系列 Se−Fe−Cu 聚合物之半導體特性。值得注意的是，以共軛阻斷含氮配體 bpp 做為連接配子之聚合物 1-bpp-2D 具有異常低之能隙 (1.58 eV)，主要是來自C−H(dipyridyl)···O(carbonyl) 以及C−H(dipyridyl)···π(dipyridyl) 弱作用力於骨架結構中進行有效的電子傳導所導致。 (此章節摘錄自Inorg. Chem. 2021, 60, 18270)

1. S/Fe/Cu systemA series of 2D semiconducting S−Fe−Cu−bpee carbonyl cluster-incorporated polymers were synthesized via three-component liquid-assisted grinding (LAG) or solution-based reaction with stoichiometric amounts of [SFe3(CO)9]2− (1), [Cu(MeCN)4]+, and 1,2-bis(4-pyridyl)ethylene (bpee), namely [SFe3(CO)9Cu2(bpee)x]n (x = 2, 1-bpee-2D-1; x = 3, 1-bpee-2D-2; x = 3.5, 1-bpee-2D-3). The structural transformation of these 2D polymers could be achieved by adding stoichiometric equivalents of bpee or 1/[Cu(MeCN)4]+, or by Hg lamp irradiation of 1-bpee-2D-1‧MeCN that produced a new structure [SFe3(CO)9Cu2(bpee)2]n (1-bpee-2D-1IR) through Cu−N bond breakage and rearrangement. The coordination modes of [SFe3(CO)9] in these bpee-containing 2D polymers and other previously characterized dipyridyl-containing [4,4'-dipyridyl (dpy), 1,2-bis(4-pyridyl)ethane (bpea), and 1,3-bis(4-pyridyl)propane (bpp)] polymers in the S−Fe−Cu system were studied, where the cluster-linked, cluster-blocked, cluster-armed, cluster-pendant, and cluster-one-armed modes were demonstrated. These bonding modes were related to the semiconducting behaviors of these polymers, where the cluster-linked mode was found to perform the best semiconductivities. These polymers possessed tunable energy gaps (1.55 ~ 1.79 eV), which was parallel to the trend of their electrical conductivities (3.26 × 10–8 ~ 1.48 × 10–6 S/cm). The effective electron-transport pathways were proved to arise not only from the polymeric backbones but also from the secondary interactions generated from the electron-rich cluster 1 and its CO ligands as well as their dipyridyls, which were supported by X-ray Photoelectron spectroscopy (XPS), X-ray absorption near-edge spectroscopy (XAS), and DFT calculations. Finally, the solid-state electrochemistry of the representative polymers showed cathodically-shifted peaks in comparison to that of [Et4N]2[1], suggesting that the incorporated 1 could effectively enhance the electron communication in these Cu–dipyridyl frameworks.2. Se/Fe/Cu system A novel family of inorganic–organic-hybrid SeFe3(CO)9−dipyridyl two- and one-dimensional Cu polymers was synthesized via the three-component liquid-assisted grinding (LAG) of [Cu(MeCN)4]+, the inorganic cluster [SeFe3(CO)9]2− (1), and rigid conjugated dipyridyls, 4,4’-dipyridyl (dpy) and 1,2-bis(4-pyridyl)ethylene (bpee), or flexible conjugation-interrupted dipyridyls, 1,2-bis(4-pyridyl)ethane (bpea) and 1,3-bis(4-pyridyl)propane (bpp). They included a cluster-linked 2D polymer, [SeFe3(CO)9Cu2(MeCN)(dpy)1.5]n (1-dpy-2D), a cluster-pendant 1D chain, [SeFe3(CO)9Cu2(dpy)3]n (1-dpy-1D), cluster-blocked 1D polymers, [SeFe3(CO)9Cu2(L)]n (1-L-1D, L = bpee, bpea), and a cluster-linked 2D polymer, [SeFe3(CO)9Cu2(bpp)2]n (1-bpp-2D). These polymers were found to possess tunable low energy gaps (1.49−1.72 eV) that increased in the order regarding their structural features: cluster-linked 1-dpy-2D and 1-bpp-2D, cluster-blocked 1-bpea-1D and 1-bpee-1D, and cluster-pendant 1-dpy-1D, indicative of the importance of the participation of cluster 1. The measured electrical conductivities of 1-bpp-2D, 1-bpea-1D, and 1-dpy-1D were 3.13×10–7, 2.92×10–7, and 2.30×10–7 S/cm, respectively, which was parallel for the trend of their energy gaps, revealing semiconducting behaviors. The surprising semiconductivity of the conjugation-interrupted bpp-linked 1-bpp-2D was mainly ascribed to electron transports via C−H(dipyridyl)···O(carbonyl) hydrogen bonds and aromatic C−H(dipyridyl)···π(dipyridyl) contacts within its closely packed 2D layers. (This chapter has been published in Inorg. Chem. 2021, 60, 18270.)