含硒之錳金屬與含碲之鉻金屬羰基團簇化合物之合成、物性、化性與半導體性質之探討

Abstract

Se−Mn−CO 系統 順磁性含硒之六錳團簇物 [{Se5Mn3(CO)9}2]4‒ [(1)2] 可經由硒粉末和 Mn2(CO)10 在 KOH/MeOH/MeCN 溶液中以 40 oC 一鍋化反應合成。(1)2 可視為由中央 Se‒Se 鍵橋接兩個 [Se5Mn3(CO)9] 片段的二聚體。當合成溫度升至 90 oC 時，發現化合物 (1)2 將熱裂解形成其自由基單體團簇物 [Se5Mn3(CO)9]•2‒ (1)，並通過高解析質譜及元素分析得相關證據。基於超導量子干涉裝置 (SQUID) 分析，其結果顯示化合物 [PPN]2[1] 在 300 K 時之有效磁矩 (μeff) 為 3.88 μB，為一四重自旋態 S = 3/2 (quartet spin state) 之物種。值得注意的是，自由基團簇物 1 的 100 K 電子順磁共振 (EPR) 光譜包含 Mn 超精細分裂和 Se 自由基信號，表明 μ-Se 自由基特徵。化合物 1 以高濃度溶於 MeCN 時 Se 自由基可自聚 (self-dimerization) 形成 (1)2，也可以被 (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) 捕獲並形成 TEMPO 加成物，[Se5Mn3(CO)9(TEMPO)]2‒ (1-TEMPO)。有趣的是，在室溫下利用二溴化烷衍生物 (CH2)nBr2 (n = 1, 2) 與 1 和 (1)2 反應可發現不同的反應模式。化合物 1 可形成 CH2 或 Se 片段插入於 Se8Mn4 的順磁團簇物 (S = 1)，[(μ4-Se2)(μ-Se2LSe)2Mn4(CO)12]2‒ (L = CH2, 2-CH2; Se, 2-Se)，而 (1)2 則形成 Se10Mn6 基底之 (CH2)nBr 官能化逆磁性團簇物 [Se10Mn6(CO)18((CH2)nBr)2]2‒ (n = 1, (1)2-CH2Br; 2, (1)2-(CH2)2Br)。此外，這些高核數 Se‒Mn‒CO 團簇物具有豐富的氧化還原特性並且在固態下呈現 CO 誘導的半導體行為，具低且可調控的光學能隙 (1.50‒1.94 eV)。這罕見的半導體性質主要來自團簇物於固態時具非典型的氫鍵 C‒H (苯基) ···O (羰基) 弱作用力，使其達成有效的電子傳輸。此系列化合物有趣的結構及不尋常的磁性表現可通經由 DFT 計算加以佐證。 Te−Cr−CO 系統 羰基碲化鉻團簇物 [Te7Cr4(CO)14]4‒ (1) 和 [Te7Cr6(CO)20]4‒ (2) 由 TeO2、Cr(CO)6 和 Et4NBr 分別在 1 M 的 KOH/MeOH/MeCN 溶液以45 oC 或 1.5 M 的 KOH/MeOH/n-Hexane 溶液中以 80 oC 一鍋化的方式合成。四鉻化合物 1 由兩個 Cr(CO)3 和兩個 Cr(CO)4 片段通過一個 μ4-η1,η1,η1,η1-Te2 和一個 μ4-η1,η2,η1,η2-Te5 連接，因此化合物 1 可被視為具有兩個 Te4Cr 和四個 Te3Cr2 五員環的三橋接扭曲立方體 (tris-homocubane) 化合物。至於六鉻化合物 2，為四個 Cr(CO)3 和兩個 Cr(CO)4 片段以一個 μ4-η1,η1,η1,η1-Te2、一個 μ6-η1,η1,η1,η1,η1,η1-Te3 和兩個 μ3-η1,η1,η1,-Te 片段連接形成一個籠狀化合物，可視為六個 Te3Cr2 五員環和兩個 Te2Cr2 四環組合而成。這些電子精確 (electron precise) 的化合物 1 和 2 在室溫下表現出不尋常的順磁性 (S = 1)，並通過 SQUID、EPR 和 DFT 計算進一步研究。此外，差分脈衝伏安法 (DPV) 顯示化合物 1 和 2 皆具有接近 0 V 的氧化峰，這意味著這些配合物可能具有氧化特性。當化合物 2 與金屬氧化劑 [Cu(MeCN)4]+ 反應時，獲得中等產率嵌入銅的籠形配位化合物 [Cu@Te7Cr6(CO)20]3‒ (Cu@2) 及 [Cu2@Te7Cr6(CO)20]2‒ (Cu2@2)。其中 Cu 原子被嵌在 Te7Cr6 籠狀骨架中，並通過高解析質譜及元素分析檢測得相關證據。此外，藉由 DFT 理論計算進一步研究 Cu@2 的結構、電化學和順磁性質。Se−Mn−CO system The hexanuclear paramagnetic Se−Mn cluster, [{Se5Mn3(CO)9}2]4− [(1)2], was synthesized via the mild one-pot reaction of Se powder and Mn2(CO)10 in concentrated KOH/MeOH/MeCN solutions at 40 oC. This Se−Mn cluster can be viewed as a dimer of two [Se5Mn3(CO)9] moieties that were bridged by a central Se−Se bond. Cluster (1)2 was found to be unstable when the synthetic temperature was raised to 90 oC, forming the radical monomer, [Se5Mn3(CO)9]•2− (1), as evidenced by X-ray analysis and infrared spectra. The magnetic measurement revealed that complex [PPN]2[1] possessed the effective magnetic moment of μeff = 3.88 μB at 300 K based on the superconducting quantum interference device (SQUID) analysis, revealing its quartet spin state (S = 3/2) at room temperature. It was worthy to note that the 100 K electron paramagnetic resonance (EPR) spectrum of the radical cluster 1 contained the Mn hyperfine splitting and Se radical signal, indicative of the μ-Se radical character. The Se radical in 1 could proceed self-dimerization to form (1)2 upon the recrystallization in concentrated MeCN solutions, and also could be trapped by (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO), giving its TEMPO adduct, [Se5Mn3(CO)9(TEMPO)]2− (1-TEMPO). Interestingly, the contrasting reactivity pattern was found in 1 and (1)2 upon the treatment with the alkyl dibromides, (CH2)nBr2 (n = 1, 2), at room temperature. The reactions with 1 led to formations of the novel di-CH2 or di-Se-inserted Se8Mn4-based paramagnetic clusters , [(μ4-Se2)(μ-Se2LSe)2Mn4(CO)12]2− (L = CH2, 2-CH2; Se, 2-Se). Whereas the reactions with (1)2 formed (CH2)nBr-functionalized Se10Mn6-based diamagnetic complexes, [Se10Mn6(CO)18((CH2)nBr)2]2− (n = 1, (1)2-CH2Br; 2, (1)2-(CH2)2Br). Furthermore, all these high-nuclearity Se−Mn−CO complexes possessed rich redox properties and CO-induced semiconducting behaviors in solids with low but tunable energy gaps (1.50−1.94 eV). The efficient electron transports were attributed to the closely packed cluster anions with several weak intermolecular interactions in solid state. The intriguing structural nature and unusual magnetic behaviors are fully understood in detail and elucidated by DFT calculations. Te−Cr−CO system The novel chromium carbonyl telluride clusters, [Te7Cr4(CO)14]4─ (1) and [Te7Cr6(CO)20]4─ (2), were synthesized from a one-pot reaction of different ratios of TeO2, Cr(CO)6, and Et4NBr in concentrated KOH/MeOH/MeCN at 45 oC or KOH/MeOH/n-Hexane at 80 oC, respectively. The tetra-chromium complex 1 consisted of two Cr(CO)3 and two Cr(CO)4 fragments that were further connected by one μ4-η1,η1,η1,η1-Te2 and one μ4-η1,η2,η1,η2-Te5 moieties. Cluster 1 could be viewed as a tris-homocubane-like structure with two Te4Cr and four Te3Cr2 five-membered rings. As for the hexa-chromium complex 2, four Cr(CO)3 and two Cr(CO)4 fragments were linked by one μ4-η1,η1,η1,η1-Te2, one μ6-η1,η1,η1,η1,η1,η1-Te3, and two μ3-η1,η1,η1-Te moieties, forming a cage-like cluster that was fused by six Te3Cr2 five-membered rings and two Te2Cr2 four-membered rings. These electron-precise complexes 1 and 2 exhibited unusual paramagnetic properties with S = 1, which were investigated by SQUID, EPR, and DFT calculations. Further, the differential pulse voltammetry (DPV) revealed that complexes 1 and 2 had oxidation peaks close to 0 V, implying that these complexes could have oxidative properties. When complex 2 was treated with metal oxidant, [Cu(MeCN)4]+, the Cu-inserted cage complex [Cu@Te7Cr6(CO)20]3‒ (Cu@2) and [Cu2@Te7Cr6(CO)20]2‒ (Cu2@2) were obtained in a moderate yield. The proposed structure of the Cu-introduced cluster Cu@2 was optimized by DFT calculations, where the Cu atom was encapsulated in the Te7Cr6 cage, detected by HR-Mass. Finally, the structures, electrochemistry, and paramagnetic properties of these rare chromium carbonyl telluride complexes and the Cu-introduced product were further studied with the aid of DFT calculations.