新穎對稱與非對稱配基之同核鎳金屬串與異核金屬串(Mox/My和Co2Re2/M)錯合物之合成與性質研究

本論文主要探討鎳金屬串錯合物的配基效應以及合成以雙核鉬金屬或錸金屬為主的新型異核金屬串錯合物並探討其鍵結資訊及所具有的特性。於本研究中主要分為兩個部分，第一部分為合成螺旋型五核鎳金屬串錯合物並採用下列四條不對稱型的有機配基: (1)甲基苯磺醯基吡啶萘啶二胺(N-(p-tolyl-sulfonyl)pyridylnaphthyridyl diamine, H2Tspnda, L1)和(2)甲基苯磺醯基苯環吡啶萘啶二胺(N-(p-tolyl-sulfonyl)phenylpyridylnaphthyridyl diamine, H2Tsphpnda, L2)以及經過在吡啶環上meta位置進行苯環修飾的(3)甲基磺醯基吡啶萘啶二胺(N-(methyl-sulfonyl)pyridylnaphthyridyl diamine, H2Mspnda, L3)和(4)甲基苯磺醯基苯環吡啶萘啶二胺(N-(methyl-sulfonyl)phenylpyridylnaphthyridyl diamine, H2Msphpnda, L4)。為了探討所合成的金屬串錯合物的特性，本論文採用固態X-ray單晶結構解析、磁化率、電子順磁共振、循環伏安法、電子吸收光譜、紅外光譜、核磁共振以及元素分析等技術進行分析鑑定與討論。第二部分則為合成異核金屬串錯合物，主要採用實驗室傳統對稱型的三吡啶二胺(tripyridyldiamine, H2tpda, L5)配基，也使用不對稱配基L1和L2進行異核金屬串的合成並探討其特性和潛在應用性。在第一部分，藉由高溫熔融萘作為溶劑進行反應可得到一系列五個鎳金屬帶正九價[Ni5]9+的鎳金屬串錯合物，分別為[Ni5(Tspnda)4](PF6) 1、[Ni5(Tsphpnda)4](PF6) 3、[Ni5(Mspnda)4](PF6)　6和[Ni5(Msphpnda)4](PF6) 9，對於這四個金屬串錯合物，其顯示出具有較短的Ni–Ni鍵長: 錯合物1為2.2646(6) Å；錯合物3為2.2943(7) Å；錯合物6為2.2436(11) Å；錯合物9為 2.2322(8) Å，並且由Ni–N的鍵長皆發現大於2.0 Å，這顯示這四個錯合物中具有金屬–金屬作用力於混價單元(mixed-valence unit [Ni2]3+, S = 3/2)上。此外，最特別的結果在於當甲基苯磺醯基置換為甲基磺醯基進行配基微調時，混價單元由原本座落在Ni(1)–Ni(2)遷移到Ni(2)–Ni(3)的位置。為了探尋這個結果，本研究採用磁化率和電子順磁共振分析進而探討這四個還原一個電子的五核鎳金屬串錯合物的磁性和鍵結特性，由電子順磁共振的結果可以發現混價單元Ni(1)–Ni(2)遷移到Ni(2)–Ni(3)會使得金屬串整體電子結構更趨於對稱，導致其在零場分裂參數上會有所不同，而這也藉由EPR的光譜擬合得到證實。藉由循環伏安法，可以發現具有四對可逆的氧化還原對並可藉由[FeCp2](PF6)氧化一個電子進而得到五個鎳金屬帶正十價[Ni5]10+的金屬串錯合物，分別為[Ni5(Tspnda)4(H2O)2](PF6)2 (2)、[Ni5(Tsphpnda)4](PF6)2 (4)、[Ni5(Mspnda)4](CF3SO3)2 (8)和[Ni5(Msphpnda)4](PF6)2 (11)。令人驚訝的是，氧化一個電子後的五核鎳金屬串具有不同的電子結構，錯合物2主要具有來自於兩終端S = 1的自旋中心而呈現反鐵磁的特性，錯合物4、8和11則因為所具有的鎳金屬皆為正二價(S = 0)並呈現逆磁特性。因此，對於本論文討論的五核鎳金屬串錯合物，具有三項重要的發現 : (1)對於還原一個電子[Ni5]9+的金屬串錯合物，其呈現一個少見的以對稱型結構、不對稱型的電子密度分佈構型，並且推測可能的原因來自於晶體堆疊所導致的影響；(2)對於氧化一個電子[Ni5]10+的錯合物，化合物4、8和11呈現文獻中第一個五核鎳金屬串具有鎳金屬以全低自旋組態(S = 0)構成的錯合物；(3)由於本實驗室在過去認為對於配基的微調並不會對金屬串的電子結構有顯著的變化，然而，隨著甲基苯磺醯基置換為甲基磺醯基，其混價單元由原本的Ni(1)–Ni(2)遷移到Ni(2)–Ni(3)，並且藉由電子順磁共振的光譜擬合所得到的零場分裂參數(D和E值)來獲得證實，這也突破了過去實驗室對於配基進行取代基微調不會對金屬串有明顯電子結構變化的觀念，而這些發現也顯示出對於配基的微調有助於探討配基效應和其鍵結特性。在第二部分則報導異核金屬串錯合物，主要藉由以雙核鉬金屬或雙核錸金屬為主並與其他金屬(如 : 鎳、鈷或釕金屬)進行合成，對於鉬系列的金屬錯合物，所得到的皆為非直線構型存在的金屬串錯合物，如: [NiMo2Ni(Tspnda)4] 14、[CoMo2Co(Tspnda)4] 15和[Mo4(Tsphpnda)3(HTsphpnda)(OAc)] 18，由於當反應處於高溫時會使得鉬金屬具有空氣敏感的現象，容易造成鉬金屬氧化並導致低產率和得到非直線構型的錯合物。然而，透過質譜以及紅外線光譜的分析可以證實具有形成五核的鉬/鎳金屬串錯合物[Mo4Ni(Tspnda)4](PF6)2 16以及[Mo4Ni(Tsphpnda)4](PF6)2 17，但並無法得到品質較好的晶體去執行單晶繞射解析。對於錸系列錯合物[Co2Re2(tpda)4Cl](PF6) 19和[Co2Re2(tpda)4(NCS)](PF6) 20，主要呈現直線型的金屬串錯合物，但是於終端位置仍有四片未配位的吡啶環懸掛於金屬串外圍，因此，可以藉由加入釕金屬鹽類來合成[Co2Re2Ru(tpda)4Cl2](PF6)2 21，但由於晶體太小且品質較差，導致無法藉由單晶結構解析來探討其鍵結資訊與相關特性，僅能由質譜證實其有成功合成出來。因此，由於金屬串本身所具有卓越的物理及化學特性，使得這些直線型的金屬串錯合物可扮演著電線的角色並期望在未來可以製程為分子電線或分子開關等電子設備。

關鍵字

分子電線；金屬串；混價化合物；鎳金屬

並列摘要

The scope of this thesis consists of two parts: (1) investigation of ligand effects on pentanickel string complexes, and (2) synthesis and characterization of novel heteronuclear metal string complexes containing dimolybdenum or dirhenium unit as the metal precursors. The first part is about the helically pentanuclear nickel string complexes. We employ the following four ligands to synthesis of (1) N-(p-tolyl-sulfonyl)pyridylnaphthyridyl diamine (H2Tspnda, L1), (2) N-(p-tolyl-sulfonyl)phenylpyridylnaphthyridyl diamine (H2Tsphpnda, L2) and the phenyl-substituted ligands of (3) N-(methyl-sulfonyl)pyridylnaphthyridyl diamine (H2Mspnda, L3) and (4) N-(methyl-sulfonyl)phenylpyridylnaphthyridyl diamine (H2Msphpnda, L4). We apply the following techniques to characterize the properties of these complexes: solid state X-ray single crystal diffraction (XRD), magnetic susceptibility (SQUID), electron paramagnetic resonance (EPR), cyclic voltammograms (CV), electron absorption spectra (UV-Vis and Near-IR), infrared spectroscopy, nuclear magnetic resonance (NMR) and element analysis (EA). The X-ray structure of one-electron-reduced [Ni5]9+ complexes [Ni5(Tspnda)4](PF6) 1, [Ni5(Tsphpnda)4](PF6) 3, [Ni5(Mspnda)4](PF6) 6 and [Ni5(Msphpnda)4](PF6) 9 show remarkably shorter Ni–Ni bond distance (2.2646(6) for 1, 2.2943(7) for 3, 2.2436(11) for 6 and 2.2322(8) Å for 9), indicative of a partial metal-metal bond interaction in the mixed-valence [Ni2]3+ (S = 3/2) unit. The most striking result is that the [Ni2]3+ site migrates from Ni(1)–Ni(2) to Ni(2)–Ni(3) when we replace p-tolyl-sulfonyl group with methyl-sulfonyl group. To investigate this result, we apply the magnetic susceptibility and EPR measurement to examine the magnetic properties of these four [Ni5]9+-core pentanickel strings and study the bonding nature of the mixed-valence [Ni2]3+ unit. The results of EPR measurements reflect the migration of mixed-valence site and the change of symmetry, which is confirmed by the spectral parameters of zero-field splitting (D and E values) in EPR simulation. Furthermore, cyclic voltammetry measurements show four reversible redox waves and display the lower potentials of the [Ni5]9+ complexes. The unusual lower potentials facilitate one-electron oxidation of these four complexes to [Ni5]10+-core forms: [Ni5(Tspnda)4(H2O)2](PF6)2 (2), [Ni5(Tsphpnda)4](PF6)2 (4), [Ni5(Mspnda)4](CF3SO3)2 (8) and [Ni5(Msphpnda)4](PF6)2 (11). Thus, we perform the oxidation reaction of these [Ni5]9+-core complexes to treat with [FeCp2](PF6). Surprisingly, the oxidized [Ni5]10+ counterparts behave differently: complex 2 exhibits an antiferromagnetic interaction with J = -13.59 cm-1 between the two terminal Ni ions, while the others (complexes 4, 8 and 11) display the diamagnetic property as all of the Ni2+ ions are in low-spin (S = 0) states. We present the following important findings in first part of the thesis : (1) For [Ni5]9+-core complexes, they present a rare example of the effect of crystal packing on the symmetric molecular structure yielding unsymmetric electronic distribution. (2) The magnetic susceptibility, EPR and Near-IR measurement confirm the spin state is S = 3/2 (a mixed-valence state) for these complexes. (3) For [Ni5]10+-core complexes, complexes 4, 8 and 11 are the first examples of all Ni2+ ions in null spin configuration for pentanickel chains. (3) Migration of mixed-valence sites from Ni(1)–Ni(2) to Ni(2)–Ni(3) when we replace p-tolyl-sulfonyl group with methyl-sulfonyl group. This finding shows roles of ligand played in bonding nature for the novel metal string complexes. The second part of the thesis is the synthesis and the characterization of the novel heteronuclear metals (molybdenum or rhenium) with other conventional metal ions (nickel, cobalt or ruthenium). We employ symmetrical tripyridyldiamine (H2tpda, L5) ligand and asymmetric ligands (L1 and L2) to explore their properties and potential application. For molybdenum complexes, we obtain the non-linear metal string complexes [NiMo2Ni(Tspnda)4] 14, [CoMo2Co(Tspnda)4] 15 and [Mo4(Tsphpnda)3(HTsphpnda)(OAc)] 18. Since the molybdenum complexes are air-sensitive especially at high temperature, we obtain low yield and non-linear metal complexes. However, we can synthesize the linear molybdenum-based metal string complexes [Mo4Ni(Tspnda)4](PF6)2 16 and [Mo4Ni(Tsphpnda)4](PF6)2 17. Even though the identities are supported by Mass and IR spectroscopy, but we are not able to obtain a good quality crystal form for X-ray diffraction measurement. On the other hand, the rhenium series complexes [Co2Re2(tpda)4Cl](PF6) 19 and [Co2Re2(tpda)4(NCS)](PF6) 20 present a linear metal chain with four pyridine ring hanging out from the metal string complexes. We treat with the ruthenium salt [Ru(COD)Cl2]n to synthesize [Co2Re2Ru(tpda)4Cl2](PF6)2 21, but we could not obtain good quality of crystal for crystal structure determination to explore the bonding nature and their properties. Overall, these extended metal-atom chain (EMAC) impersonate electric wires and we expect them to serve as molecular wires and switches in the manufacture of electronic devices because of their exotic physical and chemical properties.