本研究為使用變溫裝置偵測鈷與鎳的直線型三核金屬串錯合物M3(dpa)4Cl2 (dpa = di(2-pyridyl)amide，M = Co、Ni) 的晶體拉曼光譜，搭配密度泛函理論 (Density functional theory, DFT) 的計算，指認金屬串錯合物的分子結構、振動模式以及電子能階。由於Co3(dpa)4Cl2在結晶時會受到與其共結晶溶劑二氯甲烷影響，會形成對稱與不對稱兩種構型，我們分別對這兩種結構進行變溫以及外加磁場的實驗。由拉曼光譜在不同溫度的變化，我們認為對稱的構型在77~623 K的溫度範圍內應有三個不同結構。已知s-Co3(dpa)4Cl2的基態為雙重態，並有一個與基態能量及結構非常接近的雙重態，且它與基態可能互為簡併態。當溫度升至423 K附近會轉成六重態，最後在623 K時再抵達另一個電子能階。至於不對稱的構型在此溫度範圍內也有三個不同結構，它的基態也是雙重態，當溫度升至373 K附近它會再轉變至另一個四重態，最後在573 K時抵達新的較高能量之電子能階。我們也發現對稱的623 K與不對稱的573 K之能階擁有類似的拉曼光譜，它們可能為同一個電子能階。並藉由變溫拉曼觀察Ni3(dpa)4Cl2單態與五重態的能階轉變，發現它們拉曼光譜只有鎳與氯的伸縮振動之譜帶差異。偵測[Ni3(dpa)4Cl2]-的表面增強拉曼 (suface enhanced Raman scattering，SERS) 光譜，並且藉由比對理論計算指認其電子能階在溫度上升時，由四重態轉至雙重態，並且更正本實驗室先前的指認，把242 cm-1的振動模式更新指認為[Ni3(dpa)4Cl2]-之鎳與氯的伸縮振動。 

We used temperature-controlled Raman setup to detect the Raman spectra of the linear trinuclear metal-string complexes M3(dpa)4Cl2 (dpa = di (2-pyridyl) amide, M = Co, Ni). With the calculations of density functional theory (DFT), the molecular structures, vibrational modes and electronic energy levels of the metal-string complexes were assigned. Co3(dpa)4Cl2 exhibits symmetric and asymmetric forms (s-form and u-form) of Co−Co metal bonding, which were formed depending on temperature and solvent. We conducted the temperature-changed and external magnetic field experiments on these two forms. We found that the s-form has three different structures in the temperature range of 77 − 623 K. The ground state was doublet, and it had another doublet state lying close to the ground state, which might be a degenerate state for the ground state. When the temperature rose to 423 K, it turned into a sextet state, and finally reached another electronic level at 623 K. As for the u-form, there are also three different structures in the same temperature range. The ground state was also doublet. When the temperature rose to 373 K, it turned into a quartet state, and finally reached a new electronic energy level at 573 K. We found that the electronic energy level of the third state of s-form and u-form generated at high temperature, have similar Raman spectra implying the same electronic energy level. For Ni3(dpa)4Cl2, the transition from the singlet to the quintet state was observed by using temperature-controlled Raman spectrometer. We found the only difference between two states is the position of Ni−Cl stretching band. The surface-enhanced Raman scattering (SERS) technique was used to detect [Ni3(dpa)4Cl2]-. The transition from the quartet to the double state was assigned by comparing with the result of the DFT calculations. Finally, the band of 242 cm-1 is reassigned to the Ni−Cl stretching in the [Ni3(dpa)4Cl2]- SERS spectrum.

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