以硫氫配位鍵結之雙亞硝基鐵錯合物與單亞硝基鐵錯合物相關反應性探討

Dinitrosyl- and Mononitrosyl- Iron Complexes(DNICs) Containing [SH]- coordinate Ligand

邱暐珺

指導教授 ： 廖文峯

國立清華大學/理學院/化學系/碩士(2014年)

摘要

本研究中成功的合成出FeIII與[HS]－鍵結，具有[FeIII-SH] motif的DNIC ([K-18-crown-6-ether][(HS)2Fe(NO)2] (1) 及[PPN][(HS)2Fe(NO)2] (1-PPN))、MNIC ([PPN][(HS)3Fe(NO)] (3))以及dimerize成[PPN]2[(μ-S)Fe(SH)(NO)]2 (4) (Scheme 1)，其中complex 1 溶於水中會釋放出H2S並生成RRS，代表DNIC在hydrophobic的環境之下或許可以當作H2S的儲存和傳遞者，並且在hydrophilic的環境下再將其釋放出來，原因可能跟NO本身non-innocent的性質有關，NO扮演了調控電子的角色而讓生物體內的[HS]－有機會鍵結到Fe上，而且鍵結到Fe上之後藉由NO供給電子給Fe，讓FeIII不會被thiolate還原成FeII。
從實驗上EPR、IR、XAS、XRD綜合比較後，可以決定出含有[FeIII-SH] motif的complex 1, 1-PPN的電子結構應為high-spin FeIII (SFe = 5/2)與兩個NO－(SNO = 1)以antiferromagnetically coupled，而熱不穩定的complex 3會自然的dimerize成complex 4，其電子結構可以描述成兩個{FeIII(NO－)}7以antiferromagnetic coupled形成diamagnetic complex，從理論計算也可以輔助這一點。
另外與本實驗室最近發表的文獻提到[PPN][Fe(SH)4] (5)和[PPN]2[(μ-S)Fe(SH)]2 (6)的合成及穩定性，由實驗結果得知穩定性為1 > 3 > 5，釋放出H2S形成dimer form之穩定度為2 > 4 > 6，說明了NO越多穩定性越高，並且用理論計算和氧化還原電位去輔助說明為何有此現象。

關鍵字

雙亞硝基鐵錯合物 ； 硫化氫 ； 單亞硝基鐵錯合物

並列摘要

The formation of hydrosulfide-bound {Fe(NO)2}9 dinitrosyl iron complex (DNIC), [K-18-crown-6-ether][(HS)2Fe(NO)2] (1) ([PPN][(HS)2Fe(NO)2] (1-PPN)) and the precursor mononitrosyl iron complex (MNIC), [PPN][(HS)3Fe(NO)] (3), were synthesized and characterized. Transformation of complex 1 into Roussin’s red salt (RRS) along with release of H2S in protic solvent was probed by NBD-SCN. It may suggest that DNIC can be a role for H2S storage and transport in hydrophobic environment. This phenomenon is attributed to the characteristic of non-innocent NO to regulate electron transfer among [FeIII-SH] core, which inhibited the reduction of FeIII into FeII and prevent reductive elimination of Fe-SH bond,
The electronic structure containing [FeIII-SH] motif of complex 1, 1-PPN, 4 was determined by EPR, IR, XAS, and XRD. Complex 1 and 1-PPN can be described as high-spin FeIII (SFe = 5/2) and two NO－(SNO = 1) antiferromagnetically coupled. The thermally unstable complex 3 spontaneously dimerize into the first structurally characterized FeIII-hydrosulfide complex [PPN]2[(μ-S)Fe(SH)(NO)]2 (4). The electronic structure can be described as two {FeIII(NO－)}7 antiferromagnetic coupled to yield S = 0 diamagnetic complex.
From recently published paper, the thermally unstable [PPN][Fe(SH)4] (5) spontaneously dimerizes to form [PPN]2[(SH)Fe (μ-S)]2 (6). According to the experiment, the stability of complex 1, 3, and 5 is 1 > 3 > 5. The stability of the dimerized-form is 2 > 4 > 6. On the basis of DFT computation and reduction potential, NO serves as strong electron-donating ligand (compared to thiolate), which reduces the effective nuclear charge(Zeff) of the iron center and prevent complex 1 from dimerization. That is, the stability increases accompanied with the larger NO-coordinate ligands bound to the [FeIII-SH] motif.

並列關鍵字

DNIC ； MNIC ； H2S

參考文獻

1. Furchgott, R. F. Z., J. V. Nature 1980, 288, 373-376.

3. Kuwata, S.; Hidai, M. Coord. Chem. Rev. 2001, 213, 211–305.

7. Thomas, G.; Ramwell, P. W. Biochem. Biophys. Res. Commun. 1989, 164, 889.

8. Vanin, A. F. FEBS Lett. 1991, 289, 1.

9. Garret, R. H.; Grisham, C. M., Biochemistry 2nd 1999, p 31.