含Poly-pyrazole 或 o-(diphenylphosphine)anisole 銅亞硝基化合物的合成與鑑定及其作為生化還原酶模型化合物可能性研究

亞硝酸還原成一氧化氮是亞硝酸還原酶在氮循環中主要的反應過程。為了研究亞硝酸還原酶其中心金屬與亞硝酸的鍵結模式是否影響其反應活性，我們製備四個銅一價亞硝酸化合物，以tris (3,5-di- methylpyrazolyl) methane (L1), tris (3-tertiary butylpyrazolyl)methane (L2) and ??-(diphenylphosphine) anisole (L3)為配位基，合成[(L1)Cu-(NO2)] (1), [(L2)Cu(NO2)] (2), [Cu(L3)2(NO2)] (3a), and [((L3)2Cu)2-(NO2)](NO2) (3b) 化合物。單晶繞射結果顯示，以氮作配位的配位基的化合物，其金屬與亞硝酸鍵結型式皆以h1-N的鍵結型式，且銅中心皆為一扭曲四面體結構。化合物3a的X-ray繞射結構可看出銅原子與亞硝酸上的兩個氧原子是不對襯的模式鍵結，這是第一個以不對襯鍵結型式的銅-亞硝酸化合物，其中心銅原子也是一扭曲的四面體結構。化合物3b[((Ph2PC6H4OMe-o)2Cu)2(h-NO2)]NO2以亞硝酸做為橋接，將化合物3a經CH2Cl2/ether 再結晶，即可得化合物3b。化合物1與3a也進行其反應性探討，在各種不同溫度下加入過量醋酸加入銅一價亞硝酸化合物的除氧二氯甲烷溶液，溶液顏色由透明無色變成綠色。化合物1的UV 吸收峰在262nm 有快速的下降，而在395nm 與699nm 有上升的趨勢。化合物3a的UV吸收峰在288nm 有快速下降，在675nm 則有上升現象。這些反應皆遵守pseudo-first-order反應速率。化合物1的ΔH值為25±1 kJmol-1 而其ΔS為-51±3 JK-1mol-1，化合物3a的ΔH值為40.89 ± 0.32 kJmol-1而其ΔS was -158.48±1.18 JK-1mol-1。根據這些結果，我們的化合物可以模擬Type II 銅亞硝酸還原酶的還原活性，這有助於幫助我們了解以及檢視銅亞硝酸還原酶其中心銅原子進行亞硝酸還原的過程。

關鍵字

亞硝酸還原酶氮循環

並列摘要

The reduction of nitrite (NO2-) to gaseous nitric oxide (NO) is a key process of copper containing nitrite reductases (Cu-NiRs) in the global nitrogen cycle. To investigate the binding modes of nitrites – function relationship of Cu-NiR, we prepared four copper(I) nitrite complexes with tris(3,5-dimethylpyrazolyl) methane (L1), tris(3-tertiary-butylpyrazolyl)methane (L2) and o-(diphenylphosphine) anisole (L3) Ligands. Copper(I) complexes [(L1)Cu(NO2)] (1), [(L2)Cu(NO2)] (2), [Cu(L3)2(NO2)] (3a), and [((L3)2Cu)2(NO2)](NO2) (3b) were synthesized. The X-ray crystal structures with tripodal nitrogen-containing neutral tris(Pyrazolyl) methane ligands were mononuclear h1-N-bound nitrite complexes with a distorted tetrahedral geometry. The X-ray crystal structures of complexe 3a is found that non-symmetric binding of nitrite via both O atoms to Cu, which is first example in copper(I) nitrito system. The copper coordination geometry is significantly distorted from tetrahedral. Complexe 3b has nitrite bridge bonding mode, [((Ph2PC6H4-(o-OMe))2Cu)2(h-NO2)]NO2 which is formed by nitrite binding arrangement under CH2Cl2/ether crystallization condition. The nitrite reductase activity of complex 1 and 3c with proton source was investigated, when excess acetic acid were added to an oxygen-free, CH2Cl2 solution of copper(I) nitrite adduct at different temperature. The color of the mixture solution changes from colorless to green. The absorption band at 262 nm then rapidly decreased and those at 395 nm and 699 nm increased in intensity for complex 1. The absorption band at 288 nm then rapidly decreased and at 675 nm increased in intensity for complex 3a. These reactions followed a pseudo-first-order kinetics. The activation enthalpy ΔH was 25±1 kJmol-1 and the activation entropy ΔS was -51±3 JK-1mol-1 for complexe 1, and the activation enthalpy ΔH was 40.89 ± 0.32 kJmol-1 and the activation entropy ΔS was -158.48±1.18 JK-1mol-1 for complexe 3a. According to this result, our complexes can mimic the type II copper center nitrite reduction reactivity, which is important in order to enhance our understanding and thoroughly examine the copper center of Cu-NiRs during the nitrite reduce process.