AMT对青铜文物缓蚀作用理论研究

Theoretical studyon inhibition behavior of bronze cultural relics by AMT

5-氨基-2-巯基-1,3,4-噻二唑(AMT)能和青铜器表面铜离子作用生成一种配位型聚合物的保护膜[AMT-Cu(Ⅰ)]n,并将腐蚀层中的氯离子置换出来,避免了青铜器的进一步腐蚀.为了深入了解AMT的缓蚀作用机理,本文采用密度泛函理论(DFT)和自然键轨道理论(NBO),在B3LYP/6-31+G(d,p)水平上确定AMT中反应活性位点、活性原子所带电荷和杂化形式,并利用Multiwfn波函数分析了反应前后前线轨道能的变化.结果表明,-SH基中的S7原子能与Cu(Ⅱ)形成有效的共价键,而N6原子可与Cu(Ⅱ)形成配位键,促进聚合物膜[AMT-Cu(Ⅰ)]n的形成,并且从概念DFT的活性指数(主要为μ,η,ω,ΔEn,ΔEe)比较中发现,AMT-Cu(Ⅰ)-H较AMT的亲电性指数增加,有利于形成高聚物膜,而且反应前后AMT构型中的C、N、S却始终在同一平面,但C-S和C-N键键长和键角均有不同程度的变化.

The coordinate protective films [AMT-Cu（ I ）],, were formed by 2-Amino-5-mercapto-1, 3, 4- thiadiazole （AMT） and bivalent copper cation [Cu（ II ）]. Furthermore, the chlorine anions in bronze relic body were substituted for AMT molecules, so that the corrosion processes of bronze were stopped. In order to explored the inhibitive mechanism of AMT, the density functional theory （DFT） and natural bond orbital theory （NBO） calculation at the B3LYP/6-31q-G（d, p）were done to confirm the active re- action location, charge and hybrid character of active atoms on AMT. The transformation of frontier mo- lecular orbital energy was analyzed by Multiwfn wavefunction analyzer. The results showed that $7 at- om could formed covalent bond with Cu（ ]I ）, but N6 atom formed coordinate bond with Cu（ II ）. It was been found that the electrophilic index was improved compared with AMT from the conceptual DFT re- activity index （ μ,η,ω,△En ,△Ee ） about AMT and AMT-Cu（ I ）-H unit. It was made for form the pro- tective films, and C, N and S atoms on AMT held at the identical planar, only the C-S and C-N bond lengths and bond angles were changed.