Dao Duy Quang, Hieu Truong Dinh, Le Minh Pham Thong, Tuan Dinh, Nam Pham Cam, Obot Ime Bassey
Institute of Research and Development, Duy Tan University, 03 Quang Trung, Danang, Viet Nam.
Department of Chemistry, Hue University of Education, 34 Le Loi, Hue, Viet Nam.
J Mol Model. 2017 Aug 11;23(9):260. doi: 10.1007/s00894-017-3432-7.
Understanding the physicochemical properties of corrosion inhibitors and their chemical interactions with metal surfaces is crucial to the design of improved (i.e., more efficient) corrosion inhibitors. In this work, the physicochemical properties of six thiophene-based corrosion inhibitors (2-acetylthiophene (AT), 2-formylthiophene (FT), thiophene (Th), 2-methyl-3-thiophenthiol (MTT), 2-pentylthiophene (PT), and 2-thenylthiol (TT)) were systematically studied by performing ab initio calculations at the MP2(full)/6-31G(2df,p) level of theory. Adsorption of the inhibitors on an iron surface was also modeled by investigating the interactions of these molecules with a tetrahedral Fe cluster using the B3LYP method and the 6-311G(d,p) basis set or the LanL2DZ basis set. The calculated results indicate that the nature of the substituent group present has a significant impact on the geometric and electronic structures of the thiophene-based molecules. The presence of an electron-donating group causes the electron density in the thiophene ring to increase, while the presence of an electron-withdrawing group has the opposite effect. Accordingly, the examined molecules were ranked in order of corrosion inhibition efficiency as follows: FT ≈ AT < Th < PT < TT < MTT. The calculated binding energies demonstrated that the π-1Fe and π-3Fe interaction configurations dominated over the S-1Fe configuration for all the compounds. Natural bond orbital analysis revealed that all of the thiophene-based compounds donate electrons from the π and σ orbitals of high-electron-density regions such as C2-S1-C5 and C3-C4 or from two lone pairs on S1 to the Fe cluster. Although electron donation from the thiophene-based compounds is always the dominant electron transfer process during adsorption, the backdonation of electrons from the 3d orbital of iron to σ*-antibonding orbitals of the thiophene compounds is also observed, especially in the case of π-3Fe parallel adsorption. Graphical abstract Optimized geometry, HOMO and LUMO for the π-3Fe interaction configuration of 2-pentylthiophene and Fe cluster.
了解缓蚀剂的物理化学性质及其与金属表面的化学相互作用对于设计改进型（即更高效）缓蚀剂至关重要。在本工作中，通过在MP2(全)/6 - 31G(2df,p)理论水平上进行从头算计算，系统研究了六种噻吩基缓蚀剂（2 - 乙酰基噻吩(AT)、2 - 甲酰基噻吩(FT)、噻吩(Th)、2 - 甲基 - 3 - 噻吩硫醇(MTT)、2 - 戊基噻吩(PT)和2 - 噻吩甲醇(TT)）的物理化学性质。还通过使用B3LYP方法和6 - 311G(d,p)基组或LanL2DZ基组研究这些分子与四面体Fe簇的相互作用，对缓蚀剂在铁表面的吸附进行了建模。计算结果表明，存在的取代基的性质对噻吩基分子的几何和电子结构有显著影响。供电子基团的存在会导致噻吩环中的电子密度增加，而吸电子基团的存在则有相反的效果。因此，所研究的分子按缓蚀效率排序如下：FT≈AT < Th < PT < TT < MTT。计算得到的结合能表明，对于所有化合物，π - 1Fe和π - 3Fe相互作用构型比S - 1Fe构型占主导。自然键轨道分析表明，所有噻吩基化合物都从高电子密度区域的π和σ轨道（如C2 - S1 - C5和C3 - C4）或从S1上的两个孤对向Fe簇提供电子。虽然噻吩基化合物的电子给予始终是吸附过程中占主导的电子转移过程，但也观察到铁的3d轨道向噻吩化合物的σ*反键轨道的电子回授，特别是在π - 3Fe平行吸附的情况下。图形摘要2 - 戊基噻吩与Fe簇的π - 3Fe相互作用构型的优化几何结构、最高占据分子轨道(HOMO)和最低未占据分子轨道(LUMO) 。
