乙二胺四乙酸和乙二胺四亚甲基膦酸清除铁垢性能的量子化学计算

采用密度泛函的B3LYP方法，对所有原子采用DEF2-TZVP基组，以水为溶剂，计算了配合物分子Fe(EDTA)－和Fe(EDTMP)－的几何结构、轨道和空间位阻，分析了二者溶垢能力差异的原因.结果表明:配合物为低自旋态的六配位八面体结构，EDTA与Fe3+的结合能大于EDTMP的；EDTA由于羧基形成离域π键，加强了配位键的电子离域程度，而EDTMP的膦酸基只有σ键，从而使Fe(EDTA)－配位键的共价作用比Fe(EDTMP)－的强；Fe(EDTMP)－中膦酸基之间存在空间位阻效应，也不利于EDTMP与Fe3+的结合.

The Quantum Chemistry Calculation of the Iron Scale Cleaning Performance of Ethylenediaminetetraacetic Acid and Ethylenediaminetetramethylenephosphonic Acid

The molecular geometry, orbit and steric hindrance of the complexes of Fe(EDTA)-and Fe(EDTMP)- were calculated using the B3LYP method of density functional theory. The DEF2-TZVP basis set was used for all atoms and water was used as the solvent. The reasons for the difference in dissolving scale ability were analyzed. The results show that the complex is a low-spin six-coordinate octahedral structure. The binding energy of EDTA to Fe3+ ions is greater than that of EDTMP. The delocalized π bond of the carboxylic acid group of EDTA strengthens the electron delocalization of coordination bonds for complexes, which makes the covalent interaction of Fe(EDTA)- coordination bond stronger than that of Fe(EDTMP)-, whereas the phosphonic acid group of EDTMP has only σ bond. The steric hindrance effect between phosphonic acid groups of Fe(EDTMP)- is also not conducive to the combination of EDTMP and Fe3+ ion.