Structure, bonding, electronic and energy aspects of a new family of early lanthanide (La, Ce and Nd) complexes with phosphoric triamides: Insights from experimental and DFT studies
作者:Khodayar Gholivand、Hamid R. Mahzouni、Mehdi D. Esrafili
DOI:10.1039/c1dt11084e
日期:——
A new family of isostructural early lanthanide(III) complexes (LnXPA) of the general formula Ln(XPA)2Cl3(solv)2, where Ln = La, Ce and Nd, XPA = (4-X-C6H4NH)P(O)(NC4H8O)2, X = H, F, Cl and Br, and solv = H2O and CH3OH, is introduced. X-ray crystallography shows that the replacement of the coordinated water by a methanol molecule may reduce the symmetry level of the unit cell from the orthorhombic crystal system and the space groupFdd2 to monoclinic and C2/c. DFT calculations, at B3LYP, PBE and B3PW91 levels, have been carried out to get a better insight into the structural, electronic and energy aspects of the compounds. The large cation attraction energy (−ΔE) values in the range 269–273 kcal mol−1, at the B3PW91/ECP/6-311+G** level for the model complexes XPA–La3+ with stoichiometry 1 : 1, represent new ligands XPA as efficient complexant agents for lanthanides. The electronic nature of para substituent X has no significant effect on the Ln–ligand bonding and cation affinity of the ligands XPA. The results of atoms in molecules (AIM) analysis reveal a partial covalent contribution of the Ln–ligand interaction for the models XPA–La3+ in the absence of counterions and coordinated solvents. In the real complexes LnXPA, a closed-shell Ln–ligand interaction is established. Increasing the charge difference between nitrogen and phosphorus atoms (by ∼0.06 e) associated with a weakening of the Lp(OP)→σ*(P–N) electronic delocalization (Lp(OP) being the lone pair of the phosphoryl oxygen atom) may lead to an increase in partial multiple bond character of the P–N bonds in coordinated ligands, agreeing with the increase in ν(P–N) and 2JPH coupling constant values. The changes in electron density (ρ) and electronic energy density (H(r)) values confirm these structural reorganizations upon complexation.
在B3PW91/ECP/6-311+G**水平下,模型复合物XPA-La3+的化学计量比为1:1,其大阳离子吸引能(-ΔE)值在269-273千卡/摩尔-1的范围内,表明新配体XPA是镧系元素的有效络合剂。对映取代基X的电子性质对Ln-配体键合和配体XPA的阳离子亲和力没有显著影响。分子中原子(AIM)分析的结果表明,在没有反离子和配位溶剂的情况下,模型XPA-La3+的Ln-配体相互作用具有部分共价性质。在真实的复合物LnXPA中,建立了封闭壳Ln-配体相互作用。增加氮原子和磷原子之间的电荷差(约0.06e),伴随着Lp(OP)→σ*(P-N)电子非局域化(Lp(OP)是磷酰氧原子的孤对)的减弱,可能会导致配位配体中P-N键的部分多重键特征增加,这与在B3PW91/ECP/6-311+G**水平下,模型复合物XPA-La3+的化学计量比为1:1,其大阳离子吸引能(-ΔE)值在269