Structural and energetic preferences of pi, sigma, and bidentate cation binding (Li(+), Na(+), and Mg(2+)) to aromatic amines (Ph-(CH(2))(n)-NH(2), n = 2-5): a theoretical study.
MP2/aug-cc-pVTZ calculations have been carried out to systematically explore three distinct binding preferences, namely, monodentate binding in pi and sigma fashions to aromatic and amine groups, respectively, and the bidentate mode of Li(+), Na(+) and Mg(2+) ions with aromatic amines (Ph-(CH(2))(n)-NH(2), n = 2-5). Several model systems were devised to examine the binding strength of the interactions where the aromatic and amine motifs are not interconnected. The sensitivity of structures and energetics to the basis set superposition error (BSSE) was examined by doing the geometry optimization with a counterpoise option at the MP2/6-31G(d) and MP2/cc-pVDZ levels. Variations in the binding affinities of Li(+), Na(+), and Mg(2+) metals to pi systems and -NH(2) groups are observed. The effects of the spacer chain orientation and its length on the binding of metal ions and protons to aromatic amines are studied. It is observed that Mg(2+) binding is sensitive to the spacer chain orientation and its length, whereas Li(+) or Na(+) binding is independent of spacer chain orientation and length. Reorganization energies are estimated for the complexation of metal ions to aromatic amines. It is observed that the reorganization energy for the complexation of Mg(2+) is slightly higher than that of Li(+), Na(+), and H(+).
Molecular Modeling Group, Indian Institute of Chemical Technology, Tarnaka, Hyderabad 500 607, India.
J Srinivasa
JS
Rao
G Narahari
GN
Sastry
D000588:Amines / Q000737:chemistry*; D002244:Carbon / Q000737:chemistry; D008094:Lithium / Q000737:chemistry*; D008274:Magnesium / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D009942:Organometallic Compounds / Q000737:chemistry*; D011522:Protons; D011789:Quantum Theory; D012964:Sodium / Q000737:chemistry*; D013329:Structure-Activity Relationship; D013379:Substrate Specificity; D013816:Thermodynamics
D000588:Amines; D009942:Organometallic Compounds; D011522:Protons; D002244:Carbon; D008094:Lithium; D012964:Sodium; D008274:Magnesium