Density functional theory study of the free and tetraprotonated spheroidal macrotricyclic ligands and the complexes with halide anions: F⁻, Cl⁻, Br⁻

Abstract

Theoretical studies of the macrotricyclic tetramine hexaether (SC), its tetraprotonated form SC-4H(+), and the corresponding complexes X(-) subsetSC-4H(+) (This expression represents the structural properties of the halide inclusion complex formed though the free ligand SC-4H(+) and the halide anion X(-): the spherical halide anion X(-) is held by a tetrahedral array of (+)N--H...X(-) hydrogen bonds inside the intramolecular cavity of the tetraprotonated form SC-4H(+)) of SC-4H(+) with the halide anions: F(-), Cl(-), and Br(-) have been performed using density functional theory (DFT) with B3LYP/6-31G method implemented in the Gaussian 03 program package. The optimized geometric structures obtained from DFT calculations are used to perform Natural Bond Orbital (NBO) analysis. The three main types of hydrogen bonds (+)N--H...F(-), (+)N--H...Cl(-), and (+)N--H...Br(-) are investigated. The results indicate that hydrogen bonding interactions are dominant and the halide anions: F(-), Cl(-), and Br(-) offer lone pair electrons to the contacting sigma* (N--H) antibond orbital of SC-4H(+). For all the structures, the most pronounced changes in geometric parameters upon interaction are observed in the proton-donor molecule. The intermolecular interaction energies are predicted by using B3LYP/6-31G methods with basis set superposition error (BSSE) and zero-point energy (ZPE) correction.

Computational Design of Two-Photon Fluorescent Probes for Intracellular Free Zinc Ions

“…In NBO analysis, for each donor NBO ( i ) and acceptor NBO ( j ), the stabilization energy ( E 2 ) associated with i → j delocalization is explicitly estimated by following equation E 2 = normalΔ E i j = q i F 2 ( i , j ) ε j − ε i where q i is the i th donor orbital occupancy, ε i and ε j are diagonal elements (orbital energies), and F ( i , j ) are off-diagonal elements, respectively, associated with the NBO Fock matrix . If the stabilization interaction energy E 2 between a donor bonding orbital and an acceptor antibonding orbital is large, then there is a strong interaction between the two bonds.…”

“…where q i is the ith donor orbital occupancy, ε i and ε j are diagonal elements (orbital energies), and F(i,j) are off-diagonal elements, respectively, associated with the NBO Fock matrix. 63 If the stabilization interaction energy E 2 between a donor bonding orbital and an acceptor antibonding orbital is large, then there is a strong interaction between the two bonds.…”

“…63 If the stabilization interaction energy E 2 between a donor bonding orbital and an acceptor antibonding orbital is large, then there is a strong interaction between the two bonds. According to calculated results, the interaction energies between the probe molecules and metal ions are mainly caused by the lone pair electrons of N in the probe molecules and the virtual valence orbital and Rydberg-type orbitals of the metal ions.…”