DFT RX3LYP and RPBEPBE studies on the structural, electronic, and vibrational properties of some amino-alcohol ligands

Abstract

a b s t r a c tTo rationalize the influence of molecular architecture on metal ion selectivity and affinity, a DFT study of three amino-alcohol ligands, bis(2-hydroxyethyl)-ethane-1,2-diamine (BHEEN), and two ligands where the backbone is reinforced with cycloalkyl moieties, N,N 0 -bis(2-hydroxycyclopentyl)-ethane-1,2-diamine (Cyp 2 -EN), and N,N 0 -bis(2-hydroxycyclohexyl)-ethane-1,2-diamine (Cy 2 -EN), using the X3LYP and PBEPBE functionals with 6-31G(d,p), 6-31+G(d,p) and 6-311++G(d,p) basis sets has been conducted in combination with Quantum Theory of Atoms in Molecules (QTAIM) and Natural Bond Orbital (NBO) analyses. QTAIM analysis predicted the formation of intra-molecular N-HÁ Á ÁO-H and -HÁ Á ÁH-interactions only in Cy 2 -EN. The latter interaction in metal complexes is often interpreted as a destabilizing steric repulsion. These analyses also predicted the electron density at the ring critical point, and its Laplacian, of the cyclopentyl moiety in Cyp 2 -EN to be twice as large as those of the cyclohexyl moiety in Cy 2 -EN. It is suggested that the increased electron density within the 5-member reinforcement rings is responsible for the absence of the intramolecular interactions observed in Cy 2 EN and also contributes to its lower affinity for metal ions. The formation of the intramolecular N-HÁ Á ÁO-H bond was observed in the NBO analysis for all three ligands since values of the second-order stabilization energy E (2) caused by the charge transfer between the O lone-pair and the N-H bond was non-zero. The strength of the H-bond increased in the order Cy 2 -EN > BHEEN > Cyp 2 -EN that is consonant with a decrease in the N-HÁ Á ÁO-H distance. Because a similar trend, viz., log K ML (Cy 2 -EN) > log K ML (BHEEN) > log K ML (Cyp 2 -EN) is observed for the stability constants with all metal ions, we tentatively conclude that the ability of the ligand to transfer charge between orbitals, as described by E, is a factor that influences the ligand's ability to form complexes. A comparison between the calculated results (structure, vibrational spectra) and experimental results are used to validate the conclusions.

Can a Single Molecule of Water be Completely Isolated Within the Subnano‐Space Inside the Fullerene C60Cage? A Quantum Chemical Prospective

“…Second‐order perturbation stabilization energy, ( E (2) ) : The stabilization energy obtained, E (2) , is a measure of the hyperconjugative interaction between the donor and the acceptor natural bond orbitals 2. The E (2) values were calculated with PBE0/6‐31G(d,p) because, as just mentioned, the larger 6‐311++G(d,p) basis set yields large Δ Q values, unrealistically larger orbital occupancies (similar observations are already reported for analogous systems elsewhere),101–105 and causes the disappearance of donor–acceptor interactions, as we have previously observed 105. Nonetheless, the OH⋅⋅⋅C stabilizing effects can be described as π(CC)→σ*(OH) charge‐transfer delocalizations and, in the most stable structure, such delocalizations occur from each of the π(C9C14), π(C16C30), and π(C18C20) bonding orbitals of C 60 to the σ*(O61H62) anti‐bonding orbital of H 2 O, as well as from the π(C42C52), π(C54C60), and π(C55C58) bonding orbitals of C 60 to the σ*(O61H63) anti‐bonding orbital of H 2 O (see atom labeling in Figure 1).…”

An electronic structure theory investigation of the physical chemistry of the intermolecular complexes of cyclopropenylidene with hydrogen halides

“…The usefulness of QTAIM[45] in unveiling the details of the bonding topology in intermolecular complexes does not need to be further demonstrated. [24, 40, 70–76] Collected in Table 4 are the MP2/aug‐cc‐pVQZ values of the bond critical point (bcp) electron density, Laplacian of charge density as well as those of the most important bond descriptors.…”

A Density Functional Theory- and Atoms in Molecules-based Study of NiNTA and NiNTPA Complexes toward Physical Properties Controlling their Stability. A New Method of Computing a Formation Constant

“…54 In such a case the distance rule is invalid and examples of atoms that bond preferentially to others that are further, rather than to closer neighbors, are known. 66,67 It has been suggested recently that the presence of the five-and six-membered reinforcing rings alters the intramolecular interactions in a molecule; 68 However, the C5-atom, which is the member of this structural ring, is involved in two nonstructural rings, namely the chelating N-C5-H28-O17-Ni and non-chelating N-C5-H28-O17-H33-C9-C8 ring with RCP marked with a single circle in Figure 4. It is seen in Table 2 that the ρ RCP and  2 ρ RCP values of the non-structural ring N-C2-C3-H25-H32-C8 (0.0134 and 0.0621 au, respectively) are larger when compared with the structural chelating N-C2-C3-C3-O11-Ni ring (0.0120 and 0.0548 au, respectively).…”