DFT study of the carbon‐ and nitrogen‐pivot lariat crown ethers and their complexes with alkali metal cations: Na⁺, K⁺

Abstract

In this work, a quantum mechanical research of five lariat crown ethers(LCEs), 2-methoxy-15-crown-5(A), N-methoxy-4-aza-15-crown-5(B), N-methoxy-4-aza-18-crown-6(C), N-methoxyethyl-4-aza-18-crown-6(D), N,N'-bis(2-metho xyethyl)-4,13-diaza-18-crown-6(E), which are based on either 15-crown-5 or 18-crown-6 frameworks and contain various pendant arms extending from either carbon or nitrogen atoms on the crown frameworks, had been done using density functional theory with B3LYP/6-31G* method to obtain the electronic and geometrical structures of the LCEs and their complexes with alkali metal ions: Na(+) and K(+). The nucleophilicity of LCEs had been investigated by the Fukui functions. For complexes, the match between the cation and cavity size, the status of interaction between alkali metal ions and donor atoms in the LCEs, and the sidearm effect of the LCEs had been analyzed through the other calculated parameters, such as, highest occupied molecular orbital energy, lowest unoccupied molecular orbital energy, and energy gaps. In addition, the enthalpies of complexation reaction had been studied by the calculated thermodynamic data (298 K). The calculated results are all in a good agreement with the experimental data for the complexes.

Theoretical Design of a New Allosteric Switch and Fluorescence Chemosensor Double Functional Devices of Aza-Crown Ether

“…The optimized structures of the free ligand and metal complexes are used for natural bond orbital (NBO) calculation. The second-order perturbation stabilization energies ( E 2 ) are usually applied to reflect the interaction energies of host–guest system . The stabilization energies E 2 of complexes L /M 2+ are listed in Table .…”

“…The second-order perturbation stabilization energies (E 2 ) are usually applied to reflect the interaction energies of host−guest system. 37 The stabilization energies E 2 of complexes L/M 2+ are listed in Table 2.…”

Synthesis, Metal Ion Complexation and Computational Studies of Thio Oxocrown Ethers

“…Various quantum-chemical and force-field computations of crown ethers and of their metal complexes have been reported recently [24,26,27,28], even on the ab initio level [29,30] and the density functional level of theory (DFT) [31,32,33]. The structures of molecules play an especially significant role in determining their chemical properties.…”

Tunable Azacrown-Embedded Graphene Nanomeshes for Ion Sensing and Separation

“…All the computations reported in this manuscript are performed using density functional theory (DFT) with the hybrid functional B3LYP at the B3LYP/6-311G­(d,p) level . This functional has earlier been widely used for electronic structure calculations involving crown ethers. ,,, Cohesive energies per atom ( E coh/atom ) of the nanoporous substrates are calculated to evaluate their structural stabilities. Cohesive energy is defined as the energy required to dissociate the system into its constituent isolated atomic species and is calculated using where E system , E C , E H , E N , and E O correspond to the energies of the nanoporous substrate, isolated carbon, hydrogen, nitrogen, and oxygen atoms.…”

“…The discovery of crown ethers by Pedersen in 1967 has led to the emergence of new host–guest chemistry principles for the selective binding of cations. − Demonstration of the remarkable selectivity with which the cations crowned the macrocyclic hosts resulted in the 1987 Nobel Prize for Pedersen, jointly with Cram and Lehn for their investigations of structure-specific interactions. − Ion–dipole interactions between the cations and the negatively charged oxygen ends of the cyclic polyether rings drive the host–guest complex formation. Experiments performed in the gas phase and solution and crystalline phases have revealed the role of the size and the charge of the cation, size of the macrocyclic cavity, number of heteroatoms in the ring, and the nature of the solvating medium in determining the stabilities of the complexes. − Gas-phase investigations of these complexes using the techniques of mass spectrometry and the success in crystallization of the salt complexes, along with the availability of computational tools for probing the binding strengths, have triggered numerous studies in this area of supramolecular chemistry. Thanks to a variety of techniques like collision-induced dissociation, , infrared multiple photon dissociation spectroscopy, IR-UV double resonance spectroscopy, UV photodissociation spectroscopy, laser-induced fluorescence spectroscopy, and isothermal titration calorimetry, the complexes of crown ethers with various cations are well characterized.…”