جستجوی مقالات مرتبط با کلیدواژه "charge transfer" در نشریات گروه "شیمی"

Density functional theory dispersion corrected (DFT-D3)calculations and molecular dynamic (MD) simulation were applied to investigate the sensing ability of four types of receptors (RCs) composed of the ortho-phenylenediamine based bis-ureas for selective complexation with the anions such as Cl–, Br–, OAC–, PhCO2–, H2PO4– and HSO4– in the gas phase and DMSO. On the basis of the data obtained from B3LYP-D3/6-31G+(d,p)calculations, RCs-OAC– complexes have the maximum binding energy, whose binding energy is reduced in the presence of DMSO as the solvent. IR vibrational frequencies of the N—H bonds of the RCs showed a red-shift due to their interactions with the anions in the corresponding complexes. Moreover, HOMO-LUMO analysis indicates that due to the complexation process, ionization potential (IP) and electron affinity (EA) values decrease which confirms the electron migration from the anions to the RCs. Natural bond orbital (NBO) analysis indicates that charge transfer occurs from the anions to the RCs due to an n-type mechanism and in comparison to other ions OAC– has stronger orbital interactions with the RCs. 20 ns MD simulations in DMSO, show the specific interactions between OAC– and RC4, which confirm the ability of RC4 as a good candidate to be applied as an anion-selective sensor.

The storage capacity of hydrogen on Na-decorated born nitride nanotubes (BNNTs) is investigated by using density functional theory within Quantum Espresso and Gaussian 09. The results obtained predict that a single Na atom tends to occupy above the central region of the hexagonal rings in (5,0) and (3,3) BNNT structures with a binding energy of -2.67 and -4.28 eV/Na-atom respectively. When a single H2 molecule is absorbed by a Na decorated BNNT, electrostatic field around Na atom and consequently charge of the participating atoms in the interaction region also undergo change. According to Mulliken population and partial density of state (PDOS) analyses, it is observed that positive charge carried by Na atom decreases.Another result of this charge transfer is revealed as an increase in the magnitude of the dipole moment of BNNT-Na-1H2 with respect to BNNT-Na. The results of charge density, separation distance of atoms in adsorption region as well as the H2 binding energy show the hydrogen molecule adsorption is a physical adsorption (physisorption). In the adsorption process, a single sodium atom with losing about 0.4e of its net charge can adsorb up to six H2 molecules with the binding energy of -0.35 and -0.32 eV/ H2 molecule on (5,0) and (3,3) BNNTs respectively. A comparison of the H2 binding energy of two nanotubes implies that the (5,0) BNNT-Na is more favorable for the hydrogen molecule adsorption.

M06-2X functional was employed to study halogen-π interactions in X-C2-Y…C8H8 complexes (X, Y=H, F, Cl, and Br). In fact, interactions of mono- or di-halogenated acetylenes and planar cyclooctatetraene as an anti-aromatic π system were considered. Relationship between binding energies of the complexes and charge transfer effects was investigated. Also, electronic charge density values were calculated using atoms in molecules (AIM) method to connect properties of bond, ring, and cage critical points (BCPs, RCPs, and CCPs) to binding energies of the mentioned complexes. Size of halogen atoms has a role on strength of halogen-π interactions. Decrease of electronic charge density values at BCPs and CCPs of the complexes and increase of alteration of these values at RCPs is relatively consistent with increase of binding energies. Electron-withdrawing nature of Br atom leads to inverse charge transfer in some complexes.Description of halogen-π interactions on an anti-aromatic ring help to design new molecular systems with unique properties for crystal engineering.