Geminal Dicationic Ionic Liquids (GDILs) and Their Adsorption on Graphene Nanoflakes.

In this work, the configuration and stability of 15 geminal dicationic ionic liquids (GDILs) and their adsorption mechanism on the graphene nanoflake (GNF) are investigated using the density functional theory (DFT) method. We find that the interactions of dications ([DAm]+, [DIm]+, [DImDm]+, [DPy]+, and [DPyrr]+)) are stabilized near the anions ([BF4]-, [PF6]-, and [Tf2N]-) in the most stable configurations of GDILs through electrostatic interactions, van der Waals (vdW) interactions, and hydrogen bonding (H-bonding). Our calculations show that the adsorption of the GDILs on the GNF is consistent with the charge transfer and occurs via X···π (X = N, O, F), C-H···π, and π···π noncovalent interactions, leading to a decrease in the strength of the intermolecular interactions between the dications and anions in the GDILs. The thermochemistry calculations reveal that the formation of GDIL@GNF complexes is an exothermic and favorable reaction. The adsorption energy (Eads) calculations show that the highest Eads values for the interaction of GDILs containing [BF4]-, [PF6]-, and [Tf2N]- anions with the GNF are observed for the [DPy][BF4]@GNF (-23.56 kcal/mol), [DPy][PF6]@GNF (-29.29 kcal/mol), and [DPyrr][Tf2N]@GNF (-24.74 kcal/mol) complexes, respectively. Our results show that the adsorption of the GDILs on the GNF leads to the decrease of the chemical potential (µ), chemical hardness (η), and HOMO-LUMO energy gap (Eg) values and an increase in the electrophilicity index (ω) value of the GNF. In addition, the effect of GDIL adsorption on the UV-vis absorption spectrum was studied at the TD-M06-2X/cc-pVDZ level of theory. We find that the adsorption of GDILs results in minimal change in the shape of the main absorption peak (at λ = 363 nm) in the GNF spectrum and only shifts it to higher wavelengths. On the other hand, a new peak appears in the GNF spectrum upon adsorption of [DPy][Y] (Y = [BF4]-, [PF6]-, and [Tf2N]-) due to the relatively strong π···π interactions between the [DPy]+ dication and GNF. Finally, the transition density matrix (TDM) heat maps show that electron transfers related to the excitation states in the GDIL@GNF complexes occur mainly through π(C=C) → π*(C=C) transitions in the GNF and the transitions from [DPy]+ dication to the GNF.

DFT study of interaction of Palladium Pdn (n = 1-6) nanoparticles with deep eutectic solvents.

In this study, we use density functional theory (DFT) calculations to investigate the stability, reactivity and interactions of Palladium Pdn (n = 1-6) nanoparticles with ChCl:U and ChCl:EG based deep eutectic solvents (DESs). We find that the DES … Pdn complexes are stabilized by two types of binding; Pdn-X anchoring bonds (X = N atom of -NH2 group in urea and [Cl]- anion) and Pdn…H-X (X = C, N and O) unconventional H-bonds. Analyses based on AIM, NBO, NCI, and EDA suggest that the anchoring bonds, which are electrostatic in nature are stronger than the unconventional H-bonds, which are van der Waals in nature. The Energy Decomposition Analysis reveals that the charge transfer plays an important role in the stability of DES…Pdn complexes. Thermochemical calculations, including enthalpy (ΔH) and free energy (ΔG), indicate that the formation of the DES…Pdn complexes is exothermic and occurs spontaneously. The binding energy (ΔEb) calculations show that the ChCl:U DES has a stronger interaction with the Pdn nanoparticles than their ChCl:EG DES counterparts. On the other hand, a similar trend for the ΔEb, ΔH and ΔG values of the complexes is observed with increasing nanoparticle size of Pdn (DES…Pd5> DES…Pd6> DES…Pd4> DES…Pd3> DES…Pd2> DES…Pd1). Our results show that the magnitude of charge transfer (ΔQ) value in the complexes follow the order observed for the ΔEb values. It is also observed that increasing the energy gap Eg values of the complexes decreases the ΔEb and ΔQ values of the complexes. The reactivity parameter calculations of the complexes show that the Eg and chemical hardness (η) values of ChCl:U…Pdn and ChCl:EG…Pdn complexes decrease with an increase in the nanoparticle size. Additionally, the global electrophilicity index (ω) values of the DES…Pdn complexes increase with an increase in the Pdn nanoparticle size, while no clear trend is seen for the chemical potential (µ) values of the complexes. The urea-based DES shows better suitability towards Pdn nanoparticles than the ethylene glycol-based DES. Overall, such DESs are potentially promising green solvents for nanoparticle synthesis and activity.

Interaction of Cun, Agn and Aun (n = 1-4) nanoparticles with ChCl:Urea deep eutectic solvent.

In this study, the interaction of noble metal nanoparticles (Mn, M = Cu, Ag, and Au; n = 1-4) with ChCl:Urea deep eutectic solvent was investigated using density functional theory (DFT) method. We find that ChCl:Urea mostly interact with the Mn nanoparticles through [Cl]- anion ([Cl]-…Mn) and nonconventional H-bonds of C-H⋯Mn and N-H⋯Mn. NBO, QTAIM, NCI and EDA analyses show that [Cl]-…Mn interactions are stronger than the nonconventional H-bonds interactions. Our results indicate that the nature of [Cl]-…Mn interactions is electrostatic, while the nonconventional H-bonds of C-H⋯Mn and N-H⋯Mn are van der Waals in nature. The negative values of enthalpy (ΔH) and free energy (ΔG) for the ChCl:Urea…Mn complexes reveal that the formation of ChCl:Urea…Mn complexes is exothermic and proceeds spontaneously. The calculation of binding energy (ΔEb) of Mn nanoparticles with ChCl:Urea shows that the strength of interaction of Aun nanoparticles with ChCl:Urea is more favorable than Cun and Agn, following the order ChCl:Urea…Aun > ChCl:Urea…Cun > ChCl:Urea…Agn. Furthermore, the ΔEb, ΔH and ΔG values enhance with increasing nanoparticle size from n = 1 to n = 4, ChCl:Urea…M4> ChCl:Urea…M3> ChCl:Urea…M2> ChCl:Urea…M1 (M = Cu, Ag, and Au).