The effect of ionic liquid adsorption on the electronic and optical properties of fluorographene nanosheets

In the present study, we investigate the adsorption characteristics of six different ionic liquids (ILs) on a fully-fluorinated graphene (fluorographene, FG) surface using electronic structure studies and associated analysis methods. A systematic comparison of differences in IL binding energies (ΔEb) with fluorographene, graphene and hexagonal boron nitride surfaces indicates that fluorination strongly decreases the binding energy compared to the other two surfaces, hence resulting in the binding energetics: ΔEb (Graphene…IL) \u3e ΔEb (Hexagonal boron-nitride…IL) \u3e ΔEb (Fluorographene…IL). To probe the reasons for this difference, quantum theory of atoms in molecules (QTAIM) analysis and non-covalent interactions (NCI) analyses were carried out. Results indicate that the stability of complexes of FG surface with ILs (FG…IL) arises only due to the presence of the expected weak non-covalent intermolecular interactions. The calculation of charge transfers by employing the ChelpG method shows that the interaction of ILs with FG surface generally induces a negative charge on the FG surface. Furthermore, these interactions lead to a decrease of the HOMO-LUMO energy gap (Eg) of the FG surface, enhancing its electrical conductivity. In addition, a detailed analysis of the global molecular descriptors including the Fermi energy level (EFL), work function (WF), electronic chemical potential (μ), chemical hardness (η), global softness (S) and electrophilicity index (ω) was carried out for both the FG surface alone and the adsorbed complexes showing that there are small, but meaningful, differences in the reactivity of the surface depending on the nature of the IL. Finally, time-dependent DFT (TD-DFT) calculations of the optical properties of FG surface and FG…IL complexes reveal that the absorption spectrum of the FG surface undergoes a red shift following IL adsorption. This study demonstrates that FG provides a useful complementary tool to graphene and boron nitride materials, allowing for the fine-tuning of the optoelectronic properties of these monolayer materials. These results will assist in the development of these types of ILs for applications in optoelectronics

Homogeneous hydrogenation of electron-deficient alkenes by using iridium-complexes

It is shown and proven, that the flavonoids represent a unique class of alkenes, for which the homogeneous hydrogenation is not known till now (except for some functionalized representatives). It is proven, that assigned task could not be resolved via traditional (electrophilic) homogeneous hydrogenation. However, a new reaction was discovered, namely nucleophilic hydrogenation. At the current state the nucleophilic hydrogenation by Ir-complexes is only of academical significance. An investigation of the mechanism is needed for its practical usage. Homogeneous hydrogenation of 7-methoxy-3-(pyridin-2-yl)chromone is very effective both in its electrophilic and in nucleophilic versions, and affords the corresponding chroman-4-one in almost quantitative yield

Monoanionic Quasi-Imido Ligands Based on 1-Methyl-4-Iminopyridine and Complexes with the Main Group Elements Mg, Al and Zn.

The synthesis of a new class monoanionic nitrogen donor ligands based on (1-methylpyridin-4(1H)-ylidene)amide, abbreviated MQI (monoanionic quasi imide) and it chemistry with main group elements is reported. The electronic structure of the ligand allows delocalization of positive charge onto the N-heterocycle, which is accompanied by aromatization. The unsubstituted MQI ligand was found to form insoluble intractable products on reaction with non-transition metal alkyls, thus substituents were introduced to increase solubility and stability of those complexes and enable their study. The precursors 3,5-bis(3,5-dimethylphenyl)-1-methylpyridin-4(1H)-imine [MQIMe]H and 3,5-bis(3,5-di-tert-butylphenyl)-1-methylpyridin-4(1H)-imine [MQItBu]H both gave isolable complexes. The species {[MQItBu]MgCl(THF)}2, {[MQItBu]MgMe}2, {[MQItBu]AlMe2}2 , {[MQItBu]ZnMe}2 , and {[MQIMe]MgCl(THF)}2 were prepared. As well, [MQI]H precursors were coordinated with Lewis acidic boron- and aluminium-derived Lewis acids. Charge delocalization onto pyridine was examined by crystallography and NMR spectroscopy

Tandem dinucleophilic cyclization of cyclohexane-1,3-diones with pyridinium salts

The cyclization of cyclohexane-1,3-diones with various substituted pyridinium salts afforded functionalized 8-oxa-10-aza-tricyclo[7.3.1.0(2,7)]trideca-2(7),11-dienes. The reaction proceeds by regioselective attack of the central carbon atom of the 1,3-dicarbonyl unit to 4-position of the pyridinium salt and subsequent cyclization by base-assisted proton migration and nucleophilic addition of the oxygen atom to the 2-position, as was elucidated by DFT computations. Fairly extensive screening of bases and additives revealed that the presence of potassium cations is essential for formation of the product

Tandem dinucleophilic cyclization of cyclohexane-1,3-diones with pyridinium salts

The cyclization of cyclohexane-1,3-diones with various substituted pyridinium salts afforded functionalized 8-oxa-10-aza-tricyclo[7.3.1.02,7]trideca-2(7),11-dienes. The reaction proceeds by regioselective attack of the central carbon atom of the 1,3-dicarbonyl unit to 4-position of the pyridinium salt and subsequent cyclization by base-assisted proton migration and nucleophilic addition of the oxygen atom to the 2-position, as was elucidated by DFT computations. Fairly extensive screening of bases and additives revealed that the presence of potassium cations is essential for formation of the product