scholarly journals Synthesis and Characterization of Ion Pairs between Alkaline Metal Ions and Anionic Anti-Aromatic and Aromatic Hydrocarbons with π-Conjugated Central Seven- and Eight-Membered Rings

Molecules ◽  
2020 ◽  
Vol 25 (20) ◽  
pp. 4742
Author(s):  
Jan Bloch ◽  
Stefan Kradolfer ◽  
Thomas L. Gianetti ◽  
Detlev Ostendorf ◽  
Subal Dey ◽  
...  
Keyword(s):  
Metal Ions ◽  
Density Functional ◽  
Ion Pairs ◽  
Alkaline Metal ◽  
Functional Theory ◽  
Full Characterization ◽  
Aromatic Character ◽  
Counter Cation ◽  
Solvent Molecules

The synthesis, isolation and full characterization of ion pairs between alkaline metal ions (Li+, Na+, K+) and mono-anions and dianions obtained from 5H-dibenzo[a,d]cycloheptenyl (C15H11 = trop) is reported. According to Nuclear Magnetic Resonance (NMR) spectroscopy, single crystal X-ray analysis and Density Functional Theory (DFT) calculations, the trop‒ and trop2−• anions show anti-aromatic properties which are dependent on the counter cation M+ and solvent molecules serving as co-ligands. For comparison, the disodium and dipotassium salt of the dianion of dibenzo[a,e]cyclooctatetraene (C16H12 = dbcot) were prepared, which show classical aromatic character. A d8-Rh(I) complex of trop− was prepared and the structure shows a distortion of the C15H11 ligand into a conjugated 10π -benzo pentadienide unit—to which the Rh(I) center is coordinated—and an aromatic 6π electron benzo group which is non-coordinated. Electron transfer reactions between neutral and anionic trop and dbcot species show that the anti-aromatic compounds obtained from trop are significantly stronger reductants.

Density functional theory (DFT) calculations on the structures and stabilities of [CnO2n+1]2– and [CnO2n+1]X2 polycarbonates containing chainlike (CO2)n units (n = 2–6; X = H or Li)

2011 ◽  
Vol 89 (6) ◽  
pp. 671-687 ◽  
Author(s):  
Pablo J. Bruna ◽  
Friedrich Grein ◽  
Jack Passmore
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Ion Pairs ◽  
Dicarboxylic Acids ◽  
Polarizable Continuum Model ◽  
Weakly Bound ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Weakly Bound Complexes

The structures and stabilities of chainlike (CO2)n (n = 2–6) polycarbonates, where adjacent C atoms are linked by C–O–C bonds, were investigated at the density functional theory (DFT) level (B3PW91/6–311G(2d,p)), including dicarboxylic dianions, [CnO2n+1]2–, and the corresponding acids, [CnO2n+1]H2, and Li salts, [CnO2n+1]Li2. At equilibrium, the most stable systems have Cs, C2, or C2v symmetries. In the gas phase, these dianions are generally metastable with respect to spontaneous ejection of one electron, yet in the presence of counterions they become stabilized, for example, as [CnO2n+1]2–(Li+)2 ion pairs. [CnO2n+1]2– linkages are also stabilized as dicarboxylic acids, [CnO2n+1]H2; we find the latter to have equilibrium conformations of higher symmetry than previously reported in the literature. To the best of our knowledge, none of the [CnO2n+1]X2 (X = Li or H) compounds with n ≥ 2 have been reported in the experimental literature (albeit, the alkyl esters C2O5R2 and C3O7R2 are commercially available). All CO bonds in C2O5X2 to C6O13X2 have single- to double-bond character (≈140–118 pm), indicating that the [CnO2n+1] moieties are held together by strong chemical forces (in contrast to the weakly bound complexes (CO2)n and (CO2)n–, n > 1). Vibrational frequencies were calculated to ensure all conformations were true minima. The IR and Raman intensities show that the high intensity C=O stretching modes (1750 ± 100 cm–1) will help in the spectral characterization of these compounds. Solvation calculations using the polarizable continuum model (PCM) find that C2O52– can be formed via CO32– + CO2 as well as CO3–[Formula: see text], each reaction having ΔG298 < 0 in practically all solvents. This result confirms the experimentally observed large solubility of CO2(g) in molten carbonates, CO3M2 (M = Li, Na, or K). In contrast, starting with n = 2, the reactions [CnO2n+1]2– + CO2 do not proceed spontaneously in any solvent (ΔG298 > 0).

scholarly journals M 4Au12Ag32(p-MBA)30 (M = Na, Cs) bimetallic monolayer-protected clusters: synthesis and structure

2018 ◽  
Vol 74 (7) ◽  
pp. 987-993 ◽  
Author(s):  
Brian E. Conn ◽  
Badri Bhattarai ◽  
Aydar Atnagulov ◽  
Bokwon Yoon ◽  
Uzi Landman ◽  
...  
Keyword(s):  
Density Functional ◽  
Point Group ◽  
Group Symmetry ◽  
Framework Structure ◽  
Void Space ◽  
Functional Theory ◽  
Monolayer Protected Clusters ◽  
Counter Cation ◽  
Solvent Molecules ◽  
Asymmetric Unit Cell

Crystals of M 4Au12Ag32(p-MBA)30 bimetallic monolayer-protected clusters (MPCs), where p-MBA is p-mercaptobenzoic acid and M + is a counter-cation (M = Na, Cs) have been grown and their structure determined. The molecular structure of triacontakis[(4-carboxylatophenyl)sulfanido]dodecagolddotriacontasilver, Au12Ag32(C7H5O2S)30 or C210H150Ag32Au12O60S30, exhibits point group symmetry 3 at 100 K. The overall diameter of the MPC is approximately 28 Å, while the diameter of the Au12Ag20 metallic core is 9 Å. The structure displays ligand bundling and intermolecular hydrogen bonding, which gives rise to a framework structure with 52% solvent-filled void space. The positions of the M + cations and the DMF solvent molecules within the void space of the crystal could not be determined. Three out of the five crystallographically independent ligands in the asymmetric unit cell are disordered over two sets of sites. Comparisons are made to the all-silver M 4Ag44(p-MBA)30 MPCs and to expectations based on density functional theory.

scholarly journals Stabilization of Super Electrophilic Pd+2 Cations in Small-Pore SSZ-13 Zeolite

2019 ◽  
Author(s):  
Konstantin Khivantsev ◽  
Nicholas R. Jaegers ◽  
Iskra Z. Koleva ◽  
Hristiyan A. Aleksandrov ◽  
Libor Kovarik ◽  
...  
Keyword(s):  
Density Functional ◽  
Ion Pairs ◽  
Carbonyl Complexes ◽  
Zeolite Framework ◽  
Functional Theory ◽  
Coordination Environment ◽  
Small Pore ◽  
Ligand Free ◽  
Spectroscopic Signatures

<p>We provide the first observation and characterization of super-electrophilic metal cations on a solid support. For Pd/SSZ-13 the results of our combined experimental (FTIR, XPS, HAADF-STEM) and density functional theory study reveal that Pd ions in zeolites, previously identified as Pd<sup>+3</sup> and Pd<sup>+4</sup>, are in fact present as super electrophilic Pd<sup>+2</sup> species (charge-transfer complex/ion pair with the negatively charged framework oxygens). In this contribution we re-assign the spectroscopic signatures of these species, discuss the unusual coordination environment of “naked” (ligand-free) super-electrophilic Pd<sup>+2</sup> in SSZ-13, and their complexes with CO and NO. With CO, non-classical, highly positive [Pd(CO)<sub>2</sub>]<sup>2+</sup> ions are formed with the zeolite framework acting as a weakly coordinating anion (ion pairs). Non-classical carbonyl complexes also form with Pt<sup>+2</sup> and Ag<sup>+</sup> in SSZ-13. The Pd<sup>+2</sup>(CO)<sub>2</sub> complex is remarkably stable in zeolite cages even in the presence of water. Dicarbonyl and nitrosyl Pd<sup>+2</sup> complexes, in turn, serve as precursors to the synthesis of previously inaccessible Pd<sup>+2</sup>-carbonyl-olefin [Pd(CO)(C<sub>2</sub>H<sub>4</sub>)] and -nitrosyl-olefin [Pd(NO)(C<sub>2</sub>H<sub>4</sub>)] complexes. Overall, we show that zeolite framework can stabilize super electrophilic metal (Pd) cations, and show the new chemistry of Pd/SSZ-13 system with implications for adsorption and catalysis.<br></p>

scholarly journals Stabilization of Super Electrophilic Pd+2 Cations in Small-Pore SSZ-13 Zeolite

2019 ◽  
Author(s):  
Konstantin Khivantsev ◽  
Nicholas R. Jaegers ◽  
Iskra Z. Koleva ◽  
Hristiyan A. Aleksandrov ◽  
Libor Kovarik ◽  
...  
Keyword(s):  
Density Functional ◽  
Ion Pairs ◽  
Carbonyl Complexes ◽  
Zeolite Framework ◽  
Functional Theory ◽  
Coordination Environment ◽  
Small Pore ◽  
Ligand Free ◽  
Spectroscopic Signatures

<p>We provide the first observation and characterization of super-electrophilic metal cations on a solid support. For Pd/SSZ-13 the results of our combined experimental (FTIR, XPS, HAADF-STEM) and density functional theory study reveal that Pd ions in zeolites, previously identified as Pd<sup>+3</sup> and Pd<sup>+4</sup>, are in fact present as super electrophilic Pd<sup>+2</sup> species (charge-transfer complex/ion pair with the negatively charged framework oxygens). In this contribution we re-assign the spectroscopic signatures of these species, discuss the unusual coordination environment of “naked” (ligand-free) super-electrophilic Pd<sup>+2</sup> in SSZ-13, and their complexes with CO and NO. With CO, non-classical, highly positive [Pd(CO)<sub>2</sub>]<sup>2+</sup> ions are formed with the zeolite framework acting as a weakly coordinating anion (ion pairs). Non-classical carbonyl complexes also form with Pt<sup>+2</sup> and Ag<sup>+</sup> in SSZ-13. The Pd<sup>+2</sup>(CO)<sub>2</sub> complex is remarkably stable in zeolite cages even in the presence of water. Dicarbonyl and nitrosyl Pd<sup>+2</sup> complexes, in turn, serve as precursors to the synthesis of previously inaccessible Pd<sup>+2</sup>-carbonyl-olefin [Pd(CO)(C<sub>2</sub>H<sub>4</sub>)] and -nitrosyl-olefin [Pd(NO)(C<sub>2</sub>H<sub>4</sub>)] complexes. Overall, we show that zeolite framework can stabilize super electrophilic metal (Pd) cations, and show the new chemistry of Pd/SSZ-13 system with implications for adsorption and catalysis.<br></p>

scholarly journals A New Piano-Stool Ruthenium(II) P-Cymene-Based Complex: Crystallographic, Hirshfeld Surface, DFT, and Luminescent Studies

Crystals ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 13
Author(s):  
Mohd. Muddassir ◽  
Abdullah Alarifi ◽  
Mohd. Afzal
Keyword(s):  
Density Functional ◽  
Weak Interactions ◽  
Energy Levels ◽  
Hirshfeld Surface ◽  
Binding Energies ◽  
Orbital Energy ◽  
Aminosalicylic Acid ◽  
Full Characterization

A new complex (Ru(η6-p-cymene)(5-ASA)Cl2) (1) where 5-ASA is 5-aminosalicylic acid has been prepared by reacting the ruthenium arene precursors ((η6-arene)Ru(μ-Cl)Cl)2, with the 5-ASA ligands in a 1:1 ratio. Full characterization of complex 1 was accomplished by elemental analysis, IR, and TGA following the structure obtained from a single-crystal X-ray pattern. The structural analysis revealed that complex 1 shows a “piano-stool” geometry with Ru-C (2.160(5)- 2.208(5)Å), Ru-N (2.159(4) Å) distances, which is similar to equivalents sister complex. Density functional theory (DFT) was used to calculate the significant molecular orbital energy levels, binding energies, bond angles, bond lengths, and spectral data (FTIR, NMR, and UV–VIS) of complex 1, consistent with the experimental results. The IR and UV–VIS spectra of complex 1 were computed using all of the methods and choose the most appropriate way to discuss. Hirshfeld surface analysis was also executed to understand the role of weak interactions such as H⋯H, C⋯H, C-H⋯π, and vdW interactions, which play a significant role in the crystal environment’s stability. Moreover, the luminescence results at room temperature show that complex 1 gives a more intense emission band positioned at 465 nm upon excitation at 330 nm makes it a suitable candidate for the building of photoluminescent material.

scholarly journals Structural and computational investigation of an imine-based propeller-shaped macrocyclic cage

2021 ◽  
Vol 3 (2) ◽  
Author(s):  
Sriram Srinivasa Raghvan ◽  
Suresh Madhu ◽  
Velmurugan Devadasan ◽  
Gunasekaran Krishnasamy
Keyword(s):  
Band Gap ◽  
Density Functional ◽  
Strain Tensor ◽  
Strong Interactions ◽  
Soft Condensed Matter ◽  
Functional Theory ◽  
Self Assembling ◽  
Phenyl Rings ◽  
Crystal Volume

AbstractIn this study, we present the synthesis, spectroscopic and structural characterization of self-assembling gem-dimethyl imine based molecular cage (IMC). Self-assembling macrocycles and cages have well-defined cavities and have extensive functionalities ranging from energy storage, liquid crystals, and catalysts to water splitting photo absorber. IMC has large voids i.e., 25% of the total crystal volume thus could accommodate wide substrates. The synthesized imine-based molecular cages are stabilized by coaxial π bonded networks and long-range periodic van der Waal and non-bonded contacts as observed from the crystal structure. IMC also has typical properties of soft condensed matter materials, hence theoretical prediction of stress and strain tensor along with thermophysical properties were computed on crystal system and were found to be stable. Molecular dynamics revealed IMC is stabilized by, strong interactions between the interstitial phenyl rings. Density functional theory (DFT) based physicochemical properties were evaluated and has band gap of around 2.38ev (520 nm) similar to various photocatalytic band gap materials.

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