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Hopffgarten, Anna von

doi:10.1007/978-3-662-62492-0_4

Cited by 2 publications

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“…57 Molecular level insights into the local chemical environment was evaluated using the molecular quantum chemistry calculations. Energy Decomposition Analysis (EDA) 58 were performed by Amsterdam Density Functional (ADF) program 59 at B3LYP/TZ2P/ZORA level of theory. To account the middle range dispersion interaction energy, Grimme's dispersion correction was employed.…”

Section: Computational Detailsmentioning

confidence: 99%

Crystals of Organic Acid-Bases Complexes Defy the pKa Rule Under Compression

Das,

Pratik,

Datta

2024

Preprint

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Crystals of organic acid-base adducts are major components in the active pharmaceutical ingredients (API). These 1:1 adducts either form a co-crystal with a hydrogen-bonded motif or a salt by transfer of proton from the acid to the base. As a rule of thumb if the difference in pKa between the protonated base and the acid (ΔpKa) is ≤ 1, a co-crystal is expected while ΔpKa > 3 leads to a salt. The preferred crystalline form for 1:1 adducts of pyridine, pyridazine, pyrazine and furan with formic acid are elucidated using genetic algorithm assisted first-principles crystal structure predictions (CSP). In agreement with the ΔpKa rule, all the adducts stabilize as H-bonded co-crystals under ambient pressure. However, under isotropic pressure formic acid transfers the protons to the three nitrogenous bases forming salts of pyridinium formate, pyridazinium formate and pyrazinium formate. External pressure is found to dictate the co-crystal – salt equilibrium. The critical pressure (Pc) required to induce co-crystal → salt conversion for formic acid… pyridine/pyridazine/pyrazine is 3 GPa, 5 GPa and 15 GPa respectively. Compression is shown to enhance the electrostatic interactions between the molecules leading to additional stabilization of the ionic configurations namely, N+-H…O- in salts vis-à-vis the neutral N-H…O motifs in the co-crystals. Violating the ΔpKa rule, Pc overcomes the free-energy required for the proton-transfer (ΔGPT) to stabilize the salts. The very high ΔGPT = 177.9 kcal/mol for the furan…formic acid adduct prevents salt formation even at 30 GPa. Apart from the thermodynamic and kinetic control during crystallization, pressure acts as a key control for organic acid-base adducts.

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Section: Computational Detailsmentioning

confidence: 99%

Crystals of Organic Acid-Bases Complexes Defy the pKa Rule Under Compression

Das,

Pratik,

Datta

2024

Preprint

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“…Values similar to 2 were found for the M = Ru and Fe relatives, i.e., -96.0 and -91.7 kcal.mol -1 , respectively. The origin of the difference in interaction energy ΔEint between the homonuclear Au cluter and its heteronuclear congeners can be interpreted within the Energy Decomposition Analysis (EDA) framework given by Ziegler and Rauk,[106][107][108] according to: ΔEint = ΔEPauli + ΔEelstat + ΔEorb + ΔEdisp leading to different chemically meaningful quantities accounting for the destabilizing character of the interaction given by the repulsion between occupied orbitals (∆EPauli),…”

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confidence: 99%

On Heteronuclear Isoelectronic Alternatives to [Au₁₃(dppe)₅Cl₂]³⁺: Electronic and Optical Properties of the 18-Electron Os@[Au₁₂(dppe)₅Cl₂] Cluster from Relativistic Density Functional Theory Computations

et al. 2021

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The development of well-defined atomically precise heteronuclear nanoclusters passivated by protecting ligands is presently a booming area, owing to the fact that doping well-known homonuclear nanostructures allows fine-tuning of their properties. Here, we explore by means of density functional theory calculations the possibility of doping the central gold atom in the classical [Au13(dppe)5Cl2]3+cluster (1) by Os. Although both [Au13(dppe)5Cl2]3+ and [Os@Au12(dppe)5Cl2] have the same total number of electrons, we show that they are not isoelectronic within the formalism of the superatom model, being respectively an 8- and an 18-electron species. It results that they exhibit similar structures but present significantly different optical behaviors (ultraviolet/visible and circular dichroism). Similar results are obtained for the Ru and Fe relatives. Emission properties indicate some redshift of the T1→S1 decay with respect to [Au13(dppe)5Cl2]3+, involving an equatorial distortion of the Au12Cl2 core in the T1 state, rather than the axial distortion afforded by 1. The sizable highest occupied molecular orbital–lowest unoccupied molecular orbital gaps found for the three doped species suggest that further experimental exploration of different stable doped species derived from the ligand-protected Au12Cl2 core should be encouraged.

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Maschinen das Träumen lehren

Cited by 2 publications

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Crystals of Organic Acid-Bases Complexes Defy the pKa Rule Under Compression

Crystals of Organic Acid-Bases Complexes Defy the pKa Rule Under Compression

On Heteronuclear Isoelectronic Alternatives to [Au₁₃(dppe)₅Cl₂]³⁺: Electronic and Optical Properties of the 18-Electron Os@[Au₁₂(dppe)₅Cl₂] Cluster from Relativistic Density Functional Theory Computations

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Maschinen das Träumen lehren

Cited by 2 publications

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Crystals of Organic Acid-Bases Complexes Defy the pKa Rule Under Compression

Crystals of Organic Acid-Bases Complexes Defy the pKa Rule Under Compression

On Heteronuclear Isoelectronic Alternatives to [Au13(dppe)5Cl2]3+: Electronic and Optical Properties of the 18-Electron Os@[Au12(dppe)5Cl2] Cluster from Relativistic Density Functional Theory Computations

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On Heteronuclear Isoelectronic Alternatives to [Au₁₃(dppe)₅Cl₂]³⁺: Electronic and Optical Properties of the 18-Electron Os@[Au₁₂(dppe)₅Cl₂] Cluster from Relativistic Density Functional Theory Computations