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- Hammond, Oliver S., et al.
(författare)
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Molecular Architecture Effects on Bulk Nanostructure in Bis(Orthoborate) Ionic Liquids
- 2023
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Ingår i: Small. - : John Wiley and Sons Inc. - 1613-6810 .- 1613-6829. ; 29
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Tidskriftsartikel (refereegranskat)abstract
- A series of 19 ionic liquids (ILs) based on phosphonium and imidazolium cations of varying alkyl-chain lengths with the orthoborate anions bis(oxalato)borate [BOB]−, bis(mandelato)borate, [BMB]− and bis(salicylato)borate, [BScB]−, are synthesized and studied using small-angle neutron scattering (SANS). All measured systems display nanostructuring, with 1-methyl-3-n-alkyl imidazolium-orthoborates forming clearly bicontinuous L3 spongelike phases when the alkyl chains are longer than C6 (hexyl). L3 phases are fitted using the Teubner and Strey model, and diffusely-nanostructured systems are primarily fitted using the Ornstein-Zernicke correlation length model. Strongly-nanostructured systems have a strong dependence on the cation, with molecular architecture variation explored to determine the driving forces for self-assembly. The ability to form well-defined complex phases is effectively extinguished in several ways: methylation of the most acidic imidazolium ring proton, replacing the imidazolium 3-methyl group with a longer hydrocarbon chain, substitution of [BOB]− by [BMB]−, or exchanging the imidazolium for phosphonium systems, irrespective of phosphonium architecture. The results suggest there is only a small window of opportunity, in terms of molecular amphiphilicity and cation:anion volume matching, for the formation of stable extensive bicontinuous domains in pure bulk orthoborate-based ILs. Particularly important for self-assembly processes appear to be the ability to form H-bonding networks, which offer additional versatility in imidazolium systems. © 2023 The Authors.
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| 4. |
- Verma, Priya, et al.
(författare)
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Insights into structural, spectroscopic, and hydrogen bonding interaction patterns of nicotinamide-oxalic acid (form I) salt by using experimental and theoretical approaches
- 2023
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Ingår i: Frontiers in Chemistry. - 2296-2646. ; 11
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Tidskriftsartikel (refereegranskat)abstract
- In the present work, nicotinamide-oxalic acid (NIC-OXA, form I) salt was crystallized by slow evaporation of an aqueous solution. To understand the molecular structure and spectroscopic properties of NIC after co-crystallization with OXA, experimental infrared (IR), Raman spectroscopic signatures, X-ray powder diffraction (XRPD), and differential scanning calorimetry (DSC) techniques were used to characterize and validate the salt. The density functional theory (DFT) methodology was adopted to perform all theoretical calculations by using the B3LYP/6-311++G (d, p) functional/basis set. The experimental geometrical parameters were matched in good correlation with the theoretical parameters of the dimer than the monomer, due to the fact of covering the nearest hydrogen bonding interactions present in the crystal structure of the salt. The IR and Raman spectra of the dimer showed the red (downward) shifting and broadening of bands among (N15-H16), (N38-H39), and (C13=O14) bonds of NIC and (C26=O24), (C3=O1), and (C26=O25) groups of OXA, hence involved in the formation of NIC-OXA salt. The atoms in molecules (AIM) analysis revealed that (N8-H9...O24) is the strongest (conventional) intermolecular hydrogen bonding interaction in the dimer model of salt with the maximum value of interaction energy -12.1 kcal mol(-1). Furthermore, the natural bond orbital (NBO) analysis of the Fock matrix showed that in the dimer model, the (N8-H9...O24) bond is responsible for the stabilization of the salt with an energy value of 13.44 kcal mol(-1). The frontier molecular orbitals (FMOs) analysis showed that NIC-OXA (form I) salt is more reactive and less stable than NIC, as the energy gap of NIC-OXA (form I) salt is less than that of NIC. The global and local reactivity descriptor parameters were calculated for the monomer and dimer models of the salt. The electrophilic, nucleophilic, and neutral reactive sites of NIC, OXA, monomer, and dimer models of salt were visualized by plotting the molecular electrostatic potential (MESP) surface. The study provides valuable insights into combining both experimental and theoretical results that could define the physicochemical properties of molecules.
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| 5. |
- Verma, Priya, et al.
(författare)
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Molecular Structure, Hydrogen Bonding Interactions and Docking Simulations of Nicotinamide (Monomeric and Trimeric Models) by Using Spectroscopy and Theoretical Approach
- 2023
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Ingår i: Polycyclic aromatic compounds (Print). - 1040-6638 .- 1563-5333.
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Tidskriftsartikel (refereegranskat)abstract
- The present work focuses on the structural properties, spectroscopic signatures, intermolecular hydrogen bonding interactions, chemical and biological activity of nicotinamide (NIC) based on its monomeric and trimeric models using density functional theory and vibrational spectroscopy. FT-IR and FT-Raman spectra were obtained using the double-side forward-backward acquisition mode under vacuum. UV-Vis absorption spectra were recorded in methanol and compared with the calculated values. Geometry optimization and vibrational wavenumbers were obtained with the aid of Gaussian 09 program packages. The structural analysis of NIC revealed that the trimeric model was in better agreement with the experimental values than the monomer due to the incorporation of nearest hydrogen bond interactions. Spectroscopic results showed that NH2 and C = O groups of NIC were involved in intermolecular interactions in the trimeric model. The natural bond orbital (NBO) and quantum theory of atoms in molecules (QTAIM) analyses determined the presence, strength as well as nature of the hydrogen bonds were partially covalent. The lesser value of the HOMO-LUMO energy gap for the trimeric model indicated higher reactivity than monomer. Moreover, chemical reactivity was calculated using molecular electrostatic potential surface (MESP) and reactivity descriptors. The docking studies for NIC with several targets explored its biological activity.
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