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1.
Macromol Rapid Commun ; 44(20): e2300177, 2023 Oct.
Article in English | MEDLINE | ID: mdl-37461210

ABSTRACT

This study investigates the effect of the macromolecular architecture of poly(vinylidene fluoride) (PVDF) on its thermally induced phase separation (TIPS) behavior and polymorphic crystallization in the PVDF/γ-butyrolactone (PVDF/γ-BL) system. Preparative PVDF fractions with specific macromolecular architecture and phase constitution are generated. The results show that PVDF's macromolecular architecture, particularly the degree of branching and regio-defects, plays a significant role in its temperature-dependent crystallization and resulting polymorphic phases. While regio-defects dominate crystallization in the temperature range between 30 and 25 °C, the degree of branching becomes decisive in the 25-20 °C interval. The developed fractions of PVDF are further analyzed in terms of their molecular weight distribution, revealing that the PVDF fractions crystallized out of solution have similar molecular weight distributions with lower dispersity compared with the feed polymer. These findings are crucial for macromolecular separation and adjustment of PVDF polymorphic properties and hence for the development of tailor-made PVDF matrix materials for composites and membranes. The findings suggest the possibility of polymorphous phase tailoring of PVDF based on macromolecular architecture due to temperature-controlled crystallization out of solution and strongly motivate further research to reveal deeper knowledge of regio-defect and branching influence of PVDF solution crystallization.


Subject(s)
4-Butyrolactone , Polyvinyls , Crystallization/methods , Polyvinyls/chemistry , Macromolecular Substances/chemistry
2.
Chirality ; 35(12): 993-1011, 2023 Dec.
Article in English | MEDLINE | ID: mdl-37497749

ABSTRACT

New sulfonate-based chiral salts were prepared from amino alcohols and sodium hydroxymethanesulfonate, vinyl sulfonate, or sultone. The synthesis started with different amino acids from the chiral pool and gave the desired products in just four steps. After cation metathesis, the salts were explored as chiral solvating agents (CSAs) in NMR studies. The new chiral ionic liquids (CILs) were successfully able to interact with different chiral guest molecules and formed diastereomeric aggregates. In some cases, baseline separation was observed. The influence of the structural differences in the CIL as well as the structural requirements of the guest molecule is discussed.

3.
Chemistry ; 29(22): e202203541, 2023 Apr 18.
Article in English | MEDLINE | ID: mdl-36700523

ABSTRACT

A series of new organic donor-π-acceptor dyes incorporating a diquat moiety as a novel electron-acceptor unit have been synthesized and characterized. The analytical data were supported by DFT calculations. These dyes were explored in the aerobic thiocyanation of indoles and pyrroles. Here they showed a high photocatalytic activity under visible light, giving isolated yields of up to 97 %. In addition, the photocatalytic activity of standalone diquat and methyl viologen through formation of an electron donor acceptor complex is presented.

4.
RSC Adv ; 12(45): 29562-29568, 2022 Oct 11.
Article in English | MEDLINE | ID: mdl-36320758

ABSTRACT

In the present work experiments for single mineral flotation against LiAlO2 and melilite s.s. were carried out for seven ionic liquids (ILs). From these, IL-1 with an imidazolium cation and a bromide anion and IL-7 with a pyridinium cation and a bromide anion were selected for further flotation experiments (dosage, pH). Flotation experiments were also conducted using naphthenic acid, a conventional flotation fatty acid-based collector, and FS-2, a commercial collector in order to compare the results with ILs. Moreover, the effects of different anions in the ILs on the flotation were evaluated and a significant influence on the hardness of anions was found on the flotation process. Finally, a pre-functionalization was also explored with modified cholesterol derivatives, comparing the effect of cholesterylsulfate and cholesterylphosphate on the flotation of LiAlO2 and melilite s.s. This study is vital for the further optimization of lithium recovery from the pyrometallurgical recycling path of lithium-ion batteries and the flotation of primary minerals such as aluminosilicates.

5.
Molecules ; 27(15)2022 Jul 29.
Article in English | MEDLINE | ID: mdl-35956825

ABSTRACT

A Knoevenagel based redox-reaction promoted by intramolecular phosphine sources is presented for the first time. The influence of different diketones, aldehydes, bases and acids was investigated. The effects of different substituents were evaluated based on their electronical influence on the diketone structure. With the obtained results a mechanism is proposed, giving information about transition states formed during the reaction, which can lead to different products. This type of an internal redox transformation with a phosphine oxide moiety remaining in the molecule after the redox reaction represents a new type of reaction.


Subject(s)
Phosphines , Catalysis , Ketones/chemistry , Oxidation-Reduction , Phosphines/chemistry , Stereoisomerism
6.
RSC Adv ; 12(27): 17249-17256, 2022 Jun 07.
Article in English | MEDLINE | ID: mdl-35765460

ABSTRACT

Furfuryl amine-functionalized few-layered graphene was prepared via a mechanochemical process by a [4 + 2] cycloaddition under solvent-free conditions. By employing ball milling, active sites are merged mostly at the edge of the graphene sheets which makes them prone to Diels-Alder click reactions (D-A) in the presence of a diene precursor. Consequently, one-pot grafting with furfuryl amine onto the graphene sheets, exfoliates pristine graphite resulting in functionalized few-layered graphene which is soluble in organic solvents. Thereafter, the cleavage of the bonds in the adduct can occur by exposure to an external stimulus like temperature, to initiate a retro-Diels-Alder reaction. The success of the thermoreversible functionalization of the few-layered graphene was confirmed by Raman spectroscopy, TGA, XPS, EDX, contact angle and XRD analysis. The morphology of the samples was investigated by scanning electron microscopy and AFM. The latter was utilized to estimate graphene thickness. The results showed that functionalization proceeded under nitrogen with dry ball milling and mild temperatures efficiently.

7.
Sci Rep ; 11(1): 20443, 2021 Oct 14.
Article in English | MEDLINE | ID: mdl-34650090

ABSTRACT

In this work froth flotation studies with LiAlO2 (lithium-containing phase) and Melilite solid solution (gangue phase) are presented. The system was optimized with standard collectors and with compounds so far not applied as collectors. Furthermore, the principle of self-assembled monolayers was introduced to a froth flotation process for the first time resulting in excellent yields and selectivities.

8.
J Comput Chem ; 41(21): 1921-1930, 2020 Aug 05.
Article in English | MEDLINE | ID: mdl-32542776

ABSTRACT

Density-functional theory calculations of (TiO2 )n clusters (n = 1-5) in the gas phase and adsorbed on pristine graphene as well as graphene quantum dots are presented. The cluster adsorption is found to be dominated by van der Waals forces. The electronic structure and in particular the excitation energies of the bare clusters and the TiO2 /graphene composites are found to vary largely in dependence on the size of the respective constituents. This holds in particular for the energy and the spatial localization of the highest occupied and lowest unoccupied molecular orbitals. In addition to a substantial gap narrowing, a pronounced separation of photoexcited electrons and holes is predicted in some instances. This is expected to prolong the lifetime of photoexcited carriers. Altogether, TiO2 /graphene composites are predicted to be promising photocatalysts with improved electronic and photocatalytic properties compared to bulk TiO2 .

9.
RSC Adv ; 10(70): 42930-42937, 2020 Nov 23.
Article in English | MEDLINE | ID: mdl-35514879

ABSTRACT

The attachment of homoleptic Ru bis-terpy complexes on graphene oxide significantly improved the photocatalytic activity of the complexes. These straightforward complexes were applied as photocatalysts in a Heck reaction. Due to covalent functionalization on graphene oxide, which functions as an electron reservoir, excellent yields were obtained. DFT investigations of the charge redistribution revealed efficient hole transfer from the excited Ru unit towards the graphene oxide.

10.
Nanomaterials (Basel) ; 9(2)2019 Feb 12.
Article in English | MEDLINE | ID: mdl-30759838

ABSTRACT

The combined benefits of moisture-stable phosphonic acids and mesoporous silica materials (SBA-15 and MCM-41) as large-surface-area solid supports offer new opportunities for several applications, such as catalysis or drug delivery. We present a comprehensive study of a straightforward synthesis method via direct immobilization of several phosphonic acids and phosphoric acid esters on various mesoporous silicas in a Dean⁻Stark apparatus with toluene as the solvent. Due to the utilization of azeotropic distillation, there was no need to dry phosphonic acids, phosphoric acid esters, solvents, or silicas prior to synthesis. In addition to modeling phosphonic acids, immobilization of the important biomolecule adenosine monophosphate (AMP) on the porous supports was also investigated. Due to the high surface area of the mesoporous silicas, a possible catalytic application based on immobilization of an organocatalyst for an asymmetric aldol reaction is discussed.

11.
Appl Opt ; 57(31): 9215-9222, 2018 Nov 01.
Article in English | MEDLINE | ID: mdl-30461960

ABSTRACT

In principle, ionic liquids (ILs) can serve as stable and less harmful high-refractive-index liquids (n>1.60). However, detailed information on their complex refractive indices and dispersions is rare. Therefore, we determined the optical constants of six commercially available low-index ILs (n ca. 1.4) and two high-index ILs (n max. 2.38) synthesized by us utilizing spectroscopic ellipsometry. Furthermore, we tested the ILs as immersion liquids for different photonic crystals. Analysis of the optical properties of these photonic crystals after infiltration demonstrates potential applications of ILs in optofluidics and as index-matching liquids.

12.
Sci Rep ; 8(1): 5843, 2018 Apr 11.
Article in English | MEDLINE | ID: mdl-29643400

ABSTRACT

Dodecyl amine edge functionalized few-layer graphene oxide quantum dots were synthesized in good yields. The covalent functionalization was demonstrated with NMR and AFM-IR. The resulting structure and particle size was measured with AFM and HRTEM. The thermal stability of the compound was investigated and showed a stability of up to 220 °C. The modified graphene oxide quantum dots showed excellent solubility in various organic solvents, including ethers, methanol, toluene, n-hexane, heptane, xylene, dichloromethane and toluene. The stability of a resulting toluene solution was also proven by static light scattering measurements over several days. The excellent solubility gives the possibility of an efficient and fast spray application of the functionalized graphene oxide quantum dots to steel surfaces. Hence, the macroscopic friction behavior was investigated with a Thwing-Albert FP-2250 friction tester. A thin film of the dodecyl amine functionalized graphene oxide quantum dots on steel lowered the friction coefficient from 0.17 to 0.11 and revealed a significant corrosion inhibition effect.

13.
Int J Mol Sci ; 17(6)2016 Jun 01.
Article in English | MEDLINE | ID: mdl-27258264

ABSTRACT

A three-component oxidative dehydrogenation tandem reaction via the coupling and hydroarylation of benzaldehyde, aniline and phenylacetylene to a quinoline derivate was catalyzed by an iron-containing ionic liquid. The reaction was air mediated and could be performed under neat conditions. The iron(III) of the ionic liquid was the oxidizing species.


Subject(s)
Ionic Liquids/chemistry , Iron/chemistry , Oxidation-Reduction , Catalysis
14.
Acta Crystallogr E Crystallogr Commun ; 71(Pt 10): m177-8, 2015 Oct 01.
Article in English | MEDLINE | ID: mdl-26594424

ABSTRACT

In the unit cell of the title compound, (C21H27N2)3[CoBr4]Br·6CHCl3, the tetrabromidocobaltate(II) anion and the bromide anion are located on a crystallographic threefold rotation axis. For the [CoBr4](2-) group, the axis runs through one of the Br ligands and the Co(II) atom. All other structure moieties lie on general sites. Various tris-(1,3-dimesityl-4,5-di-hydro-1H-imidazol-3-ium) structures with different counter-ions have been reported. In the title compound, the N-C-N angle is 113.7 (5)°, with short C-N bond lengths of 1.297 (7) and 1.307 (7) Å. The two mesityl planes make a dihedral angle of 34.6 (1)° and the dihedral angles between the mesityl and N-C-N planes are 82.0 (1) and 88.5 (1)°, respectively. The imidazoline ring is almost planar, with atom deviations in the range 0.003 (5)-0.017 (5) Šfrom the best plane; the mean deviation is 0.012 (5) Å. In the crystal, non-covalent inter-actions of the C-H⋯Br type occur between the Br(-) anion and the cation, as well as between the [CoBr4](2-) anion and both the chloro-form solvent mol-ecules. These H⋯A distances are slightly shorter than the sum of van der Waals radii.

15.
Acta Crystallogr E Crystallogr Commun ; 71(Pt 8): 919-22, 2015 Aug 01.
Article in English | MEDLINE | ID: mdl-26396755

ABSTRACT

The mol-ecular structures of the chiral title compounds, [Pd(C19H28N2)2I2], (I), and [Pd(C19H28N2)Cl2(C18H15P)], (II), show a distorted square-planar coordination around the Pd(II) atoms with two halogenide (Hal) ligands each and two N-heterocyclic carbene (NHC) ligands in (I) or one NHC and one tri-phenyl-phosphane ligand in (II). The deviations of the Pd(II) atoms from the L 2Hal2 best plane (L = NHC or tri-phenyl-phosphane ligand) are 0.206 (1) Šfor (I) and 0.052 (1) Šfor (II). The crystal packings exhibit inter-molecular C-H⋯Hal hydrogen bonds.

16.
Acta Crystallogr E Crystallogr Commun ; 71(Pt 9): m160-1, 2015 Sep 01.
Article in English | MEDLINE | ID: mdl-26396865

ABSTRACT

The unit cell of the title complex, [CoBr2(C18H20N2O)2], contains 1.5 formula units per asymmetric unit with one mol-ecule sitting on a general site and a second one halved by a crystallographic twofold rotation axis passing through the Co(II) cation. Both Co(II) atoms are coordinated in a distorted tetra-hedral manner by two Br(-) ligands and two O atoms of the pyrimidinone (OPyr) groups. The Br-Co-Br coordination angles are similar [115.46 (4) and 115.20 (5)°], while the O-Co-O angles differ slightly more [102.26 (18) and 98.1 (2)°]. Similarly, the Co-Br bond lengths are almost identical [2.3721 (9), 2.3757 (10) and 2.3809 (10) Å], with a larger difference between the Co-O bond lengths [1.929 (4), 1.926 (4) and 1.955 (4) Å]. The three independent OPyr groups present envelope conformations, with three C and two N atoms lying in well defined planes with maximum deviations from the least-squares planes of 0.047, 0.031 and 0.036 Å, and the external-most C atoms protruding by 0.654 (6), 0.643 (7) and 0.656 (6) Šout of the planes. The dihedral angles between the planar fractions of the OPyr planes are 50.5 (1)° for the nonsymmetric mol-ecule and 49.7 (1)° for the symmetric one. Non-covalent inter-actions are of the C-H⋯Br type and they are weak, hardly shorter than van der Waals radii, with an H⋯Br distance range of 3.00-3.04 Å. The inter-molecular inter-actions define chains parallel to [101].

17.
Beilstein J Org Chem ; 8: 1798-803, 2012.
Article in English | MEDLINE | ID: mdl-23209514

ABSTRACT

The application of imidazolinium and amidinium salts as soft Lewis acid organocatalysts is described. These salts were suitable catalysts for the activation of unsaturated thioesters in a Diels-Alder reaction and in the ring opening of thiiranes and epoxides. The products were isolated in good yields. The mild catalysts did not cause desulfurization of the products containing a thiol or thiocarbonyl group.

18.
Top Curr Chem ; 291: 349-93, 2010.
Article in English | MEDLINE | ID: mdl-21494948

ABSTRACT

Abstract The term Lewis acid catalysts generally refers to metal salts like aluminium chloride, titanium chloride and zinc chloride. Their application in asymmetric catalysis can be achieved by the addition of enantiopure ligands to these salts. However, not only metal centers can function as Lewis acids. Compounds containing carbenium, silyl or phosphonium cations display Lewis acid catalytic activity. In addition, hypervalent compounds based on phosphorus and silicon, inherit Lewis acidity. Furthermore, ionic liquids, organic salts with a melting point below 100 degrees C, have revealed the ability to catalyze a range of reactions either in substoichiometric amount or, if used as the reaction medium, in stoichiometric or even larger quantities. The ionic liquids can often be efficiently recovered. The catalytic activity of the ionic liquid is explained by the Lewis acidic nature of their cations. This review covers the survey of known classes of metal-free Lewis acids and their application in catalysis.


Subject(s)
Aldehydes/chemistry , Ionic Liquids/chemistry , Ketones/chemistry , Lewis Acids/chemistry , Organophosphorus Compounds/chemistry , Organosilicon Compounds/chemistry , Catalysis , Molecular Structure
19.
Chem Commun (Camb) ; (39): 5910-2, 2009 Oct 21.
Article in English | MEDLINE | ID: mdl-19787138

ABSTRACT

A new class of enantiopure carbene precursors based on cheap camphor has been developed, and a restricted rotation of one N-substituent due to the C-10 methyl group of the camphor skeleton has been found; in situ prepared corresponding carbenes revealed the same behaviour.

20.
Org Biomol Chem ; 7(19): 4009-16, 2009 Oct 07.
Article in English | MEDLINE | ID: mdl-19763304

ABSTRACT

KHMDS and KOtBu are well established as strong, hindered, non-nucleophilic Brønsted bases. However, in the present work these bases are applied as highly active Lewis base catalysts for the formal [2+2] cycloaddition of ketenes with aldehydes and imines.

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