Thienyl-containing β-diketones: Synthesis, characterization, crystal structure and keto-enol kinetics

There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.

Abstract

1-phenyl-3-(2-thenoyl)-1,3-propanedione, Hbth, pKa' = 9.006(8) and 1,3-di(2-thenoyl)-1,3-propanedione, Hdtm, pKa' = 8.893(3) were prepared by the Claisen condensation of ethyl 2-thiophenecarboxylate with an appropriate ketone under the influence of lithium diisopropylamide (LDA). The group electronegativity of the thienyl group is 2.10 (Gordy scale) as calculated from a linear group electronegativity vs. methyl ester IR carbonyl stretching wavenumber relationship. A crystal structure determination of Hbth (orthorhombic, Pbca, Z = 8, R = 0.0290) shows asymmetrical enolization on the side of the phenyl group. The preferred enol isomer of β-diketones containing more than one aromatic moiety that crystallizes in the solid state is determined by the resonance driving force stabilization of the thienyl or any other aromatic group, rather than the stabilization by resonance due to the phenyl group. The slow conversion of the enol isomers to the keto-enol equilibrium position was followed in CDCl3 solution by NMR spectroscopy.

Related collections

Most cited references 65

Record: found
Abstract: found
Article: not found

Versatile Photocatalytic Systems for H2 Generation in Water Based on an Efficient DuBois-Type Nickel Catalyst

Manuela Groß, Anna Reynal, James R. Durrant … (2013)

The generation of renewable H2 through an efficient photochemical route requires photoinduced electron transfer (ET) from a light harvester to an efficient electrocatalyst in water. Here, we report on a molecular H2 evolution catalyst (NiP) with a DuBois-type [Ni(P2 R′N2 R″)2]2+ core (P2 R′N2 R″ = bis(1,5-R′-diphospha-3,7-R″-diazacyclooctane), which contains an outer coordination sphere with phosphonic acid groups. The latter functionality allows for good solubility in water and immobilization on metal oxide semiconductors. Electrochemical studies confirm that NiP is a highly active electrocatalyst in aqueous electrolyte solution (overpotential of approximately 200 mV at pH 4.5 with a Faradaic yield of 85 ± 4%). Photocatalytic experiments and investigations on the ET kinetics were carried out in combination with a phosphonated Ru(II) tris(bipyridine) dye (RuP) in homogeneous and heterogeneous environments. Time-resolved luminescence and transient absorption spectroscopy studies confirmed that directed ET from RuP to NiP occurs efficiently in all systems on the nano- to microsecond time scale, through three distinct routes: reductive quenching of RuP in solution or on the surface of ZrO2 (“on particle” system) or oxidative quenching of RuP when the compounds were immobilized on TiO2 (“through particle” system). Our studies show that NiP can be used in a purely aqueous solution and on a semiconductor surface with a high degree of versatility. A high TOF of 460 ± 60 h–1 with a TON of 723 ± 171 for photocatalytic H2 generation with a molecular Ni catalyst in water and a photon-to-H2 quantum yield of approximately 10% were achieved for the homogeneous system.

0 comments Cited 449 times – based on 0 reviews      Review now

Bookmark

Record: found
Abstract: found
Article: not found

Supramolecular Disassembly of Facially Amphiphilic Dendrimer Assemblies in Response to Physical, Chemical, and Biological Stimuli

Krishna R. Raghupathi, Jing Guo, Oyuntuya Munkhbat … (2014)

Conspectus Supramolecular assemblies formed from spontaneous self-assembly of amphiphilic macromolecules are explored as biomimetic architectures and for applications in areas such as sensing, drug delivery, and diagnostics. Macromolecular assemblies are usually preferred, compared with their simpler small molecule counterparts, due to their low critical aggregate concentrations (CAC) and high thermodynamic stability. This Account focuses on the structural and functional aspects of assemblies formed from dendrimers, specifically facially amphiphilic dendrons that form micelle or inverse micelle type supramolecular assemblies depending on the nature of the solvent medium. The micelle type assemblies formed from facially amphiphilic dendrons sequester hydrophobic guest molecules in their interiors. The stability of these assemblies is dependent on the relative compatibility of the hydrophilic and hydrophobic functionalities with water, often referred to as hydrophilic–lipophilic balance (HLB). Disruption of the HLB, using an external stimulus, could lead to disassembly of the aggregates, which can then be utilized to cause an actuation event, such as guest molecule release. Studying these possibilities has led to (i) a robust and general strategy for stimulus-induced disassembly and molecular release and (ii) the introduction of a new approach to protein-responsive supramolecular disassembly. The latter strategy provides a particularly novel avenue for impacting biomedical applications. Most of the stimuli-sensitive supramolecular assemblies have been designed to be responsive to factors such pH, temperature, and redox conditions. The reason for this interest stems from the fact that certain disease microenvironments have aberrations in these factors. However, these variations are the secondary imbalances in biology. Imbalances in protein activity are the primary reasons for most, if not all, human pathology. There have been no robust strategies in stimulus-responsive assemblies that respond to these variations. The facially amphiphilic dendrimers provide a unique opportunity to explore this possibility. Similarly, the propensity of these molecules to form inverse micelles in apolar solvents and thus bind polar guest molecules, combined with the fact that these assemblies do not thermodynamically equilibrate in biphasic mixtures, was used to predictably simplify peptide mixtures. The structure–property relationships developed from these studies have led to a selective and highly sensitive detection of peptides in complex mixtures. Selectivity in peptide extraction was achieved using charge complementarity between the peptides and the hydrophilic components present in inverse micellar interiors. These findings will have implications in areas such as proteomics and biomarker detection.

0 comments Cited 78 times – based on 0 reviews      Review now

Bookmark

Record: found
Abstract: found
Article: not found

Three-dimensional aromaticity in polyhedral boranes and related molecules.

Daniel R King (2001)

Chemical bonding models based on graph theory or tensor surface harmonic theory demonstrate the analogy between the aromaticity in two-dimensional planar polygonal hydrocarbons such as benzene and that in three-dimensional deltahedral borane anions of the type BnHn2- (6 < or = n < or = 12). Such models are supported both by diverse computational studies and experimental determinations of electron density distribution. Related methods can be used to study the chemical bonding in the boron polyhedra found in other structures including neutral binary boron hydrides, metallaboranes, various allotropes of elemental boron, and boron-rich solid-state metal borides.

0 comments Cited 66 times – based on 0 reviews      Review now

Bookmark

All references

Author and article information

Contributors

Marrigje M. Conradie: Role: ND

Alfred J. Muller: Role: ND

Jeanet Conradie: Role: ND

Journal

Journal ID (publisher): sajc

Title: South African Journal of Chemistry

Abbreviated Title: S.Afr.j.chem. (Online)

Publisher: The South African Chemical Institute (Durban )

ISSN: 1996-840X

Publication date (Print): 2008

Volume: 61

Issue: 0

Pages: 13-21

Affiliations

[1 ] University of the Free State South Africa

Article

Publisher ID: S0379-43502008000100004

SO-VID: 62f5bbe4-bf2a-48a9-9429-7d8b10a9e3d9

License:

http://creativecommons.org/licenses/by/4.0/

History

Product

SciELO South Africa

Self URI (journal page): http://www.scielo.org.za/scielo.php?script=sci_serial&pid=0379-4350&lng=en

Thienyl-containing β-diketones: Synthesis, characterization, crystal structure and keto-enol kinetics

Read this article at

Abstract

Related collections

SciELO South Africa

Most cited references 65

Versatile Photocatalytic Systems for H2 Generation in Water Based on an Efficient DuBois-Type Nickel Catalyst

Supramolecular Disassembly of Facially Amphiphilic Dendrimer Assemblies in Response to Physical, Chemical, and Biological Stimuli

Three-dimensional aromaticity in polyhedral boranes and related molecules.

Author and article information

Contributors

Journal

Affiliations

Article

History

Product

Categories

Comments

Comment on this article

Similar content 126

Cited by 2

Most referenced authors 167