The application of merocyanine photoacids has been previously largely limited to neutral and acid... more The application of merocyanine photoacids has been previously largely limited to neutral and acidic pH values. Here we introduce a new merocyanine photoacid with superior pH switching qualities. By increasing the pKa in the dark (pKadark) and the solubility we increased the reversible visible light induced pH jump to 3.5 units. Moreover, it is the first demonstration of a merocyanine photoacid able to generate a significant pH drop from a basic (pH 8.3) to an acidic (pH 5.2) environment.
Surprisingly small structural changes in Donor–Acceptor Stenhouse Adducts (DASAs) result in predi... more Surprisingly small structural changes in Donor–Acceptor Stenhouse Adducts (DASAs) result in predictable, robust and effective photochromic switches.
We have designed linear metalloligands which contain a central photoactive [Ru(NN)] unit bordered... more We have designed linear metalloligands which contain a central photoactive [Ru(NN)] unit bordered by peripheral metal binding sites. The combination of these metalloligands with Zn(II) and Fe(II) ions leads to heterometallic tetrahedral cages, which were studied by NMR spectroscopy, mass spectrometry, and photophysical methods. Like the parent metalloligands, the cages remain emissive in solution. This approach allows direct incorporation of the favorable properties of ruthenium(II) polypyridyl complexes into larger self-assembled structures.
We report photochromic donor–acceptor Stenhouse adducts (DASAs) capable of fully reversible photo... more We report photochromic donor–acceptor Stenhouse adducts (DASAs) capable of fully reversible photoisomerization with visible light in organic solvents including chloroform, acetonitrile and benzene.
Journal of the American Chemical Society, Jan 13, 2015
A molecular pentafoil knot and doubly and triply entwined [2]catenanes based on circular Fe(II) d... more A molecular pentafoil knot and doubly and triply entwined [2]catenanes based on circular Fe(II) double helicate scaffolds bind halide anions in their central cavities through electrostatic and CH···X(-) hydrogen-bonding interactions. The binding is up to (3.6 ± 0.2) × 10(10) M(-1) in acetonitrile (for pentafoil knot [2·Cl](PF6)9), making these topologically complex host molecules some of the strongest synthetic noncovalent binders of halide anions measured to date, comparable in chloride ion affinity to silver salts.
A photoswitchable ligand based on azobenzene is self-assembled with palladium(II) ions to form a ... more A photoswitchable ligand based on azobenzene is self-assembled with palladium(II) ions to form a [Pd2(E-L)4]4+ cage. Irradiation with 470 nm light results in the near quantitative switching to a monomeric species [Pd(Z-L)2]2+. The assembled structures improve the selectivity of photoswitching towards the metastable isomer and increase its thermal lifetime.
The measured changes in self-diffusion of small molecules during reactions have been attributed “... more The measured changes in self-diffusion of small molecules during reactions have been attributed “boosted mobility”. We demonstrate the critical role of changing concentrations of paramagnetic ions on nuclear magnetic resonance (NMR) signal intensities, which lead to erroneous measurements of diffusion coefficients. We present simple methods to overcome this problem. The use of shuffled gradient amplitudes allows accurate diffusion NMR measurements, even with time-dependent relaxation rates caused by changing concentrations of paramagnetic ions. The addition of a paramagnetic relaxation agent allows accurate determination of both diffusion coefficients and reaction kinetics during a single experiment. We analyze a copper-catalyzed azide-alkyne cycloaddition ‘click’ reaction, for which boosted mobility has been claimed. With our methods, we accurately measure the diffusive behavior of solvent, starting materials and product, and find no global increase in diffusion coefficients during...
A study reported in The Journal of Physical Chemistry Letters (12 (2021) 2370) of “boosted mobili... more A study reported in The Journal of Physical Chemistry Letters (12 (2021) 2370) of “boosted mobility” measured by diffusion NMR experiments contains significant errors in data analysis and interpretation. We carefully reanalyzed the same data and find no evidence of boosted mobility, and we identify several sources of error.
The apparent “boosted mobility” observed by nuclear magnetic resonance (NMR) diffusion measuremen... more The apparent “boosted mobility” observed by nuclear magnetic resonance (NMR) diffusion measurements is the result of a known artefact. When signal intensities are changing during an NMR diffusion measurement for reasons other than diffusion, the use of monotonically increasing gradient amplitudes produces erroneous diffusion coefficient values. We show that no boosted molecular mobility is observed when shuffled gradient amplitudes are applied.
Substitution-inert, redox- and photo-active ruthenium(ii) complexes based on 2,2′,6′,2′′-terpyrid... more Substitution-inert, redox- and photo-active ruthenium(ii) complexes based on 2,2′,6′,2′′-terpyridine ligands were self-assembled into discrete supramolecular cages via coordination to palladium(ii) centres and characterised by NMR, ESI-MS and X-ray crystallography.
The application of merocyanine photoacids has been previously largely limited to neutral and acid... more The application of merocyanine photoacids has been previously largely limited to neutral and acidic pH values. Here we introduce a new merocyanine photoacid with superior pH switching qualities. By increasing the pKa in the dark (pKadark) and the solubility we increased the reversible visible light induced pH jump to 3.5 units. Moreover, it is the first demonstration of a merocyanine photoacid able to generate a significant pH drop from a basic (pH 8.3) to an acidic (pH 5.2) environment.
Surprisingly small structural changes in Donor–Acceptor Stenhouse Adducts (DASAs) result in predi... more Surprisingly small structural changes in Donor–Acceptor Stenhouse Adducts (DASAs) result in predictable, robust and effective photochromic switches.
We have designed linear metalloligands which contain a central photoactive [Ru(NN)] unit bordered... more We have designed linear metalloligands which contain a central photoactive [Ru(NN)] unit bordered by peripheral metal binding sites. The combination of these metalloligands with Zn(II) and Fe(II) ions leads to heterometallic tetrahedral cages, which were studied by NMR spectroscopy, mass spectrometry, and photophysical methods. Like the parent metalloligands, the cages remain emissive in solution. This approach allows direct incorporation of the favorable properties of ruthenium(II) polypyridyl complexes into larger self-assembled structures.
We report photochromic donor–acceptor Stenhouse adducts (DASAs) capable of fully reversible photo... more We report photochromic donor–acceptor Stenhouse adducts (DASAs) capable of fully reversible photoisomerization with visible light in organic solvents including chloroform, acetonitrile and benzene.
Journal of the American Chemical Society, Jan 13, 2015
A molecular pentafoil knot and doubly and triply entwined [2]catenanes based on circular Fe(II) d... more A molecular pentafoil knot and doubly and triply entwined [2]catenanes based on circular Fe(II) double helicate scaffolds bind halide anions in their central cavities through electrostatic and CH···X(-) hydrogen-bonding interactions. The binding is up to (3.6 ± 0.2) × 10(10) M(-1) in acetonitrile (for pentafoil knot [2·Cl](PF6)9), making these topologically complex host molecules some of the strongest synthetic noncovalent binders of halide anions measured to date, comparable in chloride ion affinity to silver salts.
A photoswitchable ligand based on azobenzene is self-assembled with palladium(II) ions to form a ... more A photoswitchable ligand based on azobenzene is self-assembled with palladium(II) ions to form a [Pd2(E-L)4]4+ cage. Irradiation with 470 nm light results in the near quantitative switching to a monomeric species [Pd(Z-L)2]2+. The assembled structures improve the selectivity of photoswitching towards the metastable isomer and increase its thermal lifetime.
The measured changes in self-diffusion of small molecules during reactions have been attributed “... more The measured changes in self-diffusion of small molecules during reactions have been attributed “boosted mobility”. We demonstrate the critical role of changing concentrations of paramagnetic ions on nuclear magnetic resonance (NMR) signal intensities, which lead to erroneous measurements of diffusion coefficients. We present simple methods to overcome this problem. The use of shuffled gradient amplitudes allows accurate diffusion NMR measurements, even with time-dependent relaxation rates caused by changing concentrations of paramagnetic ions. The addition of a paramagnetic relaxation agent allows accurate determination of both diffusion coefficients and reaction kinetics during a single experiment. We analyze a copper-catalyzed azide-alkyne cycloaddition ‘click’ reaction, for which boosted mobility has been claimed. With our methods, we accurately measure the diffusive behavior of solvent, starting materials and product, and find no global increase in diffusion coefficients during...
A study reported in The Journal of Physical Chemistry Letters (12 (2021) 2370) of “boosted mobili... more A study reported in The Journal of Physical Chemistry Letters (12 (2021) 2370) of “boosted mobility” measured by diffusion NMR experiments contains significant errors in data analysis and interpretation. We carefully reanalyzed the same data and find no evidence of boosted mobility, and we identify several sources of error.
The apparent “boosted mobility” observed by nuclear magnetic resonance (NMR) diffusion measuremen... more The apparent “boosted mobility” observed by nuclear magnetic resonance (NMR) diffusion measurements is the result of a known artefact. When signal intensities are changing during an NMR diffusion measurement for reasons other than diffusion, the use of monotonically increasing gradient amplitudes produces erroneous diffusion coefficient values. We show that no boosted molecular mobility is observed when shuffled gradient amplitudes are applied.
Substitution-inert, redox- and photo-active ruthenium(ii) complexes based on 2,2′,6′,2′′-terpyrid... more Substitution-inert, redox- and photo-active ruthenium(ii) complexes based on 2,2′,6′,2′′-terpyridine ligands were self-assembled into discrete supramolecular cages via coordination to palladium(ii) centres and characterised by NMR, ESI-MS and X-ray crystallography.
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Papers by Jonathon Beves