Revealing the Hidden Costs of Organization in Host–Guest Chemistry Using Chloride-Binding Foldamers and Their Solvent Dependence

We have investigated the solvent-dependence of structural changes along with intersystem crossing of a thermally activated delayed fluorescence (TADF) molecule, 3,4,5-tri(9H-carbazole-9-yl)benzonitrile (o-3CzBN), in toluene, tetrahydrofuran, and acetonitrile solutions using time-resolved infrared (TR-IR) spectroscopy and DFT calculations. We found that the geometries of the S1 and T1 states are very similar in all solvents though the photophysical properties mostly depend on the solvent. In addition, the time-dependent DFT calculations based on these geometries suggested that the thermally activated delayed fluorescence process of o-3CzBN is governed more by the higher-lying excited states than by the structural changes in the excited states.

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Titration Simulations for Understanding of the Binding Equilibrium

10.26434/chemrxiv.12980348.v1 ◽

2020 ◽

Author(s):

Dae Hyup Sohn

Keyword(s):

Equilibrium Model ◽

Binding Sites ◽

Binding Constants ◽

Reliability Evaluation ◽

Binding Isotherm ◽

Guest Chemistry

The reliability evaluation of the predicted binding constants in numerous models is also a challenge for supramolecular host-guest chemistry. Here, I briefly formulate binding isotherm with the derivation of the multivalent equilibrium model for the chemist who wants to determine the binding constants of their compounds. This article gives an in-depth understanding of the stoichiometry of binding equilibrium to take divalent binding equilibria bearing two structurally identical binding sites as an example. The stoichiometry of binding equilibrium is affected by (1) the cooperativity of complex, (2) the concentration of titration media, and (3) the equivalents of guests. The simulations were conducted with simple Python codes.

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A New Interpretation of the Structure and Solvent Dependence of the Far UV Circular Dichroism Spectrum of Short Oligopeptides

10.26434/chemrxiv.8028134.v1 ◽

2019 ◽

Author(s):

Anshuman Kumar ◽

Reinhard Schweitzer-Stenner ◽

Bryan Wong

Keyword(s):

Density Functional ◽

Density Functional Theory Calculations ◽

Cd Spectra ◽

Functional Theory ◽

Polyproline Ii ◽

Solvent Dependence ◽

Explicit Consideration ◽

New Interpretation ◽

Implicit And Explicit ◽

Explicit Water

In this work, we carry out new time-dependent density functional theory calculations on the cationic tripeptide GAG in implicit and explicit water to determine the transitions that give rise to the observed CD signals of polyproline II and β-strand conformations. Our results reveal a plethora of electronic transitions that are governed by configurational interactions between multiple molecular orbital transitions of comparable energy. We also show that reproducing the CD spectra of polyproline II and β-strand conformations requires the explicit consideration of water molecules. The structure dependence of delocalized occupied orbitals contributes to the experimentally-observed invalidation of Flory’s isolated pair hypothesis.

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A New Interpretation of the Structure and Solvent Dependence of the Far UV Circular Dichroism Spectrum of Short Oligopeptides

10.26434/chemrxiv.8028134 ◽

2019 ◽

Author(s):

Anshuman Kumar ◽

Reinhard Schweitzer-Stenner ◽

Bryan Wong

Keyword(s):

Density Functional ◽

Density Functional Theory Calculations ◽

Cd Spectra ◽

Functional Theory ◽

Polyproline Ii ◽

Solvent Dependence ◽

Explicit Consideration ◽

New Interpretation ◽

Implicit And Explicit ◽

Explicit Water

In this work, we carry out new time-dependent density functional theory calculations on the cationic tripeptide GAG in implicit and explicit water to determine the transitions that give rise to the observed CD signals of polyproline II and β-strand conformations. Our results reveal a plethora of electronic transitions that are governed by configurational interactions between multiple molecular orbital transitions of comparable energy. We also show that reproducing the CD spectra of polyproline II and β-strand conformations requires the explicit consideration of water molecules. The structure dependence of delocalized occupied orbitals contributes to the experimentally-observed invalidation of Flory’s isolated pair hypothesis.

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Enantioselective Recognition of Chiral Guests by the Water-Soluble Chiral Keplerate {Mo132} Spherical Capsule with 30 Inner Lactate Ligands

10.26434/chemrxiv.8847923.v1 ◽

2019 ◽

Author(s):

Nancy Watfa ◽

Weimin Xuan ◽

Zoe Sinclair ◽

Robert Pow ◽

Yousef Abul-Haija ◽

...

Keyword(s):

Aqueous Solution ◽

Chiral Recognition ◽

Association Constants ◽

Water Soluble ◽

Enantioselective Recognition ◽

H Nmr ◽

Dosy Nmr ◽

Spherical Capsule ◽

Surface Pores ◽

Guest Chemistry

Investigations of chiral host guest chemistry are important to explore recognition in confined environments. Here, by synthesizing water-soluble chiral porous nanocapsule based on the inorganic metal-oxo Keplerate-type cluster, {Mo132} with chiral lactate ligands with the composition [Mo132O372(H2O)72(x-Lactate)30]42- (x = D or L), it was possible to study the interaction with a chiral guest, L/D-carnitine and (R/S)-2-butanol in aqueous solution. The enantioselective recognition was studied by quantitative 1H NMR and 1H DOSY NMR which highlighted that the chiral recognition is regulated by two distinct sites. Differences in the association constants (K) of L- and D-carnitine, which, due to their charge, are generally restricted from entering the interior of the host, are observed, indicating that their recognition predominantly occurs at the surface pores of the structure. Conversely, a larger difference in association constants (KS/KR = 3) is observed for recognition within the capsule interior of (R)- and (S)-2-butanol.

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