Impact of fluorination on the photophysics of the flavin chromophore: a quantum chemical perspective

2019 ◽  
Vol 21 (19) ◽  
pp. 9912-9923
Author(s):  
Mario Bracker ◽  
Fabian Dinkelbach ◽  
Oliver Weingart ◽  
Martin Kleinschmidt
Keyword(s):  
Aqueous Solution ◽  
Quantum Chemistry ◽  
Quantum Chemical ◽  
Fluorinated Derivatives

10-Methylisoalloxazine (MIA) and its fluorinated derivatives (6-9F-MIA) were investigated by means of quantum chemistry, looking into the influence of fluorination on fluorescence, absorption and inter-system crossing (ISC) in vacuum and in aqueous solution.

scholarly journals Quantum-Chemical Search for Keto Tautomers of Azulenols in Vacuo and Aqueous Solution

Symmetry ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 497
Author(s):  
Ewa D. Raczyńska
Keyword(s):  
Aqueous Solution ◽  
Quantum Chemical ◽  
Biologically Active ◽  
Deprotonation Reaction ◽  
Chemical Studies ◽  
Quantum Chemical Studies ◽  
Scanty Information ◽  
Derivatives Of ◽  
Common Anion ◽  
Tautomeric Mixture

Keto-enol prototropic conversions for carbonyl compounds and phenols have been extensively studied, and many interesting review articles and even books appeared in the last 50 years. Quite a different situation takes place for derivatives of biologically active azulene, for which only scanty information on this phenomenon can be found in the literature. In this work, quantum-chemical studies have been undertaken for symmetrically and unsymmetrically substituted azulenols (constitutional isomers of naphthols). Stabilities of two enol (OH) rotamers and all possible keto (CH) tautomers have been analyzed in the gas phase {DFT(B3LYP)/6-311+G(d,p)} and also in aqueous solution {PCM(water)//DFT(B3LYP)/6-311+G(d,p)}. Contrary to naphthols, for which the keto forms can be neglected, at least one keto isomer (C1H, C2H, and/or C3H) contributes significantly to the tautomeric mixture of each azulenol to a higher degree in vacuo (non-polar environment) than in water (polar amphoteric solvent). The highest amounts of the CH forms have been found for 2- and 5-hydroxyazulenes, and the smallest ones for 1- and 6-hydroxy derivatives. The keto tautomer(s), together with the enol rotamers, can also participate in deprotonation reaction leading to a common anion and influence its acid-base properties. The strongest acidity in vacuo exhibits 6-hydroxyazulene, and the weakest one displays 1-hydroxyazulene, but all azulenols are stronger acids than phenol and naphthols. Bond length alternation in all DFT-optimized structures has been measured using the harmonic oscillator model of electron delocalization (HOMED) index. Generally, the HOMED values decrease for the keto tautomers, particularly for the ring containing the labile proton. Even for the keto tautomers possessing energetic parameters close to those of the enol isomers, the HOMED indices are low. However, some kind of parallelism exists for the keto forms between their relative energies and HOMEDs estimated for the entire molecules.

Intermolecular Interactions of Pyridine in Liquid Phase and Aqueous Solution Studied by Soft X-ray Absorption Spectroscopy

2018 ◽  
Vol 232 (5-6) ◽  
pp. 705-722 ◽  
Author(s):  
Masanari Nagasaka ◽  
Hayato Yuzawa ◽  
Nobuhiro Kosugi
Keyword(s):  
Aqueous Solution ◽  
Quantum Chemical Calculations ◽  
Intermolecular Interactions ◽  
Absorption Spectroscopy ◽  
Quantum Chemical ◽  
Bulk Water ◽  
Pure Liquid ◽  
Rich Region ◽  
X Ray ◽  
X Ray Absorption

Abstract Intermolecular interactions of pyridine in liquid and in aqueous solution are studied by using soft X-ray absorption spectroscopy (XAS) at the C, N, and O K-edges. XAS of liquid pyridine shows that the N 1s→π* peak is blue shifted and the C 1s→π* peak of the meta and para sites is red shifted, respectively, as compared with XAS of pyridine gas. These shifts in liquid are smaller than those in clusters, indicating that the intermolecular interaction of liquid pyridine is weaker than that of pyridine cluster, as supported by the combination of quantum chemical calculations of the core excitation and molecular dynamics simulations of the liquid structure. On the other hand, XAS spectra of aqueous pyridine solutions (C5H5N)x(H2O)1−x measured at different molar fractions show that in the pyridine rich region, x>0.7, the C and N 1s→π* peak energies are not so different from pure liquid pyridine (x=1.0). In this region, antiparallel displaced structures of pyridine molecules are dominant as in pure pyridine liquid. In the O K-edge XAS, the pre-edge peaks sensitive to the hydrogen bond (HB) network of water molecules show the red shift of −0.15 eV from that of bulk water, indicating that small water clusters with no large-scale HB network are formed in the gap space of structured pyridine molecules. In the water rich region, 0.7>x, the N 1s→π* peaks and the O 1s pre-edge peaks are blue shifted, and the C 1s→π* peaks of the meta and para sites are red-shifted by increasing molar fraction of water. The HB network of bulk water is dominant, but quantum chemical calculations indicate that small pyridine clusters with the HB interaction between the H atom in water and the N atom in pyridine are still existent even in very dilute pyridine solutions.

Complexation of Cm(III) with Fluoride in Aqueous Solution in the Temperature Range from 20 to 90 °C. A Joint TRLFS and Quantum Chemical Study

2010 ◽  
Vol 114 (47) ◽  
pp. 15626-15634 ◽  
Author(s):  
Andrej Skerencak ◽  
Petra J. Panak ◽  
Volker Neck ◽  
Michael Trumm ◽  
Bernd Schimmelpfennig ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Quantum Chemical ◽  
Quantum Chemical Study ◽  
Chemical Study ◽  
Temperature Range

A Quantum-chemical Study of the Corrosion Inhibition of Iron by Means of Aniline Derivatives in Hydrochloric Acid

CORROSION ◽  
1976 ◽  
Vol 32 (5) ◽  
pp. 183-187 ◽  
Author(s):  
JAN VOSTA ◽  
JAROSLAV ELIASEK ◽  
PETR KNIZEK
Keyword(s):  
Hydrochloric Acid ◽  
Quantum Chemistry ◽  
Organic Compounds ◽  
Corrosion Inhibition ◽  
Quantum Chemical ◽  
Quantum Chemical Study ◽  
Electrochemical Corrosion ◽  
Chemical Study ◽  
Substituted Anilines ◽  
Inhibition Process

Abstract When various properties of organic compounds are to be expressed, it is necessary to explore the connection between their experiment and theory. To determine the mechanism of the inhibition process by organic materials, the electron structure of a set of organic compounds is studied and correlated with their electrochemical corrosion measurements. This paper discusses the inhibition of corrosion in 5% hydrochloric acid by means of p-substituted anilines with respect to quantum chemistry.

Sign in / Sign up

Export Citation Format

Share Document