Hyoung-Ryun Park

Physicochemical properties of quinolone antibiotics in various environments

The progress and photosensitivity of quinolone antibiotics are briefly described. By the photolysis of nalidixic acid, the loss of -COOH group is observed. The photoreaction of fluoroquinolones involves heterolytic C-F bond fragmentation. The protonation and divalent cation complexation equilibria are also examined. The spectroscopic properties of these drugs are intensively investigated in biological mimetic systems such as AOT reverse micelle, and H(2)O-CH(3)OH and H(2)O-CH(3)CN mixed solvents. For ofloxacin and norfloxacin, the excited-state intramolecular charge transfer (ICT) is observed. So, fluorescence spectra exhibit reverse solvatochromism in mixed solvents. The change of radiative and non-radiative rate constant can also be explained using this ICT. The influence of dielectric effects of solvent is more significant compared with the specific hydrogen bonding interaction. Theoretical treatments support all of these results.

Spectroscopic Properties of Fluoroquinolone Antibiotics in Water–methanol and Water–acetonitrile Mixed Solvents¶

Abstract The fluorescence properties of ofloxacin (OFL), norfloxacin (NOR) and flumequine (FLU) were studied in H2O–CH3OH and H2O–CH3CN mixed solvents because these solvents were thought to behave as a biological mimetic system. The emission spectra of OFL and NOR were very sensitive to the composition of the solvents. In the Lippert–Mataga analysis of the steady-state fluorescence data of OFL and NOR, clear reverse solvatochromism was exhibited in both mixed solvents. This observation can be explained by the twisted excited-state intramolecular charge transfer, which is accelerated by water. Theoretical treatments further support these results. The radiative and nonradiative rate constants were analyzed as a function of solvent dipolarity–polarizability (π*) and hydrogen-bond donor acidity (α). These results were well consistent with the suggested mechanism of the excited-state chemical process of OFL and NOR, which depended upon the solvent–solute interactions such as bulk dielectric effects and specific hydrogen-bonding interactions. However, the influence of dielectric effects was more significant. The solvent structures of H2O–CH3CN and the preferential solvation by water were also examined. The emission spectra of FLU do not exhibit any characteristic responses to the properties of the environment.

Spectroscopic Properties of Quercetin Derivatives, Quercetin‐3‐O‐rhamnoside and Quercetin‐3‐O‐rutinoside, in Hydro‐organic Mixed Solvents

The characteristic fluorescence properties of quercetin‐3‐O‐rhamnoside (QCRM) and quercetin‐3‐O‐rutinoside (QCRT) were studied in CH3OH–H2O and CH3CN–H2O mixed solvents. Although QCRM and QCRT are known as nonfluorescent molecules, significant fluorescence emissions were discovered at 360 nm in CH3OH and CH3CN when they were promoted to the second excited state. The emission band is broad and structureless and the intensity decreases quickly as the H2O composition in the solvent increases. When the amount of H2O exceeds 60% in both mixed solvents, this emission disappears due to the formation of the distorted excited state. This state will be formed due to the strong intermolecular hydrogen bonding between the polar groups of solute and H2O. As the composition of CH3OH or CH3CN in solvent becomes large, the number of molecules having several intramolecular hydrogen bonding increases. Some of these molecules will be changed to a fluorescent species during the decay process, after excitation. The theoretical calculation further supports these results. The change of the lifetimes, quantum yields, and radiative and nonradiative rate constants of molecules was also examined as a function of solvatochromic parameters for CH3OH–H2O and CH3CN–H2O.

Spectroscopic Properties of Various Quinolone Antibiotics in Aqueous–organic Solvent Mixtures¶

Abstract The spectroscopic properties of enoxacin (ENO), oxolinic acid (OXO) and nalidixic acid (NAL) were studied in various H2O–CH3OH and H2O–CH3CN mixed solvents because these solvents were thought to behave as a biological mimetic system. ENO has piperazinyl group, but OXO and NAL do not have this substituent. The fluorescence emission spectra of ENO were very sensitive to the composition of the solvents. In the Lippert–Mataga analysis of the steady-state fluorescence data, clear reverse solvatochromism was exhibited for ENO in both mixed solvents. This observation can be explained using the excited state twisted intramolecular charge transfer (TICT) from the nitrogen of the piperazinyl group to the keto oxygen. Theoretical calculations further support this observation. The nonradiative and radiative rate constants of these molecules were analyzed as a function of dipolarity–polarizability (π*) and hydrogen bond donor acidity (α) of the mixed solvents. These results for ENO were consistent with the suggested mechanism of the TICT very well. The influence of bulk dielectric effect was more significant relative to the specific hydrogen bonding interactions. The emission spectra of OXO and NAL do not exhibit any characteristic responses to the properties of the solvent.

New class of scorpionate: tris(tetrazolyl)-iron complex and its different coordination modes for alkali metal ions.

We report formation of a new metallascorpionate ligand, [FeL3](3-) (IPtz), containing a Fe core and three 5-(2-hydroxyphenyl)-1H-tetrazole (LH2) ligands. It features two different binding sites, oxygen and nitrogen triangles, which consist of three oxygen or nitrogen donors from tetrazole. The binding affinities of the complex for three alkali metal ions were studied using UV spectrophotometry titrations. All three alkali metal ions show high affinities and binding constants (>3 × 10(6) M(-1)), based on the 1:1 binding isotherms to IPtz. The coordination modes of the alkali metals and IPtz in the solid were studied using X-ray crystallography; two different electron-donor sites show different coordination numbers for Li(+), Na(+), and K(+) ions. The oxygen triangles have the κ(2) coordination mode with Li(+) and κ(3) coordination mode with Na(+) and K(+) ions, whereas the nitrogen triangles show κ(3) coordination with K(+) only. The different binding affinities of IPtz in the solid were manipulated using multiple metal precursors. A Fe-K-Zn trimetallic complex was constructed by assembly of an IPtz ligand, K, and Zn precursors and characterized using X-ray crystallography. Oxygen donors are coordinated with the K ion via the κ(3) coordination mode, and nitrogen donors are coordinated with Zn metal by κ(3) coordination. The solid-state structure was confirmed to be a honeycomb coordination polymer with a one-dimensional infinite metallic array, i.e., -(K-K-Fe-Zn-Fe-K)n-.

Spectroscopic Properties of Morin in Various CH3OH–H2O and CH3CN–H2O Mixed Solvents

The specific fluorescence properties of morin (3,2′,4′,5,7‐pentahydroxyflavone) were studied in various CH3OH–H2O and CH3CN–H2O mixed solvents. Although the dihedral angle is large in the S0 state, morin has an almost planar molecular structure in the S1 state owing to the very low rotational energy barrier around the interring bond between B and the A, C ring. The excited state intramolecular proton transfer (ESIPT) at the S1 state cannot occur immediately after excitation, S1 → S0 fluorescence can be observed. Two conformers, Morin A and B have been known. At the CH3OH–H2O, Morin B will be the principal species but at the CH3CN–H2O, Morin A is the principal species. At the CH3OH–H2O, owing to the large Franck–Condon (FC) factor for S2 → S1 internal convernal (IC) and flexible molecular structure, only S1 → S0 fluorescence was exhibited. At the CH3CN–H2O, as the FC factor for S2 → S1 IC is small and molecular structure is rigid, S2 → S0 and S1 → S0 dual fluorescence was observed. This abnormal fluorescence property was further supported by the small pK1 value, effective delocalization of the lone pair electrons of C(2′)–OH to the A, C ring, and a theoretical calculation.

A study on the moving mechanism for flower robot

As a service robot, we proposed a flower robot which has several functions, such as moving mechanism, sensing ability, and home appliance functions. Among the various functions, the moving function of the flower robot is very important function. The moving flower robot can be divided as a flower, a stem and leaves. We tried to mimic the blooming of flower, the swaying of the stem and the stirring of the leaves in the wind. For the actuation of the flower robot, we used micromotors and tendon mechanisms. From the motions of the flower, the stem and the leaves, the desired target positions are decided. In addition, based on inverse kinematics and trajectory generations, the overall control system for the moving flower robot is constructed. Through the various experiments, the performances of each part of the flower robot are verified and the characteristics are discussed.

Formation of the Metal Complexes between Protoporphyrin IX and Divalent Metal Cations in the Environment

Protoporphyrin IX is very slightly soluble in water whereas it is soluble in acidic as well as in basic aqueous solution. The UV-vis absorption spectrum of the protoporphyrin IX shows a very sharp and strong maximum absorption peak at 400 nm in acetonitrile-water mixture solution (1∶1v/v). The maximum absorption peaks reacted with divalent transition metal ions such as Cu2+, Zn2+, Fe2+ were shifted to a longer wavelength and the absorbance of the maximum peak decreased as the contents of metal ions increased. However, the absorbance of the maximum absorption peak combined with representative divalent metal ion, Mg2+ has nearly same value and the peak did not shifted. The formation constant (Kf) of the metal protoporphyrin IX complexes reacted with Cu2+, Zn2+, Fe2+ in acetonitrile-water mixture solution (1∶1v/v) were found to be 370, 418 and 24, respectively.

CCDC 1017827: Experimental Crystal Structure Determination

Related Article: Jung Hee Choi, Ji Yeon Ryu, Yu Jin Park, Halima Begum, Hyoung-Ryun Park, Hee Jin Cho, Youngjo Kim, Junseong Lee|2014|Inorg.Chem.Commun.|50|24|doi:10.1016/j.inoche.2014.10.007