Showing papers by "Ji Yeon Ryu published in 2019"

Mitochondrial Localization of Highly Fluorescent and Photostable BODIPY-Based Ruthenium(II), Rhodium(III), and Iridium(III) Metal Complexes.

Abstract: A new N,O-based BODIPY ligand was synthesized and further utilized to develop highly fluorescent and photostable Ru(II), Rh(III), and Ir(III) metal complexes. The complexes were fully characterized by different analytical techniques including single-crystal XRD studies. The photostabilities and live cell imaging capabilities of the complexes were investigated via confocal microscopy. The complexes localized specifically in the mitochondria of live cells and showed negligible cytotoxicities at a concentration used for imaging purposes. They also exhibited high photostabilities, with fluorescence intensities remaining above 50% after 1800 scans.

Extremely Active Ethylene Tetramerization Catalyst Avoiding the Use of Methylaluminoxane: [iPrN{P(C6H4-p-SiR3)2}2CrCl2]+[B(C6F5)4]−

Abstract: Sasol's original ethylene tetramerization catalyst requires the use of expensive MMAO, a low working temperature (∼60 °C), and generates polyethylene (PE) as a side product. In this study, we developed an upgraded catalytic system that successfully avoids the need for MMAO. [(PNP)CrCl2]+[B(C6F5)4]−‐type species was obtained from the reaction of CrCl3(THF)3, [PhN(H)Me2]+[B(C6F5)4]−, and iPrN[P(C6H4‐p‐Si(nBu)3)2]2 (2) as well as from simply reacting 2 with [CrCl2(NCCH3)4]+[B(C6F5)4]−. The bulky (nBu)3Si‐substituents play the crucial role of preventing the formation of the inactive [(PNP)2CrCl2]+[B(C6F5)4]−. The prepared [2‐CrCl2]+[B(C6F5)4]− combined with iBu3Al was extremely active (>4000 kg/g‐Cr/h), performed well at a high temperature of up to 90 °C, and generated a negligible amount of PE (0.03 wt%). Screening the performance with a series of iPrN[P(C6H4‐p‐SiR3)2]2 further supported that bulky R3Si‐substituents are crucial not only to achieve extremely high activities but also to minimize the generation of PE. Structure of a [(PNP)CrCl2]+[B(C6F5)4]− species was elucidated by X‐ray crystallography.

A Series of Quinolinol-Based Indium Luminophores: A Rational Design Approach for Manipulating Photophysical Properties.

Abstract: An approach to the design of a series of quinolinol-based indium complexes that can exhibit different optical properties is proposed. Mono-incorporated (Inq1 and InMeq1), bis-incorporated (InMeq2), and tris-incorporated (Inq3 and InMeq3) indium quinolinate complexes have been prepared. These complexes have also been characterized by X-ray crystallography. The photophysical properties of these complexes have also been examined by a combination of experimental and theoretical techniques. The indium complexes with a single quinolinol ligand (Inq1 and InMeq1) showed higher quantum efficiency than those with two or three quinolinate ligands; in particular, InMeq1 exhibited the highest quantum yield [ΦPL = 59% in poly(methyl methacrylate) film]. The insights into the nature of these findings were obtained by the sequential synthesis of the quinolinol-based indium luminophores and a detailed investigation of their structural stability.

Preparation of Pincer Hafnium Complexes for Olefin Polymerization.

Abstract: Pincer-type [Cnaphthyl, Npyridine, Namido]HfMe2 complex is a flagship among the post-metallocene catalysts. In this work, various pincer-type Hf-complexes were prepared for olefin polymerization. Pincer-type [Namido, Npyridine, Namido]HfMe2 complexes were prepared by reacting in situ generated HfMe4 with the corresponding ligand precursors, and the structure of a complex bearing 2,6-Et2C6H3Namido moieties was confirmed by X-ray crystallography. When the ligand precursors of [(CH3)R2Si-C5H3N-C(H)PhN(H)Ar (R = Me or Ph, Ar = 2,6-diisopropylphenyl) were treated with in situ generated HfMe4, pincer-type [Csilylmethyl, Npyridine, Namido]HfMe2 complexes were afforded by formation of Hf-CH2Si bond. Pincer-type [Cnaphthyl, Sthiophene, Namido]HfMe2 complex, where the pyridine moiety in the flagship catalyst was replaced with a thiophene unit, was not generated when the corresponding ligand precursor was treated with HfMe4. Instead, the [Sthiophene, Namido]HfMe3-type complex was obtained with no formation of the Hf-Cnaphthyl bond. A series of pincer-type [Cnaphthyl, Npyridine, Nalkylamido]HfMe2 complexes was prepared where the arylamido moiety in the flagship catalyst was replaced with alkylamido moieties (alkyl = iPr, cyclohexyl, tBu, adamantyl). Structures of the complexes bearing isopropylamido and adamantylamido moieties were confirmed by X-ray crystallography. Most of the complexes cleanly generated the desired ion-pair complexes when treated with an equivalent amount of [(C18H37)2N(H)Me]+[B(C6F5)4]-, which showed negligible activity in olefin polymerization. Some complexes bearing bulky substituents showed moderate activities, even though the desired ion-pair complexes were not cleanly afforded.

Selective Self-Assembly of a Rectangular Ruthenium Supramolecule from an Unsymmetrical Bridging Unit.

Abstract: Herein, we report the synthesis of an unsymmetrical diruthenium bridging unit containing a multidentate oxamate ligand and the subsequent formation of a rectangular supramolecule. The reaction of oxamate 1, 2-((4-bromo-2,6-dimethylphenyl)amino)-2-oxo-acetic acid, and [(p-cymene)RuCl2]2 affords a novel unsymmetrical diruthenium acceptor clip 2, where two ruthenium metal centers are ligated with either [O,O] or [N,O]. The molecular clip 2 and bipyridine donor self-assemble to form two-dimensional rectangular supramolecule 3. Self-assembly can produce seven possible isomers depending on the position of the substituted bromoaryl groups. However, 1H NMR spectroscopic investigation indicated only two different isomers in the reaction mixture. A single isomer is isolated via crystallization, and X-ray crystallography confirms that the product is a C1 symmetric two-dimensional rectangular supramolecule, in which two bromoaryl groups are located in the farthest position from each other. Theoretical calculations su...

Preparation of Half- and Post-Metallocene Hafnium Complexes with Tetrahydroquinoline and Tetrahydrophenanthroline Frameworks for Olefin Polymerization

Abstract: Hafnium complexes have drawn attention for their application as post-metallocene catalysts with unique performance in olefin polymerization. In this work, a series of half-metallocene HfMe2 complexes, bearing a tetrahydroquinoline framework, as well as a series of [Namido,N,Caryl]HfMe2-type post-metallocene complexes, bearing a tetrahydrophenanthroline framework, were prepared; the structures of the prepared Hf complexes were unambiguously confirmed by X-ray crystallography. When the prepared complexes were reacted with anhydrous [(C18H37)2N(H)Me]+[B(C6F5)4]-, desired ion-pair complexes, in which (C18H37)2NMe coordinated to the Hf center, were cleanly afforded. The activated complexes generated from the half-metallocene complexes were inactive for the copolymerization of ethylene/propylene, while those generated from post-metallocene complexes were active. Complex bearing bulky isopropyl substituents (12) exhibited the highest activity. However, the activity was approximately half that of the prototype pyridylamido-Hf Dow catalyst. The comonomer incorporation capability was also inferior to that of the pyridylamido-Hf Dow catalyst. However, 12 performed well in the coordinative chain transfer polymerization performed in the presence of (octyl)2Zn, converting all the fed (octyl)2Zn to (polyolefinyl)2Zn with controlled lengths of the polyolefinyl chain.

Crystal structure of 1,4-bis-[5-(2-meth-oxy-phen-yl)-2H-tetra-zol-2-yl]butane.

Abstract: The title compound, C20H22N8O2, was synthesized by the coupling reaction of a sodium tetra­zolate salt and di­bromo­butane in a molar ratio of 2:1. The reaction can produce several possible regioisomers and the title compound was separated as the major product. The X-ray crystallographic study confirmed that the title compound crystallizes in the monoclinic P21/c space group and possesses a bridging butyl­ene group that connects two identical phenyl tetra­zole moieties. The butyl­ene group is attached not to the first but the second nitro­gen atoms of both tetra­zole rings. The dihedral angles between the phenyl groups and the adjacent tetra­zolyl rings are 5.32 (6) and 15.37 (7)°. In the crystal, the mol­ecules form centrosymmetric dimers through C—H⋯O hydrogen bonds between a C—H group of the butyl­ene linker and the O atom of a meth­oxy group.