Chang Yeon Lee

Beyond pristine MOFs: carbon dioxide capture by metal–organic frameworks (MOFs)-derived porous carbon materials

Porous carbon materials were synthesized by simple pyrolysis of various zinc-containing MOFs. These materials exhibited superior CO2 capacities compared to those of the pristine MOFs. Moreover, the porous carbon materials, in contrast to their parent MOFs, showed an excellent CO2 separation ability under humid conditions.

Self‐Assembly of Novel Thiophene‐Based BODIPY RuII Rectangles: Potential Antiproliferative Agents Selective Against Cancer Cells

Novel Ru (2+2) rectangles were designed and synthesized by self-assembly of a new thiophene-functionalized dipyridyl BODIPY ligand, BDPS, and ruthenium(II) precursors. The complexes exhibited dose-dependent antiproliferative activities against cancer cells, in which some compounds selectively kill cancer cells. The net fluorescence due to BODIPY allowed us to visualize their location inside cancer cells. Moreover, the metalla-rectangles displayed substantial propensity to bind with biomolecules.

Efficient Energy Transfer (EnT) in Pyrene- and Porphyrin-Based Mixed-Ligand Metal–Organic Frameworks

Designing and synthesizing the ordered light-harvesting systems, possessing complementary absorption and energy-transfer process between the chromophores, are essential steps to accomplish successful mimicking of the natural photosynthetic systems. Metal-organic frameworks (MOFs) can be considered as an ideal system to achieve this due to their highly ordered structure, superior synthetic versatility, and tailorable functionality. Herein, we have synthesized the new light-harvesting mixed-ligand MOFs (MLMs, MLM-1-3) via solvothermal reactions between a Zr6 cluster and a mixture of appropriate ratio of 1,3,6,8-tetrakis(p-benzoic acid)pyrene and [5,10,15,20-tetrakis(4-carboxy-phenyl)porphyrinato]-Zn(II) ligands. The identical symmetry and connectivity of the two ligands of the MLMs was the key parameter of successful synthesis as a single MOF form, and the ample overlap between the emission spectrum of pyrene and the absorption spectrum of porphyrin provided the ideal platform to design an efficient-energy transfer (EnT) process within the MLMs. We obtained the nanoscale maps of the fluorescence intensities and lifetimes of microsize MLM grains for unambiguous visualization of EnT phenomena occurring between two ligands in MLMs. Moreover, due to complementary absorption and energy transfer between the two ligands in the MLMs, our MLMs performed as superior photoinduced singlet-oxygen generators, verifying the enhanced light-harvesting properties of the pyrene- and porphyrin-based MLMs.

In Vitro Mechanistic Study of the Anti-inflammatory Activity of a Quinoline Isolated from Spondias pinnata Bark

The search for new plant-based anti-inflammatory drugs continues in order to overcome the detrimental side effects of conventional anti-inflammatory agents, both steroidal and nonsteroidal. This study involves the quinoline SPE2, 7-hydroxy-6-methoxyquinolin-2(1 H)-one, isolated from the EtOAc fraction of Spondias pinnata bark. Structure elucidation was done using analytical spectroscopic methods including Fourier transform infrared spectroscopy, high-resolution electrospray ionization mass spectrometry, nuclear magnetic resonance spectroscopy, and single-crystal X-ray crystallography. The anti-inflammatory activity of SPE2 was evaluated in a lipopolysaccharide (LPS)-stimulated murine macrophage RAW 264.7 model. SPE2 effectively suppressed LPS-induced overproduction of pro-inflammatory mediators such as nitric oxide (NO), tumor necrosis factor (TNF)-α, interleukin (IL)-6, and IL-1β, and reactive oxygen species. Expression levels of NO synthesizing enzyme, cyclooxygenase-2, TNF-α, IL-6 and IL-1β were also determined to return to normal after SPE2 treatment. Localization of NF-κB was evaluated by confocal microscopy and Western blotting, which showed a dose-dependent reduction of NF-κB inside the nucleus and an increase in cytoplasmic NF-κB with SPE2 treatment. Collectively, the results suggest that SPE2 has anti-inflammatory activity via inhibition of NF-κB activation.

BODIPY-based Ru(II) and Ir(III) organometallic complexes of avobenzone, a sunscreen material: Potent anticancer agents

The use of organic compounds with known medicinal properties in the synthesis of metal-based complexes is an important alternative to improve the biological activity of metal-based drugs. The reaction of [M(arene)Cl2]2 (Mu202f=u202fRu, areneu202f=u202fp-cymene and Mu202f=u202fIr, areneu202f=u202fpentamethylcyclopentadienyl, cp*) with avobenzone (1-(4-tert-butylphenyl)-3-(4-methoxyphenyl)propane-1,3-dione, AVBH) and KOH in methanol leads to the formation of the neutral complexes [Ru(p-cymene)(AVB)Cl] 1 and [Ir(cp*)(AVB)Cl] 2 (cp*u202f=u202fpentamethylcyclopentadienyl). Subsequent reaction of 1 and 2 with pyridyl derivative-BODIPY ligands, BDP and BDPCC (BODIPYu202f=u202fboron dipyrromethene, BDPu202f=u202f4-dipyridine boron dipyrromethene, BDPCCu202f=u202f4-ethynylpyridine boron dipyrromethene) in methanol gives a series of four new dicationic supramolecules: [Ru2(p-cymene)2(AVB)2BDP][2CF3SO3] 3, [Ir2(cp*)2(AVB)2BDP][2CF3SO3] 4, [Ru2(p-cymene)2(AVB)2BDPCC][2CF3SO3] 5 and [Ir2(cp*)2(AVB)2BDPCC][2CF3SO3] 6. The synthesized complexes are fully characterized using multiple analytical techniques, including elemental analysis, 1H NMR, 13C NMR, 19F NMR (NMRu202f=u202fNuclear Magnetic Resonance), Infrared Radiation (IR), Electrospray Ionization-Mass Spectrometry (ESI-MS), Ultraviolet-visible (UV-Vis) and fluorescence spectroscopy. The structures of these complexes are further rationalized using density functional theory (DFT) calculations. The antiproliferative activity of the neutral and dinuclear cationic complexes is evaluated in vitro in different human cancer cell lines. These complexes are found to be active against different cancer cell lines with half maximal inhibitory concentration (IC50) values between 1 and 5u202fμM. Complexes 5 and 6 displayed the lowest IC50 values in all the cell lines studied. The activity of 5 and 6 is comparable to that of the well-known chemotherapy drug doxorubicin. Detailed biophysical studies indicate that complexes 5 and 6 exhibit very good Deoxyribonucleic acid (DNA) binding properties, causing the unwinding of the double helix, which is a probable reason for their high cytotoxicity.