• Journal of Photoscience
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• v.10 no.2
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• pp.185-187
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• 2003

The preparation and the photophysics of organometallic Pt(II) and Ir(III) complexes with 6-ch1oro-3-phenylpyridazine (H6Clppdz) are reported. $K_2$PtCl$_4$ and IrCl$_3$ㆍn$H_{2}O$ cleanly cyclometalate with H6Clppdz, forming the corresponding chloro-bridged dimers, (6Clppdz)Pt($\mu$-Cl)$_2$Pt(6Clppdz) and (6Clppdz)$_2$Ir($\mu$-Cl)$_2$Ir(6Clppdz)$_2$ in good yield. These chloro-bridged dimers are cleaved with acetylacetone (Hacac) to give the corresponding monomer, (6Clppdz)Pt(acac) and (6Clppdz)$_2$ Ir(acac), respectively. Both complexes show bright orange luminescence at room temperature and the emission wavelengths are different depending on the metal and the structure of complexes. (6Clppdz)Pt(acac) shows two sharp emission bands in shorter wavelength ($\lambda$$_{em}$=541 and 580 nm), while (6Clppdz)$_2$ Ir(acac) shows a broad emission band in longer wavelength ($\lambda$$_{em}$=615 nm). Strong spinorbit coupling due to the heavy metal atom allows for the formally forbidden mixing of the $^1$MLCT with the $^3$MLCT and $^3$$\pi$-$\pi$$^{*}$ states.

• Journal of Information Display
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• v.3 no.1
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• pp.6-10
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• 2002

We have synthesized a new green Ir(III) complex fac-tris-(3-methyl-2-phenyl pyridine)iridium(III) $Ir(mpp)_3$ and fabricated phosphorescent polymer light-emitting device using it as a triplet emissive dopant in PVK. $Ir(mpp)_3$ showed absorption centered at 388 nm corresponding to the $^1MLCT$ transition as .evidenced by its extinction coefficient of the order of $10^3{\cdot}$ From the PL and EL spectra of the $Ir(mpp)_3$ doped PVK film, the emission maximum was observed at 523 nm, due to the radiative decay from the $^3MLCT$ state to the ground state, confirming a complete energy transfer from PVK to $Ir(mpp)_3$. The methyl substitution has probably caused a red shift in the absorption and emission spectrum compared to $Ir(mpp)_3$. The device consisting of a 2 % doped PVK furnished 4.5 % external quantum efficiency at 72 $cd/m^2$ (current density of 0.45 $mA/cm^2$ and drive voltage of 13.9 V) and a peak luminance of 25,000 $cd/m^2$ at 23.4 V (494 $mA/cm^2$). This work demonstrates the impact of the presence of a methyl substituent at the 3-position of the pyridyl ring of 2-phenylpyridine on the photophysical and electroluminescence properties.

• Journal of the Korean Chemical Society
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• v.38 no.8
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• pp.598-602
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• 1994

Light-induced electron transfer reaction within binuclear complex $(NC)_5FeII-L-CoIII(NH_3)_5$ was studied with steady-state photolysis and the rate constants were measured for various bridging lignands. klight and quantum yields for BP, PHEN, DAP having conjugation between metal binding sites were about $3{\times}10^{-2} sec^{-1}$ and 1, and for BPEA having no conjugation were about $2{\times}10^{-4} sec^{-1}$ and 0.03. Light-induced electron transfer reaction within binuclear complex was proved to be the chemical mechanism which had charge transfer excited state MLCT*.

• Analytical Science and Technology
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• v.20 no.5
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• pp.406-412
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• 2007

The formation of inclusion complexes between ${\beta}$-cyclodextrin and diethylenetriamine substituted-pyridine copper(II) perchlorate; [Cu(dien)(sub-py)] $(ClO_4)_2$, were studied by spectrophotometric methods. On account of charge-transfer band(MLCT) and $^2T_2{\rightarrow}^2E$, the two high peaks were observed as an inclusion complex for the [${\beta}$-CD]$[Cu(dien)(p-Cl-py)]^{2+}$ in the ultraviolet region of the spectrum. The ${\beta}$-CD and $[Cu(dien)(sub-py)]^{2+}$ ion formed a 1:1 complex, and the formation constants were decreased with the increasing temperatures, due to weak binding energy between ${\beta}$-CD and $[Cu(dien)(sub-py)]^{2+}$ ion. This reaction was controlled by enthalpy. In a correlation of the Hammett substituent constants and formation constants for the reaction, formation constants were increased by strong binding energy in the inclusion complexes when electron donating groups were substituted in pyridine ring.

• Bulletin of the Korean Chemical Society
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• v.35 no.2
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• pp.448-456
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• 2014

A series of seven Ru(II) complexes bearing NHC ligands have been synthesized. The electronic structures of these complexes were analysed by spectroscopic and electrochemical methods and further examined by theoretical calculations. Data show that absorption maxima are dependent on the HOMO level rather than the HOMO-LUMO gaps.

• Bulletin of the Korean Chemical Society
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• v.19 no.1
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• pp.86-93
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• 1998

Trans-4-(9-anthrylethenyl)-4'-methyl-2,2'-bipyridine(t-aemb) and its bipyridyl Ru complex $[Ru(bpy)_2(t-aemb)](PF_6)_2$ (bpy=2,2'-bipyridine) 1 have been prepared and their excited state properties have been studied. t-Aemb exhibits solvent-dependent fluorescence and efficient trans→cis photoisomerization. 1 shows very weak fluorescence and its photochemically reactive. Fluorescence is wavelength-dependent. While the excitation into the MLCT band makes the complex fluorescent, direct absorption by the t-aemb ligand leads to the photoreaction of t-aemb ligand and no fluorescence is observed. 1 is considered to behave in part as bichromophoric molecule in which $[Ru(bpy)_3](PF_6)_2$ and anthryl group are covalently linked by ethenyl linkage. Because anthryl moiety is not effectively conjugated with bipyridylethenyl moiety due to steric hindrance, weak fluorescence can be explained due to the efficient energy or electron transfer.

• Rapid Communication in Photoscience
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• v.4 no.1
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• pp.22-24
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• 2015

A new trinuclear complex $[Ru(TPrPc)(CO)]_2[Ru(pytpy)_2](PF_6)_2$ (TPrPc = 2,7,12,17-tetra-n-propylporphycenato dianion and pytpy = 4'-(4-pyridyl)-2,2':6',2"-terpyridine) has been synthesized and characterized as the first example of a discrete molecular wire containing metalloporohycenes as a building block. The trinuclear complex shows multiple-step redox behavior in 0.1 M n-$Bu_4NPF_6$-dichloromethane. The mononuclear $[Ru(pytpy)_2]^{2+}$ precursor shows emission at 640 nm (deaerated acetone, 298 K) upon illumination at the metal-to-ligand charge transfer (MLCT) band at 495 nm, but the trinuclear molecular wire is found to be non-emissive upon photoexcitation at the central $[Ru(pytpy)_2]^{2+}$ entity, indicating an efficient quenching ability of the axially-linked, ruthenium(II)-porphycene chromophores in an intramolecular fashion.

• Bulletin of the Korean Chemical Society
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• v.31 no.5
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• pp.1314-1318
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• 2010

The $[Ru(tpy)_2]Cl_2$ (tpy:2,2':6',2"-terpyridine) complex was synthesized and its structure was confirmed by $^1H$-NMR and elemental analysis. Its binding mode toward DNA was compared with the well-known $[Ru(bpy)_3]Cl_2$ (bpy:2,2-bipyridyl), using isotropic absorption, linear dichroism(LD) spectroscopy, and an energy minimization study. Compared to $[Ru(bpy)_3]^{2+}$, the $[Ru(tpy)_2]^{2+}$ complex exhibited very little change in its absorption pattern, especially in the MLCT band, upon binding to DNA. Furthermore, upon DNA binding, both Ru(II) complexes induced a decrease in the LD magnitude in the DNA absorption region. The $[Ru(tpy)_2]^{2+}$ complex produced a strong positive LD signal in the ligand absorption region, which is in contrast with the $[Ru(bpy)_3]^{2+}$ complex. Observed spectral properties led to the conclusion that the interaction between the ligands and DNA bases is negligible for the $[Ru(tpy)_2]^{2+}$ complex, although it formed an adduct with DNA. This conclusion implies that both complexes bind to the surface of DNA, most likely to negatively charged phosphate groups via a simple electrostatic interaction, thereby orienting to exhibit the LD signal. The energy minimization calculation also supported this conclusion.

• Proceedings of the Korean Society of Dyers and Finishers Conference
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• 2011.03a
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• pp.36-36
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• 2011

We synthesized new dye sensor based on indole compound. Through the UV-vis absorptions, we analyzed chemosensing properties to explain metal binding properties. The peak absorptions increased at 472 nm when added metal cations($Cd^{2+}$, $Cu^{2+}$, $Hg^{2+}$, $Fe^{2+}$, $Zn^{2+}$, $Ni^{2+}$ and $Cr^{3+}$) and gradually decreased the peak at 516 nm. Thus, this UV-Vis absorption behavior clearly showed the metal binding reaction. To measure energy level of used dye sensor, HOMO/LUMO energy value was calculated with cyclovaltagramm(CV) and using computational calculation method, in which we estimated the optimum structure of dye sensor. CV and computational calculation method, both compared to find suitable geometric structure. (with almost same energy values.) From the computational calculation, dye sensor has plane structure. So, Amine and ketone in the dye sensor faced each other and makes position to bind metal cations. In addition, these positions was supported pull-push electron system and generated MLCT process, when the dye sensor was bonded with the metal cations and resulted chemosensing properties. Through the electrochemical and computational calculation method analyze, we proposed the chemosensing principles that the dye sensor bind the metal cation between ketone and amine. Finally, the formation type of metal ion bindings was determined by Job's plot measurements.

• Bulletin of the Korean Chemical Society
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• v.32 no.12
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• pp.4321-4326
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• 2011

A new series of heteroleptic cyclometalated iridium(III) complexes has been synthesized and characterized by absorption, emission and cyclic voltammetry studies: $(pqx)_2Ir(acac)$ (1), $(dmpqx)_2Ir(acac)$ (2) and $(dfpqx)_2Ir(acac)$ (3) where pqx=2-phenylquinoxalinate, dmpqx=2-(2,4-dimethoxyphenyl)quinoxalinate, dfpqx=2-(2,4-difluorophenyl) quinoxalinate and acac=acetylacetonate anion. The reaction of excess acetylacetone with ${\mu}$-chloride-bridged dimeric iridium complex, $[(C\^N)_2Ir({\mu}-Cl)]_2$, gives a complex 1 and an unusual hydridoiridium(III) complex, $(pqx)IrH(acac)_2$ (4). The complex 1, 2 and 3 show their emissions in an orangered region (${\lambda}_{PL,max}$ = 583-616 nm), and the emission maxima can be tuned by the change of substituent at phenyl ring of 2-phenylquinoxaline ligand. The phosphorescent line shape indicates that the emissions originate predominantly from $^3MLCT$ states with little admixture of ligand-based $^3({\pi}-{\pi}^*)$ excited states. The structures of complex 3 and 4 are additionally characterized by a single crystal X-ray diffraction method. The complex 3 shows a distorted octahedral geometry around iridium(III) metal ion. A strong trans influence of the phenyl ring is examined. In complex 4, there are two discrete molecules which are mirror images each other at the ratio of 1:1 in an unit cell. We propose that the phosphorescent complex 1, 2 and 3 are possible candidates for the phosphors in OLEDs applications.