• Bulletin of the Korean Chemical Society
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• 제17권6호
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• pp.515-520
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• 1996

Simple conditions were discovered to afford tripyrranes by reaction of 2,5-bis(α-hydroxymethyl)furan or 2,5-bis(α-hydroxy-α-phenylmethyl)thiophene with excess pyrrole in the presence of acid catalyst. Stepwise synthesis of porphyrins with core-ligand modification and synthesis of meso-tetraarylporphyrins bearing two different substituents in cis orientation have developed as building blocks for the various porphyrin-based model systems. Consequently, 21-thia-23-oxa-10,15-diphenylporphyrin (28), 21-oxa-10,15-diphenylporphyrin (29) and 21-oxa-23-carba-12-aza-10,15-diphenylporphyrin (30) were synthesized by acid-catalyzed [3+1] condensation between tripyrranes and 2,5-bis(α-hydroxymethyl)pyrrole or 2,5-bis(α-hydroxy-α-phenylmethyl)thiophene. The synthetic pathway described here gave regioisomerically pure porphyrins and thus overcame the synthetic problems associated with separation and purification of regioisomeric mixture.

• 한국자기공명학회논문지
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• 제10권2호
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• pp.175-187
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• 2006

Binding interactions between a positively charged porphyrin derivative TMAP(meso-tetra(p-trimethylanilinium-4-yl)porphyrin) and triple helical $(dT)_{12}{\cdot}(dA)_{12}{\cdot}(dT)_{12}$, as well as double helical $(dA)_{12}{\cdot}(dT)_{12}$ have been studied with NMR, UV and CD spectroscopy to obtain the detailed information about the binding mode and binding site. UV melting studies showed both DNA duplex and triple helix represented very similar UV absorption patterns upon binding TMAP, but the presence of third strand of triple helical $(dT)_{12}{\cdot}(dA)_{12}{\cdot}(dT)_{12}$, inhibited improvement in thermal stability in terms of melting temperature, $T_m$. In addition, the TMAP molecule is thought to bind to the major groove, according to CD and NMR data. But absence of the clear isosbestic point in UV absorption spectra represented that binding of TMAP to DNA duplex as well as DNA triplex did not show a single binding mode, rather complex binding modes.

• Mass Spectrometry Letters
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• 제2권2호
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• pp.49-52
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• 2011

Competitive binding of $C_{60}$ and $C_{70}$ to meso-substituted porphyrins was studied by mass spectrometry (MS). Electrospray ionization MS was employed to acquire the mass spectra of 1 : 1 porphyrin-fullerene complexes formed in a mixture of mesosubstituted porphyrin and fullerite to determine the ratio of complexes between $C_{60}$ and $C_{70}$. Matrix-free laser desorption ionization MS was used to obtain the mass spectra of fullerite to measure the mole fraction of $C_{60}$ and $C_{70}$. The binding constant ratio ($K_{70}$/$K_{60}$) was determined from the mass spectral data. The difference in standard Gibbs free energy change, ${\Delta}({\Delta}G^o)_{70-60}$, for the competitive binding of $C_{60}$ and $C_{70}$ was calculated from $K_{70}$/$K_{60}$. Of the five porphyrins, tetraphenyl, tetra(4-pyridyl), tetra(4-carboxyphenyl), tetra(3,5-di-tert-butylphenyl), and tetra(pentafluorophenyl) porphyrins, the first three non-bulky porphyrins yield negative values of ${\Delta}({\Delta}G^o)_{70-60}$, whereas the other two bulky porphyrins result in positive values of ${\Delta}({\Delta}G^o)_{70-60}$. This result indicates that $C_{70}$ binding to porphyrin is thermodynamically favored over $C_{60}$ binding in non-bulky porphyrins, but disfavored in bulky ones. It also suggests that the binding mode of $C_{70}$is different between non-bulky and bulky porphyrins, which is in line with previous experimental findings of the "side-on" binding to non-bulky porphyrins and the $C_{60}$-like "end-on" binding to bulky porphyrins.

• Bulletin of the Korean Chemical Society
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• 제35권10호
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• pp.3052-3058
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• 2014

In this article, we have designed and synthesized a novel donor-${\pi}$-acceptor (D-${\pi}$-A) type porphyrin-based sensitizer (denoted UI-5), in which a carboxyl anchoring group and a 9,9-dimethyl fluorene were introduced at the meso-positions of porphyrin ring via phenylethynyl and ethynyl bridging units, respectively. Long alkoxy chains in ortho-positions of the phenyls were supposed to reduce the degree of dye aggregation, which tends to affect electron injection yield in a photovoltaic cell. The cyclic voltammetry was employed to determine the band gap of UI-5 to be 1.41 eV based on the HOMO and LUMO energy levels, which were estimated by the onset oxidation and reduction potentials. The incident monochromatic photon-to-current conversion efficiency of the UI-5 DSSC assembled with double-layer (20 nm-sized $TiO_2$/400 nm-sized $TiO_2$) film electrodes appeared lower upon overall ranges of the excitation wavelengths, but exhibited a higher value over the NIR ranges (${\lambda}$ = 650-700 nm) compared to the common reference sensitizer N719. The UI-5-sensitized cell yielded a relatively poor device performance with an overall conversion efficiency of 0.74% with a short circuit photocurrent density of $3.05mA/cm^2$, an open circuit voltage of 0.54 mV and a fill factor of 0.44 under the standard global air mass (AM 1.5) solar conditions. However, our report about the synthesis and the photovoltaic characteristics of a porphyrin-based sensitizer in a D-${\pi}$-A structure demonstrated a significant complex relationship between the sensitizer structure and the cell performance.

• Bulletin of the Korean Chemical Society
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• 제24권4호
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• pp.446-452
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• 2003

Some new nanohybrid materials have been synthesized by intercalating the oxotitanium(IV) meso-tetrakis(4- sulfonatophenyl) porphyrin$(O=Ti^{(IV)} TSPP)$ into the Zn/Al layered double hydroxides (LDHs), and their structures and photophysical properties have been investigated by various laser spectroscopic techniques. According to the XRD pattern of the synthesized nanohybrid materials, the macrocycle plane of $O=Ti^{(IV)}$ TSPP are grafted perpendicular to the LDH layers. The $O=Ti^{(IV)}$ TSPP-intercalated LDH exhibits band broadening of the absorption spectrum and a blue shift of Q-band as compared to that observed in solution. Resonance Raman spectral measurements demonstrate that the positively charged LDHs give rise to a slight decrease of the electronic density of the porphyrin ring accompanying a small change of the electronic distribution of the $O=Ti^{(IV)}$ TSPP. Consequently the LDH environment affects the energies of the two highest occupied molecular orbitals (HOMOs) of the $O=Ti^{(IV)}$) TSPP, $a_{1u}$ and $a_{2u}$, producing a mixed orbital character. Being consistent with these electronic structural changes of $O=Ti^{(IV)}$ TSPP in LDH, both the fluorescence spectral change and the fsdiffuse reflectance transient measurements imply that the photoexcitation of the $O=Ti^{(IV)}$ TSPP intercalated into LDH undergoes fast relaxation to the O=Ti(IV) $TSPP^+-LDH^- $charge transfer (CT) state within a few picoseconds, followed by a photoinduced electron transfer between the O=Ti(IV) TSPP and LDHs with a rate constant greater than %1×10^{10}S^{-1}$. No evidence is found for back electron transfer. In conclusion, the $O=Ti^{(IV)}$ TSPP intercalated LDH seems to be a possible candidate for an artificial reaction center for an efficient solar energy conversion system.

• Journal of Photoscience
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• 제9권2호
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• pp.178-181
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• 2002

Pyropheophorbide and pheophorbide-photosensitizers as chlorin analogues are promising new compounds for PDT because the chlorin analogues are activated with much longer red light at > 670nm and produce less long-term normal tissue phototoxicity than Photofrin. The various chlorin derivatives can be obtained by moditying peripheral substituted group among which meso-H, vinyl group and exocyclic ring are the most active positions. These characteristics prompted us to introduce various groups for constructing modified pyropheophorbide and pheophorbide a compounds. A stereospecific introduction of various double bonds at 3-position was performed to methylpheophorbide a to give a long hydrophobic moiety and cyclic derivatives. Chlorin-C$_{60}$ dyad and chlorin- $C_{60}$-porphyrin triad also were easily prepared by the reaction of terminal aldehyde of methyl pyropheophorbide a. For the reaction on meso $\delta$-position bromination and Vismeier formylation can occur. N,N-dimethylaminoacrolein also reacted on $\delta$-position and was cyclized to isobacteriochlorin, but other modification has not been succeeded. Exocyclic keto function was also modified to give purpurin derivatives, bicyclic and spiro compounds. In this presentation we report a series of modified pyropheophorbide and pheophorbide a derivatives.s.

• Bulletin of the Korean Chemical Society
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• 제23권2호
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• pp.281-285
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• 2002

The photophysical properties and the singlet oxygen generation efficiencies of meso-tetraphenyl-trithiasapphyrin $(S_3TPS)$ and meso-tetmkis(p-methoxy phenyl)-trithiasapphy rin ((p-MeO)-$S_3TPS$) have been investigated, utilizing steady-state and time-resolved spectroscopic methods to elucidate the possibility of their use as photosensitizers for photodynamic therapy (PDT). The observed photophysical properties were compared with those of other porphyrin-like photosensitizers in geometrical and electronic structural aspects, such as extended ${\pi}$ conjugation, structural distortion, and internal heavy atoms. The steady-state electronic absorption and fluorescence spectra were both red-shifted due to the extended ${\pi}$-conjugation. The fluorescence quantum yields were measured as very small. Even though intersystem crossing rates were expected to increase due to the increment of spin orbital coupling, the triplet quantum yields were measured as less than 0.15. Such characteristics can be ascribed to the more enhanced internal conversion rates compared with the intersystem crossing rates. Furthermore, the triplet state lifetimes were shortened to -1.0 ${\mu}s$ as expected. Therefore, the singlet oxygen quantum yields were estimated to be near zero due to the fast triplet state decay rates and the inefficient energy transfer to the oxygen molecule as well as the low triplet quantum yields. The low efficiencies of energy transfer to the oxygen molecule can be attributed to the lower oxidation potential and/or the energetically low lying triplet state. Such photophysical factors should be carefully evaluated as potential photosensitizers that have extended ${\pi}$-conjugation and heavy core atoms synthesized for red-shifted absorption and high triplet state quantum yields.