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Styrenated phenols are usually synthesized by the reaction of styrene and phenol under acid catalysts. Styrenated phenol involving high content of di-styrenated phenol (DSP) was synthesized, which can be used to prepare styrenated phenol alkoxylate. The solid catalyst used in this study was prepared by impregnation method. SO4 2- on SO4 2-/ZrO2 catalyst was introduced from an aqueous 1M-H2SO4 solution. The catalysts were characterized by SEM images, XRD patterns, and FT-IR spectra. The catalytic activity was examined by measuring the conversion of phenol and styrene in a liquid-phase batch reactor. Almost 100% conversion of both phenol and styrene over 15-SO4 2-/ZrO2 catalyst were obtained at reaction temperature of 100 °C and reaction time of 6 hr. Amount of catalyst to the reactants was 15 wt%. At same reaction conditions, selectivity of MSP, DSP, and TSP were 23.6%, 52.1%, and 5.4%, respectively. It was known that the selectivity to DSP was increased as IR absorption peak of 1236 cm-1 corresponding to O–S–O bonds was increased.

Rh-SP dyad bearing rhodamine (Rh) and spiropyran (SP) moieties was prepared. Reversible photochromic reaction was observed between colorless and nonfluorescent c-Rh-SP and c-Rh-MC with purple color and red fluorescence. Rh-SP can act as a triple chemosensor for Al3+, , and CN −, by absorption and fluorescence spectral changes. The results show colorless solution and orange fluorescence with Al3+, red solution and bright orange fluorescence with , and yellow solution and weak green fluorescence with CN −.

Spiropyran-cored polyamidoamine (PAMAM) dendrons (SP-PAMAMs) were prepared and their solvatochromic and photochromic properties investigated. As with simple merocyanine (MC), MC-PAMAM shows negative solvatochromism. On UV irradiation, colorless SP-PAMAM transforms into colored MC-PAMAM and the reaction occurs a little faster in a more polar solvent. In the dark, MC-PAMAM returns to SP-PAMAM much more slowly in a more polar solvent. On addition of Cu2+, the color of SP-PAMAM solution in acetonitrile changes from colorless to orange, whereas neither color change nor absorption spectral changes are observed with the addition of other metal cations.

E-mail: ejs@sunchon.ac.krReceived July 5, 2013, Accepted July 17, 2013Key Words : Porphyrin, Diprotonated porphyrin, Spiropyran, Merocyanine, AggregationPorphyrin (Por) has a strong absorption characteristics inthe range of sunlight due to a chemical structure of highconjugation and rigidity, good redox properties, and well-established synthetic methods. Accordingly, porphyrin-basedmulticomponent compounds have been investigated in avariety of applications such as artificial light-harvestingantenna, molecular energy storage devices, solar cells, opto-electronic switches, and photodynamic therapy.

The porphyrin-incorporated arylether dendrimers ZnP-D1 and ZnP-D4 were investigated to discover the influence of dendritic environments for the axial ligation of pyridine and photoinduced electron transfer by methyl viologen. Absorption and fluorescence spectra of ZnP, ZnP-D1, and ZnP-D4 were measured in dichloromethane with the addition of pyridine or methyl viologen dichloride. Axial ligation of pyridine was confirmed by red-shifted absorption spectrum. The complex formation constants Kf (Table 1) for axial coordination of pyridine on ZnP, ZnP-D1, and ZnP-D4 were estimated to be 4.4 × 10 3 M �1 , 3.3 × 10 3 M �1 , and 1.7 × 10 3 M �1 , respectively. The photoinduced electron transfer to methyl viologen dichloride was confirmed by fluorescence quenching. Stern-Volmer constants Ksv for ZnP, ZnP-D1, and ZnP-D4 were calculated to be 2.6 × 10 3 , 2.5 × 10 3 , and 2.1 × 10 3 , respectively. ZnP-D4 surrounded by 4 aryl ether dendrons shows the smallest Kf and Ksv values, with comparison to ZnP and ZnP-D1.

Zinc porphyrin, Azacrown ether, Cation recognition, Axial coordinationIt is very interesting that the presence or absence of hydrogen atoms can remarkably influence operation of molecular systems as well as natural systems. Induction of structural changes of natural receptors through the variations in the pH of the environ-ment is one of the most versatile methods to regulate the activity by enhancing or diminishing the receptor’s binding efficacy.

Benzyl arylether dendrimers with zinc porphyrin core and terminal vinyl groups have been synthesized and their photophysical properties and the influence of dendritic environments were investigated. Free base porphyrin-cored benzyl arylether dendrimers 1a-1c and 3a-3c, and their zinc derivatives 2a-2c and 4a-4c have been prepared. Absorption spectra are similar for all porphyrin-cored benzyl arylether dendrimers, except that absorption intensity at 280 nm increases in the higher generation of dendrimer. Fluorescence spectra are similar with two bands for all free base porphyrin dendrimers 1a-1c and 3a-3c, although fluorescence intensity ratio of shorter wavelength emission band to longer wavelength band varies with the generation of dendrimer. Emission efficiencies of 1a-1c and 3a-3c are lower than that of TTP. Emission efficiencies of 2a-2c and 4a-4c are higher than that of ZnTTP. Absorption and emission properties of 1a-1c, 2a-2c, 3a-3c, and 4a-4c were affected negligibly with dendritic environments.

Azobenzene, Isomerization, Au nanoparticle, Organic-inorganic nanohybrid, Absorption spectraRecently, inorganic nanoparticles have attracted greatattention because nanoparticles exhibit interesting size-dependent physical and chemical properties due to inter-mediate size between single molecules and bulk materials.

Azobenzene-cored dendrons having the photoisomerizable azobenzene core and terminal vinyl groups have been prepared. Absorption bands of azobenzene-cored dendrons are similar except more intense 280 nm band in higher generation azobenzene dendron. All three azobenzene-cored dendrons show reversible photoisomerization similar to simple azobenzene, irrespective of the generation of dendron. On 350 nm irradiation, absorption band around 344 nm decreases and 436 nm band increases. Photoisomerization reactions are very fast for all three azobenzene-cored dendron and the reaction efficiency is dependent of its generation and solvent. In the dark, slow thermal reversion to original absorption spectrum is observed.

and other molecular electronicand photonic devices, because of their attractive electronicand redox properties and with the ease of modification bythe development of various synthetic routes. The fact thatthere are many sites on the porphyrin at which to attachelectron-releasing or electron-withdrawing groups suggeststhat tremendous electronic modulation of the porphyrinshould be possible.

Four 1-(9-anthryl)-2-heteroarylethene derivatives containing sulfur or oxygen atom such as 1-(9-anthryl)-2-(2-thiophenyl)ethene (ATE), 1-(9-anthryl)-2-(2-benzo[ b ]thiophenyl)ethene (ABTE), 1-(9-anthryl)-2-(2-furanyl)ethene (AFE), and 1-(9-anthryl)-2-(2-benzofuranyl)ethene (ABFE) have been prepared and their excited state properties have been investigated in cyclohexane, acetonitrile, and methanol. These sulfur- or oxygen-heteroaromatic ring derivatives show solvent-dependent fluorescence and photoisomerization behavior, due to the intramolecular charge-transfer character of the lowest S 1 state. Substituent effect on fluorescence and photoisomerization of ATE further supports the contribution of the intramolecular charge-transfer character to the lowest S 1 state, which is more increased by the introduction of electron-withdrawing substituent into anthracene ring.

Noncovalently linked electron donor-acceptor dyad consisting of zinc tetratolylporphyrin and pyridine-appended ruthenium trisbipyridine complex was prepared, via axial coordination of pyridine moiety in ruthenium trisbipyridine complex on zinc tetratolylporphyrin. For the purpose of comparison, axial coordination of pyridine-appended 2,2'-bipyridine on zinc tetratolylporphyrin was also investigated. The K values were determined based on absorption or fluorescence studies. The fluorescence of zinc tetratolylporphyrin was efficiently quenched upon axial coordination of pyridine moiety, probably due to the photoinduced electron transfer from zinc tetratolylporphyrin to ruthenium trisbipyridine, supported by free energy estimation.

in the last ten years because oftheir thermal and optical stability and fatigue resistance. Wereport here the preparation of trans-1-(9-anthryl)-2-(2-thienyl)ethene (t-AThE), a thiophene derivative of trans-1-(9-anthryl)-2-phenylethene (t-APE), and its absorption andfluorescence spectral data and photoisomerization behavior. While stilbene shows very weak fluorescence due to veryefficient two-way photoisomerization

The fluorescence and photoisomerization quantum yields of trans-1-(9-anthryl)-2-(4-pyridyl)ethene ( t-4APyE), 1-(10-methyl-9-anthryl)-2-(4-pyridyl)ethene (t-4-MeAPyE), and 1-(10-chloro-9-anthryl)-2-(4pyridyl)ethene (t-4-ClAPyE) were measured in cyclohexane, acetonitrile, and methanol at room temperature. Polar solvents result in the drastic reduction of fluorescence quantum yield and increase of photoisomerization quantum yield for all three compounds. These results are probably due to the stabilization of intramolecular charge transfer (ICT) excited state in polar solvent. The higher contribution of ICT in the presence of more electron-donating methyl substituent, manifested by largest positive fluorescence solvatochromism, indicates that the pyridine ring acts as an electron acceptor. Protonation or methylation makes pyridine ring stronger electron acceptor and causes long-wavelength ground state charge transfer absorption band and complete quenching of fluorescence. The fluorescence from t-4-APyE derivatives can be switched off responding external stimuli viz. medium polarity, protonation, or methylation.

The fluorescence quenching of various substituted tetraphenylporphyrins and their zinc complexes by ruthenium(II) tris(2,2′-bipyridine) has been investigated in dichloromethane. While fluorescence quenching was not effective for free base porphyrins, but in the case of zinc porphyrins fairly efficient. Plots for the Stern–Volmer quenching constant versus the calculated free energy change (Δ G red ) for photoinduced oxidative electron transfer (ET) processes from the excited singlet porphyrins to ruthenium(II) tris(2,2′-bipyridine) were shown to be linear. Among porphyrins/ruthenium(II) tris(2,2′-bipyridine) pairs examined in this study, ZnTMeOPP/ruthenium(II) tris(2,2′-bipyridine) pair exhibited most efficient fluorescence quenching as predicted to carry out most favorable photoinduced oxidative electron transfer processes by the calculated free energy changes (Δ G red ).

The fluorescence properties and photoisomerization behavior for trans and cis isomers of 1-(9-anthryl)-2-(2-pyrazinyl)ethene (APzE). a diaza analogue of 1-(9-anthryl)-2-phenylethene (9-APE), were studied. The fluorescence maximum (λ 1 ). quantum yield ( Φ t ) and lifetime ( τ t ) of t -APZE were solvent-dependent reflecting the intramolecular charge transfer character in the lowest excited singlet state. However, in polar protic solvent, some discrepancy was observed probably due to protonation on the nitrogen atoms. The photoisomerization of t -APzE was observed even in very nonpolar solvent, in contrast that the parent t -9-APE did not photoisomerize in any solvent and photoisomerization of monoaza analogues t 1-(9-anthryl)-2-( n -pyridyl)ethenes ( n -APyE) was very inefficient in nonpolar solvent. The quantum yield of the trans → cis photoisomerization ( Φ t → c ) of t -APzE was also solvent-dependent. Not only the inverse dependence for Φ f -and Φ t → c , of t -APzE on the temperature and the solvent polarity but also hiacetyl-sensitized photoisomerization experiment indicate that the photoisomerization of t -APzE occurs, at least in part, via the excited singlet state. In air-saturated solution, another side photoproduct was observed in all solvent examined and identified as anthraquinone, a photo-oxidation product. For c -APzE, the τ t , is too short to measure and Φ t , is relatively low. Quantum yields of fluorescence and cis→trans photoisomerization of c -APzE in various solvent and temperature indicate singlet mechanism for the cis → trans photoisomerization of c -APzE in polar solvent but mixed singlet/triplet mechanism in nonpolar solvent. On irradiation of c -APzE, the photo-oxidation product was not generated at all in any solvent. In n -hexane, photocyclization competing with photoisomerization was observed both for t - and c -APzE.

Recently, the development of chemosensor associated with fluoroionophore has attracted great attention. Fluoroionophore is a compound combining the ionophore and fluorophore, where ionophore binds selectively with a specific ion and fluorophore generates a fluorescence signal upon ion binding. Depending on the nature of fluorophore-ionophore interaction in fluoroionophore, fluorescence properties of fluorophore such as fluorescence intensity or fluorescence wavelength maximum may be influenced by ion capture of ionophore. Sensitivity of fluorophore may be associated with the ionic recognition ability of the ionophore, if the fluorophore may be perturbed by the coordination of cation. The recent increase of interest in the synthesis of crown ether derivatives incorporating different fluoroionophores is recently due to their application as alkali metal ion sensors in biochemical analysis and medical diagnostics. In particular, azacrown ether, a typical ionophore, acts as an electron-rich donor as well as a ligand of the cation. The electron pair on the nitrogen heteroatom in electron-rich azacrown ether could be transferred towards electron deficient fluorophore in a π-conjugated D-A arrangement, through the charge transfer interaction between ionophore, an electron donor, and fluorophore, an electron acceptor. The efficient intramolecular charge transfer takes part in the modification of the first electronic transition state of the fluorophore and may lead to weaken the fluorescence from fluorophore. Upon binding of a cation into ionophore cavity, the electron pair on nitrogen heteroatom of ionophore is stabilized and the intramolecular charge transfer is inhibited. Therefore, the original electronic configuration of the unsubstituted fluorophore is recovered, so that fluorescence may be strengthened. Many fluoroionophores including stilbenyl-, aryl-, or styryl-crown ether derivatives containing a stilbene, styrene or aryl moiety as a fluorophore and a crown ether/azacrown ether moiety as an ionophore have been investigated. However, the main disadvantage of these fluoroionophore is the relatively small changes in fluorescence intensity upon cation binding. Incorporation of more efficient fluorophore such as anthracene into fluoroionophore may lead to more remarkable change of fluorescence signal depending on the cation binding. Recent work has concerned the binding of various fluorophores to the N-phenylaza-15-crown-5 and their spectroscopic and complexation properties. This paper concerns the synthesis of N-phenylaza-15-crown-5 derivative containing anthrylethene chromophore and the effect of the complexation with various alkali metal cations on the absorption and fluorescence behavior. We prepared N-[4-(2-anthracen-9-yl-vinyl)-phenyl]-aza15-crown-5 (1), a azacrown ether derivative containing 1-(9anthryl)-2-phenylethene (9-APE) moiety, by Wittig coupling between N-[4-formyl-phenyl]-aza-15-crown-5 and 9bromomethylanthracene. It is known that t-9-APE, a styrene derivative containing highly fluorescent anthracene, shows fairly strong fluorescence (Φf = 0.45, λf = 476 nm in acetonitrile), coming from the locally excited state which the excitation energy is localized on anthracene ring. For 1-(9-anthryl)-2-(4-methoxyphenyl)ethene (MeO-APE) containing an electron donating substituent methoxy group, fluorescence becomes weak and is red-shifted (Φf = 0.028, λf = 494 nm in acetonitrile) due to the contribution of the intramolecular

The axial coordination of aza analogues of 1-(9-anthryl)-2-phenylethene to zinc 5,10,15,20-tetratolylporphyrin (ZnTTP) was investigated. E -1-(9-Anthryl)-2-( n -pyridyl)ethenes ( n = 2, 3 and 4) ( E - n -APyE), the Z isomers ( n = 2 and 4) ( Z - n -APyE) and E -1-(9-anthryl-2-(2-pyrazinyl)ethene ( E -APzE) were tested as aza analogues of 1-(9-anthryl)-2-phenylethene. E -2-APyE, Z -2-APy and E -APzE did not form a complex with ZnTTP. ZnTTP formed a complex with E -3-APyE, but complexation of ZnTTP with Z -3-APyE could not be observed because Z -3-APyE was not available. E -4-APyE and Z -4-APyE showed a considerable difference in their ability to form a complex with ZnTTP. In order to examine the effect of the solvent polarity, the results in dichloromethane were compared with those in toluene. The extent of coordination of E -4-APyE to ZnTTP in dichloromethane was significantly reduced due to the E → Z photoisomerization of E -4-APyE on UV irradiation. However, because the photoisomerization of E -4-APyE was very inefficient in toluene, the extent of coordination of E -4-APyE to ZnTTP in toluene remained unchanged on UV irradiation for up to 2 h. Therefore a change in solvent affected the photoresponsiveness of the system.

The quantum yields of fluorescence and photoisomerization of trans -1-(9-anthryl)-2-( n -pyridyl)ethenes ( n = 2, 3 or 4) (t n -ApyE) and the corresponding cis isomers ( n = 2 or 4) (c- n -APyE) were measured in various solvents. t-3-APyE is strongly fluorescent, but does not undergo photoisomerization, similar to trans -1-(9-anthryl)-2-phennylethene (t-9-APE). The fluorescence and photoisomerization of t-2-APyE and t-4-APyE are strongly influenced by the solvent polarity. In non-polar solvents, they show relatively strong fluorescence, but no photoisomerization to the corresponding cis isomers. As the solvent polarity is increased, the fluorescence intensity decreases and the photoisomerization to the cis isomer becomes efficient. An intramolecular charge transfer excited state is suggested to contribute to the photoisomerization. A singlet mechanism is proposed from the inverse relationship between the fluorescence and photoisomerization quantum yields over the range of solvent polarity and temperature used. A much weaker solvent effect was observed on the fluorescence and photoisomerization of c-2-APyE, and the fluorescence and photoisomerization of c-4-APyE were found to be independent of the solvent polarity. Efficient isomerization to the trans isomer was observed in both non-polar and polar solvents.

Eun Ju ShinDepartment of Chemistry, Sunchon National University, Sunchon, Chonnam 540-742, KoreaReceived February 25, 2004Key Words : Diarylethene, Pyrrole, Indole, Fluorescence, Intramolecular charge transferDiarylethenes are generally known to perform reversiblephotochemical cis-trans isomerization. However, 1-(9-anthryl)-2-phenylethene(9-APE) executes efficient cis →trans photoisomerization but do not undergo reverse trans →cis photoisomerization.

The photocycloaddition reaction of khellin with dimethylfumarate (DF) was investigated. The singlet excited state of khellin is efficiently quenched by DF without giving any cycloadduct. Azulene quenching and the effect of olefin concentration on the photocycloaddition quantum yield indicate that the photoreaction proceeds through a triplet excited state only. These results are further confirmed by the triplet sensitization of the photoreaction and the external heavy atom effects on the photoreaction quantum yield.

The photophysical properties of a 4t,5′-C 4 -cyclomonoadduct (F-2) of 8-methoxypsoralen (8-MOP) with thymidine were compared with those of 5,7-dimethoxycoumarin (DMC), 4t,5′-dihydropsoralen (DHP) and 8-MOP. The magnitudes of the fluorescence quantum yields are in the order DMC > DHP > F-2 > 8-MOP, which is exactly the opposite of the order for the temperature dependence of the fluorescence in ethanol. For DMC, DHP, 8-MOP and F-2 the ratios of the phosphorescence quantum yields to the fluorescence quantum yields are 0.056, less than 0.01, 0.68 and 5.6 and the phosphorescence lifetimes are 0.88 s, 0.88 s, 0.76 s and 1.2 s respectively, in ethanol at 77 K. The phosphorescence-to-fluorescence ratio increases sharply while the phosphorescence lifetime decreases by the external heavy-atom effect. At 77 K, the fluorescence maximum is very red shifted in isopentane compared with that in ethanol, and phosphorescence is not observed in isopentane. The solvent dependence of the fluorescence of the compounds is probably due to a change in the rate of internal conversion rather than to intersystem crossing.

The photophysical properties of 5(E)-styryl-1,3-dimethyluracil (5(E)-SDU) were investigated. The fluorescence quantum yield and the lifetime are low and short relative to those of the parent aromatic hydrocarbon; this is probably because of the contribution of the n,π* state to the fast radiationless decay. However, the fluorescence of 5(E)-SDU at room temperature is not significantly affected by the solvent polarity, the presence of salts or the pH. This observation indicates that the 1(n,π*) state lies above the lowest 1(π,π*) state and that the vibronic mixing between the two states is not extensive. The highly positive fluorescence and the fluorescence excitation polarization confirm that the lowest excited singlet state has the π,π* configuration. The strong temperature dependence of the fluorescence intensity may be due to the operation of the activated process of twisting in the first excited singlet state competing with flurescence, and the rotation barrier is estimated to be 3.0 kcal mol−1. The strong quenching of fluorescence intensity by ethyl iodide at room temperature may be indicative of inefficient intersystem crossing. Moreover, only very weak phosphorescence is detected at 77 K and its quantum yield is too low to estimate in either isopentane-ethyl ether (1:1, v/v) or ethanol, supporting the idea of inefficient intersystem crossing suggested by laser flash photolysis results. Therefore, the major radiationless process appears to be internal conversion including rotatory radiationless decay. From the relatively long phosphorescence lifetime and its highly negative polarization the lowest triplet state is considered to be the 3(π,π*) state.

The photolysis of a dilute acetonitrile solution of 5(Z)-styryl-1,3-dimethyluracil in the presence of oxygen gives the dehydrocylized product in 26.7% yield. Adding benzophenone to the 5(E)-styryl-1,3-dimethyluracil solution improved the yield of the photocyclization owing to the efficient E → Z photoisomerization due to benzophenone sensitization. Studies on the salt, sensitization and quenching effects on the photocyclization of the compound indicate that the photocyclization occurs from the lowest excited singlet (1π, π*) state of 5(Z)-styryl-1,3-dimethyluracil.

1,4,5,8-Tetraazaphenanthrene (TAP) has close-lying n,π* and π,π* singlet states and therefore shows very weak fluorescence (Φf = 0.001); laser flash photolysis indicated that it undergoes efficient intersystem crossing (Φisc = 0.95). The intensity of fluorescence of TAP increases on addition of sodium acetate because N-Na cation coordination elevates the lowest excited 1(n,π*) state to a higher energy. Because of mixing between the lowest excited 1(n,π*) state and 1(π,π*), TAP shows the heavy-atom effect, which is generally not observed in the pure 1(n,π*) state. Since the phosphorescence lifetime is relatively long (about 0.5 – 0.8 s) and the phosphorescence is negatively polarized, the lowest triplet state has the π,π* configuration. The photoreactivity of TAP is compared with the photophysical parameters of azaphenanthrenes.

Photolysis of 5(E)-styryl-1,3-dimethyluracil(5(E)-SDU) with some olefins, such as tetramethylethylene, methyl crotonate, dimethyl ethylidenemalonate, and dimethyl maleate in dichloromethane yields [2+2] cycloadducts along with E\ightleftarrowsZ photoisomerization and photocyclization products of 5-SDU. The [2+2] cycloaddition reaction with olefins occurs on the 5,6-double bond of uracil ring rather than the expected central double bond.

The cis–trans photoisomerization of 5-styryl-1,3-dimethyluracil is investigated. The fluorescence and photoisomerization quantum yields in various solvents of different viscosity and polarity, the effect of salt, pH, and heavy atom on the fluorescence and photoisomerization, the triplet sensitization of the photoisomerization, and the azulene quenching of the direct and sensitized isomerization indicate the singlet mechanism for the direct photoisomerization of the compound. The laser flash photolysis at room temperature showed a weak triplet–triplet absorption indicating some intersystem crossing from the excited singlet state to the triplet state.