New soluble methylendioxy-phenoxy-substituted zinc phthalocyanine derivatives: Synthesis, photophysical and photochemical studies

The syntheses of new three phthalonitriles (1, 2 and 3), together with photophysical and photochemical properties of the resulting peripherally and non-peripherally tetrakis- and octakis 3,4-(methylendioxy)-phenoxy-substituted zinc phthalocyanines (4, 5 and 6) are described for the first time. Complexes 4, 5 and 6 have been synthesized and characterized by elemental analysis, IR, ¹H NMR spectroscopy, electronic spectroscopy and mass spectra. Complexes 4, 5 and 6 have good solubility in organic solvents such as CHCl₃, DCM, DMSO, DMF, THF and toluene and are mainly not aggregated (except for complex 6 in DMSO) within a wide concentration range. General trends are described for singlet oxygen, photodegradation, fluorescence quantum yields, triplet quantum yields and triplet life times of these complexes in DMSO and toluene. Complex 4 has higher singlet oxygen quantum yields, fluorescence quantum yields, triplet quantum yields and triplet life times than complexes 5 and 6. The effect of the solvents on the photophysical and photochemical parameters of the zinc(II) phthalocyanines (4, 5 and 6) are also reported.     

Synthesis, characterization and comparative studies on the photophysical and photochemical properties of metal-free and zinc(II) phthalocyanines with phenyloxyacetic acid functionalities

The synthesis and characterization of new peripherally and non-peripherally tetra-substituted metal-free and zinc(II) phthalocyanines with 2-, 3- and 4-phenyloxyacetic acid functionalities are described for the first time in this study. The new compounds have been characterized by elemental analysis, FT-IR, UV-Vis, MALDI-TOF and ¹H-NMR spectra. Photodegradation, singlet oxygen and fluorescence quantum yields, and fluorescence lifetimes of these compounds are studied in dimethylformamide (DMF). The influence of the substituent position on the phthalocyanine framework (non-peripherally or peripherally), central metal ion (metal-free or zinc) and the position of the COOH group (2-, 3- or 4-position on the phenyloxyacetic acid) on the spectroscopic, photophysical and photochemical properties have been investigated. Non-peripherally zinc(II) phthalocyanines (1b and 2b) and peripherally zinc(II) phthalocyanine (4b) gave good singlet oxygen quantum yields (Φ_Δ) (0.37, 0.39 and 0.38, respectively) which indicate the potential of the complexes as photosensitizers in applications of PDT.     

Solvent and central metal effects on the photophysical and photochemical properties of 4-benzyloxybenzoxy substituted phthalocyanines

The synthesis and characterization of new peripherally tetra-4-benzyloxybenzoxy substituted metal-free, zinc and lead phthalocyanines are described for the first time in this study. The influence of various organic solvents and the nature of the central metal ion on the spectroscopic, photophysical and photochemical properties has been investigated. General trends are described for photodegradation, singlet oxygen and fluorescence quantum yields, and fluorescence lifetimes of these compounds in different solvents. Photophysical and photochemical properties of phthalocyanine compounds are very useful for photodynamic therapy applications. Especially high singlet oxygen quantum yields are very important for Type II mechanism. The studied phthalocyanine compounds showed good singlet oxygen generation and these compounds show potential as Type II photosensitizers. The fluorescences of the studied compounds are effectively quenched by 1,4-benzoquinone in different solvents.     

Synthesis, photophysical and photochemical properties of aryloxy tetra-substituted gallium and indium phthalocyanine derivatives

The synthesis, photophysical and photochemical properties of the tetra-substituted aryloxy gallium(III) and indium(III) phthalocyanines are reported for the first time. General trends are described for photodegradation, singlet oxygen, fluorescence, and triplet quantum yields and triplet lifetimes of these compounds. The introduction of phenoxy and tert-butylphenoxy substituents on the ring resulted in lowering of fluorescence quantum yields and lifetimes, and triplet quantum yields, and an increase of k_IC, k_ISC, and k_F. Photoreduction of the complexes was observed during laser flash photolysis. The singlet oxygen quantum yields (Φ_Δ), which give an indication of the potential of the complexes as photosensitizers in applications where singlet oxygen is required (Type II mechanism) ranged from 0.41 to 0.91. Thus, these complexes show potential as Type II photosensitizers.     

The synthesis and photophysicochemical properties of low-symmetry zinc phthalocyanine analogues

The synthesis of a low-symmetry derivative, zinc mono-carboxy substituted phthalocyanine, ZnPc-COOH (4) has been reported. The photochemical and photophysical properties of ZnPc-COOH (4), ZnTMPyPc (5), ZnttbPc (6) and a previously synthesized low-symmetry derivative, ZnttbIPc (7), in various organic solvents are reported. The red-shifting of the spectra of 4 and 5 (relative to that of unsubstituted zinc phthalocyanine, ZnPc) is a function of the electron-donating sulfur-containing substituents attached to the periphery of the molecule. High triplet quantum yields (Ф_T) generally occur in response to substitution on the zinc phthalocyanine ring periphery. The highest Ф_T values and triplet lifetimes (τ_T) occur in DMSO for all derivatives as a result of the solvent's high viscosity. The strongly electron-withdrawing imido fused ring of ZnttbIPc (7) stabilizes it against photo-oxidative degradation relative to the other derivatives.     

Solvent effects on the photochemical and fluorescence properties of zinc phthalocyanine derivatives

The effects of solvents on the singlet oxygen, photobleaching and fluorescence quantum yields for zinc phthalocyanine (ZnPc) and its derivatives; (pyridino)zinc phthalocyanine ((py)ZnPc), zinc octaphenoxyphthalocyanine (ZnOPPc) and zinc octaestronephthalocyanine (ZnOEPc), is presented. The effects of the solvents on the ground state spectra are also discussed. The largest red shift of the Q band was observed in aromatic solvents, the highest shift being observed for 1-chloronaphthalene. Higher singlet fluorescence quantum yields were observed in THF for ZnPc and ZnOPPC. Also in the same solvent phototransformation rather than photobleaching was observed for ZnOPPc. Split Q band in the emission and excitation spectra of ZnOPPc was observed in some solvents and this is explained in terms of the lowering of symmetry following excitation.     

Synthesis and photophysical properties of lead phthalocyanines

This work reports on the synthesis and photophysical parameters of tetra-and octa-substituted new lead phthalocyanines. The complexes synthesized are: 1,4-(tetraphenoxyphthalocyaninato)lead (7a), 1,4-(tetra-tert-butylphenoxyphthalocyaninato)lead (7b), 2,3-(tetraphenoxyphthalocyaninato)lead (8a), 2,3-(tetra-tert-butylphenoxyphthalocyaninato)lead (8b), 2,3-octaphenoxyphthalocyaninatolead (9a) 2,3-[octakis(4-t-butylphenoxyphthalocyaninato)]lead (9b). Photophysical properties were studied for these complexes in a dimethylsulfoxide, dimethylformamide, toluene, tetrahydrofuran and chloroform. The fluorescence spectra were different from excitation spectra due to demetallation upon excitation. High triplet quantum yields ranging from 0.70 to 0.88 (in DMSO, DMF and toluene) and low triplet lifetimes (20–50 μs in DMSO, and <10 μs in the rest of the solvents) were observed due to the presence of heavy atom.     

Synthesis,photophysical and photochemical properties of tetra- and octa-substituted gallium and indium phthalocyanines

The synthesis, photophysical and photochemical properties of the tetra- and octa-[4-(benzyloxyphenoxy)] substituted gallium(III) and indium(III) phthalocyanines are reported for the first time. The new compounds have been characterized by elemental analysis, IR, ¹H NMR spectroscopy and electronic spectroscopy. General trends are described for quantum yields of photodegredation, fluorescence quantum yields and lifetimes, triplet lifetimes and triplet quantum yields as well as singlet oxygen quantum yields of these compounds in dimethylsulfoxide (DMSO). Substituted indium phthalocyanine complexes (7b–9b) showed much higher quantum yields of triplet state and shorter triplet lifetimes, compared to the substituted GaPc derivatives due to enhanced intersystem crossing (ISC) in the former. The gallium and indium phthalocyanine complexes showed phototransformation during laser irradiation due to ring reduction. The singlet oxygen quantum yields (Φ_Δ), which give an indication of the potential of the complexes as photosensitizers in applications where singlet oxygen is required (Type II mechanism) ranged from 0.51 to 0.94. Thus, these complexes show potential as photodynamic therapy of cancer.     

Comparative studies of photophysical and photochemical properties of solketal substituted platinum(II) and zinc(II) phthalocyanine sets

A complete set of platinum(II) solketal substituted phthalocyanines has been synthesized and characterized. To evaluate their potential as Type II photosensitizers for photodynamic therapy, comparative studies of their photophysical and photochemical properties with analogous zinc(II) series have been achieved: electronic absorption, fluorescence quantum yields, lifetimes, and fluorescence quenching by benzoquinone, as well as singlet oxygen generation and photodegradation. It appears that platinum(II) phthalocyanines are worth being used as Type II photosensitizers, as they exhibit good singlet oxygen generation and appropriate photodegradation.     

Synthesis,photophysical and nonlinear optical properties of microwave synthesized 4-tetra and octa-substituted lead phthalocyanines

This work presents the photophysical and nonlinear optical behaviour of newly synthesized complexes: 2,(3)-tetrakis(4-benzyloxyphenoxyphthalocyaninato) lead (5a) and 2,3-octakis(4-benzyloxyphenoxyphthalocyaninato) lead (6a). The nonlinear optical behaviour of complexes 5a and 6a are compared with those of 2,(3)-tetraphenoxyphthalocyaninato lead (5b), 2,(3)-tetrakis(4-t-butylphenoxyphthalocyaninato) lead (5c), 2,3-octaphenoxyphthalocyaninato lead (6b) and 2,3-octakis(4-t-butylphenoxyphthalocyaninato) lead (6c). The synthesis of 5a and 6a was performed using microwave irradiation. Photophysical properties were studied for these complexes in dimethylsulfoxide, dimethylformamide, toluene, tetrahydrofuran and chloroform. The fluorescence spectra were different from excitation spectra due to demetallation upon excitation. High triplet quantum yields ranging from 0.80 to 0.86 (in DMSO, DMF and toluene) and low triplet lifetimes (20–50 μs in DMSO, and <10 μs in the rest of the solvents) were observed due to the presence of heavy atom. Nonlinear optical properties were studied in dimethylsulfoxide. The optical limiting threshold intensity (I_lim) for the PbPc derivatives were calculated and ranged from 2.1 to 6.6 W/cm².     

Synthesis and properties of axially-phenoxycyclotriphosphazenyl substituted silicon phthalocyanine

An hydroxyl substituted hexa(phenoxy)cyclotriphosphazene (3) is reacted with silicon phthalocyanine (4), SiPc(Cl)₂, to give an axially-disubstituted phenoxycyclotriphosphazenyl silicon phthalocyanine (5). In this study, an axially phosphazene substituted phthalocyanine complex synthesized at the first time. Newly synthesized silicon phthalocyanine complex has been fully characterized by elemental analysis, ESI mass spectrometry, FT-IR, ¹H, ¹³C and ³¹P NMR spectroscopy. Photophysical (fluorescence quantum yield and lifetime) and photochemical (singlet oxygen generation and photodegradation quantum yield) properties of complex 5 are reported in DMSO. The fluorescence quenching behaviour of this complex by 1,4-benzoquinone (BQ) is also reported in DMSO.     

Synthesis and photophysical properties of metal free, titanium, magnesium and zinc phthalocyanines substituted with a single carboxyl and hexylthio groups

2,3,9,10,16,17,23,24-Octakis(hexylthio)phthalocyanines (4a-6a) and 2-carboxy-9,10,16,17,23,24-hexakis(hexylthio)phthalocyanines (4b-6b) were synthesized using a one-pot method by cyclotetramerization of the phthalonitriles: 4,5-bis(hexylthio)phthalonitrile and carboxylic acid phthalonitrile. 2-Carboxycatecholato-2,3,9,10,16,17,23,24-octakis(hexylthio)phthalocyaninatotitanium(IV) (8) was prepared from 2,3,9,10,16,17,23,24-octakis(hexylthio)phthalocyaninatooxotitanium(IV) (7). The structures of these compounds were characterized by using elemental analyses, UV-Vis, FT-IR, ¹H NMR and mass spectroscopies. Their photophysical properties were also studied. The Φ_F values are 0.12, 0.02, 0.10, 0.06, 0.10, 0.06, 0.65, 0.80 and the Φ_T values are 0.58, 0.56, 0.57, 0.64, 0.22, 0.48, 0.17, 0.12 for 4-8, respectively. The Φ_F value for complex 8 is higher than ever reported for phthalocyanine complexes. The triplet lifetimes (τ_T) values for all the complexes were generally good, ranging from 50 to 310 μs, and generally increased in the presence of the single carboxyl group. These complexes showed reasonable triplet quantum yields and lifetimes, and hence have potential for use as photosensitizers in photodynamic therapy (PDT) of cancer.     

Synthesis and photophysical properties of porphyrins with fluorenyl pendant arms

Symmetrical-A₄-porphyrins bearing four fluorene donor moieties TOFP (5,10,15,20-tetra(4-(2 methyloxyfluorenyl)phenyl)porphyrin) as well as eight fluorene arms OOFP (5,10,15,20-octa(3,5-(2-methyloxyfluorenyl)phenyl)porphyrin) were synthesized and characterized. Preliminary photophysical properties are reported. In comparison to the reference tetraphenylporphyrin TPP, the luminescence properties are slightly improved. The fluorescence quantum yields of tetrafluorenylporphyrin TOFP (1) and octafluorenylporphyrin OOFP (2) are 0.10 and 0.13, respectively.     

Synthesis and properties of crown ether functionalized coumarin substituted zinc phthalocyanine

The novel 6,7-[15-crown-5]-3-[p-(2,3-dicyanophenoxy)phenyl]coumarin (1) and its non-peripherally substituted zinc phthalocyanine complex (2) have been prepared and characterized by elemental analysis, ¹H NMR (for compound 1), MALDI-TOF, FT-IR and UV-Vis spectral data. Fluorescence intensity changes of compound 1 have been determined by addition of Na⁺ or K⁺ ions at 25 °C in THF. The effects of the chromenone crown ether substituent of the phthalocyanine molecule on the photophysical (fluorescence quantum yield and lifetime) and photochemical (singlet oxygen generation and photodegradation) properties were also investigated. The fluorescence of the zinc phthalocyanine complex is effectively quenched by addition of 1,4-benzoquinone (BQ).     

Syntheses,crystal structures,and photophysical properties of two 2-D coordination polymers

Two coordination polymers, [Mn(dipt)(m-BDC)₃] _n (1) and [Pb(mip)(1,4-NDC)] _n (2) [dipt?=?2-(2,4-dichlorophenyl)-1H-imidazo[4,5-f][1,10]phenanthroline, mip?=?2-(3-methoxyphenyl)-1H-imidazo[4,5-f][1,10]phenanthroline, m-BDC?=?isophthalic acid, 1,4-NDC?=?naphthalene-1,4-dicarboxylic acid], have been synthesized by hydrothermal reactions and characterized by elemental analysis, thermogravimetric analysis, infrared spectrum, and single-crystal X-ray diffraction. Single-crystal X-ray diffraction reveals that 1 and 2 have 1-D chain architecture. Complex 1 has a 2-D-layered structure constructed from C–H···O hydrogen bonds. Complex 2 has a 2-D-layered structure constructed from N–H···O hydrogen bonds and π–π interactions. TG analyses suggest 1 and 2 have excellent thermal stabilities from hydrogen bonds and π–π interactions. Mn(II) in 1 has trigonal bipyramidal geometry surrounded by three carboxylate oxygen atoms from three monodentate bridging m-BDC and two nitrogen atoms from one dipt. Pb(II) has [:PbN2O4] pentagonal bipyramidal geometry in 2. The luminescent properties for dipt, mip, 1, and 2 are also presented.     

Simultaneous studies of pressure effect on charge transport and photophysical properties in organic semiconductors: A theoretical investigation

High-mobility and strong luminescent materials are essential as an important component of organic photodiodes, having received extensive attention in the field of organic optoelectronics. Beyond the conventional chemical synthesis of new molecules, pressure technology, as a flexible and efficient method, can tune the electronic and optical properties reversibly. However, the mechanism in organic materials has not been systematically revealed. Here, we theoretically predicted the pressure-depended luminescence and charge transport properties of high-performance organic optoelectronic semiconductors, 2,6-diphenylanthracene (DPA), by first-principle and multi-scale theoretical calculation methods. The dispersion-corrected density functional theory (DFT-D) and hybrid quantum mechanics/molecular mechanics (QM/MM) method were used to get the electronic structures and vibration properties under pressure. Furthermore, the charge transport and luminescence properties were calculated with the quantum tunneling method and thermal vibration correlation function. We found that the pressure could significantly improve the charge transport performance of the DPA single crystal. When the applied pressure increased to 1.86 GPa, the hole mobility could be doubled. At the same time, due to the weak exciton coupling effect and the rigid flat structure, there is neither fluorescence quenching nor obvious emission enhancement phenomenon. The DPA single crystal possesses a slightly higher fluorescence quantum yield ～ 0.47 under pressure. Our work systematically explored the pressure-dependence photoelectric properties and explained the inside mechanism. Also, we proposed that the external pressure would be an effective way to improve the photoelectric performance of organic semiconductors.     

Chromenone 12-crown-4 substituted zinc phthalocyanine complexes: investigation of spectral, photophysical and photochemical properties

The synthesis of novel 6,7-[(12-crown-4)-3-[p-(3,4-dicyanophenoxy)phenyl]coumarin (1), 6,7-[(12-crown-4)-3-[p-(2,3-dicyanophenoxy)phenyl]coumarin (2), and their corresponding tetra-(chromenone 12-crown-4)-substituted zinc (II) phthalocyanine complexes (3 and 4) have been prepared. These new compounds have been characterized by elementel analysis, (1)H NMR (1 and 2), MALDI-TOF, IR and UV-Vis spectral data. The fluorescence intensity changes for 1 and 2 by addition of Na(+) or K(+) ions have been determined at 25°C in THF. Intensity of the binding Na(+)- and K(+)-complexes (1 and 2) have decreased. The effects of the chromenone crown ether on the phthalocyanine molecule concerning photophysical and photochemical properties are also investigated. Photodegredation, singlet oxygen, fluorescence quantum yields, and fluorescence lifetimes of zinc phthalocyanine complexes (3 and 4) are also examined in DMSO.     

Characterization and physicochemical studies of the conjugates of graphene quantum dots with differently charged zinc phthalocyanines

Unsubstituted zinc phthalocyanine (ZnPc), 2,9,16,23-tetrakis[4-(N-methylpyridyloxy)]-phthalocyanine (ZnTPPcQ) and Zn tetrasulfo phthalocyanine (ZnTSPc) were non-covalently (electrostatic and/or π–π interaction) attached to graphene quantum dots (GQDs) to form GQDs-Pc nanoconjugates. Relative to Pcs alone, the presence of GQDs improved the triplet quantum yields with the following values: GQDs-ZnPc (0.73), GQDs-ZnTPPcQ (0.76) and GQDs-ZnTSPc (0.67). Respective Förster resonance energy transfer (FRET) efficiencies were calculated to be 0.81, 0.80 and 0.28. However, singlet oxygen generating abilities of the as-synthesized nanoconjugates were relatively low due to the screening effect of GQDs and quenching in water. This study shows that, the type of Pc, loading and solvent used are among the vital properties to consider when constructing GQD-nanoconjugate systems with optimal triplet quantum yield properties and investigation of their physicochemical properties.     

Synthesis, luminescence properties, and theoretical insights of N-alkyl- or N,N-dialkyl-pyrene-1-carboxamide

We report the synthesis and photophysical properties of N-alkyl- or N,N-dialkyl-pyrene-1-carboxamide. These derivatives, as well as pyrene, exhibited blue emission. N-Alkyl-type derivatives exhibited strong fluorescence emission (Φ_fl = 0.61 in EtOH) in both nonpolar and polar solvents. On the other hand, N,N-dialkyl-type derivatives showed weak fluorescence emission (Φ_fl <0.01) due to vibrational deactivation. However, in highly viscous solvents such as glycerin, the quantum efficiencies of N-alkyl-type (Φ_fl = 0.91) and N,N-dialkyl-type (Φ_fl = 0.082) derivatives were increased. We also investigated the fluorescence mechanism of these compounds using time-dependent density-functional theory (TD-DFT). From these results, we find that highly fluorescent pyrene-1-carboxamide derivatives can be designed by introducing an appropriate functional group at the nitrogen atom of the amide. Thus, N,N-dialkyl-type pyrene-1-carboxamide has considerable potential for use in applications such as environmental response sensors and probes.