Synthesis, photophysical and photochemical properties of poly(oxyethylene)-substituted zinc phthalocyanines

The synthesis, photophysical and photochemical properties of the tetra- and octa-poly(oxyethylene)substituted zinc (II) phthalocyanines are reported for the first time. The new compounds have been characterized by elemental analysis, IR, 1H and 13C NMR spectroscopy, electronic spectroscopy and mass spectra. General trends are described for photodegradation, singlet oxygen, triplet state and fluorescence quantum yields, and triplet and fluorescence lifetimes of these compounds in dimethylsulfoxide (DMSO). Photophysical and photochemical properties of phthalocyanine complexes are very useful for PDT applications. The effects of the substituents on the photophysical and photochemical parameters of the zinc(II) phthalocyanines (3a, 5a and 6a) are also reported. The singlet oxygen quantum yields (Phi(Delta)), which give an indication of the potential of the complexes as photosensitizers in applications where singlet oxygen is required (Type II mechanism) ranged from 0.60 to 0.72. Thus, these complexes show potential as Type II photosensitizers. The fluorescence of the complexes was quenched by benzoquinone (BQ).     

Effect of alicyclic ring size on the photophysical and photochemical properties of bis(arylidene)cycloalkanone compounds

A series of bis(arylidene)cycloalkanone compounds based on cyclobutanone, cyclopentanone, cyclohexanone and cycloheptanone, C4-C7, respectively, with a D-π-A-π-D structure containing the same donor and acceptor but different alicyclic rings was prepared. The effects of alicyclic ring size on the photophysical, photochemical and electrochemical properties of these compounds were investigated systematically. We found that an increase of the number of carbons in the central alicyclic ring leads to changes in geometry, which has significant effects on the conjugation, and photophysical and photochemical properties. These effects include decreases in the fluorescence quantum yield, transient lifetimes, peak extinction coefficients, and the singlet oxygen quantum yield with the increase of the ring size. The one-photon absorption spectra, the two-photon absorption (2PA) spectra, and the fluorescence spectra all show a hypsochromic shift with increasing ring size. The results of this study provide guidance for the design of new cycloketone-based D-π-A-π-D 2PA compounds for photopolymerization and photodynamic therapy applications.     

Synthesis, photophysical and photochemical properties of substituted zinc phthalocyanines

The synthesis, photophysical and photochemical properties of the 4-({3,4,5-tris-[2-(2-ethoxyethoxy)ethyloxy]benzyl}oxy) and 4-({3,4,5-tris-[2-(2-ethoxyethoxy)ethyloxy]benzyl}thio) zinc(ii) phthalocyanines are reported for the first time. The new compounds have been characterized by elemental analysis, IR, (1)H and (13)C NMR spectroscopy, electronic spectroscopy and mass spectra. General trends are described for photodegradation, singlet oxygen, fluorescence and triplet excited state quantum yields, and triplet state and fluorescence lifetimes of these compounds in dimethylsulfoxide (DMSO). The fluorescence of the complexes was quenched by benzoquinone (BQ). The effects of the substitution on the photophysical and photochemical parameters of the zinc(II) phthalocyanines (6, 7 and 8) are also reported. Photophysical and photochemical properties of phthalocyanine complexes are very useful for PDT applications. The substituted Zn(II) phthalocyanines showed high triplet and singlet oxygen quantum yields. High singlet oxygen quantum yields are very important for Type II mechanism. Thus, these complexes show potential as Type II photosensitizers.     

Photophysicochemical and fluorescence quenching studies of benzyloxyphenoxy-substituted zinc phthalocyanines

Photochemical and photophysical measurements were conducted on peripheral and non-peripheral tetrakis- and octakis(4-benzyloxyphenoxy)-substituted zinc phthalocyanines (1, 2 and 3). General trends are described for photodegradation, and fluorescence quantum yields, triplet lifetimes and triplet quantum yields as well as singlet oxygen quantum yields of these compounds in dimethylsulphoxide (DMSO) and toluene. The fluorescence of the complexes is quenched by benzoquinone (BQ), and fluorescence quenching properties are investigated in DMSO and toluene. The effects of the solvents on the photophysical and photochemical parameters of the zinc(II) phthalocyanines (1, 2 and 3) are also reported. Photophysical and photochemical properties of phthalocyanine complexes are very useful for PDT applications.     

Cyclohexenylphenyldiazene: a simple surrogate of the azobenzene photochromic unit

We have carried out an experimental and computational study on the ground- and excited-state photochemical and photophysical properties of (1-cyclohexenyl)phenyldiazene (CPD), a species formally derived from azobenzene in which one of the phenyl rings is replaced by a 1-cyclohexene substituent. The results show that CPD does substantially behave like azobenzene, but with a higher (approximately 70%) Phi(Z-->E) (npi*) photoisomerization quantum yield, calling for CPD as an effective alternative of azobenzene itself with new functionalization possibilities. By use of state-of-the-art ab initio CASPT2//CASSCF minimum energy path computations, we have identified the most efficient decay and isomerization routes of the absorbing singlet (pipi*), S1 (npi*), T1, and S0 states of CPD. The resulting mechanistic scheme agrees with experimental findings and provides a rationale of the observed photoisomerization quantum yields. Furthermore, this study provides a deep insight on the photophysical and photochemical properties of compounds based on the -N=N- double bond which supplies a general model for the photoreactivity of azobenzene-type compounds in general. This is expected to be a useful guideline for the design of novel photoreactive azo compounds.     

Synthesis,characterization, and determination of photophysicochemical properties of peripheral and nonperipheral tetra‐7‐oxy‐3,4‐dimethylcoumarin substituted zinc,indium phthalocyanines

The photochemical and photophysical properties of peripheral and nonperipheral zinc and indium phthalocyanines containing 7‐oxy‐3,4‐dimethylcoumarin synthesized were investigated in this study. 7‐Hydroxy‐3,4‐dimethylcoumarin ( 1 ) was synthesized via Pechmann condensation reaction and then the phthalonitrile derivatives [4‐(7‐oxy‐3,4‐dimethylcoumarino)phthalonitrile ( 2 ) and 3‐(7‐oxy‐3,4‐dimethylcoumarino)phthalonitrile ( 3 )] were synthesized by nucleophilic aromatic substitution. Phthalocyanine compounds containing coumarin units on peripheral ( 4 and 5 ) and nonperipheral ( 6 and 7 ) positions were prepared via cyclotetramerization of phthalonitrile compounds. All compounds' characterizations were performed by spectroscopic methods and elemental analysis. The phthalocyanine derivatives' ( 4–7 ) photochemical and photophysical properties were studied in DMF. The photophysical (fluorescence quantum yields and lifetimes) and photochemical (singlet oxygen and photodegradation quantum yields) properties of these novel phthalocyanines ( 4 – 7 ) were studied in DMF. They produced good singlet oxygen (e.g., Φ_Δ = 0.93 for 7 ) and showed appropriate photodegradation (in the order of 10^?5), which is very important for photodynamic therapy applications.     

A comprehensive investigation of the interrelationships between spectroscopy and photochemistry and substituents of some azulenic derivatives

Several azulenic dyes, including six azulene hydrocarbons, two azulene aldehydes, and two olefinic azulenes, have been synthesized to survey their photophysics and photochemistry. These azulenes display S(2)-->S(0) emission, but with several differences. This is the most remarkable characteristic of the effect of orbital control on color and excited state properties of the azulenic compounds. This paper emphasizes how emission spectra and photochemistry of azulenic compounds are influenced by their chemical structure and solvent. The emission spectra of the azulene hydrocarbons suggest that their excited state properties can be controlled by their molecular structure and size. It was confirmed by emission and (1)H NMR spectroscopy that azulene monoaldehyde is protonated in a strong acid, such as trifluoroacetic acid (TFA). Photochemistry of styrylazulenes was observed during irradiation. Azulenic compounds are thermally stable and color tunable, and hence they are good candidates as non-linear optical materials. Based on their unique photochemical and photophysical characteristics, novel azulenic dyes can be constructed for different uses.     

Benzylidene-oxazolones as molecular photoswitches

The synthesis and photochemical study of a family of molecular switches inspired by the green fluorescent protein (GFP) chromophore is presented. These compounds can be easily synthesized, and their photophysical properties may be tuned. Due to their efficient photoisomerization and high stability, these compounds can be switched on/off by using light and heat or light with different wavelengths.     

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.     

Intramolecular NH/pi complexes of 2-allylaniline derivatives in the ground and excited states

The photochemical and photophysical properties of three 8-allyl-1,2,3,4-tetrahydroquinolines (1a-c) have been studied. These compounds exhibit a 2-allylaniline-like photochemical behavior, undergoing photocyclization to lilolidines (3a-c). The absorption, emission, and excitation spectra of 1a-c, employing convenient model compounds for comparison, demonstrate the formation of a NH/pi intramolecular ground-state complex (AB). This species can absorb light at long wavelengths (330-340 nm), giving rise to the corresponding excited complex AB*. Emission from AB* is red-shifted (420 nm) with respect to that observed when the monomer A is excited (lambda(exc) = 300 nm). These experimental results have been rationalized by means of density-functional theory calculations.     

超分子体系中的光物理和光化学过程

总结了我们组近几年来对超分子体系中的光物理和光化学过程所做的工作,包括三个部分：(1)微反应器控制的有机光化学反应的选择性,(2)疏水、疏脂作用对光物理和光化学过程的影响,(3)超分子体系中的电子转移、能量传递和光化学转换。     

Photoreactivity of the nonsteroidal anti-inflammatory 2-arylpropionic acids with photosensitizing side effects.

The photoreactivity of the nonsteroidal anti-inflammatory 2-arylpropionic acids benoxaprofen, carprofen, naproxen, ketoprofen, tiaprofenic acid, and suprofen is reviewed with special emphasis on fundamental photophysical and photochemical properties. The absorption and emission properties of the excited states of these drugs as well as their main photodegradation routes are summarized. The photochemical mechanisms are discussed on the basis of product studies and detection of short-lived intermediates by means of laser flash photolysis. After dealing with the unimolecular processes, attention is focused on the photosensitized reactions of key biomolecules, such as lipids, proteins or nucleic acids. Finally, a short section on the photobiological effects on simple biological models is also included. Although some earlier citations are included, the literature coverage is in general limited to the last decade.     

The photo-physicochemical properties of an octa-substituted zinc phthalocyanine containing 1,2,4-triazole moieties

4,5-Bis(2-(4-(4-methoxybenzylamino)-5-oxo-3-p-tolyl-4,5-dihydro-1H-1,2,4-triazol-1-yl)ethoxy)-substituted zinc(II) phthalocyanine (4) was synthesized from a phthalonitrile derivative (3). The compounds were characterized by several spectral methods such as electronic absorption, FT-IR, ¹H NMR, ¹³C NMR, mass spectrometry, and elemental analyses. The photophysical and the photochemical properties of 4 were investigated in DMSO and DMF. The solvent effect on the photochemical and photophysical properties for 4 is also discussed.     

偶氮苯光致异构化对紫精-曙洪络合的调控

报导了α，ω－偶氮苯，紫精双发色团化合物的合成与性质研究，结果表明偶氮苯的光致顺反异构化以可调控与之相连的紫精与曙红络合行为，其作用程度的强弱与连接两者的亚甲基链的长度有关，借助ＨＮＭＲ通过对构象进行分析解释了上述的研究结果。     

STUDIES ON HUMAN LENS: I. ORIGIN AND DEVELOPMENT OF FLUORESCENT PIGMENTS

Fluorescence spectra of normal mature human lenses have been measured and at least eight species with distinct emission characteristics identified. To determine the specific photochemical and photophysical processes responsible for the origin and development of these fluorophores, emission behavior of the products generated by successive irradiation of young human lenses (3-6 y old) as well as of L-tryptophan solution have been systematically monitored. Fluorescent products that resulted from this irradiation were comparable to many of the fluorophores detected in aged lenses, indicating that light plays a major role in the development of these pigments. In addition to photogenerated species, there are other compounds in human lenses, presumably advanced glycosylated end products, with marked fluorescence properties. Several oxidation products of tryptophan including N-formylkynurenine or its derivatives, beta-carboline or its derivatives, and anthranilic acid have been identified in the mature human lens. The development of several photoproducts also was attributed to endogenous ascorbate-mediated Maillard reaction products, which undergo photoconversion by the visible light. Although some of these chromophores could act as photosensitizers, the sensitizing efficiency of many are low. Conversely, the near-UV filtering capability of these colored compounds conceivably could protect the vitreous and retina from development of any photochemical lesion.     

三苯基硫鎓盐衍生物激光闪光光解的研究

The photochemical and photophysical behaviors of tri(4-tert-butoxycarbonyl oxyphenyl) sulphonium salts have been investigated. In argon-satureted acetonitrile, the quantum yields of Bronsted acid formed during photolysis of these compounds was abount 0.5. In the transient absorption spectrum excited by 266nm in mathanol and dioxane an evident absorption peak at 360 nm decayed in accordance with pseudo-first-order reaction was observed. In the presence of poly-p-hydroxystyrene or diphenyl sulphide, the apparent second-order reaction decay rate constsnts were 107 and 108 L﹒mo-1﹒s-1, respectively. Results indicated that the transient absorption peak at 360nm was attributed to the diphenyl sulphide radical cations formed in photolysis of sulphonium salts, which were proposed by abstraction of hydrogen from solvent or polymer to yield the photonic acid and diphenyl sulphide as listed in eqns. (1) and (2). The influence of non-nuncleophilic anions of title compounds on their photochemical behavior was just less important.     

Luminescence and Stability of 1,4,5-Triaryl-1,2,3-Triazoles

The fluorescence, phosphorescence, and photochemical properties of di- and triaryl-substituted-1,2,3-triazoles are reported in this work. The ease of synthesis of regioisomers of substituted triazoles enables a systematic study on the correlation between regiochemistry and excited state properties, which include the solvent dependence of fluorescence, energy gap between singlet and triplet emitters, and propensity to photon-triggered transformations. The triazoles that carry electron (e)-donor and e-acceptor aryl substituents show high fluorescence quantum yields in weakly polar solvents and exhibit solvent-dependent fluorescence. The luminescence properties of these compounds in glass matrices at 77 K are characterized. The thermal and photo-stability, two parameters that are crucial to their potential utilities in optical devices, of these compounds are determined. The position of the e-donor substituent has a significant impact on the fluorescence emission energy and solvent sensitivity, singlet-triplet energy gap, and photochemical reactivity and stability. The experimental observations on the structural correlation with the photophysical and photochemical properties are explained by quantum chemical calculations. This study provides a rationale on the placement of substituent on a donor-acceptor type fluorophore to maneuver a range of photo-related properties.     

STUDIES ON HUMAN LENS: I. ORIGIN AND DEVELOPMENT OF FLUORESCENT PIGMENTS

Abstract
Fluorescence spectra of normal mature human lenses have been measured and at least eight species with distinct emission characteristics identified. To determine the specific photochemical and photophysical processes responsible for the origin and development of these fluorophores, emission behavior of the products generated by successive irradiation of young human lenses (3–6 y old) as well as of L-tryptophan solution have been systematically monitored. Fluorescent products that resulted from this irradiation were comparable to many of the fluorophores detected in aged lenses, indicating that light plays a major role in the development of these pigments. In addition to photogenerated species, there are other compounds in human lenses, presumably advanced glycosylated end products, with marked fluorescence properties.
Several oxidation products of tryptophan including N -formylkynurenine or its derivatives, β-carboline or its derivatives, and anthranilic acid have been identified in the mature human lens. The development of several photoproducts also was attributed to endogenous ascorbate-mediated Maillard reaction products, which undergo photoconversion by the visible light. Although some of these chromophores could act as photosensitaizers, the sensitizing efficiency of many are low. Conversely, the near-UV filtering capability of these colored compounds conceivably could protect the vitreous and retina from development of any photochemical lesion.     

Probing the photochemical mechanism in photoactive yellow protein

Selectively bridged model compounds related to the chromophore in photoactive yellow protein have been synthesized where the single bond adjacent to the benzene ring (bond 1) and where both bond 1 and the adjacent double bond (bond 2) are bridged. They were compared to the nonbridged reference compound regarding their photophysical properties using steady-state and time-resolved fluorescence at various temperatures. Quantum chemical calculations were additionally performed and showed that several conformers are populated in the ground state. The neutral model compounds show that the nonradiative deactivation channel is linked to both single- and double-bond twisting. The relative importance of single-bond twisting is increased for the corresponding deprotonated hydroxy compounds with an enhanced donor character. The simultaneous photochemical activity of both single and double bonds explains the ease of photochemical isomerization in the confined environment of the natural PYP protein and also of the primary step in the vision process in rhodopsin.     

Dual chromophore-nitroxides: novel molecular probes, photochemical and photophysical models and magnetic materials

Over the last decades scientists have faced growing requirements in novel methods of fast and sensitive analysis of antioxidant status of biological systems, spin redox probing and spin trapping, investigation of molecular dynamics, and of convenient models for studies of photophysical and photochemical processes. In approaching this problem, methods based upon the use of dual chromophore-nitroxide (CN) compounds have been suggested and developed. A CN consists of two molecular sub-functionality (a chromophore and a stable nitroxide radical) tethered together by spacers. In the dual compound the nitroxide is a strong intramolecular quencher of the fluorescence from the chromophore fragment. Reduction to hydroxylamine, oxidation of the nitroxide fragment or addition of an active radical yield the fluorescence increase and the parallel decay of the fragment electron spin resonance (ESR) signal. At certain conditions the dual molecules undergo photomagnetic switching and form excited state multi-spin systems. These unique properties of CN were intensively exploited as the basis for several methodologies, which include molecular probing, modeling intramolecular photochemical and photophysical processes, and construction of new magnetic materials.