THE TRIPLET AND RADICAL SPECIES OF HAEMATOPORPHYRIN AND SOME OF ITS DERIVATIVES

Abstract— Nanosecond laser flash photolysis and pulse radiolysis have been used to generate and characterise the triplet state, and semioxidised and semireduced radicals of haematoporphyrin, and three 0 -acyl compounds derived from it (the monoacetate, the diacetate and the disuccinate).
After 347 nm irradiation in water containing 2% Triton X-100, haematoporphyrin forms the triplet state (φ_T= 0.92) and photoionises monophotonically (φ_I= 0.03). For the O -acyl derivatives, φ_T approaches unity and photoionisation is reduced. In acetone the triplet yield of all four compounds are close to unity. The difference and corrected spectra for the triplet species are presented and decay rates ( k ₁˜10⁴s^-1) and oxygen quenching constants ( k _Q˜1.5times10⁹ M ^-1s^-1) for the triplet state have been measured. The difference and corrected spectra for the semi-reduced species in methanol and semi-oxidised species in aqueous Triton X-100 are presented.
The photophysical characteristics in fluid solution of haematoporphyrin and its 0 -acyl derivatives are rather similar to those previously recorded for other photosensitising porphyrins.     

THE RELATIONSHIP BETWEEN CARCINOGENIC ACTIVITIES OF POLYCYCLIC AROMATIC HYDROCARBONS AND THEIR SINGLET, TRIPLET, AND SINGLET-TRIPLET SPLITTING ENERGIES AND PHOSPHORESCENCE LIFETIMES

Abstract— The energies of the lowest excited singlet, E_s, and triplet, E_t, states, and singlet-triplet splitting energies, ΔE_s,t, were determined on 18 carcinogenic and 31 noncarcinogenic polycyclic aromatics. A highly significant correlation was found between carcinogenic activity and the energy of the excited singlet state. Compounds with an E_s < 312 kJ/mol were 4.8 times more likely to be carcinogens than those compounds with E_s 312 kJ/mol (P= 0.015). Compounds whose singlet energies fell within the narrow range of 297 ≤E_s≤ 310 kJ/mol were 22.8 times more likely to be carcinogens than those compounds which fell outside this range (P= 0.00006). A significant correlation between carcinogenic activity and E_t energies was not found, while the correlation involving ΔE_s,t energies was intermediate between the E_s and E_t correlations. The phosphorescence lifetimes, τ_p, of the 18 carcinogenic aromatics and 27 of the noncarcinogenic aromatip were determined, and were shown not to be correlated with carcinogenic activity. When either the E_t or ΔE_s,t energies were plotted as a function of E_s it was found that the carcinogens tended to form in an elliptical cluster. Compounds whose E_s and E_t energies placed them within the ellipse were 9.7 times more likely to be carcinogens than those compounds which fell outside the ellipse (P= 0.002), while with the E_s, ΔE_s,t ellipse, compounds which fell inside were 20.6 times more likely to be carcinogens than those which fell outside (P= 0.0004). E_s, E_t, ΔE_s,t and τ_p values were also determined on 12 carcinogenic and 4 noncarcinogenic alkyl substituted benz[a]anthracenes. There was no significant difference between the carcinogens and noncarcinogens and the “elliptical” correlation predicted both the carcinogens and noncarcinogens to be carcinogenic. The results suggest that either some property(ies) of the lowest excited singlet state, but not its energy, or some molecular property(ies) which runs parallel to singlet state energies may be important in determining carcinogenic activity in polycyclic aromatics.     

卟啉化合物的热化学研究 Ⅱ. 四苯基卟啉及其衍生物的标准燃烧能和生成焓

用自行安装的精密静弹燃烧量热计测定了四苯基卟啉(TPP)、四甲苯基卟啉(T_((PCH)_3)PP)、四对甲氧苯基卟啉(T_((P-OCH)_3)PP)和四邻氨苯基卟啉(T_((O-NH)_2)PP)的标准燃烧能,并计算出标准生成焓。样品 1.将苯甲醛加入沸腾的丙酸中迥流30分钟后冷至50～60℃,加入乙醇,冷却,过滤,紫色产物用甲醇洗,干燥后得TPP粗品。将粗品溶于迥流的二氯甲烷,加入溶于苯的DDQ迥流30分钟,蒸除溶剂,残渣溶于氯仿,氧化铝-氯仿柱层析,氯仿-甲醇重结晶制得纯TPP.     

Cis/trans ISOMERIZATION OF CAROTENOIDS BY THE TRIPLET CARBONYL SOURCE 3-HYDROXYMETHYL-3,4,4-TRIMETHYL-1,2-DIOXETANE*

Abstract— The interaction of biological carotenoids with 3-hydroxymethyl-3,4,4-trimethyl-1,2-dioxetane (HTMD), a thermodissociable source of electronically excited ketones, was investigated using reversed-phase high-performance liquid chromatography. Incubation of the all-trans isomers of β-carotene, lycopene and canthaxanthin with HTMD led to significant trans-to-cis isomerization, with cis isomers accounting for 20–50% of products formed (the balance assigned as oxidation products). The isomers forming from all-trans-β-carotene were identified as 9-cis-, 13-cis- and 15-cis-β-carotene by cochromatography of cis isomer standards and by on-line diode array absorbance spectroscopy. An HTMD-dependent cis-to-trans isomerization was observed in incubations started with 15-cis-β-carotene, and it occurred more rapidly and to a greater extent than the isomerization of all-trans-β-carotene. The isomer patterns generated from lycopene and β-carotene are generally similar to those reported recently for various human tissues (Stahl et al, 1992, Arch. Biochem. Biophys. 294 , 173–177).     

在Lewis酸催化下N-苯乙基甘氨酸衍生物的分子内环化反应研究及苯并-3-氮杂环庚酮-1衍生物的合成

本文报导了不同N-苯乙基甘氨酸衍生物在Lewis酸催化下的分子内环化反应的若干规律,以及苯并-3-氮杂环庚酮-1衍生物的合成.     

THE PHOTOCHEMICAL INTERACTION BETWEEN THE TRIPLET STATE OF 8-METHOXYPSORALEN AND THE MELANIN PRECURSORL–3, 4 DIHYDROXYPHENYLALANINE

Abstract— The photochemical interaction between 8-methoxypsoralen (8-MOP) and the melanin precursorL–3,4-dihydroxyphenylalanine(dopaH₂) has been studied using laser flash photolysis. Triplet excited 8-MOP was thus found to abstract electrons from dopaH₂ ( k ∼ 2 × 10⁹ dm³ mol^-1 s^-1) to form semireduced 8-MOP and semioxidised dopaH₂.The technique of pulse radiolysis was used to establish separately the spectra of (a) the semi-reduced form of 8-MOP at pH 6.5 and (b) the semioxidised forms of dopaH₂ at pH 6.5, 5.8, 4.6 and 3.3. The corresponding λ_max and extinction coefficients found were: for 8-MOP at pH 6.5, λ_max= 350 nm (= 9050 dm³ mol^-1 cm^-1); for dopa at pH 6.5, λ_max= 305 nm (ε= 12000 dm³ mol^-1 cm^-1) and for dopaH at pH 3.3, λ= 305 nm (ε= 5900 dm³ mol^-1 cm^-1).     

NANOSECOND KINETIC ABSORPTION AND CALORIMETRIC STUDIES OF CYCLOPENTENONE: THE TRIPLET, SELF-QUENCHING, AND THE PREDIMERIZATION BIRADICALS

The photolysis of 2-cyclopentenone has been studied by a combination of kinetic absorption spectrophotometry and time-resolved photoacoustic calorimetry. The lifetime of the cyclopentenone triplet is strongly concentration dependent and corresponds to a value of 380 +/- 75 ns at infinite dilution in acetonitrile. The biradical intermediate (or pair of isomeric biradicals) immediately preceding formation of photodimer forms with very high efficiency upon quenching of triplet cyclopentenone by a second ground state cyclopentenone molecule and has an energy of 47 kcal/mol relative to two molecules of reactant. Quenching of the cyclopentenone triplet by conjugated dienes is much slower than expected, which is the reason that early estimates of the triplet lifetime were much too short.     

碱土金属氧化物和过氧化物的O1s电子结合能测定

通过在谱仪真空中对碱土金属氧化物作原位加热, 使其表面碳酸盐分解, 然后记录其晶格氧的O_(1s)电子结合能. 结果表明测得的MgO, CaO, SrO和BaO 的O_(1s)结合能明显地低于大部分文献报导的数值. 本文测得的碱土金属氧化物的O_(1s)电子结合能与氧原子上的Sanderson电荷分数有合理的相关性. 本文测得的BaO_2的O_(1s)结合能是530.9 eV, 它比文献报导的数值要低.     

量热滴定法测定苯丙氨酸、亮氨酸、蛋氨酸、色氨酸的热力学函数

本文用美国Tronae Model 1250微机控制的量热滴定仪,测定了苯丙氨酸、亮氨酸、蛋氨酸、色氨酸加质子反应热△H,加质子反应常数logβ,并从而得到△G和△S。由于自然界光学活性起源是化学进化研究的一个重要课题,地球上生命组织的蛋白质,除甘氨酸外,所有氨基酸都是L型。在光学活性起源理论中,其中最有倾向性看法是:宇称不守恒的弱相互作用,通过中性流联合电磁相互作用,使手性分子两对映体的电子键能显出差别。根据Weinberg Salam弱电统一理论,算出D与L分子的能量差10~(-12)—10~(-18)eV。本文拟利用微量量热技术,来观察四对D、L氨基酸在加质子反应中宏观热力学函数有无差异。     

N-3-ALKYLATION OF URACIL AND DERIVATIVES VIA N-1-BOC PROTECTION

An easy and efficient synthesis of 3-alkyluracils is described. Thus, BOC-protection at N-1 of uracil permits selective alkylation at N-3. This protecting group can be removed under very mild conditions.     

QUANTUM YIELDS FOR THE CYCLIZATION AND CONFIGURATIONAL ISOMERIZATION OF 4E, 15Z-BILIRUBIN

Extraction of a solution of bilirubin configurational isomers in chloroform with an aqueous solution of human serum albumin was found to remove selectively the 4Z,15E-isomer. This phenomenon was used to develop a method for the purification of the 4E,15Z-isomer of bilirubin. The quantum yield for the cyclization and configurational isomerization of the 4E,15Z-isomer bound to a molar excess of human serum albumin was measured at 450 and 510 nm. The quantum yield for cyclization to form lumirubin was 0.12 and 0.19 at 450 and 510 nm, respectively. The quantum yield for configurational isomerization to form 4Z,15Z-bilirubin was 0.03 and 0.05 at 450 and 510 nm. An analysis of previously published data on the quantum yield for the formation of lumirubin from 4Z, 15Z-bilirubin bound to human serum albumin suggests that all of the formation of lumirubin may occur via consecutive photochemical processes with the 4E,15Z-isomer as an intermediate.     

A NOVEL AND EFFICIENT SYNTHESIS OF 3-ARYL AND 3-HETEROARYL SUBSTITUTED-1H-INDAZOLES AND THEIR MANNICH DERIVATIVES

ABSTRACT

A general and highly convenient procedure for the synthesis of 3-heteroaryl and 3-aryl substituted-1H-indazoles has been developed. These compounds (3a–f) were synthesized in good yield by refluxing the NaHSO₃ adduct of heteroaromatic and aromatic aldehyde and phenyl hydrazine in DMF. This procedure is more general and shorter than earlier methods. Five new 3-hetero-aryl substituted-1H-indazoles were synthesized and characterized. New Mannich derivatives of 3-(1H-pyrrol-2-yl)-1H-indazole (3a) and 3-(1H-indol-3-yl)-1H-indazole (3b) were prepared from morpholine and formaldehyde.     

PHYTOCHROME MODELS: PART 10. CONCENTRATION,SONICATION AND TEMPERATURE AFFECTING THE POPULATION OF THE GROUND-STATE CONFORMERS OF BILIVERDIN DIMETHYL ESTER IN SOLUTION*

UV-vis absorption and fluorescence spectroscopy were used to show that in alcoholic solutions (methanol, ethanol, 2-methylbutan-1-ol, and 2-octanol) concentration, temperature, and sonication affect the relative populations of the more rigid stretched and the more flexible helically coiled conformers of biliverdin dimethyl ester. In aromatic solvents, e.g. toluene, no such effects could be detected. At concentrations larger than 3 10^-5M in the alcoholic solvents aggregates and monomeric coiled species prevail. Upon dilution, the fraction of stretched monomeric conformers increases. Heating and sonication at concentrations smaller than 3 10^-5M further and irreversibly increase the fraction of the stretched conformers. The activation parameters for this change are compatible with the assessment that no equilibrium is attained between the two families of conformers even after several hours at room temperature, since the barriers arc higher than kT at this temperature. The present results and those previously reported on the excited-state processes of biliverdin dimethyl esters are explained on the basis of a scheme in which the eight possible ring B/C isomers of biliverdin dimethyl ester are interconverted through intra-and intermolecular proton transfers, rotations around C-C single bonds, and E-Z photoisomerizations around C = C double bonds.     

THE PHOTOPHYSICS AND PHOTOCHEMISTRY OF THE NEAR-UV ABSORBING AMINO ACIDS-III. CYSTINE AND ITS SIMPLE DERIVATIVES

Abstract— The photochemistry of cystine and some of its analogues is reviewed. Topics discussed include the absorption spectra of disulfides, the photochemistry of alkyl disulfides and other more highly substituted disulfides including cystine, photooxidation of disulfides, and photochemical interactions of cystine derivatives with other molecules of biological interest.     

THE BEHAVIOR OF N-PHENYLIMINOPHOSPHORANE TOWARDS o- AND p-QUINONES. NEW SYNTHESIS OF DIOXAZOLE AND OXADIAZOLE DERIVATIVES

ABSTRACT

N-Phenyliminophosphorane (1) reacts with 9,10-phenanthrenequinone (2a) to give the new products 2-phenylphenanthro[9,10-d][1,3,2]dioxazole (4a) and (10Z)-10-(phenylimino)-9(10H) phenanthrenone (4b). The reaction of 1 with 1,2-naphthoquinone (2b) afforded both the dioxazole derivative 5a and the known 2-anilino-naphthoquinone-1,4-anil (5b). On the other hand, 2,6-di-tert-butyl-2,3-diphenyl-2,3-dihydro-1,2,3-benzoxadiazole (6) was obtained from the reaction of (2c) with phosphinimine (1). Application of reagent 1 on 2d and 2e renders (6E)-2,3,4,5-tetrahalogeno-6-(phenylimino)-2,4-cyclohexadien-1-one 7a and 7b, respectively. Moreover, p-quinones (3a–3c) react with phosphinimine (1) to yield products 8, 9 and 10, respectively. Mechanisms accounting for the formation of the new products are discussed and the probable structures of the products are presented based on analytical and spectroscopic data.     

PHOTOCHEMICAL INVESTIGATIONS OF OXAZINE, THIAZINE AND SELENAZINE DYES. THE REACTIVITY OF PROTOLYTIC TRIPLET FORMS IN ELECTRON TRANSFER REACTIONS

Abstract— The photoreduction of oxonine, thionine and selenine with the reducing agent allylthiourea was investigated by flash photolysis. The oxonine triplet state was produced by triplet-triplet energy transfer with 9,10-dibromoanthracene as donor. For all three dyes the rate constant of the electron transfer is considerably higher for the acid triplet form than that of the corresponding reaction of the basic triplet form. It is shown that the higher reactivity of the acid triplet can be related to its higher reduction potential which is available from the difference of the pK values of triplet and semiquinone of the dye.     

PHOTOPHYSICAL PROPERTIES OF NUCLEIC ACID COMPONENTS—1. THE PYRIMIDINES: THYMINE, URACIL, N, N-DIMETHYL DERIVATIVES AND THYMIDINE

Abstract— Low-temperature (and some room temperature) absorption and emission, fluorescence and phosphorescence, data including quantum yields and lifetimes have been obtained from the title pyrimidine bases as a function of the nature of the solvent environment. Modest vibrational resolution has been observed for the first time in the absorption spectra, particularly for thymine and uracil. The excitation spectra also show structure. The quantum yields of fluorescence (φ_F) and phosphorescence are independent of the excitation wavelength. Thymine, thymidine and uracil have profoundly different photophysical properties in polar-aprotic vs polar-protic solvents. The N, N-dimethyl substitution of thymine and uracil produces photophysical changes comparable to the solvent change for the unsubsti-tuted bases. The species involved in the emission processes is the keto (lactam) form. It is probable that ^1,3(n,π*) state(s) has(have) changed order relative to a lowest ¹(π,π*) state as a consequence of both the solvent change and N, N-dimethyl substitution. The lowest triplet state is assigned as ³(n π*). We propose that an important factor contributing to the previously reported excitation wavelength dependence of φ_F and φ_T1 (φ_isc) for nucleic-acid components is the equilibrium coexistence of H-bonded and non-H-bonded forms each having different photophysical properties. Consideration is given of the impact of the significantly different photophysical properties of nucleic-acid bases as a function of the nature of the solvent upon the photochemical properties.     

THE IN VITRO PHOTOCHEMISTRY OF BIOLOGICAL MOLECULES-III. ABSORPTION SPECTRA, LIFETIMES AND RATES OF OXYGEN QUENCHING OF THE TRIPLET STATES OF β-CAROTENE, RETINAL AND RELATED POLYENES

Abstract— The triplet-triplet absorption spectra of six polyenes have been characterised using flash photolysis, in the presence of anthracene as sensitizer, and pulse radiolysis, in the absence of a sensitizer. The polyenes include several which contain carbonyl groups whose triplet states, unlike retinal , could not be detected unsensitized by flash photolysis. The triplet lifetimes appear to be a function of the number of conjugated double bonds, and vary between 7 and 14 μ sec. In general, the longer the polyene, the shorter the lifetime. An empirical linear relation was found between the frequencies of the polyene triplet-triplet absorption maxima, and the frequencies of the corresponding ground singlet-singlet maxima. The rate constants for quenching by oxygen of nine polyene triplet states were determined to lie in the range 2–7 × 10⁹ M ^-1 sec^-1. The possible mechanisms for oxygen quenching of triplet states are discussed and analogies between the results for oxygen quenching of polyenes and of polyacenes are drawn. The rate constant for oxygen quenching of all- trans -β-carotene triplet was the same in benzene and hexane.     

A PREVIOUSLY UNREPORTED INTENSE ABSORPTION BAND AND THE pK, OF PROTONATED TRIPLET METHYLENE BLUE

Abstract— Excitation by a Q-switched giant ruby laser (1.2 J output at 694 nm ?50 ns flash) of 2–10 µM solutions of methylene blue in water, 30% ethanol in water or 50 v/v% water-CH₃CN at pH values in the range 2.0–9.3 converted the dye essentially completely to its T₁ state. The absorption spectrum of T₁ dye was measured in different media at pH 2.0 and 8.2 by kinetic spectrophotometry. Previously reported T-T absorption in the violet in acidic and alkaline solutions and in the near infrared in alkaline solution was confirmed. Values found for these absorptions in the present work with 30% ethanol in water as solvent are λ_max - 370nm, ε_max, - 13,200 M^-1 cm^-1 at pH 2 and λ_max,?420nm, ε_max 9000 M^-1 cm^-1, λ_max, - 840 nm, ε_max - 20,000 m ^-1 cm^-1 at pH 8.2. Long-wavelength T-T absorption in acidic solution is reported here for the first time: λ_max, ? 680 nm, e_max? 19,000 M cm^-1 in 30% ethanol in water at pH 2. Observation of a pH-independent isobestic point ? 720 nm confirms that the long-wavelength absorptions are due to different protonated states of the same species, MB⁺(T₁) and MBH²⁺(T₁). The pK_a of MBH²⁺(T₁) in water was determined from the dependence on pH of absorption at 700 and 825 nm to be 7.1₄± 0.1 and from the kinetics of decay of triplet absorption to be 7.2. The specific rate of protonation of MB⁺(T₁) by H₂PO₄ in water at pH 4.4 was found to be 4.5 ± 0.4 times 10⁸M^-1s^-1.     

A THEORETICAL STUDY ON THE STRUCTURES AND ENERGIES OF DIMER AND TRIMER OF DELTIC ACID （2，3—DIHYDROXYCYCLOPROPENE—1—ONE）

<正> The structures of deltic acid,its diner, and its trimer have been studied by semiempirical chemical method AMI.The stabilization energies of dinerization and trinerization are 32 and 65 kJ/mol- aspectively. The length of hydrogen-bond R(O...H-0) in diner is 3.04A,while the sane bond is slightly longer in trimer(R=3.06A).