Chemiluminescence in anisotropic microenvironment: splitting of chemiluminescence efficiency for charge-transfer-induced decomposition of optically active bicyclic dioxetanes bearing a 2-hydroxy-1,1′-binaphthyl-4-yl moiety under chiral recognition

Four optical isomers of dioxetane 2 bearing a 2-hydroxy-1,1′-binaphthyl-4-yl moiety decomposed with accompanying emission of light on treatment with three base systems. The chemiluminescence efficiencies of all isomers were practically the same for tetrabutylammonium fluoride (TBAF) in DMSO system, whereas they split into two diastereomer-groups for 18-crown-6 ether complex of t-BuOK in benzene-THF system. For the base system using t-BuOK complex of optically active crown ether, (Ra,Ra)-7 or (Sa,Sa)-7, the chemiluminescence efficiencies split further into four. The shape of chemiluminescence spectrum, maximum wavelength, and the rate of decomposition were also different between each of the four stereoisomers.     

Rotamer-dependent chemiluminescence in the intramolecular charge-transfer-induced decomposition of bicyclic dioxetanes bearing a hydroxyaryl group

Base-induced chemiluminescent decomposition of acylamino-substituted dioxetane 1b bearing a 3-hydroxyphenyl group proceeded according to dual phase kinetics due to syn-anti isomerism of the aryl group. For dioxetane 7 bearing a 6-hydroxynaphthalen-2-yl group, syn- and anti-rotamers were each isolated and their structures were determined by X-ray single crystallographic analysis. Both rotamers underwent base-induced decomposition accompanied by the emission of red light to exclusively give the same keto imide 8. However, a marked difference in chemiluminescence efficiency was observed between anti-7 and syn-7.     

Solvent-promoted chemiluminescent decomposition of a bicyclic dioxetane bearing a 4-(benzothiazol-2-yl)-3-hydroxyphenyl moiety

An aprotic polar solvent such as N-methylpyrrolidone (NMP) promoted the thermal decomposition of bicyclic dioxetane bearing a 4-(benzothiazol-2-yl)-3-hydroxyphenyl moiety 1 without the addition of any base. This solvent-promoted decomposition (SPD) gave light as effectively as the base-induced decomposition (BID) in an aprotic polar solvent. SPD caused intramolecular CT-induced chemiluminescence similar to BID, but, in contrast to BID, SPD proceeded through a pathway with a large negative entropy of activation. Dioxetane 1 was also shown to give light due to excited state intramolecular proton transfer (ESIPT) upon heating in p-xylene.     

Synthesis and fluoride-induced chemiluminescent decomposition of bicyclic dioxetanes substituted with a 2-hydroxynaphthyl group

Five bicyclic dioxetanes bearing a 2-hydroxynaphthyl group, 1aA-1eA, were synthesized and their chemiluminescent decomposition was examined by the use of tetrabutylammonium fluoride (TBAF) as a base in DMSO. It was found that these dioxetanes hold completely the ‘odd/even’ relationship between the substitution pattern of hydroxy as a trigger on the naphthalene ring and their chemiluminescent efficiency, and that dioxetane 1aA exhibited chemiluminescence with the highest efficiency among those for the oxynaphthyl-substituted dioxetanes hitherto known. The significant change in chemiluminescent efficiency depending on the substitution pattern was clarified to be attributed to the marked change in singlet-chemiexcitation efficiency for charge-transfer-induced chemiluminescence (CTICL) of 1aA-1eA. In respect of the rate of CTICL-decomposition, ‘odd/even’ relationship was observed for 1aA-1dA.     

Intramolecular charge-transfer-induced chemiluminescent decomposition of 1,2-dioxetanes bearing a phenylmethanide anion

Dioxetanes (1) bearing a phenyl moiety substituted with a methylene or methine having an electron-withdrawing group(s) (-CH₂-Ew or -CH(X)-Ew) and dioxetane (2) bearing a 3-(1-cyanoethenyl)phenyl group were synthesized. Treatment of dioxetanes (1) with tetrabutylammonium fluoride (TBAF) caused their decomposition with accompanying emission of light with maximum wavelength at 530-758 nm. The Michael addition of a bis(methoxycarbonyl)methanide anion to dioxetane (2) produced initially an unstable dioxetane bearing a phenylmethanide anion, decomposition of which gave light with maximum wavelength at 710-740 nm. Intramolecular cyclopropanation without decomposition of the dioxetane ring took place concurrently for the Michael reaction-induced decomposition of 2 with the bis(methoxycarbonyl)chloromethanide anion.     

Chemiexcitation efficiency for the charge-transfer-induced chemiluminescent decomposition of 3-hydroxyphenyl-substituted dioxetanes in an aqueous system

The decomposition of 3-oxyphenyl-3-methoxy-4-(2′-spiroadamantane)-1,2-dioxetane (A) and 5-tert-butyl-4,4-dimethyl-1-(3-oxyphenyl)bicyclo[3.2.0]heptane (B) in NaOH/H₂O gives light in poor yield, which is several orders of magnitude lower than that in aprotic solvents. To understand the poor chemiluminescence efficiency in NaOH/H₂O, we investigated the behaviors of the authentic emitters, methyl 3-oxidobenzoate (C) and 2,2,4,4-tetramethyl-3-oxopentyl 3-oxidobenzoate (D). We found that D was weakly fluorescent though hydrolyzed in NaOH/H₂O, and estimated that the singlet-chemiexcitation efficiency Φ_S was 6.1 × 10⁻³ for the decomposition of B in NaOH/H₂O. On the other hand, Φ_S for A could not be estimated, since C was hydrolyzed too rapidly to observe its fluorescence.     

Color modulation for intramolecular charge-transfer-induced chemiluminescence of bicyclic dioxetanes bearing a 3-hydroxy-5-naphthylphenyl moiety in the coordination sphere

Bicyclic dioxetanes 2a, 2b, and 3, bearing a 3-hydroxy-5-naphthylphenyl moiety underwent charge-transfer-induced decomposition with accompanying emission of light, the color of which changed from red to blue responding to a complex of crown ether with potassium t-butoxide used as a base. Furthermore, they afforded unusual chemiluminescence, the spectra of which displayed two peaks in some cases. It was observed for chemiluminescences in the coordination sphere with crown ether that their spectra did not coincide with the spectra of authentic emitters.     

Organic superbase-induced chemiluminescent decomposition of a hydroxyaryl-substituted dioxetane: Unique effect of a bifunctional guanidine base on the chemiluminescence profile of a bicyclic dioxetane bearing a 4-(benzoxazol-2-yl)-3,5-dihydroxyphenyl moiety

Organic superbases represented by TBD (1,5,7-triazabicyclo[4.4.0]dec-5-ene) effectively induced the decomposition of hydroxyaryl-substituted dioxetanes in acetonitrile to give bright light. The color of the chemiluminescence from a dioxetane bearing a 4-(benzoxazol-2-yl)-3,5-dihydroxyphenyl moiety varied depending on the base used. In addition to this change in the color of emission, TBD increased the chemiluminescence efficiency 2- to 5-fold compared to the results with other base systems and accelerated decomposition of the dioxetane. These unique effects of TBD may be due to its “bifunctional” character, which is different from those of other organic superbases. Chemiluminescent decomposition of the dioxetane was effectively induced by superbases even in apolar p-xylene.     

Alkaline metal ion-enhanced chemiluminescence of bicyclic dioxetanes bearing a hydroxyaryl group with an ‘even’ substitution pattern

Bicyclic dioxetane 5 bearing a 3-hydroxynaphthalen-2-yl group and its analogs 14 and 15 decomposed to give light with efficiencies of only 0.002-0.005% in a tetrabutylammonium fluoride (TBAF)/THF system, which was as expected for dioxetanes with a so-called ‘even’ substitution pattern. However, the chemiluminescence efficiencies (Φ^CL) markedly increased when these dioxetanes were decomposed with alkaline metal t-butoxide in THF. This enhancement of Φ^CL by alkaline metal ion was most likely due to the highly ordered conformation of an aromatic ring by chelate formation of the metal ion with both an oxido anion and oxygen atom of a tetrahydrofuran ring in an intermediary dioxetane like 12. Alkaline metal ion-enhanced chemiluminescence was similarly observed for dioxetane 6 bearing a 2-hydroxyphenyl group.     

Intramolecular charge-transfer-induced decomposition promoted by an aprotic polar solvent for bicyclic dioxetanes bearing a 4-(benzothiazol-2-yl)-3-hydroxyphenyl moiety

Bicyclic dioxetanes 3a-d bearing a 4-(benzothiazol-2-yl)-3-hydroxyphenyl group decomposed to give the corresponding keto esters 4a-d accompanied by the emission of bright light when simply dissolved in an aprotic polar solvent such as N-methylpyrrolidone (NMP) or DMF at 50-100 °C. This solvent-promoted decomposition (SPD) was effectively a chemiluminescence process caused by the hydrogen bonding of a phenolic OH with a solvent molecule(s). The characteristics of the chemiluminescence in SPD resembled those in base-induced decomposition (BID), which occurs through an oxidoaryl-substituted dioxetane 5 by an intramolecular charge-transfer-induced decomposition (CTID) mechanism. Both free energies of activation, ΔG(doubledagger)(SPD) and ΔG(doubledagger)(BID), increased in the order 3a < 3b < 3c < 3d, and were linearly correlated with each other. However, SPD showed features different from those of BID in terms of enthalpy of activation and entropy of activation. SPD had large negative values for ΔS(doubledagger) (ca. -71 J mol(-1) K(-1)) regardless of the substituent R at the 5-position for 3a-d, while the ΔS(doubledagger) values for BID changed from 0.5 to -22 J mol(-1) K(-1) as R became smaller. The enthalpy of activation ΔH(doubledagger) for SPD was 14-21 kJ mol(-1) smaller than that for BID.     

Marked difference in singlet-chemiexcitation efficiency between syn-anti isomers of spiro[1,2-dioxetane-3,1′-dihydroisobenzofuran] for intramolecular charge-transfer-induced decomposition

Spiro[1,2-dioxetane-3,1′-dihydroisobenzofuran] syn-3 bearing a hydroxy group at the 6-position (as a model syn-rotamer of parent dioxetane 4 bearing a 3-hydroxyphenyl group) and its isomer anti-3 (as a model anti-rotamer of 4) were synthesized. When these spiro-dioxetanes were treated with tetrabutylammonium fluoride (TBAF) in DMSO, anti-3 emitted light with high efficiency (Φ^CL = 0.41), while the respective value for syn-3 was only 1/10 for anti-3. This significant difference in Φ^CL between syn-3 and anti-3 was attributed to the difference in their singlet-chemiexcitation efficiencies.     

Color modulation for chemiluminescence of a dioxetane bearing a 3-(anthracen-9-yl)-5-hydroxyphenyl moiety induced by a complex of crown ether with potassium tert-butoxide

Color modulation was first observed for CT-induced chemiluminescent decomposition of a dioxetane bearing a 3-(anthracen-9-yl)-5-hydroxyphenyl induced by a complex of crown ether with potassium tert-butoxide in benzene system. The phenomenon is rationalized by conformational change of a biaryl moiety in the emitter, which is induced by steric interaction of anthryl and a plane of crown ether complex.     

Chemiluminescent decomposition of a dioxetane bearing a 3-(1-cyanoethenyl)phenyl moiety induced by Michael addition of an anion of malonate

A thermally stable dioxetane bearing a 3-(1-cyanoethenyl)phenyl group (1) was synthesized. Michael addition of an anion of malonate (3a,b) to a dioxetane (1) substituted with a 3-(1-cyanoethenyl)phenyl moiety took place to give an intermediary dioxetane bearing a benzylic anion, which decomposes rapidly with accompanying emission of crimson light. When an anion of chloromalonate (3c) was used as a base, intramolecular cyclopropanation of 3c occurred concurrently with the Michael-addition-induced chemiluminescent decomposition.     

Base-induced decomposition of dioxetanes bearing a 3-hydroxyphenyl moiety substituted with a proton-donating group at the 4-position: effect of intramolecular hydrogen bonding on decomposition rate and chemiluminescence efficiency

Bicyclic dioxetanes bearing a 3-hydroxyphenyl moiety substituted with an amidomethyl group (3a-c) or a hydroxymethyl group (4) were synthesized. On treatment with tetrabutylammonium fluoride in CH₃CN, they decomposed rapidly with accompanying emission of blue light. Their decomposition rates and chemiluminescence efficiencies were found to be affected by the intramolecular hydrogen bonding between the phenoxy anion and the adjacent proton-donating group.     

Synthesis and properties of polyimides from 4,4′-binaphthyl-1,1′,8,8′-tetracarboxylic dianhydride

4,4′-Binaphthyl-1,1′,8,8′-tetracarboxylic dianhydride was synthesized from 4-chloro-1,8-naphthalic anhydride and polymerized with aromatic and pliphatic diamines in m-cresol or N-methyl-2-pyrrolidinone (NMP). The polyimides, except for two derived from p-phenylenediamine and hydrazine, are soluble in 1,1,2,2-tetrachloroethane and NMP. Their intrinsic viscosities ranged from 0.36 to 2.20 dL/g. The polymers showed excellent thermal and thermooxidative stabilities and displayed weak glass transition temperatures. Young's moduli of some polymer films were in the range of 2.5 and 5.4 GPa at 30°C. The aliphatic polyimides exhibited a stronger fluorescence than the aromatic polyimides. © 1995 John Wiley & Sons, Inc.     

Base-induced chemiluminescent decomposition of bicyclic dioxetanes bearing a (benzothiazol-2-yl)-3-hydroxyphenyl group: a radiationless pathway leading to marked decline of chemiluminescence efficiency

Charge-transfer-induced decomposition (CTID) of bicyclic dioxetanes 1b-d bearing a 3-hydroxylphenyl moiety substituted with a benzothiazol-2-yl group at the 2-, 6-, or 5-position was investigated, and their chemiluminescence properties were compared to each other, based on those for a 4-benzothiazolyl analogue 1a. Dioxetanes 1c and 1d underwent CTID to give the corresponding oxido anions of keto esters 8c or 8d in the singlet excited state with high efficiencies similarly to the case of 1a. On the other hand, 1b showed chemiluminescence with quite low efficiency, though it gave exclusively keto ester 2b. The marked decline of chemiluminescence efficiency for 1b was attributed to 1b mainly being decomposed to 8b through a radiationless pathway, in which intramolecular nucleophilic attack of nitrogen in the benzothiazolyl group to dioxetane O-O took place to give cyclic intermediate cis-11.     

Fluoride-induced chemiluminescent decomposition of dioxetanes bearing a siloxyaryl moiety to produce an alkyl aryl ketone as an emitter

Tetrabutylammonium fluoride induces the decomposition of 1-tert-butyl-4,4-dimethyl-5-(3-siloxyphenyl)-2,6,7-trioxabicyclo[3.2.0]heptane (4a) in DMSO to form an oxyanion of aromatic ketone (14a) as an emitter with high singlet-chemiexcitation yield comparable with that for a chemically initiated electron exchange luminescence (CIEEL) active dioxetane producing an oxyanion of aromatic ester as an emitter. A 7-siloxynaphthalen-2-yl analog (4b) was found on similar treatment to emit light with the maximum wavelength the longest among CIEEL-active dioxetanes hitherto known.     

一种新型的含联二萘结构的手性聚芳醚酮的合成及表征

目前,对于外消旋体的拆分已经越来越引起人们的关注,在药物化学领域中尤为突出,原因是手性药物的两个对映体虽然在物理和化学性质上大多相同,但其在药效及药物动力学方面却表现出很大的差别,目前尚没有通用的手性固定相用于外消旋体的拆分,为了解决这一问题,以淀粉、纤维素以及其衍生物制备的手性固定相已被人们广泛使用。