Chromophore Moieties Research Articles

Vinyl monomers bearing chromophore moieties and their polymers. IV. Fluorescence and photosensitizing behavior of 8‐acryloyloxyquinoline and its polymer

Acrylic monomers bearing electron-donating quinolyl moiety, i.e., 8-acryloyloxyquinoline (AQ) was prepared and polymerized. It was found that the fluorescence intensity of AQ was much lower than that of P(AQ) at the same chromophore concentration. The fluorescence of P(AQ) could be quenched by electron-deficient vinyl monomers, such as acrylonitrile (AN) and methyl methacrylate (MMA). This is another example of the “fluorescence structural self-quenching effect” termed by us previously, and demonstrates again that this phenomenon is not an accidental but a general one for acrylic monomers bearing electron-donating chromophores. The photopolymerization of acrylonitrile (AN) sensitized by AQ and P(AQ) as well as combining with carbon tetrabromide (CBr4) was studied kinetically. From the rates of the polymerization (Rp) and overall activation energies obtained for these four systems, it was found that Rp sensitized by the binary systems was much higher than by AQ or P(AQ) alone, while the molecular weights of the resulting P(AN) were lower. The fluorescent analysis of the resulting P(AN) in solution showed that the sensitizers also entered into the P(AN) chains. A mechanism of charge transfer complex (CTC) formation was tentatively suggested for the photopolymerization of AN initiated by these four systems. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1087–1093, 1997

Photophysics and Biological Applications of 7-Azaindole and Its Analogs

7-Azaindole is the chromophoric moiety of 7-azatryptophan, which is an alternative to tryptophan as an optical probe of protein structure and dynamics. The great power of the 7-azaindole chromophore is that it is red shifted both in absorption and emission from tryptophan, that its fluorescence decay is single exponential in water under appropriate conditions, and that its emission is sensitive to solvent. In addition, 7-azatryptophan can be incorporated into synthetic peptides and bacterial protein. In this article, the interactions of 7-azaindole with its environment are discussed. Special attention is directed to the difference in its fluorescence properties in water as opposed to nonaqueous solvents. The sensitivity of 7-azaindole to its environment is demonstrated and then exploited by studying it and its analogs in peptides and in complexes with larger proteins containing many tryptophan residues.

Vinyl monomers bearing chromophore moieties and their polymers. III. Synthesis and photochemical behavior of acrylic monomers having phenothiazine moieties and their polymers

Four acrylic monomers bearing phenothiazine moieties, i.e., N-acrylyl-phenothiazine (APT), N-acrylyl-2-chlorophenothiazine (ACPT), N-acrylyl-2-acetylphenothiazine (AAPT), and 10-acrylyl-1-azaphenothiazine (AAzPT) were synthesized by dehydrohalogenation of the corresponding N-(β-chloropropionyl)-substituted phenothiazine derivatives with 1,8-diazabicyclo[5.4.0]undec-5-ene (DBU). These monomers could easily be polymerized by initiation with AIBN. The emission fluorescence spectra of the monomers and their polymers were recorded, which showed that the polymers displayed much stronger fluorescence than their corresponding monomers at the same chromophore concentrations. This phenomenon, as termed as “structural self-quenching effect,” was commonly observed for acrylic monomers bearing chromophore moieties and ascribed to the coexistence of the electron-donating chromophore and the electron-accepting double bond in the same molecule. Because of the formation of exciplex, the monomer APT, as well as ACPT, AAPT, AAzPT, and their polymers, could initiate the photopolymerization of AN. The charge transfer phenomenon between P(APT), P(ACPT), and C60 was also explored. © 1996 John Wiley & Sons, Inc.

Vinyl monomers bearing chromophore moieties and their polymers. I. Initiation and photochemical behavior of N‐acryloyl‐N′‐phenylpiperazines and their polymers

Two novel acrylic monomers bearing aromatic tertiary amino groups, i.e., N-acryloyl-N′-phenylpiperazine (APP) and N-methacryloyl-N′-phenylpiperazine (MPP) are synthesized by the reaction of N-phenylpiperazine and the corresponding acryloyl chlorides in the presence of triethylamine. They can be polymerized easily by using AIBN as an initiator or photopolymerized without any sensitizer. The photochemical behavior of APP, MPP, and their polymers are explored by recording the fluorescence spectra in solution. It has been found that the fluorescence intensities of these monomers are dramatically lower than those of their polymers in the same chromophore concentration, and such phenomenon is termed as “structural self-quenching effect” (SSQE). The strong fluorescence of these polymers can be quenched by adding electron-deficient monomers which have no chromophore moieties such as MMA, AN, etc., and their Stern–Volmer constants are determined. It is observed that the higher the electron-deficiencies of the quenchers, the higher the Stern–Volmer constants, which means stronger quenching effect. The SSQE displayed by APP and MPP make them useful as probes to pursue their photopolymerization process. As polymerizable aromatic tertiary amines, APP and MPP themselves or combining with organic peroxides such as BPO can initiate the photopolymerization or thermal polymerization of vinyl monomers such as MMA, AN by free radical nature, and at the same time enter the polymer chain. © 1996 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 34:1881–1888, 1996

Vinyl monomers bearing chromophore moieties and their polymers. I. Initiation and photochemical behavior ofN-acryloyl-N?-phenylpiperazines and their polymers

Two novel acrylic monomers bearing aromatic tertiary amino groups, i.e., N-acryloyl-N′-phenylpiperazine (APP) and N-methacryloyl-N′-phenylpiperazine (MPP) are synthesized by the reaction of N-phenylpiperazine and the corresponding acryloyl chlorides in the presence of triethylamine. They can be polymerized easily by using AIBN as an initiator or photopolymerized without any sensitizer. The photochemical behavior of APP, MPP, and their polymers are explored by recording the fluorescence spectra in solution. It has been found that the fluorescence intensities of these monomers are dramatically lower than those of their polymers in the same chromophore concentration, and such phenomenon is termed as “structural self-quenching effect” (SSQE). The strong fluorescence of these polymers can be quenched by adding electron-deficient monomers which have no chromophore moieties such as MMA, AN, etc., and their Stern–Volmer constants are determined. It is observed that the higher the electron-deficiencies of the quenchers, the higher the Stern–Volmer constants, which means stronger quenching effect. The SSQE displayed by APP and MPP make them useful as probes to pursue their photopolymerization process. As polymerizable aromatic tertiary amines, APP and MPP themselves or combining with organic peroxides such as BPO can initiate the photopolymerization or thermal polymerization of vinyl monomers such as MMA, AN by free radical nature, and at the same time enter the polymer chain. © 1996 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 34:1881–1888, 1996

Efficient synthesis of a carbocyclic core moiety with the stereochemistry of the C-1027 chromophore

A stereoselective and concise route to the bicyclo[7.3.0]dodecadiyne core moiety ( 26) of the C-1027 chromophore ( 1) through highly efficient LiN(TMS) 2 CeCl 3-mediated cyclization of alkynyl aldehyde 24 has been established.

Vinyl monomers bearing chromophore moieties and their polymers. II. Fluorescence and initiation behavior ofN-(4-N′,N′-dimethylaminophenyl)maleimide and its polymer

A maleimide bearing electron-donating chromophore, N-(4-N′,N′-dimethylaminophenyl)-maleimide (DMAPMI) was synthesized from N, N-dimethylaminoaniline and maleic anhydride in the presence of acetic anhydride and sodium acetate. DMAPMI can be easily copolymerized with vinyl acetate (VAc). In addition, it can be easily homopolymerized by UV light irradiation or by using AIBN or BPO as an initiator. The fluorescence spectra of DMAPMI and its polymer or copolymer were recorded and compared at the same chromophore concentrations. It was observed that the fluorescence emission intensity of DMAPMI was much lower than those of its polymers. This may be due to the occurrence of intermolecular charge transfer interaction between the electron-donating dimethylaminophenyl moiety and acrylic electron-accepting carbon-carbon double bond in the monomer. The model compound, N-(4-N′, N′-dimethylaminophenyl)succinimide (DMAPSI), which has no carbon-carbon double bond, displayed the same fluorescence behavior as DMAPMI polymers. The fluorescence of DMAPMI polymers and DMAPSI can be quenched by electron-deficient compounds such as AN, TCNE, MMA, etc. All these results supported the above conclusion. This is another example of the “fluorescence structural self-quenching effect” termed by us previously and demonstrates again that this phenomenon is not an accidental but a general one for acrylic monomers bearing electron-donating chromophores. Study of the initiation behavior of DMAPMI and its polymer showed that they could initiate the photopolymerization of AN, by combination with BPO, they could also initiate the thermopolymerization of vinyl monomers such as MMA. © 1996 John Wiley & Sons, Inc.

Anthocyanin Intramolecular Interactions. A New Mathematical Approach To Account for the Remarkable Colorant Properties of the Pigments Extracted from Matthiola incana

In the last few years, a series of investigations has brought to light a mechanism of stabilization of the colorant properties of certain anthocyanins. Intramolecular interactions take place between the chromophore moiety of the anthocyanin and one of its aromatic acid residues, which folds over the chromophore and thus confers protection against hydration and subsequent formation of colorless forms. In our continuing study of the physicochemical properties exhibited by acylated natural anthocyanins, we report here on a series of five structurally related pigments extracted from the violet flowers of Matthiola incana. These pigments all bear the same chromophore moiety, i.e., the cyanidin aglycon, but differ in the degree of glycosylation and acylation. Acidity constants for the deprotonation and hydration equilibria of the flavylium cation, together with rate constants for the hydration step alone were determined from UV−visible absorption measurements. The data support the existence of intramolecular, n...

Novel Types of Polyesters Containing Second-Order Nonlinear Optically Active Chromophores with High Density

This article describes the syntheses and second-order nonlinear optical (NLO) properties of novel types of polyesters containing second-order NLO active chromophores with high density, which were obtained by condensation polymerization using two comonomers with the N,N-dialkyl-4-nitroaniline or N,N-dialkyl-4-((4-cyanophenyl)azo)aniline moiety. The polyesters were synthesized by condensation polymerization between isophthalic acid derivatives and N-substituted diethanolamines using tri- phenylphosphine and diethyl azodicarboxylate as the condensation reagents in dimethyl sulfoxide (DMSO) or 1-methyl-2-pyrrolidinone (NMP). The obtained amorphous polyesters exhibited good solubility in common organic solvents and provided optical-quality films by spin-coating. The SHG measurements of the spin-coated films of the resulting polyesters were carried out by the Maker fringe method using a Q-switched Nd:YAG laser (1064 nm) as an exciting beam after corona-poling. One of the polyesters, which was prepared from 5-(2-(N-methyl-4-nitroanilino)ethoxy)isophthalic acid and N-(4-((4-cyanophenyl)- azo)phenyl)diethanolamine, exhibited the large second-order NLO coefficient, d33, of 202 pm/V. On the other hand, a polyester containing chromophore moieties with the highest density, which was prepared from 5-{(1,3-bis(4-((4-cyanophenyl)azo)-N-methylanilino)-2-propyl)oxy}isophthalic acid and N-(4-((4- cyanophenyl)azo)phenyl)diethanolamine, exhibited good temporal stability of the second-order nonlinearity at ambient temperature.

Macromolecularization of fullerenes and the charge transfer complex formation of fullerenes with polymers having electron‐donating or electron‐accepting moieties

AbstractC60 was bonded to allylamine homopolymer (PALA) and its copolymers with styrene, 2‐hydroxypropyl methacrylate etc. as a pendant functional group. The polyallylamine bonded C60 displays fluorescence at room temperature although C60 does not in itself. This may be due to the lessening of highly symmetrical shape of C60. Some C60‐amine adducts are prepared as the model of polyallylamine‐C60 for the clarification. C60 doped poly(tetrahydrofurfuryl methacrylate) film has been prepared and its optical non‐linearity has been investigated. The charge transfer complexes formation of C60 with polymers having electron‐donating chromophore moieties such as poly(dimethylaminostyrene), poly(acryloylphenothiazine), poly(acryloylphenoxazine) and poly(styrene‐co‐dimethylaminophenylmaleimide) as well as with polymer having electron‐accepting chromophore moiety poly(cyanophenylacrylamide) have been manifested.

Self-assembly of non-linear optical chromophores through ionic interactions

Ionic attractions were applied to the construction of non-linear optical (NLO) chromophoric monolayers. In order to fully utilize such an interaction, stilbene-type NLO chromophores having a long alkyl chain and an anionic group at one end of the chain were designed; of this family of chromophores, sodium 11-[4-(trans-4′-pyridylstyryl)oxy] undecan-1-yl sulfate (3) was synthesized. By allowing a few minutes, this anionic chromophore self-assembles successfully on a cationically charged surface, which is prepared by treating clean fused silica with 3-aminopropyltriethoxysilane and then with iodomethane. The pyridine moiety of the self-assembled chromophore can be methylated to augment the molecular hyperpolarizability, β. The characteristics of the monolayer were examined viacontact angle measurements, UV–VIS spectroscopy, grazing-angle FTIR spectroscopy, and NLO property measurements.

Synthesis, Characterization, and Second-Order Optical Nonlinearity of a Polyurethane Structure Functionalized with a Hemicyanine Dye

A new polyurethane structure with a hemicyanine dye attached to the polymer side chain was synthesized by the step growth polymerization in a reaction between (E)-N-butyl-4-[2-[4-[bis(2-hydroxyethyl)amino]phenyl]ethenyl]pyridinium tetraphenylborate and 2,4-toluene diisocyanate. The molecular weight of the final product was determined to be Mn = 12 000 and Mw/Mn = 1.67. The polymer is soluble in dimethylformamide and can be processed into optical quality films by spin casting. No evidence of melting was detected by differential scanning calorimetry, suggesting that this polymer presents an amorphous phase. It shows a glass transition temperature of 121 °C. The macroscopic second-order hyperpolarizability χ(2) of this polyurethane was determined by measuring the second harmonic generation (SHG) for a thin polymer film. The χ(2) value was in the range 1.8 × 10-7 to 5.0 × 10-7 esu, depending upon poling conditions. This high second-order activity seems to prove the earlier prediction about a possible enhancement in the nonlinear second-order properties of organic materials triggered by utilizing the strong electron-accepting nature of the pyridinium group. In the presented polymer, the alignment of the nonlinear chromophore moieties induced by electric poling exhibits an extended temporal stability, due to the stabilizing function of the hydrogen bridges formed between the neighboring polyurethane chains, preventing the relaxation of oriented molecular dipoles.

On the coordination sites of 2-aminocyclopentene-1-dithiocarboxylic acid to Ni(II), Pd(II) and Pt(II): A resonance Raman investigation

Abstract Resonance Raman spectroscopy has been used to clarify the controversial chelation mode of 2-aminocyclopentene-1-dithiocarboxylic acid (acda) in its complexes with Ni(II), Pd(II) and Pt(II). The results strongly suggest that a (S,S) chelation mode is involved in this series of square-planar complexes. A previous assignment, based on infrared results only, is now extended, and the metal-sulfur stretching modes in the complexes are now assigned for the first time, on basis of the resonance Raman results. In the case of the Ni(II) complex, a selective enhancement of distinctive chromophoric moieties was observed, suggesting the presence of two charge-transfer transitions not resolved under the broad absorption band in the optical spectrum.

Capillary zone electrophoretic determination of C 2C 18 linear saturated free fatty acids with indirect absorbance detection

The potential of capillary zone electrophoresis for the separation of linear saturated fatty acids in their free form was evaluated. With increasing chain length, difficulties arise from decreasing analyte solubility in aqueous media, increasing occurrence of analyte aggregation and decreasing separation selectivity between successive homologues. A solution was to use electrolytes containing cyclodextrins (CDs) and methanol. The separation of C 2C 14 fatty acid homologues differing in only one carbon atom was achieved in less than 10 min using a purely aqueous electrolyte with trimethyl-β-CD as an additive. The separation of C 7C 18 homologues was completed in under 20 min with electrolytes containing up to 60% methanol, in addition to the aforementioned CD. In the presence of the CD, analyte solubility is enhanced through the inclusion of the alkyl chain of the acid in the CD cavity, while separation selectivity is improved because the stability constants of the inclusion complexes increase with increasing chain length of the acid. The lack of a suitable chromophore moiety was circumvented through the optimization of indirect absorbance detection conditions. p-Anisate was selected as the chromogenic species. The minimum detectable concentrations are of the order of (1–2)·10 −6 mol l −1 (0.2–0.5 ppm) and detection linearity was established over at least three orders of magnitude of concentration. The quantitative analysis of a coco oil extract sample is presented, showing results almost identical with those obtained by gas chromatography. Owing to the close values for response factors resulting from the indirect detection principles, a rapid percentage composition can be obtained by corrected peak area normalization.

Investigation of Tb 3+ ion fluorescence properties in γ-irradiated poly(ethylene oxide)-TbCl 3 blended systems

Degradation of polymers by γ-irradiation using Tb 3+ ion as a fluorescence probe was investigated. When poly(ethylene oxide) blended with TbCl 3 films were γ-irradiated in air, the fluorescence intensity of Tb 3+ was found to be greatly increased and the molecular weights of PEO were decreased. These results suggest that radiolysis caused chain degradation of PEO and produced carbonyl groups at the end of the cleaved polymer chain. The chromophore moiety produced transfers energy to Tb 3+ ion located within the non-irradiative energy trasfer distance. It is suggested that blended films of PEO with Tb 3+ may be used as convenient and fast detectors of γ-irradiation doses.

Molecular Orientation and Stacking of Perylenetetracarboxylic Diimide Derivatives in Langmuir-Blodgett Monolayers: Part I

The molecular organization in Langmuir-Blodgett (LB) monolayers for five organic dyes with a common chromophore moiety was studied. With the use of transmission and reflection-absorption (FT)IR spectroscopy (RAIRS), the orientation of the chromophore units in the LB monolayer was determined. The results obtained with carbonyl and C=C stretching vibrations exclude a flat-on orientation of the chromophore moiety and may be rationalized in terms of a tilted head-on organization of the chromophore on the Ag, ZnS, and Ge surfaces. The tilt angle, φ, formed between the direction of the dynamic dipole moment and the normal to the surface of the film was determined from the combined infrared data obtained in a transmission geometry and in RAIRS. The aromatic-aromatic interaction plays a significant role in determining the molecular alignment in the Langmuir and LB monolayers.

Diastereoselective synthesis of methyl α-kedarosaminide, a carbohydrate moiety of the enediyne antitumor antibiotic kedarcidin chromophore

Methyl α-kedarosaminide ( 9), a carbohydrate moiety of the enediyne antitumor antibiotic kedarcidin chromophore, was synthesised from d-threonine. Stereoselective reduction of the allyl ketone 5 derived from d-threonine was a key step in the synthesis, which was achieved by using Me 4NBH(OAc) 3 for intramolecular hydride delivery.

Synthesis, antileukemic evaluation and peroxidating ability of heterosubstituted anthracene-9,10-dione analogues: 5,8-[(aminoalkyl)amino]naphtho[2,3- d]thiazole-4,9-diones and 5,8-[(aminoalkyl)amino]naphtho[2,3- c] [1,2,5]thiadiazole-4,9-diones

The syntheses of a number of heterosubstituted ametantrone analogues, 5,8-bis[(aminoalkyl)amino]naphtho[2,3- d]thiazole-4,9-diones and 5,8-bis[(aminoalkyl)amino]naphtho[2,3- c] [1,2,5]thiadiazole-4,9-diones, have been performed. It was evidenced that this modification in the chromophore moiety has a negative effect on antileukemic activity. This modification also favors the affinity of the compounds toward NADH dehydrogenase and influences the redox potential.

Use of the transform method in the interpretation of the Raman excitation profiles of a bichromophoric system

AbstractThe use of the transform method was extended so as to permit the treatment of the resonance Raman effect with the participation of two interfering electronic transitions. The relevant equations were tested in the model system [Ru(bipy)2(violurate)]PF6, the Raman excitation profiles of which show clearly the presence of two chromophoric moieties. The present results strongly suggest that the two relevant excited states participate by means of Albrecht's A terms, whereas the vibronic coupling by the B term is not decisive. The independence of the two chromophoric moieties is reflected in distinct displacements of the respective potential minima.

Synthesis and absolute stereochemistry of the aminosugar moiety of antibiotic C-1027 chromophore

Stereocontrolled synthesis and absolute stereochemistry of the aminosugar moiety of C-1027 chromophore have been disclosed.