1-Pyrene carboxaldehyde

Pyrene carboxaldehyde and a series of pyrene carboxylic acids were found useful as fluorescence probes in describing the constitution of inverted micelles of certain calcium alkarylsulfonates in hydrocarbon media. 1-Pyrene carboxaldehyde is a convenient probe for studying the particle sizes of micelles in the region of lOOA. A series of graded probes, pyrene carboxylic acids with varying alkyl chain length, have been used to determine internal fluidity and micro-polarity as a function of distance from the polar core of these Inverted micelles. Pyrene exclmer to monomer fluorescence intensity ratio and fluorescene lifetime provided the means of measurement of internal fluidity and micropolarity, respectively. 

Much remains to be learned, however, regarding the limits of applicability of the fluorescence probe technique to aggregates in non-polar media. A number of obvious experiments are conspicuous by their absence from the published literature. For example, 1-pyrene carboxaldehyde is a well known probe which has been used to measure the microscopic polarity of sodium dodecyl sulfate micelles in aqueous medium (5) there is, however, no account of its use in non-polar media. 

Pyrene Carboxaldehyde Probe Studies. Fluorescence spectra of 1-pyrene carboxaldehyde in nonane solutions of sulfonates A and B and In an octane solution of Aerosol OT are compared to the probe spectra in pure hydrocarbon media in Figure 1. Parts (a) and (b) are of sulfonates A and B systems, respectively part (c) is of aerosol OT system. They were constructed at different gain settings and therefore the intensities shown for the individual system are not directly comparable. The fluorescence intensity of 1-pyrene carboxaldehyde in nonane alone is much weaker than in either the sulfonate A or sulfonate B solution. Aerosol OT containing solubilized H.O does not enhance the fluorescence intensity of 1-pyrene carboxardehyde as much as sulfonates A and B, but the band maximum is shifted as expected for this probe in a water-rich medium. 

We measured the time-dependent anisotropy of 1-pyrene carboxaldehyde in sulfonate A and B systems. The results are shown in Figure 2. Relaxation times determined from the unconvoluted anisotropy decays for sulfonates A and B in heptane solution were found to be 7 ns and 28 ns, respectively. 

In order to test further the applicability of 1-pyrene carboxaldehyde as a fluorescent probe, we applied Keh and Valeur s method (4) to determine average micellar sizes of sulfonate A and B micelles. This method is based on the assumption that the motion of a probe molecule is coupled to that of the micelle, and that the micellar hydrodynamic volumes are the same in two apolar solvents of different viscosities. For our purposes, time averaged anisotropies of these systems were measured in two n-alkanes hexane and nonane. The fluorescence lifetime of 1-pyrene carboxaldehyde with the two sulfonates in both these solvents was found to be approximately 5 ns. The micellar sizes (diameter) calculated for sulfonates A and B were 53 5A and 82 lOA, respectively. Since these micelles possesed solid polar cores, they were probably more tightly bound than typical inverted micelles such as those of aerosol OT. Hence, it was expected that the probe molecules would not perturb the micelles to an extent which would substantially affect the micellar sizes measured. 

Pyrene Carboxaldehyde in Calcium Alkarylsulfonates. Our work shows that 1-pyrene carboxaldehyde as a fluorescent probe for the sulfonate systems behaves very much the same as rhodamine B (1 ) and anillnonaphthalene sulfonate (2), whose fluorescence intensities in hydrocarbon media are enhanced in the presence of inverted micelles. However, the intensity Increase observed with AOT was considerably less than that observed with the sulfonates. It is speculated that... 

The internal rotational relaxation times of 1-pyrene carboxaldehyde in sulfonate systems may offer some indication of the extent of probe binding to the inverted micelle. In the absence of any background fluorescence interference to the time-dependent anisotropy decay profile, the internal rotational relaxation time should correlate with the strength of binding with the polar material in the polar core. However, spectral interference from the aromatic moieties of sulfonates is substantial, so that the values of internal rotational relaxation time can only be used for qualitative comparison. 

Pyrene carboxaldehyde has utility as a fluorescent probe in some Inverted micellar systems containing solubilized Inorganic species in the polar core. Its fluorescence lifetime is ca. 5 ns thus it is an appropriate probe for measuring micellar sizes which are approximately lOOA. 

Carbofinan. atrazine, metolachlor, and their byproducts were separated on HPTLC plates containing fluorescent indicator. Several single and dual solvent systems were investigated for resolution by one-dimensional development. The quantification of the compounds was carried out by densitometric scanning. 1-pyrene carboxaldehyde detected chlorpyrifos and its byproducts with a sensitivity of 0.5-0.05 pg, but dansyl chloride, NBD-Cl, DPH, and Rhodamine 6G were also investigated and compared to fluorescence quench detection (131b) (Table 10). 

DNA and RNA quantification, SNP typing, hybridization, and structural alteration have been widely carried out by modified oligonucleotides possessing pyrene derivatives [104-113]. As is known, pyrene-1-carboxaldehyde fluorescence is considerably dependent on solvent polarity [114], being strong in methanol but insignificant in nonpolar solvents [115]. Owing to this property, Tanaka and collaborators developed a pyrenecarboxamide-tethered modified DNA base, PyU 46, and applied it to SNP discrimination in DNA [116-120],... 

Pyrene-1-carboxaldehyde and 7-alkoxycoumarins belong to this class of polarity probes. 

Kalyanasundaran K. and Thomas J. K. (1977a) Solvent-Dependent Fluorescence of Pyrene-3-Carboxaldehyde and its Applications in the Estimation of Polarity at Micelle-Water Interfaces,/. Phys. Chem. 81, 2176-2180. 

Many other applications have been described for these compounds and the hst is so extensive that it is impossible to cover each example here. Nevertheless, it is noteworthy that appropriately substituted 4-arylidene-5(4r/)-oxazolones, for example, 359 and 360 have been reported as organic Iruninophores" " and electrophotographic light-sensitive materials," respectively. The use of apoca-rotenoid derivatives such as 362 as monomolecular films has also been described." For new materials, a number of water-insoluble oxazolones have been used for dyeing or printing synthetic fibers" and, in this context, 4-(pyren-1-ylmethylene)-2-substituted-5(4/i/)-oxazolones 357, prepared from pyrene-1-carboxaldehyde, have... 

Diamino-2,l>3-benzothiadiazole 201 undergoes cyclization on reaction with selected aromatic aldehydes <2004T2953>. Thus, reactions with pyrene-l-carboxaldehyde or naphthalene-1-carboxaldehyde in refluxing toluene produce the corresponding imidazoles 202 in moderate yields, whereas reactions with /i-(Ar,Ar-dimethylamino)benz-aldehyde and /i-[Ar,Ar-di(4-methylphenyl)amino]benzaldehyde under similar conditions gave the corresponding 5-imino derivatives 203 (Scheme 13). 

Table 6 lists the absorption characteristics of the series of UV-sensitive monomers investigated [218]. Aliphatic oxime acrylates show absorption maxima below 230 nm, while benzophenone oxime acrylate shows an absorption maximum at 252 nm. It is important to note that while benzophenone has absorption at 360 nm owing to the n-n transition, the corresponding oxime has no strong absorption above 300 nm. Pyrene-1-carboxaldehyde oxime acrylate (POA) and 9-phenanthrenecarboxaldehyde... 

K2CO3. No side reactions like the Cannizzaro or Knoevenagel reactions are observed on treatment with C-200. In the reaction with benzaldehyde and furfural the products 71 (R = Ph and 2-furyl) are formed nearly quantitatively. Bulky aromatic aldehydes such as pyrene-l-carboxaldehyde and aliphatic aldehydes are also suitable substrates for this process. ( )-acyclic a,/ -unsaturated ketones 74 can be prepared by use of a similar HWE reaction of 2-oxoalkanephosphonates 72 with aliphatic aldehydes 73 under the influence of barium hydroxide C-200 (Scheme 5.14) [36]. The HWE procedure employing activated Ba(OH)2 is applicable to the structurally complex, base-sensitive aldehydes which are susceptible to elimination and/or epimerization under the traditional basic conditions of the HWE reaction using NaH. For instance, when phosphonate 75 and aldehyde 76 are exposed to 0.8 equiv. activated Ba(OH)2 in aqueous THF at 20°C, (//-enone 77 is obtained in 70% yield (Scheme 5.14) [37]. 

The fluorescence quantum yields of pyrene-1-carboxaldehyde in water and methanol are 0.98 and 0.07/ an effect attributed to solvent effects on 7c,n and n,n states. Cycloaddition reactions of 1-naphthonitrile to 1,2-dimethyl-cyclopentene are attributed to both and Lj, states.It is pointed out that although dual fluorescence is known, this is the first example of divergent reaction from two nearly isoenergetic singlet states. An analysis of the u.v. spectra of some acyl pyridines, including a theoretical examination of the molecular geometry, and excited states of bipyrimidine compounds have also been made. Photo tautomerism and the fluorescence of the cation of 4-amino-pyrazole[3,4-iflpyrimidine, an analogue of adenine, has been published by Wierzchowski et Intramolecular heteroexcimer formation in... 

Quendiii of Exdted States.—Much research has been adapted from early observations that micelles could drastically alter the fluorescence lifetime of pyrene and the efficiency of excimer formation. The various mechanisms of excited-state transformation have been reviewed. " The polarity of the micellar surface may be estimated from the fluorescence spectrum of pyrene 2-carboxaldehyde " giving rise to the conclusion that sodium laurylsulphate (e=45) has a more polar surface than cetyltrimethylammonium bromide (e = 18). The fluidity of the site of solubilization may be estimated from fluorescence polarization " in surfactants of general structure (104). The Si... 

The quantum yield is an indicator of how efficient a particular process is. However, some care must be taken in comparing quantum yields for different systems, because the quantum yield is always measured relative to other processes in the molecule. For example, pyrene derivative. The reason this is not reflected in the quantum yields is that we must also consider competing processes. The ISC rate for pyrene-3-carboxaldehyde is also much faster than that for benzene due to the ability to access a ( ,tt ) state that is not available for benzene. This competing ISC process limits the amount of fluorescence, and by coincidence the two compounds end up with the same fluorescence quantum yield. Thus, while the quantum yield tells you about the efficiency of a process for a given molecule, it alone cannot tell you why the process is or is not efficient. 

Some other photophysical probes which were used for following the sol-gel transitions include 7-azaindole, 1- and 2-naphthols, pyrene-3-carboxaldehyde , ReCl(C03)bipyridine (as a probe for cage rigidity) , thymol blue and Rhodamine Photochromic compounds were also used for the investigation of the sol-gel... 

Matsni K., Morohoshi T., Yoshida S. Photochromism of spiropyran in sol-gel glass and plasma-polymerized films. Proc. MRS Int. Meeting Adv. Mater. 1989 12 203-208 Matsni K., Nakazawa T. Fluorescence probes ofpyrene and pyrene-3-carboxaldehyde for the sol-gel process. Bnll. Chem. Soc. Jpn. 1990 63 11-16... 

The interaction of cationic fluorocarbon and hydrocarbon surfactants was studied by Tamori et al. [145]. The mixed cmc of diethanolheptadecafluoro-2-2-undecanolammonium chloride and dodecyltrimethylammonium chloride was determined by electric conductivity measurements. Partition coefficients of alcohols (methanol and C4F7H2OH) and a fluorescent probe (pyrene-3-carboxaldehyde) between micelles and the bulk aqueous phase were determined. The data interpreted by a regular solution theory fitted an interaction parameter /3 = 1, indicating a much smaller repulsive interaction between the two cationic surfactants than that between an anionic fiuorinated surfactant and an anionic hydrocarbon-type surfactant. The weak repulsion between the two cationic surfactants was explained by a large difference in their cmc values. 

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