Pyrene amine

A disadvantage of the use of pyrene is that the extent of excimer formation depends on the bulk concentration of pyrene in the membranes. For this reason, several groups have synthesized covalently linked pyrenes or pyrene-amine conjugates. " Examples of such molecules are... 

Medenwald suggests that the infrared spectrum of aminoaza-pyrene (238) favors the imino form. Di-(2-quinolyl) amine has been reported to exist in two modifications, one of which was the imino form 239, but this seems improbable. 

In contrast to 6-azidobenzo[/)]thiophene, which yields only benzo[i]thiophen-6-amine (9 %) and JVh,Ar(1-diethylbenzo[/)]thiopheiie-6,7-diamine (25 % bp 175-177 C/0.7 Torr), 6-azido-2,3-dibromobcnzojhjthiophene (1 a, R = R2 = Br) on irradiation in diethylamine in the presence of pyrene, a triplet nitrene quenching agent, yields a mixture of 2,3-dibromo-./V6,./V6-diethyl-benzo[5]thiophene-6,7-diamine (2a, R1 = R2 = Br 13%) and the 8W-thieno[2,3-r]azepine 3a.14<1 Likewise, methyl 6-azidobenzo[6]thiophene-2-carboxylate (lb, R1 = C02Me R2 = H) yields the thienoazepine ester 3b.147... 

Figure 15.14 The NHS ester of a pyrene butyric acid derivative can be used to modify a carbon nanotube by adsorption of its rings onto the surface of the tube. The NHS ester groups then can be used to couple amine-containing molecules to form amide bonds.

Figure 15.15 An aldehyde derivative of pyrene can be used to couple a hydrophilic amino-PEG-carboxylate spacer by reductive amination. The resultant derivative then can be used to coat a carbon nanotube through pyrene ring adsorption and result in a water-soluble derivative containing terminal carboxylates for coupling amine-containing ligands.

This procedure is described by Lock 2 a modification using a small amount of phenol has been published.3 The patent literature discloses the use of a tertiary amine, such as pyridine, and its combination with other solvents for the monobromination of pyrene with elemental bromine.4 Brominating agents, such as N-bromosuccinimide5 and N-bromohydantoins,6 have also been used. 

A first generation poly(amido amine) dendrimer has been functionalized with three calyx[4]arenes, each carrying a pyrene fluorophore (4) [30]. In acetonitrile solution the emission spectrum shows both the monomer and the excimer emission band, typical of the pyrene chromophore. Upon addition of Al3+ as perchlorate salt, a decrease in the excimer emission and a consequent revival of the monomer emission is observed. This can be interpreted as a change in the dendrimer structure and flexibility upon metal ion complexation that inhibits close proximity of pyrenyl units, thus decreasing the excimer formation probability. 1H NMR studies of dendrimer 4 revealed marked differences upon Al3+ addition only in the chemical shifts of the CH2 protons linked to the central amine group, demonstrating that the metal ion is coordinated by the dendrimer core. MALDI-TOF experiments gave evidence of a 1 1 complex. Similar results have been obtained for In3+, while other cations such as Ag+, Cd2+, and Zn2+ do not affect the luminescence properties of... 

A variety of these physisorbed molecules were used as anchor points for covalent immobilization in a so-called hybrid approach [16]. That is the case of bifunctional pyrenes (i.e. 1 -pyrenebutanoic acid sucdnimidyl ester, pyrene maleimide) or polymers with terminal amine/carboxylic groups that have been used to covalently immobilize proteins, functionalized oligonucleotides, and so on, (Figure 3.9) [43,44]. 

Meats, charbroiled, smoked, or fried Many, largely polycycUc aromatic hydrocarbons such as benzo[a]pyrene, and heterocyclic amines... 

Modification of PAA/Au grafts with the amine and alcohol functionalized pyrenes 2 and 3 produced highly fluorescent films [23]. These deriva-tized films exhibited both monomer and excimer fluorescence. The relative amounts of monomer and excimer emission depended on the pyrene concentration used in the derivatization process. When modest concentrations... 

Aromatic amines Benzo anthracenes Benzo fluoranthracenes Benzo pyrenes Benzoic acids Carbazoles Chrysenes Dibenzo thiophenes Fluorenes Imidazoles Indoles Naphthalenes... 

To keep the probe specifically at the primary amine side chains, we have used pyrenecarboxaldehyde and attached it covalently to polyethylenimine by reduction with sodium borohydride of the Schiff base formed between the probe aldehyde and the polymer primary amine. Such reductive alkylation has been used widely with primary amines of enzymes.43,44 For three different adducts to the polymer, the extent of coupling with pyrene, expressed relative to units of monomer residues,... 

As Fig. 15b illustrates, the graphical relation appears to be linear for an interaction number of 3 to 4, if A 1. Alternatively, for A = 1, linearity is evident (Fig. 15c) when the interaction number is 5 to 6. Thus a large value of A is compatible with the smallest interaction number. Excimer formation occurs within the fluorescence lifetime, about 8 nsec. Within that time the pyrene-labeled amine side chains must approach within about 4 A of each other. For the 5.3% pyrenylpolyethylenimine derivative in ethanol, where no ground-state association occurs, the effective local concentration of pyrene on the polymer matrix is about 10-2 M, as calculated from excimer fluorescence. In aqueous solution, where clusters form within the polymer matrix, the effective local concentration of pyrene adduct must be even greater. The quantitative assessment of fluorescence intensities (Fig. 15) points to a minimum interaction number of 3 to 4 pyrenyl-labeled amine side chains, within the 8 nsec lifetime. Since A 1, it appears from (12) that kDM(A) kMD + kD. Thus excimer formation must be very rapid in the polymer environment. We can conclude, therefore, that the primary-amine side chains of poly-ethylenimine are very flexible and mobile. 

The Balz-Schiemann synthesis can be applied not only to substituted anilines but also to aminobiphcnyls1,131 or amino-substituted fused polyaromatic compounds, such as naphthalene,1114,119,129 anthracene,136 phenanthrene,1135 acenaphthene,133 fluorene,1,131,134 benzanthracene,130 136 pyrene,136 chrysene,136 fluoranthene,131 fluorenone,1,131 anthra-quinone,1,137,139,140 benzanthrone,1,117,118 phenanthraquinone,138 or xanthone.132 Fluorinated pyridines,1,141"146 methylpyridincs,126,147 149 pyridinecarboxylic acids,150 quinolines,1,151 isoquinolines,152 quinazolone,1 thiazoles,153,154 isothiazoles,156 benzothiazoles,157 thiadiazoles,155 and thiophenes154 can also be obtained from the corresponding aminated heterocycles. Modified Balz-Schiemann methods are recommended for amino nitrogen-containing heterocycles, the diazonium salts of which are rather water-soluble and unstable (a violent explosion was reported for pyridine-3-diazonium tetrafluoroborate).159 These new techniques have also been specially adapted for pyrazol-, imidazol-, or triazolamines which fail to react under classical conditions.158... 

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