1- pyrenylmethyl group

Benzyl or pyrenylmethyl groups containing phosphonium salts produce the respective carbon centered cations after a heterolytic bond rupture according to Equation 11.24 (Scheme 11.9) [37-39]. These cations are assumed to be the initiating species in cationic polymerization. 

Because of releasing very stable cations upon irradiation, phosphonium salts containing pyrenylmethyl groups are excellent initiators for photopolymerization of convenient monomers such as epoxides and vinyl monomers [35,39]. 

A fourfold decrease in the IDIIM ratio was observed for the 5.3% peracetylated pyrenylmethyl polyethylenimine derivative in glycerol compared to methanol. The higher viscosity of the glycerol limits the mobility of the attached pyrene group necessary to form excimer, decreases the association rate, and hence lowers ID/IM. These samples at 77°C showed essentially no excimer emission. Clearly, diffusion of the pyrene moieties attached to the polymer side chains is necessary for excimer formation. 

Figure 4.7 exhibits examples of diblock copolymers with irreversible photo-response. Polymer 30 contains photolabile protecting groups attached to carboxylic groups in the side chains. Upon UV irradiation, photosolvolysis of the pyrenylmethyl ester occurs, 1-pyrenemethanol is cleaved from the polymer chain and carboxylic add groups are released. As a consequence, the hydrophobic block turns into a hydrophilic PMAA block. Core-shell micelles formed by 30 disappeared after irradiation with UV light at 365 nm. This design was further validated with other chromophores (polymers 31-34). °... 

Leuckart reaction.—1-Aminoalkylpyrenes. A mixture of morpholine and 90 %-formic acid heated slowly to 200° to remove water as well as unchanged amine and acid by distillation, 1-pyrenecarboxaldehyde and 90%-formic acid added, refluxed 4 hrs. at 182-185°, and the product isolated as the hydrochloride N-(1-pyrenylmethyl)morpholine hydrochloride. Y 95%.—Good yields are obtained when the N of the dialkylamine part is attached to 2 methyl or ethyl groups, or when it is part of a heterocyclic system. The presence of formic acid is essential to the success of the reaction. F.e., limitations, and methods s. E. Marcus and J. T. Fitzpatrick, J. Org. Ghem. 25, 199 (1960). 

Reagent for prepn. of 1-pyrenylmethyl esters, photolabile protecing group. Fluorescent labelling reagent for anal, of carboxylic acids. Dark-red cryst. Mp 112°. Stable in dark at 0°. 

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