Aggregation behavior of (S)-(−)-N-benzylpyrrolidine-2-methanol in the synthesis of the AFI structure in the presence of dopants

The aggregation behavior of (S)-(−)-N-benzylpyrrolidine-2-methanol (BPM) in the crystallization of the aluminophosphate AlPO-5 (AFI-type structure) in the presence of different dopants has been studied by fluorescence spectroscopy. A strong influence of the presence and chemical nature of dopants within the AFI network has been observed on the formation of BPM dimers inside the AFI channels. It has been found that the presence of Mg2+ ions reduces the dimer aggregation whereas the presence of Zn2+ favours the dimer formation. In addition, there seems to exist a strong interaction between the dopant cations embedded in the AFI network and the BPM dimers that causes a notable blue-shift of the dimer fluorescence band in all the doped materials, especially in the Zn-doped one. Such a strong interaction suggests a close location of both species, and thus an eventual direction of the BPM molecules over the incorporation and distribution of the Zn2+ cations in the framework. This result, together with the eventual helicoidal arrangement of the SDA molecules that was previously demonstrated by computational simulations to be the most thermodynamically stable one, suggests an eventual helicoidal distribution of the Zn2+ ions within the AFI network.