Journal of Physical Chemistry A, Vol.124, No.47, 9811-9817, 2020
N-(2-Aminoethyl)-2-(hexylthio) Acetamide-Functionalized Pillararene for the Selective Detection of L-Trp through Guest-Adaptive Multisupramolecular Interactions
Tryptophan (Trp) is very necessary for biosystems; therefore, high-efficient detection of Trp is an important subject. Hereof, based on our early research works on fluorescent sensors, we rationally designed and synthesized a fluorescent sensor (SNP5) based on N-(2-aminoethyl)-2-(hexylthio) acetamide-functionalized pillararene, which showed high selectivity and sensitive recognition for L-Trp (LOD = 2.19 x 10(-8 )M). Moreover, SNP5 exhibited aggregation-induced emission enhancement fluorescence. Within SNP5, the pillararene group could act as N-H center dot center dot center dot pi- and C-H center dot center dot center dot pi-interaction sites, as well as a H-bond-interaction site; meanwhile, the N-(2-aminoethyl)-2-(hexylthio) acetamide group also served as a multihydrogen-bonding site. As a result, SNP5 could selectively detect L-Trp through the synergy of the pillararene group and the N-(2-aminoethyl)-2-(hexylthio) acetamide group. Compared with previous work, the results of this work support the strategy that changing the functionalized group of the pillararene can adjust the selectivity of the pillararene-based sensor and achieve the detection of different amino acids. The detection mechanism was specifically researched through experiments and theoretical calculations including frontier orbitals, electrostatic potential, and the independent gradient model approach. Interestingly, these theoretical calculations not only supported the experimental results but also provided a visualized understanding of guest-adaptive multisupramolecular interactions between SNP5 and L-Trp.