The objective of this work is the synthesis of water-soluble oligochitosan derivatives with electron deficient aromatic rings for selective and rapid adsorption of amitriptyline through pi-pi complexation. Oligochitosan was chemically modified under homogeneous conditions in dimethyl sulfoxide (DMSO). (1)H NMR, FT-IR, and MALDI-TOF were employed in characterization, confirming that the electron deficient aromatic rings were chemically attached to the backbone of oligochitosan. Thromboelastography (TEG) revealed functionalized oligochitosan derivatives did not affect blood clotting. (1)H NMR was also utilized to observe the aromatic-aromatic interaction between electron deficient aromatic rings on oligochitosan and electron rich aromatic rings in amitriptyline. The chemical shift variation of aromatic protons in oligochitosan derivatives was followed to monitor the aromatic-aromatic interaction. Upfield shift of aromatic protons on benzenesulfonyl and dinitrobenzenesulfonyl groups was observed upon the addition of amitriptyline, supporting the formation of pi-pi complexes through aromatic-aromatic interactions. Dinitrobenzenesulfonyl rings show a larger variation in chemical shift due to the presence of the electron deficient nitro groups.