Synthesis, enhanced spectroscopic characterization and electrochemical grafting of N-(4-aminophenyl)aza-18-crown-6: Application of DEPT, HETCOR, HMBC-NMR and X-ray photoelectron spectroscopy

This work describes the synthesis, characterization and electrochemical grafting of N-(4-aminophenyl)aza-18-crown-6 (4APA18C6). The key step in the synthesis is the reaction of N-phenylaza-18-crown-6 (PA18C6) with sodium nitrite. The compound, N-(4-nitrosophenyl)aza-18-crown-6 (NOPA18C6) could not be isolated purely from the reaction mixture, but a reduction of the residue with SnCl2 gave the desired azacrown ether, N-(4-aminophenyl)aza-18-crown-6 (4APA18C6).To confirm its proposed structure detailed characterization techniques such as elemental analysis, FT-IR, 1H NMR, 13C NMR, DEPT, HETCOR, HMBC and ESI mass-spectrometry were used. Due to the importance of azacrown compounds in the field of analytical chemistry, in the derivatization of dyes, chemical sensors and ionic extraction, as molecular receptors, grafting of 4APA18C6 on the glassy carbon (GC) surface has been investigated by amine oxidation to gain new insight into the modification area. The oxidation mechanism has been established, and the results are in accordance with the attachment of amines to a glassy carbon surface by cyclic voltammetry. The modification of 4APA18C6 molecules onto the glassy carbon surface was verified by cyclic voltammetry (CV), X-ray photoelectron spectroscopy (XPS) reflection–absorption infrared spectroscopy (RAIRS) and ellipsometry. The film on the GC surface was formed according to the layer-by-layer mechanism and the ellipsometric thickness was obtained around 11.5 ± 1.1 nm.