Novel heteroaromatic species for sensitive electrochemical detection of dopamine and tyrosine

Two new π-conjugated systems, an aza[4]helicene derivative (HL1) and a thiophene-based olefin (HL2), were synthesized in high yields (60–80%) under mild and cost-effective conditions. Their structures were confirmed by ¹H and ¹³C NMR, FT–IR, and HRMS analyses. Both compounds display strong UV–Vis absorption (λ_max = 378–405 nm) and intense blue-to-green fluorescence with large Stokes shifts (3779–4448 cm^–1), reflecting extended π-conjugation. The materials were subsequently applied to screen-printed carbon electrodes (SPCEs) to develop electrochemical sensors for dopamine (DA) and D–tyrosine (Tyr). The modified electrodes were characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Both HL1- and HL2-based SPCEs enabled simultaneous detection of DA and Tyr in the presence of uric acid (UA) as an interferent. Notably, HL2/SPCE exhibited superior analytical performance, offering a wide linear response range (0–500 µM), low detection limits (0.7022 µM for DA and 0.6274 µM for Tyr), and high sensitivities of 0.645 µA µM^–1 cm^–2 and 0.256 µA µM^–1 cm^–2, respectively. These findings highlight its potential for preliminary biosensing applications and provide a promising platform for further optimization toward real biological sample analysis.