Sintesis Kemosensor Azina Asimetris Hibrida vanilin–p-nitrobenzaldehida dan Vanilin–p-nitrosinamaldehida

Maria Lilita Guterres, Prof. Drs. Bambang Purwono, M.Sc., Ph.D.

2026 | Tesis | S2 Ilmu Kimia

 Kemosensor hibrida azina p-NBVA dan p-NCVA berhasil disintesis melalui reaksi kondensasi basa Schiff berbantuan sonikasi, dengan jalur intermediet hidrazon terbukti lebih efisien dibandingkan jalur melalui vanilin azina (VA). Struktur kedua senyawa berhasil dikonfirmasi melalui karakterisasi ATR-IR, GC-MS/LC-MS, serta spektroskopi ¹H- dan ¹³C-NMR. Introduksi satu gugus vinil pada p-NCVA menghasilkan perpanjangan sistem ?-konjugasi yang memberikan peningkatan sensitivitas terhadap ion CN? dibandingkan p-NBVA, meskipun tidak memberikan perubahan yang signifikan terhadap karakteristik optiknya. Kedua kemosensor menunjukkan selektivitas tinggi terhadap CN? dengan respons kolorimetri pada daerah tampak (540–550 nm), sedangkan studi mekanistik mengonfirmasi bahwa proses pengenalan berlangsung melalui mekanisme deprotonasi gugus hidroksil fenolik yang bersifat reversibel. Selain itu, kedua kemosensor berhasil diaplikasikan dalam bentuk kertas strip dan mampu mendeteksi sianida pada sampel nyata ubi hutan (Dioscorea hispida Dennst.), sehingga berpotensi dikembangkan sebagai metode deteksi sianida yang cepat, sederhana, dan berbasis naked-eye untuk aplikasi keamanan pangan.

Two hybrid azine-based colorimetric chemosensors, p-nitrobenzaldehyde–vanillin azine (p-NBVA) and p-nitrocinnamaldehyde–vanillin azine (p-NCVA), were successfully synthesized. A vinyl group was introduced into p-NCVA to extend the ?-conjugation system and enhance the intramolecular charge transfer (ICT) process. The compounds were synthesized via a sonochemical Schiff base condensation method through two reaction pathways: hydrolysis of symmetric azine VA and the hydrazone intermediate pathway involving p-nitrobenzaldehyde and p-cinnamaldehyde. The hydrazone pathway successfully improved the product yield and purity. The synthesized compounds were characterized using FT-IR, ATR-IR, GC-MS, LC-MS, UV-Vis, and 1H- and 13C-NMR spectroscopy. The chemosensing performance was evaluated through solvatochromic, ionochromic, interference, response time, reversibility, and host–guest interaction studies using 1H-NMR analysis, as well as real-sample applications.

Solvatochromic studies revealed a bathochromic shift of up to 170 nm with increasing solvent polarity. Ionochromic and interference studies demonstrated that the chemosensors were selective toward CN? ions, as indicated by distinct color changes and UV–Vis spectral shifts in DMF solution. Response time studies showed that p-NBVA exhibited a faster response toward CN? detection, whereas p-NCVA provided better signal stability. ^1H-NMR titration analysis indicated that the interaction mechanism between the chemosensors and CN? ions occurred through deprotonation of the phenolic (–OH) group, thereby enhancing the ICT process. The sensitivity of the chemosensors was demonstrated by LOD values of 4.43 × 10?? M for p-NCVA and 4.99 × 10?? M for p-NBVA. The introduction of a single conjugated vinyl group into p-NCVA increased the sensitivity toward CN? anion detection by 11.22%. The chemosensors maintained their colorimetric response for up to eight reversible cycles. Applications using wild yam samples through solution-based and paper strip methods demonstrated the potential of both compounds as simple colorimetric chemosensors for food safety monitoring.

Kata Kunci : ion sianida, donor–?–akseptor (D–?–A), kemosensor, azina, intramolecular charge transfer (ICT), basa Schiff.