Benzoxazole Iminocoumarins as Multifunctional Heterocycles with Optical pH-Sensing and Biological Properties: Experimental, Spectroscopic and Computational Analysis

Galić, Marina; Čikoš, Ana; Persoons, Leentje; Daelemans, Dirk; Vrandečić, Karolina; Karnaš, Maja; Hranjec, Marijana; Vianello, Robert (2026) Benzoxazole Iminocoumarins as Multifunctional Heterocycles with Optical pH-Sensing and Biological Properties: Experimental, Spectroscopic and Computational Analysis. Chemosensors, 14 (1). ISSN 2227-9040

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Abstract

A novel series of benzoxazole-derived iminocoumarins was synthesized via a Knoevenagel condensation and fully characterized using NMR, UV–Vis spectroscopy, and computational methods. Their photophysical properties were systematically examined in solvents of varying polarity, revealing pronounced effects of both substituents and solvent environment on absorption maxima and intensity. Derivatives bearing electron-donating substituents on the coumarin core exhibited distinct and reversible pH-responsive spectral shifts, confirming their potential as optical pH probes. Experimental pKa values derived from absorption titrations showed excellent agreement with DFT-calculated data, validating the proposed protonation-deprotonation equilibria and associated electronic structure changes. Structure–property relationships revealed that electron-donating groups enhance intramolecular charge transfer, while electron-withdrawing substituents modulate spectral response and stability. In parallel, the compounds were evaluated for antiproliferative, antiviral, and antifungal activities in vitro. Strong electron-donating substituents were associated with potent but non-selective cytotoxicity, whereas derivatives bearing electron-withdrawing groups displayed moderate and more selective antiproliferative effects against leukemia cell lines. Antifungal screening revealed moderate inhibition of phytopathogenic fungi, particularly for compounds with electron-withdrawing or methoxy substituents. Overall, these findings demonstrate that benzoxazole iminocoumarins represent a promising class of multifunctional heterocycles with potential applications as optical pH sensors and scaffolds for bioactive compound development.

Item Type:	Article
Uncontrolled Keywords:	iminocoumarins; benzoxazole derivatives; optical pH sensors; solvent effects; DFT calculations; spectroscopic characterization; antiproliferative activity; antifungal activity
Subjects:	NATURAL SCIENCES > Chemistry > Theoretical Chemistry NATURAL SCIENCES > Chemistry > Organic Chemistry NATURAL SCIENCES > Chemistry > Applied Chemistry
Divisions:	NMR Center
Projects:	Project title Project leader Project code Project type Dizajn, sinteza i računalna analiza novih optičkih kemijskih pH osjetilnih derivata benzazola-BenzpHSens Robert Vianello; Marijana Hranjec; Ida Boček IP-2020-02-8090 HRZZ Sinteza novih benzazolnih heterocikla kao potencijalnih antitumorskih i antibakterijskih agensa Marijana Hranjec IP-2024-05-7208 HRZZ
Depositing User:	Ema Buhin Šaler
Date Deposited:	02 Feb 2026 09:09
URI:	http://fulir.irb.hr/id/eprint/11203
DOI:	10.3390/chemosensors14010015

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