Role of Aromatic Moiety in the Probe Property toward Picric Acid: Synthesis, Crystal Structure, Spectroscopy, Microscopy, and Computational Modeling of a Knoevenagel Condensation Product of D-Glucose

Molecular probes for picric acid (PA) in both solution and solid states are important owing to their wide usage in industry. This paper deals with the design and development of a glucosyl conjugate of pyrene (L-1) along with control molecular systems, possessing anthracenyl (L-2), naphtyl (L-3), and phenyl (L-4) moieties, via Knoevenagel condensation of 2,4-pentanedione with D-glucose. The selectivity of L-1 toward PA has been demonstrated on the basis of fluorescence and absorption spectroscopy, and the species of recognition by electrospray ionization mass spectrometry. The role of the aromatic group in the selective receptor property has been addressed among L-1, L-2, L-3, and L-4. The structural features of the {L-1 + PA} complex were established by density functional theory computations. L1 was demonstrated to detect PA in solid state selectively over other nitroaromatic compounds (NACs). To study the utility of L-1 in film, cellulose paper strips coated with L1 were used and demonstrated the selective detection of PA. The observed microstructural features of L1 and its complex {L1 + PA} differ distinctly in both atomic force microscopy and scanning electron microscopy, all in the support of the complex formation. Thus, L-1 was demonstrated as a sensitive, selective, and inexpensive probe for PA over several NACs by visual, spectral, and microscopy methods.