Improved solubility and bioactivity of theophylline (a bronchodilator drug) through its new nitrate salt analysed by experimental and theoretical approaches

Abstract Synthesis, crystal structure, vibrational spectroscopy, quantum chemical studies and biological activity of the new semi organic compound, Theophyllinium Nitrate [C 7 H 9 N 4 O 2 ) + . (NO 3 ) - ], are reported here. Crystals of Theophyllinium nitrate (TN) were grown by slow solvent evaporation technique. The crystal packing is dominated by N–H ··· O intermolecular hydrogen bonds. The cations and anions are aggregated almost parallel leading to a lamellar structure. This molecular aggregation features two alternate hydrogen bonded chain C 2 2 (8) and C 2 1 (6) motifs. Further, a bifurcated ring R 1 2 (4) motifs is also seen. This aggregated molecular sheets are parallel to ( 2 ¯ 06 ) and ( 20 6 ¯ ) planes of the crystal. The solubility test is carried out to enhance the physico–chemical activity of the compound. The atomic charge distribution on different atoms of TN has been calculated by Mulliken charge analysis. A detailed interpretation of FT-IR and FT-Raman spectra of TN show that most of the bands are matching between the experimental and theoretical methods. The strong intensity bands and shifting of bands due to intermolecular hydrogen bonds are also investigated. The NBO analysis is carried out to elucidate the stability of the molecule and charge delocalization within the molecule. The HOMO–LUMO analysis reveals molecular stability and chemical reactivity of the present compound. Also, the compound was examined for its antibacterial activity and found to exhibit notable activity against Pseudomonas aeruginosa . This shows that the present compound is a good candidate for the antimicrobial agent apart from its inherent Bronchodilator drug property. Hence, the new compound (TN) may be a good alternative for patients with Chronic Obstructive Pulmonary Disease (COPD) and bacterial infections.