Abstract
A new hydrogen-bonded charge-transfer (HB-CT) complex formed between the donor 2-amino-4-methoxy-6-methylpyrimidine (AMMP) and theπ-acceptor 2,5-dihydroxy-p-benzoquinone (DHBQ) was investigated in both solid and solution states. The investigation was conducted using UV-Vis, CHN, FTIR,1H NMR, XRD, and TG-DTA analyses. The molecular composition of the CT complex in MeOH was found to be 1 : 1. The formation constant (KCT), molecular extinction coefficient (ε), and several other spectroscopic physical parameters were evaluated at different temperatures. The thermodynamic properties of the CT interaction in MeOH were studied by calculating the enthalpy (ΔH°), entropy (ΔS°), and free energy (ΔG°). The thermodynamic parameters indicated that van der Waals interactions and hydrogen bonding occur between AMMP and DHBQ in MeOH. The CHN, FTIR, and TG-DTA measurements confirmed that the solid HB-CT complex forms in a 2 : 1 ratio, i.e., [(AMMP)2(DHBQ)], and exhibits high stability. Moreover, XRD analysis was used to establish that the mean particle size of the complex is 23 nm. Finally, the solid HB-CT complex was screened for its antibacterial, antifungal, and antioxidant activities. It shows good activity against various bacterial and fungal species. Furthermore, the HB-CT complex exhibits good DPPH scavenging activity.
Highlights
Aminopyrimidines are very important N-heterocyclic compounds that have numerous pharmaceutical applications and biological activities [15,16,17]. ey are present in both natural and synthetic products [18]
Previous studies on hydrogen-bonded charge-transfer (HB-CT) complexes [27,28,29,30] and the well-documented biological importance of aminopyrimidines prompted us to investigate the ability of the simple pyrimidine derivative 2-amino-4-methoxy-6-methylpyrimidine (AMMP) as an electron donor in an HB-CT complex with the electron acceptor 2,5-dihydroxy-p-benzoquinone (DHBQ) in both solid and solution states (Scheme 1). e reaction stoichiometry, HB-CT properties, and thermal stability of the complex in MeOH have been Journal of Chemistry estimated using UV-Vis spectrometry, whereas the solid HB-CT complex was characterized using FTIR spectroscopy, 1H NMR, powder XRD, and TG/DTA. e antifungal and antibacterial activities of the HB-CT complex were explored, and the antioxidant activity of the new HB-CT complex against DPPH radicals was evaluated
E electronic absorption spectra of all solutions were recorded in the region from 700 to 300 nm with a UV-Vis spectrophotometer (Shimadzu UV-1800, Japan), which was connected to a temperature controller unit (Shimadzu TCCZUOA). e CHN contents were measured with a microanalyzer (PerkinElmer 2400, USA). e FTIR spectra of the AMMP, DHBQ, and their solid HB-CT complex were measured as KBr discs using a Frontier spectrometer (PerkinElmer, USA). 1H NMR (600 MHz) spectra were recorded on a Bruker DPX spectrometer using 10 mg of the sample in dimethyl sulfoxide (DMSO)-d6 and TMS as an internal standard
Summary
Aminopyrimidines are very important N-heterocyclic compounds that have numerous pharmaceutical applications and biological activities [15,16,17]. ey are present in both natural and synthetic products [18]. Aminopyrimidines contain important groups that can act as electron donors or proton acceptors, and the study of their CT complexes helps to understand the nature of their CT interactions [25, 26]. Previous studies on HB-CT complexes [27,28,29,30] and the well-documented biological importance of aminopyrimidines prompted us to investigate the ability of the simple pyrimidine derivative 2-amino-4-methoxy-6-methylpyrimidine (AMMP) as an electron donor in an HB-CT complex with the electron acceptor 2,5-dihydroxy-p-benzoquinone (DHBQ) in both solid and solution states (Scheme 1). E antifungal and antibacterial activities of the HB-CT complex were explored, and the antioxidant activity of the new HB-CT complex against DPPH radicals was evaluated Journal of Chemistry estimated using UV-Vis spectrometry, whereas the solid HB-CT complex was characterized using FTIR spectroscopy, 1H NMR, powder XRD, and TG/DTA. e antifungal and antibacterial activities of the HB-CT complex were explored, and the antioxidant activity of the new HB-CT complex against DPPH radicals was evaluated
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