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Herein, we used the aqueous extract of Uncaria tomentosa L. barks (Cat’s claw bark [CCb]) for the biofabrication of silver nanoparticles (CCb-Ag-NPs). The effects of different parameters (Uncaria tomentosa L. aqueous extract, silver nitrate [AgNO3] ratio, temperature, and pH) on the formation of the nanoparticles were investigated using UV scan as a preliminary tool for the detection of surface plasmon resonance of CCb-Ag-NPs. The optimal ratio was 1:7 (Uncaria tomentosa L. extract: 1 mM AgNO3 solution). Fourier-transform infrared spectroscopy revealed the functional groups of both CCb extract and the CCb-Ag-NPs, whose dispersion and quasispherical morphologies were characterized using scanning electron microscopy and transmission electron microscopy. Particle sizes ranged from 19.2 to 38.5 nm. The zeta potential of CCb-Ag-NPs was −34.44 mV. According to energy-dispersive X-ray analysis, the CCb-Ag-NPs contained 28.87% silver. The formation of Ag-NPs was also confirmed by X-ray diffraction pattern analysis. Pristine CCb-Ag-NPs showed antibacterial activity against three pathogenic bacterial strains: Escherichia coli (ATCC 25922), E. coli (ATCC 8739), and Pseudomonas aeruginosa (ATCC 90274). Antibacterial activity increased significantly after loading CCb-Ag-NPs on antibiotic discs containing meropenem and cefoxitin. Low concentrations of CCb-Ag-NPs also enhanced the germination percentage, coleoptile length, and radical root length of Triticum aestivum.

New charge transfer complex associated with hydrogen bonding between 2-amino-4,6-dimethoxypyrimidine (ADMP) with chloranilic acid (H2CA) was studied in solution and solid state. The solution studies were carried out in three polar solvents ethanol (EtOH), methanol (MeOH) and acetonitrile (ACN). The formed complex exhibited new absorption maxima above 500 nm. The molecular composition was done by job and photometric titration methods where the complex proceeded through 1:1 ratio. Moreover, the stability constant was calculated by Bensie-Hildebrand equation, the highest value was in methanol and least one in ethanol. The solid complex was synthesised and characterised by elemental analysis and infrared spectra, and they confirmed the formation of 2:1 (donor: acceptor) complex and its structure included charge transfer besides hydrogen bonding. DFT computations using the hybrid method B3LYP-DFT at the basis set 6-31G(d,p) were running out in gas phase to support the mechanism of complex formation in solid state. [ABSTRACT FROM AUTHOR]

A new proton transfer (PT) complex formed on the reaction between 2,6-dichloro-4- nitrophenol (DCNP) as a proton donor and 2-amino-4,6-dimethoxypyrimidine (ADMP) as a proton acceptor has been investigated and characterized experimentally and theoretically. The experimental work has been carried out in three different polar solvents, including methanol, ethanol, and acetonitrile as well as in the solid state. The molecular composition of the PT complex was determined employing Job's and photometric titration methods to be 1:1 in all studied solvents confirming that the complex's stoichiometry is solvent-independent. The PT formation constant (KPT) and the molar extinction coefficient (ε) in the selective solvents were calculated using the modified Benesi-Hildebrand equation. The KPT values are highest in the protic solvent (EtOH) and lowest in the aprotic solvent (ACN). The spectroscopic physical parameters have been determined, where the more negative ΔG° was recorded in EtOH and was in good agreement with the PT formation constant. Furthermore, a sensitive spectrophotometric method for determining ADMP is proposed and validated statistically. The solid complex was synthesized and characterized, utilizing elemental analysis, ¹H NMR, and FT-IR spectroscopy and they confirmed the formation of 1:1 PT complex. The optimized geometries of DCNP, ADMP, and the proton transfer DCNP-ADMP complexes were calculated using B3LYP and CAM-B3LYP methods as well as 6-31++G (d,p) basis sets. The reactivity descriptors were used to describe the electron transfer processes among the DCNP and ADMP molecules. The significant electron density of 0.142 e was transferred from ADMP to DCNP. The electronic spectra of DCNP-ADMP complex were predicted using Time-dependent density functional theory (TD-DFT) calculations and compared with the experimental data. [ABSTRACT FROM AUTHOR]

UV–Vis spectroscopy was used to investigate two new charge transfer (CT) complexes formed between the K+-channel-blocker amifampridine (AMFP) drug and the two π-acceptors 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) and tetracyanoethylene (TCNE) in different solvents. The molecular composition of the new CT complexes was estimated using the continuous variations method and found to be 1:1 for both complexes. The formed CT complexes' electronic spectra data were further employed for calculating the formation constants (KCT), molar extinction coefficients (εCT), and physical parameters at various temperatures, and the results demonstrated the high stability of both complexes. In addition, sensitive spectrophotometric methods for quantifying AMFP in its pure form were proposed and statistically validated. Furthermore, DFT calculations were used to predict the molecular structures of AMFP–DDQ and AMFP–TCNE complexes in CHCl3. TD-DFT calculations were also used to predict the electronic spectra of both complexes. A CT-based transition band (exp. 399 and 417 nm) for the AMFP–TCNE complex was calculated at 411.5 nm (f = 0.105, HOMO-1 → LUMO). The two absorption bands at 459 nm (calc. 426.9 nm, f = 0.054) and 584 nm (calc. 628.1 nm, f = 0.111) of the AMFP–DDQ complex were theoretically assigned to HOMO-1 → LUMO and HOMO → LUMO excitations, respectively. [ABSTRACT FROM AUTHOR]