Spectroscopic and DFT study of atenolol and metoprolol and their copper complexes

Molecular conformation, vibrational spectroscopic and NBO analysis of atenolol and atenolol-hydrochlorothiazide cocrystals

Geometry optimization of atenolol (ATN) in the gas phase was carried out using B3LYP-D3BJ/6-31++G(d,p), CAM-B3LYP/6-31++G(d,p) and M06-2X/6-31++G(d,p) levels of DFT. The computed structural parameters were compared with the data obtained by single crystal X-ray diffraction experiment. Chemical reactivity (electronegativity, electrophilicity, hardness, chemical softness and chemical potential) was predicted with the help of HOMO- LUMO energy values. Experimental FT-IR was recorded and the calculated values were also analyzed using the same level of DFT. A complete vibrational spectrum was made to analyze the potential energy distribution (PED). Stability of the molecule arising from hyperconjugative interaction was analyzed by the natural bond orbital (NBO) analysis. The molecular electrostatic potential map was used to detect the possible electrophilic and nucleophilic sites in ATN molecule. Cocrystallization of atenolol-hydrochlorothiazide (ATN-HCTZ) was performed and the structure was analyzed by powder X-ray diffraction. NBO analysis was carried out on the ATN-HCTZ cocrystal for the elucidation of inter and intra-molecular hydrogen bonding interactions in the structure. Atenolol interaction with human serum albumin (HSA) was investigated by a molecular docking study.

The Triple Mechanisms of Atenolol Adsorption on Ca-Montmorillonite: Implication in Pharmaceutical Wastewater Treatment

The adsorption of atenolol (AT) from aqueous solutions by Ca-montmorillonite (SAz-2) was investigated in batch studies under different physicochemical conditions. The AT existed in neutral un-dissociated form at pH 10, and was adsorbed on dioctahedral smectite (SAz-2) obeying the Langmuir isotherm with a maximum adsorption capacity of 330 mmol/kg. The kinetic adsorption suggested that both strong and weak adsorption sites existed on SAz-2 and participated in the adsorption mechanisms. The amount of exchangeable cations desorbed from SAz-2 during AT adsorption was linearly correlated with the amounts of adsorbed AT having slopes of 0.43, which implied that a cation exchange based adsorption mechanism was also in place. A comprehensive basal spacing change of SAz-2 was observed after AT adsorption on the clay mineral when tested with or without AT recrystallization. The intercalation of AT into the SAz-2 interlayers did not result in swelling due to the low adsorption capacity of the drug. Prominent interactions between the pharmaceutical molecule and SAz-2 were evidenced by apparent shifts of the infrared absorption bands after adsorption. The interlayer configurations and hydrogen bonding of AT on SAz-2 were also supported by infrared, X-ray diffraction and thermogravimetric analyses. This study suggested that SAz-2 is an excellent material to remove not only AT from pharmaceutical wastewater, but can potentially remove many other β-receptor blocker drugs. The results helped us to understand the possible interlayer configurations and adsorption mechanisms of the drugs on natural clay mineral based adsorbents.

Improved Enantioselectivity for Atenolol Employing Pivot Based Molecular Imprinting

In the last few decades, molecular imprinting technology went through a spectacular evolution becoming a well-established tool for the synthesis of highly selective biomimetic molecular recognition platforms. Nevertheless, there is still room for advancement in the molecular imprinting of highly polar chiral compounds. The aim of the present work was to investigate the favorable kosmotropic effect of a ternary complex involving a polar chiral template (eutomer of atenolol) and a functional monomer, bridged by a central metal ion through well-defined, spatially directional coordinate bonds. The efficiency of the chiral molecular recognition was systematically assessed on polymers obtained both by non-covalent and metal-mediated molecular imprinting. The influence on the chromatographic retention and enantioselectivity of different experimental variables (functional monomers, cross-linkers, chaotropic agents, metal ions, porogenic systems, etc.) were studied on both slurry packed and monolithic HPLC columns. Deliberate changes in the imprinting and rebinding (chromatographic) processes, along with additional thermodynamic studies shed light on the particularities of the molecular recognition mechanism. The best performing polymer in terms of enantioselectivity (α = 1.60) was achieved using 4-vinyl pyridine as functional monomer and secondary ligand for the Co(II)-mediated imprinting of S-atenolol in the presence of EDMA as cross-linker in a porogenic mixture of [BMIM][BF₄]:DMF:DMSO = 10:1:5, v/v/v.

Competition and enhancement effect in coremoval of atenolol and copper by an easily regenerative magnetic cation exchange resin

This paper aimed to investigate the removal of combined Cu²⁺ and atenolol (ATL) in aqueous solution by using a newly synthesized magnetic cation exchange resin (MCER) as the adsorbent. The MCER exhibited efficient removal performance in sole, binary, pre-loading and saline systems. The adsorption kinetics of Cu²⁺ and ATL fitted both pseudo-first-order and pseudo-second order model, while better described by pseudo-second order model in binary system. In mixed Cu²⁺ and ATL solution, the adsorption of ATL was suppressed due to direct competition of carboxylic groups, while Cu²⁺ adsorption was enhanced because of the formation of surface complexes. This increasing in heterogeneity was demonstrated by adsorption isotherms, which were more suitable for Freundlich model in binary system, while better described by Langmuir model in sole system. As proved by FTIR and XPS spectra, both amino and hydroxyl groups of ATL could form complexes with Cu²⁺. Decomplexing-bridging interaction was elucidated as the leading mechanism in coremoval of Cu²⁺ and ATL, which involved [Cu-ATL] decomplexing and newly created Cu- or ATL sites for additional bridging. For saline system, the resulting competition and enhancement effects in mixed solution were amplified with the addition of co-existing cations. Moreover, the MCER could be effectively regenerated by 0.01 M HCl solution and maintain high stability over 5 adsorption-desorption cycles, which render it great potential for practical applications.

Synthesis and characterization of modified carrageenan microparticles for the removal of pharmaceuticals from aqueous solutions

In the present study, carrageenan microparticles were synthesized using spray-drying method and used as biosorbents for the removal of pharmaceutical compounds. The cross-linking reaction of iota-carrageenan (iCAR) and kappa-carrageenan (kCAR) with glutaraldehyde (GLA) at different concentrations (2.5% or 5% (w/w), mass of GLA per mass of CAR) was studied (iCAR/GLA2.5, iCAR/GLA5, kCAR/GLA2.5, kCAR/GLA5). The physicochemical properties of the novel cross-linked polymers were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). Swelling studies were in accordance with the polymer properties, showing the lowest swelling degree (19%) by using the iCAR/GLA5 microparticles. The optimal kCAR/GLA5 microparticles were successfully employed for the removal of Metoprolol (MTPL) from aqueous samples. The adsorption capacity of the adsorbents was investigated using a batch adsorption procedure and the kinetics and thermodynamics of the adsorption process were further investigated. It was found that the adsorption isotherms agree well with the Langmuir-Freundlich model. The maximum adsorption capacity (Qm) was achieved in pH 6, whereas an increase of Qm was observed increasing the temperature (from 109 at 20°C to 178 mg/g at 40°C). Kinetic studies showed that the adsorption process on iCAR/GLA5 microparticles followed pseudo-second-order rate mechanism. Finally, a new phenomenological model of the adsorption process was proposed in order to extract information on the relevant sub-processes.