Electron Spin Resonance Studies Research Articles

Photoactive Fe Catalyst for Light-Triggered Alkyd Paint Curing.

Herein, we show that the photoactive complexes [(Cp)Fe(arene)]+ (Cp = cyclopentadienyl; arene = C6H6, C6H5Me) act as latent catalysts that allow for photochemical control over the onset of alkyd paint curing, without the need for antiskinning agents such as the volatile 2-butanone oxime normally used to prevent curing during paint storage. The highly soluble neutral complexes [(Cp)Fe(Ch)] and [(Cp)Fe(Ch′)] (Ch = cyclohexadienyl, Ch′ = methylcyclohexadienyl) readily convert to the photoactive complexes [(Cp)Fe(arene)]+ upon oxidation in alkyd, allowing the latter to be dosed in a wide range of concentrations. Infrared and Raman studies show similar spectral changes of the alkyd paint matrix as have been observed in alkyd curing mediated by well-known, industrially applied cobalt- and manganese-based catalyst Co(neodecanoate)2 and [(Me3TACN)2Mn2(μ-OOCR)3](OOCR). The [(Cp)Fe(Ch)]/[(Cp)Fe(arene)]+ system performs equally well as these cobalt- and manganese-based catalysts in terms of drying time and outperform the manganese catalyst by showing a hardness development (increase) similar to that of the cobalt-based catalyst. Based on electron paramagnetic resonance and light–activity studies, we propose that photolysis of [(Cp)Fe(arene)]+ generates short-lived active FeII species, explaining the desired latency. The [(Cp)Fe(Ch)]/[(Cp)Fe(arene)]+ alkyd curing systems presented herein are unique examples of intrinsically latent paint curing catalysts that (1) are based on an abundant and harmless transition metal (Fe), (2) do not require any antiskinning agents, and (3) show favorable performance in terms of drying times and hardness development.

Magnetic sludge-based biochar derived from Fenton sludge as an efficient heterogeneous Fenton catalyst for degrading Methylene blue

Fenton sludge was converted into magnetic sludge-based biochar (SMBC) using a one-step pyrolysis process and employed as a novel heterogeneous catalyst to activate hydrogen peroxide (H2O2) for the oxidative removal of methylene blue (MB). The crystal structure and catalytic activity of SMBC are strongly affected by the pyrolysis temperature. X-ray powder diffraction, Mössbauer, and scanning electron microscope-energy dispersive spectrometer analyses were conducted to determine the crystal phase transfer of iron (Fe) oxides at different pyrolytic temperatures and retention times. The results revealed that the catalytic efficiency of SMBC was strongly related to the crystal phase of Fe oxides. The catalyst obtained at 800 °C for 1 h exhibited superior catalytic properties and degraded 98.56% of the MB (100 mg·L−1) in 3 min via the synergistic effect of Fe3O4, Fe0, and biochar. Free radical quenching experiments and electron paramagnetic resonance studies demonstrated that ·OH, O2·− and 1O2 participated in the H2O2 system, and·OH radicals were promptly generated owing to the catalysis of the SMBC. Aging tests were repeated for four cycles in three conditions to examine the stability of the material. The results showed that SMBC was relatively stable in non-aerated and aqueous conditions, but its activation performance was severely inhibited in an oxygen environment. Furthermore, the catalytic ability of SMBC was maintained at 88.13% after the 4th run. This study presents a cost-effective method of converting ferric sludge to an environmentally friendly catalyst that enables H2O2 activation for degrading refractory organic contaminants.

Large π-Conjugated Metal-Organic Frameworks for Infrared-Light-Driven CO2 Reduction.

It remains challenging to excite traditional photocatalysts through near-infrared (NIR) light. Attempts to use NIR-light-response materials for photochemical reduction usually suffer from inapposite band position due to extremely narrow band gaps. Here, we report that large π-conjugated organic semiconductor engineered metal-organic framework (MOF) can result in NIR-light-driven CO2 reduction catalyst with high photocatalytic activity. A series of mesoporous MOFs, with progressively increased macrocyclic π-conjugated units, were synthesized for tuning the light adsorption range and catalytic performance. Attainment of these MOFs in single-crystal form revealed the identical topology and precise spatial arrangements of constituent organic semiconductor units and metal clusters. Furthermore, the ultrafast spectroscopic studies confirmed the formation of charge separation state and the mechanism underlying photoexcited dynamics. This combined with X-ray photoelectron spectroscopy and in situ electron paramagnetic resonance studies verified the photoinduced electron transfer pathway within MOFs for NIR-light-driven CO2 reduction. Specifically, tetrakis(4-carboxybiphenyl)naphthoporphyrin) MOF (TNP-MOF) photocatalyst displayed an unprecedentedly high CO2 reduction rate of over 6630 μmol h-1 g-1 under NIR light irradiation, and apparent quantum efficiencies (AQE) at 760 and 808 nm were over 2.03% and 1.11%, respectively. The photocatalytic performance outperformed all the other MOF-based photocatalysts, even visible-light-driven MOF-based catalysts.

Activation of peroxymonosulfate by magnetic CuFe2O4@ZIF-67 composite catalyst for the study on the degradation of methylene blue

In this research, a novel magnetically recoverable composite catalyst, CuFe2O4 @ZIF-67, was synthesized. CuFe2O4 @ZIF-67 composite catalyst was applied to degrade methylene blue (MB) in water by activating peroxymonosulfate (PMS). The results showed that the degradation rate of MB (20 mg/L) reached 98.9% in 30 min in the 0.2-CuFe2O4 @ZIF-67 (75 mg/L) + PMS (125 mg/L) system. Both electron paramagnetic resonance (EPR) studies and radical quenching experiments revealed that SO4−•, •OH, 1O2 and •O2− were involved in the degradation of MB. We proposed a catalytic mechanism of PMS activation by CuFe2O4 @ZIF-67. With the synergistic effect of Co3+/Co2+, Fe3+/Fe2+ and Cu2+/Cu+ redox cycles, it can keep its outstanding catalytic activity. Recycling tests showed that the removal rate of MB can still be maintained above 85%, indicating that CuFe2O4 @ZIF-67 has good reusability. In general, owing to its reusability and excellent catalytic activity, the CuFe2O4 @ZIF-67 composite catalyst has a good application prospect in water pollution control.

Modulation of the Directionality of Hole Transfer between the Base and the Sugar-Phosphate Backbone in DNA with the Number of Sulfur Atoms in the Phosphate Group.

This work shows that S atom substitution in phosphate controls the directionality of hole transfer processes between the base and sugar-phosphate backbone in DNA systems. The investigation combines synthesis, electron spin resonance (ESR) studies in supercooled homogeneous solution, pulse radiolysis in aqueous solution at ambient temperature, and density functional theory (DFT) calculations of in-house synthesized model compound dimethylphosphorothioate (DMTP(O-)═S) and nucleotide (5'-O-methoxyphosphorothioyl-2'-deoxyguanosine (G-P(O-)═S)). ESR investigations show that DMTP(O-)═S reacts with Cl2•- to form the σ2σ*1 adduct radical -P-S[Formula: see text]Cl, which subsequently reacts with DMTP(O-)═S to produce [-P-S[Formula: see text]S-P-]-. -P-S[Formula: see text]Cl in G-P(O-)═S undergoes hole transfer to Gua, forming the cation radical (G•+) via thermally activated hopping. However, pulse radiolysis measurements show that DMTP(O-)═S forms the thiyl radical (-P-S•) by one-electron oxidation, which did not produce [-P-S[Formula: see text]S-P-]-. Gua in G-P(O-)═S is oxidized unimolecularly by the -P-S• intermediate in the sub-picosecond range. DFT thermochemical calculations explain the differences in ESR and pulse radiolysis results obtained at different temperatures.

Products of Prolonged Autoxidation of Simple Dihydric Phenols in the Presence of Copper(II) Ions – An Electron Spin Resonance Study

Electron spin resonance (ESR) spectroscopy was used for characterizing the products obtained by prolonged autoxidation of simple dihydric phenols (hydroquinone, catechol, and 4-methylcatechol) in the presence of copper(II) ions. Room temperature ESR spectra revealed that both paramagnetic copper(II) ions and organic radicals are present in obtained autoxidation products similarly to the humic acid complexed copper(II) ions. The ratio of organic radical signal intensity to the copper(II) ion signal intensity suggests that the smallest amount of copper(II) ions is incorporated in the hydroquinone autoxidation product while the highest amount of copper(II) ions is incorporated in the autoxidation product of catechol. Satisfactory computer simulations of experimental ESR spectra were obtained by considering only one type of copper(II) ion binding site for hydroquinone autoxidation product and two distinct types of copper(II) ion binding sites for catechol and 4-methylcatechol autoxidation products. Parameters obtained by the computer simulation of ESR spectra indicated prevalent ionic bonding of copper(II) ions in polymeric matrices with tetrahedral distortion at copper(II) ion binding sites and negligible exchange interactions between them. Products obtained by the hydroquinone and catechol autoxidation have more similar characteristics in comparison to the product obtained by the 4-methylcatechol autoxidation where more expressed ionic bonding of copper(II) ions, and smaller tetrahedral distortion are present. Due to the dipolar interactions of oxygen-centered organic radicals in autoxidation products with paramagnetic copper(II) ions, their ESR linewidths are larger and g-values smaller in comparison to the values found in humic acids from various soil types.

Synthesis of SrBaFexMo2-xO6 (x=1.0, 1.1, 1.3 and 1.4) double perovskites by sonication: characterization and electron spin resonance studies

This paper presents influence of ultrasound-assisted method on structure, tolerance factor, density and Electron spin resonance studies of SrBaFexMo2-xO6 (x = 1.0, 1.1, 1.3 and 1.4) (SBFMO) double perovskite. SrBaFexMo2-xO6 double perovskite was synthesized by sonochemical procedure at low temperature (9500C) under Ar/ H2 atmosphere. X-ray diffraction studies revealed a single phase with a cubic crystal structure for all the samples. The existence of all elements (Sr, Ba, Fe, Mo, O) contamination-free in the required percentage in SBFMO compound has been analyzed by Energy Dispersive X-ray Spectroscopy (EDS). Goldschmidt Tolerance factor 't' has been used to quantitatively predict the stability 1 and closeness of A2BxB12-xO6. Density measurements for all samples of SrBaFexMo2-xO6 (x = 1.0, 1.1, 1.3 and 1.4) were done both theoretically and experimentally. Electron Spin Resonance (ESR) spectra of SrBaFexMo2-xO6 (x = 1.0, 1.1, 1.3 and 1.4) were studied to determine the iron state in the compound by varying magnetic field at a constant frequency (X-Band).

Copper-doped carbon dots with enhanced Fenton reaction activity for rhodamine B degradation.

The Fenton reaction has attracted extensive attention due to its potential to be a highly efficient and environmentally friendly wastewater treatment technology. Noble copper-doped carbon dots (CuCDs) are prepared through a simple one-step hydrothermal method with 3,4-dihydroxyhydrocinnamic acid, 2,2′-(ethylenedioxy)bis(ethylamine) and copper chloride, endowing the Fenton reaction with enhanced catalytic activity for rhodamine B (RhB) degradation. The effects of the concentration of CuCDs, temperature, pH, oxygen (O2), metal ions and polymers on the catalytic activity of CuCDs are investigated. It is worth noting that electron transfer happening on the surface of CuCDs plays a vital role in the RhB degradation process. As evidenced by radical scavenger experiments and electron spin resonance (ESR) studies, CuCDs significantly boost the formation of hydroxyl radicals (˙OH) and singlet oxygen (1O2), facilitating the Fenton reaction for RhB degradation. Due to the strong oxidation of ROS generated by the Fe2+ + H2O2 + CuCD system, RhB degradation may involve the cleavage of the chromophore aromatic ring and the de-ethylation process. Additionally, the toxicity of RhB degradation filtrates is assessed in vitro and in vivo. The as-prepared CuCDs may be promising catalytic agents for the enhancement of the Fenton reaction.

Bonding Ability of Isopthalic Acid-bis(thiosemicarbozone) to Manganese and Cobalt Metal Ions: Preparation, Spectral Investigation, Computational and in vitro Antipathogenic Screening

Manganese and cobalt complexes have been designed and prepared with a tetradentate ligand i.e. isopthalic acid-bis(thiosemicarbozone) (IPBT), which bind to metal ions via donor atoms present in ligand. Different spectroscopic techniques viz. nuclear magnetic resonance, infra red, mass, electronic spin resonance and analytical studies have been used to determine the chemical composition of synthesized IPBT and its Mn(II) and Co(II) complexes. The spectroscopic data exposed that IPBT behaves in a tetradentate (N2S2) mode by having ability to bind with metal ions through N2S2 atoms. An octahedral structure for manganese and cobalt complexes has been suggested on the basis of spectroscopic as well as analytical studies. The ligand (IPBT) and its metal(II) complexes have been screened to determine their antipathogenic activity against some selective microorganisms S. aureus, P. aeruginosa, E. coli, A. niger, M. phasolina and P. glomerata. In this experimental work, well diffusion and poisoned food techniques have been introduced for screening purpose and as standard drugs neomycin and chlorothalonil have been used. Data for antipathogenic screening exposed that metal complexes exerted higher activity towards all examined microbes (bacteria and fungi) even than ligand.

Degradation of tetracycline hydrochloride through efficient peroxymonosulfate activation by B, N co-doped porous carbon materials derived from metal-organic frameworks: Nonradical pathway mechanism

• B, N co-doped carbon porous material was derived from metal-organic frameworks. • B-NC shows excellent performance in PMS activation and TC removal. • Singlet oxygen ( 1 O 2 ) was the domain active species in B-NC/PMS system. • Electron transfer was another non-radical oxidation pathway of B-NC/PMS system. • B-NC catalyst has relatively good stability for PMS activation. Peroxymonosulfate (PMS) based advanced oxidation process has been proved to be an efficient method for Antibiotic treatment. B, N co-doped carbon porous material was derived from metal-organic frameworks. B-NC catalysts showed excellent efficiency for removal of tetracycline hydrochloride. Nitrogen doping essentially changed the degradation pathway of tetracycline hydrochloride, while boron doping provided more active sites. through more defect sites, which is closely related to the adsorption and catalytic performance of the catalyst. The major active species of B-NC/PMS system was singlet oxygen ( 1 O 2 ) through quenching experiments and electron paramagnetic resonance (EPR) studies. Electron transfer was another non-radical oxidation pathway of B-NC/PMS system. This provides a new idea for the selective oxidation of antibiotics by metal-free activated PMS.

Revealing the catalytic pathway of a quinone-mediated oxygen reduction reaction in aprotic Li-O2 batteries.

Soluble redox species that facilitate the oxygen reduction reaction by mediating the LiO2 intermediate and consequently the formation of the Li2O2 have attracted considerable interest for Li-O2 batteries. Based on extensive radical studies, this work discloses a distinct solution reaction route when a quinone derivative was employed as a redox mediator.

A mononuclear iron(III) complex with unusual changes of color and magneto-structural properties with temperature: synthesis, structure, magnetization, multi-frequency ESR and DFT study.

From the reaction of 2-hydroxy-6-methylpyridine (L) with iron(II) tetrafluoroborate, a new mononuclear iron(III) octahedral complex [FeL6](BF4)3 has been isolated. The color of the complex reversibly changed from red at room temperature to yellow-orange at the liquid nitrogen temperature. Magnetization measurements indicate that iron(III) in [FeL6](BF4)3 is in a high-spin state S = 5/2, from room temperature to 1.8 K. The high-spin ground state of iron(III) is also confirmed by DFT calculations. Although the spin-crossover of the complex is not observed, X-band and multifrequency high-field/high-frequency electron spin resonance (ESR) spectroscopy shows rather uncommon iron(III) spectra at room temperature and an unusual change with cooling. Spectral simulations reveal that the S = 5/2 ground state multiplet of the complex can be characterized by the temperature independent axial zero-field splitting parameter of |D| = +2 GHz (0.067 cm-1) while the value of the rhombic parameter E of the order of some tenths MHz increases on lowering the temperature. Single crystal X-ray diffraction (SCXRD) shows that the iron(III) coordination geometry does not change with temperature while supramolecular interactions are temperature dependent, influencing the iron(III) rhombicity. Additionally, the DFT calculations show temperature variation of the HOMO-LUMO gap, in agreement with the changes of color and ESR-spectra of the iron(III) complex with temperature.

Enzymatic glycoengineering-based spin labelling of cell surface sialoglycans to enable their analysis by electron paramagnetic resonance (EPR) spectroscopy.

A novel method for spin labelling of sialoglycans on the cell surface is described. C9-Azido sialic acid was linked to glycans on live cells via CSTII-catalysed α2,3-sialylation utilizing azido-sialic acid nucleotide as a sialyl donor, which was followed by attachment of a spin label to the azide via click reaction. It enables the study of cell surface sialoglycans by EPR spectroscopy.

Electron Paramagnetic Resonance and Optical Studies of Thermoluminescence Processes in Mn-Doped YAlO3 Single Crystals

A detailed electron paramagnetic resonance (EPR), optical absorption, luminescence, and thermoluminescence (TL) study of Mn-doped YAlO3 (YAP) single crystals was performed. The crystals were grown by the Czochralski method from stoichiometric (Y/Al = 1) and yttrium-rich (Y/Al = 1.04) melts and codoped with either Si or Hf ions. The EPR measurements revealed the presence of only one type of Mn2+ center, that is, isolated Mn ions occupying Y sites (MnY2+). It was found that only in yttrium-rich crystals, the MnY2+ ions undergo recharging to MnY3+ under ionizing irradiation, indicating that this process requires the availability of sufficiently deep electron traps. The initial charge state is fully restored only after subsequent warming above 600 K. The presented results demonstrate, moreover, that MnY3+ + e → MnY2+ recombination is not the most efficient excitation channel of the green 4T1 → 6A1 emission of MnY2+, possibly because of the huge energy difference between the recombination (>5.39 eV) and excitation (3 eV) energies. In contrast, energy transfer to MnY2+ proves to be dominant. A general model of trapping and recombination mechanisms responsible for TL of YAP:Mn crystals above room temperature is proposed. Besides MnY2+ ions and the defect-related electron and hole traps intrinsic to the YAP lattice, the model includes also unintentional dopants such as FeAl2+ acting as deep hole traps, as well as MnAl4+ and CrAl3+ ions acting both as deep hole and electron traps.

Cotton Fabric Modified with a PAMAM Dendrimer with Encapsulated Copper Nanoparticles: Antimicrobial Activity.

A new methodology for modifying textile materials with dendrimers containing nanoparticles was developed. This involved a combination of eosin Y and N-methyldiethanolamine (MDEA) for reducing the copper ions in the dendrimer complex by enabling a photochemical reaction under visible light and ambient conditions. The conversion of copper ions into nanoparticles was monitored using scanning electron microscopy (SEM) and by performing colorimetric, fluorescence, and electron paramagnetic resonance (EPR) studies. Regardless of the concentration of the photoinitiator eosin Y, it discolored completely upon illumination. Three types of cotton fabrics were compared as antimicrobial materials against Bacillus cereus. One of the fabrics was dyed with a first-generation PAMAM dendrimer which had been functionalized with eight 1,8-naphthalimide fluorophores. Another fabric was dyed with a dendrimer–copper complex, and the third was treated by conversion of the complex into copper nanoparticles encapsulated into the dendrimer. An enhancement in the antimicrobial activity of the textiles was achieved at higher dendrimer concentrations, under illumination with visible light. The fabric modified with the copper nanoparticles encapsulated inside the dendrimer exhibited the best antibacterial activity because it had two photosensitizers (PS), as both 1,8-naphthalimide fluorophores and copper nanoparticles were contained in the dendrimer molecules. The presence of oxygen and suitable illumination activated the photosensitizers to generate the reactive oxygen species (singlet oxygen (1O2) and other oxygenated products, e.g., anion radicals, hydroxyl radicals, and hydrogen peroxide) responsible for destroying the bacteria.

Application of EPR Spectroscopy in TiO2 and Nb2O5 Photocatalysis

The interaction of light with semiconducting materials becomes the center of a wide range of technologies, such as photocatalysis. This technology has recently attracted increasing attention due to its prospective uses in green energy and environmental remediation. The characterization of the electronic structure of the semiconductors is essential to a deep understanding of the photocatalytic process since they influence and govern the photocatalytic activity by the formation of reactive radical species. Electron paramagnetic resonance (EPR) spectroscopy is a unique analytical tool that can be employed to monitor the photoinduced phenomena occurring in the solid and liquid phases and provides precise insights into the dynamic and reactivity of the photocatalyst under different experimental conditions. This review focus on the application of EPR in the observation of paramagnetic centers formed upon irradiation of titanium dioxide and niobium oxide photocatalysts. TiO2 and Nb2O5 are very well-known semiconductors that have been widely used for photocatalytic applications. A large number of experimental results on both materials offer a reliable platform to illustrate the contribution of the EPR studies on heterogeneous photocatalysis, particularly in monitoring the photogenerated charge carriers, trap states, and surface charge transfer steps. A detailed overview of EPR-spin trapping techniques in mechanistic studies to follow the nature of the photogenerated species in suspension during the photocatalytic process is presented. The role of the electron donors or the electron acceptors and their effect on the photocatalytic process in the solid or the liquid phase are highlighted.

An iron–based biochar for persulfate activation with highly efficient and durable removal of refractory dyes

The magnetic biochar catalyst (Fe@BC) was synthesized by pyrolyzing Fe–tanned collagen fiber based on the tanning process and used as a high–efficiency and recyclable persulfate (PS) activator to degrade refractory dyes. In this study, methylene blue (MB) was chosen as a model pollutant to evaluate the performance of the Fe@BC/PS system. Results illustrated that MB was completely removed within 20 min with a rate constant (kobs) of 0.2246 min–1, which was much higher than that of pure biochar (0.0497 min–1), and high mineralization efficiency (92%) for MB degradation was obtained. Notably, the MB removal rate still reached 72% after 20 cycles. The high catalytic activity and excellent recycling performance could be attributed to the uniformly dispersed iron species, abundant oxygen functional groups, and defective carbon matrix. Radical quenching experiments and electron paramagnetic resonance studies illustrated that SO4•– was the predominant free radical for MB degradation. Moreover, other refractory dyes could also be rapidly and efficiently removed from the Fe@BC/PS system. This work is expected to propose a promising catalyst for the degradation of refractory dyes and open a new possibility for the durable removal of refractory organic dyes.

Characterization of a fluorescent 1,8-naphthalimide-functionalized PAMAM dendrimer and its Cu(ii) complexes as cytotoxic drugs: EPR and biological studies in myeloid tumor cells

The activity and interacting ability of a polyamidoamine (PAMAM) dendrimer modified with 4-N-methylpiperazine-1,8-naphthalimide units (termed D) and complexed by Cu(ii) ions, towards healthy and cancer cells were studied. Comparative electron paramagnetic resonance (EPR) studies of the Cu(ii)-D complex are presented: coordination mode, chemical structure, flexibility and stability of these complexes, in the absence and presence of myeloid cancer cells and peripheral blood mononuclear cells (PBMC). The interactions of Cu(ii) ions in the biological media at different equilibrium times were studied, highlighting different stability and interacting conditions with the cells. Furthermore, flow cytometry and confocal analysis, trace the peculiar properties of the dendrimers in PBMC and U937 cells. Indeed, a new probe (Fly) was used as a potential fluorescent tool for biological imaging of Cu(ii). The study highlights that dendrimer and, mainly, the Cu(ii) metallodendrimer are cytotoxic agents for the cells, specifically for U937 tumor cells, inducing mitochondrial dysfunction, ROS increase and lysosome involvement. The metallodendrimer shows antitumor selectivity, fewer affecting healthy PBMC, inducing a massive apoptotic cell death on U937 cells, in line with the high stability of this complex, as verified by EPR studies. The results underline the potentiality of this metallodendrimer to be used as anticancer drug.

Dynamics of multiferroic LiCuVO4 influenced by electric field

We present the electron spin resonance study of the influence of an electric field on the low-field multiferroic magnetic state in LiCuVO4. The shift of the magnetic resonance spectra in the electric field has been observed experimentally. Symmetry analysis has been conducted in order to describe the static properties of the magnetic system. The low-frequency dynamics of LiCuVO4 in magnetic and electric fields was considered in the framework of hydrodynamic approach. It was shown that the application of the external electric field leads to the change of the configuration of the magnetic system before and after spin-flop reorientation. Satisfactory agreement was obtained between the results of experimental studies and theoretical consideration.

Dzyaloshinskii-Moriya anisotropy effect on field-induced magnon condensation in the kagome antiferromagnet α−Cu3.26Mg0.74(OH)6Br2

We performed a comprehensive electron spin resonance, magnetization and heat capacity study on the field-induced magnetic phase transitions in the kagome antiferromagnet $\alpha-Cu_3Mg(OH)_6Br_2$. With the successful preparation of single crystals, we mapped out the magnetic phase diagrams under the $c$-axis and $ab$-plane directional magnetic fields $B$. For $B\|c$, the three-dimensional (3D) magnon Bose-Einstein condensation (BEC) is evidenced by the power law scaling of the transition temperature, $T_c\propto (B_c-B)^{2/3}$. For $B\|ab$, the transition from the canted antiferromagetic (CAFM) state to the fully polarized (FP) state is a crossover rather than phase transition, and the characteristic temperature has a significant deviation from the 3D BEC scaling. The different behaviors of the field-induced magnetic transitions for $B\|c$ and $B\|ab$ could result from the Dzyaloshinkii-Moriya (DM) interaction with the DM vector along the $c$-axis, which preserves the $c$-axis directional spin rotation symmetry and breaks the spin rotation symmetry when $B\|ab$. The 3D magnon BEC scaling for $B\|c$ is immune to the off-stoichiometric disorder in our sample $\alpha-Cu_{3.26}Mg_{0.74}(OH)_6Br_2$. Our findings have the potential to shed light on the investigations of the magnetic anisotropy and disorder effects on the field-induced magnon BEC in the quantum antiferromagnet.