ESR Spectral Analyses Research Articles

Acylpyrazolone based Square pyramidal Cu(II) complexes: Synthesis, Structural characterization, DFT and antiproliferative properties

σ-donating acylpyarazolone HLb ligand and its Copper complex [Cu(HLb)2(DMF)] were synthesized. [Cu(HLa)2(DMSO)] complex is synthesized from the previously reported HLa ligand. Single crystal analysis revealed the Square Pyramidal geometry of both the complexes with one oxygen fromDMF and DMSO attached at an apical site in the [Cu(HLb)2(DMF)] and [Cu(HLa)2(DMSO)] complexes, respectively and four oxygens of the ligand coordinated to the centralcopper metal at an equatorial position. The electronic spectra of both the complexes have been analyzed using UV–visible spectroscopy. The study investigated the molecular specification utilising the B3LYP/6-31G and B3LYP/LANL2DZ basis set formalism for DFT computational analysis to provide a perfect correlation and comparison with all the experimental values. The Hirshfeld surface area analysis was done to investigate the intermolecular interactions or secondary molecular interaction. The magnetic behaviour of both the synthesized complexes was identified by ESR spectral analysis. Using three different cancer cell lines NCI-H23 (Lung adenocarcinoma cells), HepG2 (Hepatocellular carcinoma) and SH-SY5Y (Neuroblastoma cells), cytotoxicity of both the copper complexes was examined and wound healing assay on [Cu(HLb)2(DMF)] complex was done to check the cell migration.

Facile in situ construction of novel hybrid 3D-BiOCl@PDA heterostructures with vacancy induced charge transfer for efficient visible light driven photocatalysis and antibacterial activity

Combining a wide band BiOCl semiconductor with organic π-conjugated systems is critical for increasing its light absorption and charge carrier mobility at heterojunction interfaces for efficient photocatalysis. In this study, we described a bioinspired dopamine-assisted one-pot route as an environmentally benign method to construct multifunctional in situ hybrid 3D-BiOCl@PDA heterostructure photocatalysts in an aqueous medium under mild conditions. The versatile role of dopamine was utilized for the controlled integration of 3D-BiOCl (001) hierarchical microspheres while simultaneously modified their surfaces with thin layers of PDA via its in situ polymerization. TGA, UVDRS, and XPS revealed that PDA thickness and its cooperative chelating effect with BiOCl nanosheet at a hybrid interface allowed effective charge transfers, and band-edge shift, induced oxygen defects for extended visible light absorptions. The resulting hybrids exhibited evidently multifunctional photocatalytic performance for complete RhB dye removal (12 times), enhanced selective benzyl alcohol oxidation (>99 benzaldehyde) and excellent antibacterial activity against Staphylococcus aureus (99.9%) than bare BiOCl under identical conditions. Furthermore, the hybrids showed excellent photostability and recyclability for up to five reaction cycles. These highly enhanced results are attributed to their 3D-structural features and close contact between PDA and BiOCl. Based on the results of active species experiments and ESR spectral analysis a possible Z-scheme photocatalytic mechanism has been proposed for the hybrid heterostructure system. Hence, the present work is an effective noble metal-free strategy for creating novel hybrid BiOCl heterostructures with multifunctional properties for visible light photocatalytic applications.

Comparative studies of structural and optical properties of Nb2O5–Sb2O3–TeO2 glass and glass-ceramics

A new, transparent antimony-tellurite glass and glass-ceramic systems doped with Nb2O5 have been prepared by using the conventional melt quenching method and heat treatment process, respectively. Various physical, optical and structural studies were reported through XRD, TEM, SEM, ultraviolet-visible, Raman, infrared and ESR investigations. XRD analysis of glass and glass-ceramic samples revealed their amorphous and crystalline natures, respectively. The Williamson-Hall approach was used to determine the average crystallite size of synthesised glass-ceramics and the values were found to be in the range of 23 to 85 nm. The SEM result reveals that glass-ceramics contain perspicuous and haphazardly distributed nanoclusters possessing sizes in the range of 45 to 120 nm. TEM analysis shows the size of particles in the glass-ceramics is in the range of 10 to 90 nm. The Eopt of the glass system has decreased from 2·873 to 2·606 eV, whereas in the glass-ceramic system it is observed to increase from 1·340 to 1·748 eV. Raman and infrared spectral analysis confirm the existence of various structural units such as TeO4, TeO3+1, TeO3, NbO6, NbO4, SbO3 in the glass and glass ceramic systems.The ESR spectral analysis reveals that the (Δg‖/Δg^) parameter seems to decrease from 4·444 to 2·453 in glass sytem, whereas in glass-ceramics it is observed to increase from 2·357 to 4·188. Glass transition temperature and onset crystalline temperatures are influenced by the Nb2O5 in both glass and glass-ceramic samples.

Shielding behavior of MoO3-doped lead borate glasses towards gamma irradiation assessed through collective optical, FTIR, and ESR spectral analysis

Glasses from the base binary lead borate (70PbO–30B2O3 wt%) and samples containing additional (0.2, 0.5, 0.75 wt% MoO3) were prepared by normal melting-annealing technique. Characterization of the optical, FTIR, ESR spectral properties of the prepared glasses were measured before and after been subjected to gamma irradiation (6 Mrad). Optical spectra of the glasses revealed pronounced UV absorption bands extending from 200 to 330 nm for the base undoped glass and extended within the UV to additional bands at 360 and 390 nm in the MoO3-doped glasses. The collective UV absorption bands were related to both unavoidable contaminated trace iron impurities (Fe3+) together with absorption due to divalent lead ions (Pb2+). With MoO3- doped glasses, the hexavalent state was assumed to be dominant due to the absence of any visible bands and only two extra UV bands are identified. FTIR spectra showed distinct vibrational bands due to triangular and tetrahedral borate groups in their different characteristic wavenumbers. Beside the sharing of some PbO4 but the two borate groups are highly identified due to the ease of mobility and vibrations of the borate groups containing the lightest weight boron element in glass forming oxides. The addition of MoO3 caused minor effect on the FTIR spectra, because of their low doping percent. Gamma irradiation caused the disappearance of some UV peaks and this was correlated with suggested photochemical reactions and similar behaviour was correlated with the ESR measurements after irradiation. Both spectral data indicated the presence of molybdenum mainly in the hexavalent state. FTIR spectra after irradiation confirmed the stability of the studied high metal oxide lead borate glasses, i.e. their shielding behaviour towards gamma irradiation.

Synthesis, characterization, antimicrobial screening and cytotoxic properties of Cu(II) and Zn(II) complexes with bidentate hydroxylated 1,3-diaryl-2-propene-1-ones ligand

A series of binary metal complexes (halo, hydroxyl and methoxy substituted bis(2-(E)acryloyl)naphthalen-1-yl)oxy)Cu(II) and Zn(II) (C1? ?C10)) of Cu2+ and Zn2+ ions derived from bi-coordinated hydroxylated 1,3- -diaryl-2-propene-1-ones were synthesized. The newly synthesized metal complexes were structurally determined by FT-IR, 1H-NMR, 13C-NMR, ESR spectral, XRD and TGA analyses. The FT-IR and ESR studies demonstrated that interactions between metal ions with ligands occur through carbonyl oxygen and deprotonated hydroxyl oxygen and correspond to square-planar geometry for all complexes. The metal complexes were screened in-vitro and evaluated for their antimicrobial and cytotoxic activities. The complexes C1 and C4 showed significant antimicrobial activity while the remaining complexes showed moderate antimicrobial activity against the tested pathogens. The complexes were evaluated for cytotoxic activity against the organism Artemia salina. Complexes C2?C5 exhibited LC50 values of 630.45, 969.99, 921.94 and 918.41 ?M mL-1, respectively. Furthermore, the complexes were evaluated for their anticancer activity against the liver cancer cell line Hep G2 in comparison with the 5-fluorouracil standard. Complex C5 showed a significant IC50 value of 58.94 ?g mL-1. Therefore, the present study is useful for the development of a new class of antimicrobial and anticancer agents.

Synthesis, structural elucidation, pharmacological and molecular docking studies of terpolymer transition metal complexes

A novel monomer (terpolymer) was prepared by mixing of 2-amino-6-nitro-benzimidazole, 2,5-diaminophenol and formaldehyde. Based on the impressive material utilities and therapeutic potential, Cu2+, Ni2+, Co2+ and Zn2+ metal ions were mixed with terpolymer to form different metal chelates. UVVis., IR, 1H NMR, ESR spectral data analysis showed that the prepared metal chelates were of square planar geometry. The molecular mass of polymer was determined using gel permeation chromatography technique. Thermo gravimetric technique was utilized to measure the thermal withstanding ability of terpolymer chelates. The electron transfer mechanism of the metal complexes was investigated by the aid of cyclic voltammetry. The prepared compounds were also screened for antimicrobial efficiency against bacterial strains (B. subtilis, E. coli and S. aureus) and fungal strains (C. albicans, A. niger and A. flavus). The observed results indicated that the chelates showed greater antimicrobial efficiencies than terpolymer ligand. Furthermore, the SOD biomimetic activity of prepared metal chelates was accessed and copper complex was found to possess high antioxidant potential with IC50 value of 0.94 µM. Antituberculosis capacities of terpolymer and its metal chelates was assessed against M. tuberculosis H37Rv strain using MABA assay protocol. Copper complex was found to possess good antitubercular activity with MIC value of 6.20 mg/mL. Molecular docking study was conducted to assess the target for antitubercular activity. It was found that copper complex could be a potent inhibitor of pantothenate synthetase enzyme (a potential target for development of antitubercular drug) of M.tuberculosis with binding energy of -9.8 kcal/mol. Overall copper complex showed good antimicrobial, antioxidant and antitubercular activity when compared to other metal complexes and terpolymer ligand.

Synthesis, spectral, photoluminescence, DFT studies and bioassay of new Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) complexes of 1-ethyl-4-hydroxy-3-(nitroacetyl) quinolin-2(1H)-one

The complexation between 1-ethyl-4-hydroxy-3-(nitroacetyl)quinolin-2(1H)-one, H2L with iron(III), cobalt(II), nickel(II), copper(II) and zinc(II) has been accomplished. The structure of the resulting complexes has been elucidated through elemental analyses, FT-IR,1H NMR, electronic, mass spectra, powder XRD, and ESR spectral analyses, as well as magnetic susceptibility, molar conductance measurements and thermal analyses. The analytical and spectroscopic data show complexes of the general formula [(L)MX(H2O)m(EtOH)n]·yZ; where: M = Fe, Ni, Cu or Zn; X = NO3− or nil, m = 3 or 4, n = 1 or nil and Z = EtOH or H2O and y = 0.5, 1 or 2 and [(L)2Co (H2O)(EtOH)]·½ EtOH. The lower values of molar conductance indicate the non-electrolytic nature of these complexes, suggesting that the ligand behaves as a dibasic bidentate in all complexes except Co(II) complex, in which the ligand acts as monobasic bidentate. The shape of ESR spectrum of copper(II)complex revealed octahedral geometry. The XRD patterns for the ligand and its metal complexes indicate crystalline nature with nano particle sizes. Structural parameters of the ligand and its metal complexes were calculated on the basis of DFT level using Gaussian 09 and the data correlated with the experimental results. The photoluminescence (PL) properties of the ligand and its metal complexes were investigated the dispersion of the ligand‏ into silica matrix has been successfully used in developing latent fingerprint sensor on non-porous surfaces. The antimicrobial activity of the ligand and its complexes was studied against E. coli, P. vulgaris, S. aureus, K. pnemonia and C. albicans.These compounds were evaluated for their cytotoxic effect on Ehrlish Ascities Carcinoma cells lines (EAC). Among the tested compounds, Co(II) and Ni(II)- complexes exhibited more potent activity with an IC50 value of 12.5 and 15 μg/ml respectively, comparable to cisplatin.

Interaction of 2-Methyl Phenol by Methanol in the Presence of Palladium-Containing Dealuminum Mordenite

Some selected solid complexes of the Schiff base ligand HL derived from Sulfadiazine with Co(II), Ni(II) and Cu(II) ions were synthesized and characterized by Micro-analysis, FTIR, Electronic, Mass, and ESR Spectral Analyses, Magnetic susceptibility and Molar Conductance Measurements. The disappearance of ν(O-H) hydroxyl band of the phenolic and the lowering shift of the stretching frequency of the ν(CH=N) azomethine band in the ligand after complexation, indicated the coordination through the phenolic oxygen atom (after deprotonation) and azomethine nitrogen atom respectively of the Schiff base ligand HL. The lower values of molar conductance indicate the non-electrolytic nature of these complexes. The ESR spectrum of the HL copper complex has octahedral geometry. The molecular structures of the investigated compounds were studied by PM3 method, also the heat of formations, HOMO, LUMO and dipole moments were calculated to confirm the geometry of the ligand and the it's complexes. The antimicrobial screening of the synthesized compounds HL and its complexes 1-3 were investigated. The Schiff base ligand HL showed weaker to significant activity against one or more bacterial and fungal strains. In most of the cases higher activities were exhibited upon coordination with metal ions(II). In addition, calculations in silico, the Pharmacokinetic parameters have promising features for applying the ligand as drug.

ESR analyses of picket fence MnII and 6th ligand coordinated FeIII porphyrins (S = 5/2) and a CoII(hfac) complex (S = 3/2) with sizable ZFS parameters revisited: a full spin Hamiltonian approach and quantum chemical calculations.

The fictitious spin-1/2 (effective spin-1/2) Hamiltonian approach has been the putative method to analyze the conventional fine-structure/hyperfine ESR spectra of high spin metallocomplexes with sizable zero-field splitting (ZFS) tensors since the early 1950s, and the approach gives salient principal geff-values far from g = 2 without explicitly affording their ZFS values in most cases. The experimental geff-values thus determined, however, never agree with those (gtrue-values) of the true principal g-tensors, which are obtainable from reliable quantum chemical calculations. We have recently derived exact or extremely accurate analytical expressions for the geff/gtrue relationships for the spin quantum number S's up to S = 7/2 (T. Yamane et al., Phys. Chem. Chem. Phys., 2017, 19, 24769-24791). In this work, we have removed the limitation of the collinearity between g- and ZFS tensors and derived the generalized geff/gtrue relationships. To illustrate the usefulness of the present approach, we have revisited important typical high spin systems with large ZFS values such as picket fence metalloporphyrins with MnII (S = 5/2) (Q. Yu et al., Dalton Trans., 2015, 44, 9382-9390), a 6th ligand coordinated porphyrin with FeIII (S = 5/2) (Y. Ide et al., Dalton Trans., 2017, 46, 242-249) and a pseudo-octahedral CoII (S = 3/2)(hfac)2 complex (D. V. Korchagin et al., Dalton Trans., 2017, 46, 7540-7548), completing the ESR spectral and magnetic susceptibility analyses and gaining significant physical insights into their electronic structures. The off-principal axis extra peaks overlooked in the documented spectra of the picket fence MnII porphyrins have fully been assigned, affording their accurate true g-, hyperfine and ZFS tensors, for the first time. For the CoII complex, the occurrence of the non-collinearity between the g- and ZFS tensors has been discussed by using the generalized geff/gtrue relationships. We have attempted to carry out reliable DFT-based and ab initio quantum chemical calculations of their magnetic tensors, in which spin-orbit couplings are incorporated, reproducing the experimental true tensors. We emphasize that the incorporation of multi-reference nature in the electron configuration is important to interpret the magnetic tensors for the CoII complex.

Cytotoxic and Antimicrobial Activities of Piperazine Bridged dithiocarbamate Homo Binuclear Mixed Ligand Complexes of Cu(II) with Amino acids

A new series of Cu(II) mixed ligand complexes with bridging piperazine dithiocarbamate along with chelated amino acids such as glycine, alanine, phenylalanine, methionine, tyrosine and cystine in the deprotonated form have been prepared. The synthesized complexes are characterized by thermal, elemental, metal, nitrogen and sulphur, UV-Vis, infra-red, ESR Spectral analysis magnetic susceptibility and powder XRD studies. The above studies are used for establishing the structure and composition of the complexes. Biological evaluation such as antibacterial, antifungal and anticancer properties have also been carried out on these complexes based on agar disc diffusion and MTT based assay method respectively

Synthesis, spectroscopic, anticancer and antibacterial studies of Ni(II) and Cu(II) complexes with 2-carboxybenzaldehyde thiosemicarbazone

Ni(II) and Cu(II) complexes of 2-carboxybenzaldehyde thiosemicarbazone (L) were synthesized and investigated by their spectral and analytical data. These newly synthesized complexes have a composition of M(L)X(H2O)2 (where M=Ni(II), Cu(II) and X=Cl−, NO3-, CH3COO−) and (L) is the tridentate Schiff base ligand. The ligand and its complexes have been characterized on the basis of analytical, molar conductivity, magnetic susceptibility measurements, FT-IR, ESR, 1H NMR and electronic spectral analysis. All the compounds were non-electrolytic in nature. On the basis of spectral studies an octahedral geometry has been assigned for Ni(II) and a tetragonal geometry for Cu(II) complexes. The ligand and its metal complexes were screened for their anticancer studies against human breast cancer cell lines MCF-7 and calculated minimum inhibitory concentration and also for antibacterial activity using Kirby–Bauer single disk susceptibility test.

Synthesis, characterization, catalytic, antimicrobial, DNA binding and cleavage studies of N-functionalized tetraazamacrocyclic binuclear copper(II) complexes

A series of binuclear copper(II) complexes of N-functionalized cyclam derivatives has been prepared by the Schiff base condensation of 1,8-[bis(3-formyl-2-hydroxy-5-methyl)benzyl]-l,4,8,11-tetraazacyclo-tetradecane (PC-a), 1,8-[bis(3-formyl-2-hydroxy-5-bromo)benzyl]-l,4,8,11-tetraazacyclo-tetradecane (PC-b) with appropriate aliphatic diamines, and copper(II) perchlorate. All the complexes were characterized by elemental, FT-IR, UV–Vis, ESI and ESR spectral analysis. The room temperature magnetic moment studies depicts the presence of an antiferromagnetic interaction in the binuclear complexes, which is also observed from the broad ESR spectra with a g value of 2.10–2.11. Variable-temperature magnetic susceptibility study of the complex [Cu2L2a](ClO4)2 shows that the calculated −2J value is 219 cm−1, which conveys a spin–spin interaction between the two copper(II) ions. The catechol oxidation and hydrolysis of 4-nitrophenylphosphate were carried out by using the complexes as a catalyst. All the above metal complexes were screened for antimicrobial and human pathogenic fungal activity. The binding of the complexes to calf thymus DNA (CT-DNA) has been investigated with UV–Vis and fluorescence spectroscopy. All complexes display significant cleavage property of circular plasmid pBR322 DNA into linear form. Spectral, electrochemical, magnetic and catalytic studies support the distortion of the copper ion geometry that arises as the macrocyclic ring size increases.

Photolytic cleavage of Co–C bond: A mechanistic study for the formation of solvent coordinated cobalt(II) complex

Alkyl(pyridine)cobaloxime complexes (where, alkyl groups are methyl, ethyl, etc.) were synthesized and characterized by various spectral techniques. Their primary photochemical behaviours were studied by continuous photolysis and laser flash photolysis in both acetonitrile and methanol under oxygen saturated and argon saturated conditions. The transient absorption spectra were recorded at various time scales like 0.2 μs, 1 μs and 10 μs after laser flash, which show absorption maximum at 470 nm in methanol because of homolytic cleavage of Co–C for all these complexes. The kinetic analysis of the transient species for all these complexes shows first order kinetics. Laser flash photolysis studies in acetonitrile, the formation of cobalt(II) species was confirmed by transient band observed around 440 nm and also by ESR spectral analysis. The transient band observed around 340 nm is assigned to the formation of new acetonitrile coordinated cobalt(II) complex by the reaction between the intermediate cobalt(II) species and the solvent molecule in microsecond time scale. The present investigations provide more information on the charge transfer photochemistry of cobaloxime complexes from nanosecond to second time scale.

Synthesis, spectral characterization and antioxidant activity studies of a bidentate Schiff base, 5-methyl thiophene-2-carboxaldehyde-carbohydrazone and its Cd(II), Cu(II), Ni(II) and Zn(II) complexes

A new Schiff base bidentate ligand (L), 5-methyl thiophene-2-carboxaldehyde-carbohydrazone and its metal (Cu(II), Cd(II), Ni(II) and Zn(II)) complexes with general stoichiometry [M(L)2X2] (where X=Cl) were synthesized. The ligand and its metal complexes were characterized by elemental analyses, IR, 1H NMR, ESR spectral analyses, and molar conductance studies. The molar conductance data revealed that all the metal chelates are non-electrolytes. IR spectra showed that ligand (L) is coordinated to the metal ions in a bidentate manner with N and O donor sites of the azomethine-N, and carbonyl-O. ESR and UV–Vis spectral data showed that the geometrical structure of the complexes are Orthorhombic. Furthermore, the antioxidant activity of the ligand and its complexes was determined by hydroxyl radical scavenging, DPPH, NO, reducing power methods in vitro. The obtained IC50 value of the DPPH activity for the copper complex (IC50=66.4μm) was higher than other compounds. Microbial assay of the above complexes against Staphylococcus aureus, Escherichia coli, Rhizocotonia bataticola and Alternaria alternata showed that copper complex exhibited higher activity than the other complexes.

Joint analysis of ESR lineshapes and 1H NMRD profiles of DOTA-Gd derivatives by means of the slow motion theory.

The "Swedish slow motion theory" [Nilsson and Kowalewski, J. Magn. Reson. 146, 345 (2000)] applied so far to Nuclear Magnetic Relaxation Dispersion (NMRD) profiles for solutions of transition metal ion complexes has been extended to ESR spectral analysis, including in addition g-tensor anisotropy effects. The extended theory has been applied to interpret in a consistent way (within one set of parameters) NMRD profiles and ESR spectra at 95 and 237 GHz for two Gd(III) complexes denoted as P760 and P792 (hydrophilic derivatives of DOTA-Gd, with molecular masses of 5.6 and 6.5 kDa, respectively). The goal is to verify the applicability of the commonly used pseudorotational model of the transient zero field splitting (ZFS). According to this model the transient ZFS is described by a tensor of a constant amplitude, defined in its own principal axes system, which changes its orientation with respect to the laboratory frame according to the isotropic diffusion equation with a characteristic time constant (correlation time) reflecting the time scale of the distortional motion. This unified interpretation of the ESR and NMRD leads to reasonable agreement with the experimental data, indicating that the pseudorotational model indeed captures the essential features of the electron spin dynamics.

Preparation Characterization and Antibacterial Studies of Chelates of Schiff Base Derived from4‐Aminoantipyrine, Furfural and o‐phenylenediamine

A new series of transition metal complexes of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) were synthesized from the Schiff base ligand derived from 4‐aminoantipyrine, furfural and o‐phenylenediamine. The structural features were derived from their elemental analyses, infrared, UV‐visible spectroscopy, NMR spectroscopy, thermal gravimetric analyses, ESR spectral analyses and conductivity measurements. The data of the complexes suggested square planar geometry for the metals with primary valency two. Antimicrobial screening tests were performed against bacteria. The comparative study of the MIC values of the Schiff base and its metal complexes indicate that the metal complexes exhibit greater antibacterial activity than the free ligand.

Synthesis, thermal and spectral studies of Co(Π),Ni(Π) and Cu(Π) complexes of Schiff base ligand derived from 1,6- diaminohexane and salicyladehyde

Cobalt (Π), Nickel (Π) and Copper (Π) complexes, with Schiff base ligand derived from 1, 6- diaminohexane and salicyladehyde (salhex) have been synthesized and characterized by elemental analysis, conductance measurements, magnetic susceptibility measurements, IR, electronic spectra, ESR spectral studies and thermal analysis. IR spectra suggested that salhex acts as tetra dentate dibasic ligand. The possible geometries of the complexes are assigned on the basis of ESR, electronic spectra as well as the magnetic moment values. The thermal behaviour of Cu (Π) complexes is studied using thermogravimetric analysis (TGA) technique. The different thermodynamic and kinetic parameters are calculated using Coats-Redfern method.

Effect of Annealing on DLC Characteristics by ESR Spectral Analysis

Effect of Annealing on DLC Characteristics by ESR Spectral Analysis

ESR study on carboxymethyl chitosan radicals in an aqueous solution

Carboxymethyl chitosan (CMCTS) at a highly concentrated aqueous solution forms hydrogel by ionizing irradiation. To study on radiation-induced reaction mechanism of CMCTS in an aqueous solution, CMCTS radicals formed by reactions with OH radical were observed by ESR method. As a result of ESR spectral analysis, CMCTS radicals were identified as radicals on carboxymethyl groups.

ARAGONITE TO CALCITE TRANSFORMATION STUDIES BY ESR OF Mn2+ IONS IN SINOTAIA INGALLSIANA

We have studied paramagnetic Mn 2+ ions present in the freshwater snail, Sinotaia ingallsiana (FS), Viviparus which are abundant in Thailand. The FS shells in our study were ground into fine powder. A set of seven samples was each then separately annealed for 2 hours in air atmosphere at 300°C, 400°C, 500°C, 600°C, 700°C, 800°C and 900°C, respectively. Our detailed ESR spectral analyses of FS show that Mn 2+ ions enter Ca 2+ sites during a biomineralization process. The hyperfine coupling constant (A) and zero-field splitting (D) in the ESR spectrum of Mn 2+ in calcite and aragonite were determined. The spreading of the non-central allowed transitions was analyzed and the experimental transitions were attributed. For calculating the hyperfine coupling constant, five methods for calculating the zero-field splitting, based on the analysis of the allowed and forbidden transitions, were provided. The values of the hyperfine coupling constant range from 87.50 to 89.00 G and those of the zero-field splitting range from 110.00 to 116.00 G.