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In this paper, we report the synthesis, characterization, and X-ray structure analysis of one octahedral Ni(II) complex, [Ni(HL1 )2](BF4)2*H2O, formed by coordination of two ligands with NNS donor atom sets (HL1 ligand, (E)-2-(1-(thiazol-2-yl)ethylidene)hydrazine-1-carbothioamide), and Ni(III) complex, [Ni(L2 )(N3)3], formed by coordination of one hydrazone ligand coordinated through NNO donor set and three azide anions (HL2Cl ligand, (E)−1-(2-oxo-2-(2-(1-(pyridin-2- yl)ethylidene)hydrazinyl)ethyl)pyridin-1-ium chloride), complemented by DFT calculations. To the best of our knowledge this is the first Ni(III) complex obtained under ambient conditions.

The HL ligand, (E)-2-(1-(thiazol-2-yl)ethylidene)hydrazine-1-carbothioamide, was obtained from the condensation reaction of thiosemicarbazide and 2-acetylthiazole in water. The reaction of the HL ligand with the metal salt MnCl2·4H2O in a molar ratio 1:1 in methanol/water mixture results in the formation of bis Mn(II) complex with composition [MnL2]. Complex 1 crystallizes in the triclinic crystal system with space group P−1. The Mn(II) ion is hexacoordinated with two tridentate ligands L through NNS sets of donor atoms. The geometry around the Mn is described as a distorted trigonal prism (Fig. 1). The reaction of the ligand HL with Fe(BF4)2·6H2O in a molar ratio 1:1 in methanol results in the formation of bis Fe(III) complex with composition [Fe(L)2]BF4·H2O. The Fe(III) ion with L form six-coordinate complex in which two deprotonated ligand molecules coordinate in a mer arrangement, forming a distorted octahedral complex by chelation through NNS sets of donor atoms (Fig. 1). Complex 2 crystallizes in the orthorhombic crystal system with space group Pbca.

Poster presented at The Training School of COST action CA21101 COSY ,,Multiscale modeling of the properties of compounds: From isolated molecules to 3D materials relevant for industrial and astrophysical application", Belgrade, Serbia, 19th – 22nd September 2023.

The condensation product of 7-acetyl-6-azaindole and Girard’s T reagent ((E)-2-(2-(1-(1H-pyrrolo[2,3-c]pyridin-7-yl)ethylidene)hydrazineyl)-N,N,N-trimethyl-2-oxoethan-1-aminium, HL ligand) was used as a ligand in the reaction with Cu(BF4)2·6H2O and NaN3. The reaction led to the formation of a binuclear Cu(II) complex containing two end-to-end (di-µ-1,3-N3) azide bridges, as well as two NNO-donor hydrazone ligands, forming an axially elongated square pyramidal geometry around each Cu(II) center.

The condensation product of 7-acetyl-6-azaindole and Girard’s T reagent ((E)-2-(2-(1- (1H-pyrrolo[2,3-c]pyridin-7-yl)ethylidene)hydrazineyl)-N,N,N-trimethyl-2-oxoethan-1-aminium, HL ligand) was used as a ligand in the reaction with Cu(BF4)2·6H2O and NaN3. The reaction led to the formation of a binuclear Cu(II) complex containing two end-to-end (di-µ-1,3-N3) azide bridges, as well as two NNO-donor hydrazone ligands, forming an axially elongated square pyramidal geometry around each Cu(II) center.

Fe(III) and Mn(II) complexes with condensation product of thiosemicarbazide and 2-acetylthiazole (HL1, (E)-2-(1-(thiazol-2-yl)ethylidene)hydrazine-1-carbothioamide) have been synthesized and characterized by single-crystal X-ray diffraction, IR spectroscopy, and elemental analysis. In both complexes, the thiosemicarbazone ligand is coordinated in deprotonated form through the NNS donor set of atoms. However, while Fe(III) complex is in the doublet ground state with distorted octahedral geometry, the coordination environment around Mn(II) is distorted trigonal-prismatic, and the sextet state is found to be the ground state. DFT calculations were performed to rationalize spin state preferences, and continuous shape measure describes the deviation from ideal six-coordinated polyhedral geometries in the ground and excited states. Antimicrobial activity (against a panel of Gram-negative and Gram-positive bacteria, two yeast, and one fungal strain), brine shrimp assay, and DPPH radical scavenging activity of both complexes were evaluated, and these results relate to the electronic structure of the complexes.

Mn(II) and Fe(III) complexes with condensation product of thiosemicarbazide and 2-acetylthiazole have been synthesized and characterized by single-crystal X-ray diffraction. Two complexes have the same ligand system – bis tridentate coordination of the thiosemicarbazone ligand through the NNS donor set of atoms. Furthermore, the central metal ions in both cases have the same d5 electronic configuration. However, measured magnetism and analysis of the crystal geometries show that these two complexes have a different number of unpaired electrons. We rationalized the results by electronic structure calculations based on density functional theory. High-spin Mn(II) complex has trigonal-prismatic geometry with ionic metal-ligand bonding. Hund's rule of maximum multiplicity is responsible for its sextet spin-ground state. On the other hand, low-spin Fe(III) complex has octahedral coordination and strong metal-ligand covalency with delocalization of spin density toward ligands. Low-spin, doublet state is favored because of the nephelauxetic effect, i.e., smaller pairing energy in Fe(III) complex. Our results show that the difference in the electronic structure of the two complexes, i.e., different spin-ground states, directly affects these molecules' structure, magnetism, reactivity, and biological activities.

The ligand (HLCl) was synthetized by the reaction of 2-acetylpyridine and Girard’s P reagent in molar ratio 1 : 1 in ethanol (1–2 drops of cc. HCl were added). The reaction of hydrazone ligand with the metal salt Ni(BF4)2·6H2O and NaN3 in a molar ratio 1:1:4 in methanol/acetonitrile/water mixture results in the formation of Ni(III) complex with composition [NiL(N3)3]. The tridentate ligand (HLCl) is coordinated in deprotonated, formally neutral, form to the nickel ion through NNO set of donor atoms forming two five-membered chelate rings and the other three coordination sites are occupied by meridionally coordinated azide anions. The ligand (HLCl) was characterized by elemental analysis, IR and NMR spectroscopy and structure of the complex was defined by X-ray analysis, IR and EPR spectroscopy, molar conductivity and elemental analysis. DFT calculations were performed to determine stability and rationalise formation of Ni(III) complex.

The ligand (HLCl) was synthetized by the reaction of 2-acetylpyridine and Girard’s P reagent in molar ratio 1 : 1 in ethanol (1–2 drops of cc. HCl were added). The reaction of hydrazone ligand with the metal salt Ni(BF4)2·6H2O and NaN3 in a molar ratio 1:1:4 in methanol/acetonitrile/water mixture results in the formation of Ni(III) complex with composition [NiL(N3)3]. The tridentate ligand (HLCl) is coordinated in deprotonated, formally neutral, form to the nickel ion through NNO set of donor atoms forming two five-membered chelate rings and the other three coordination sites are occupied by meridionally coordinated azide anions. The ligand (HLCl) was characterized by elemental analysis, IR and NMR spectroscopy and structure of the complex was defined by X-ray analysis, IR and EPR spectroscopy, molar conductivity and elemental analysis. DFT calculations were performed to determine stability and rationalise formation of Ni(III) complex.

Mn(II) and Fe(III) complexes with condensation product of thiosemicarbazide and 2-acetylthiazole have been synthesized and characterized by single-crystal X-ray diffraction. Two complexes have the same ligand system – bis tridentate coordination of the thiosemicarbazone ligand through the NNS donor set of atoms. Furthermore, the central metal ions in both cases have the same d5 electronic configuration. However, measured magnetism and analysis of the crystal geometries show that these two complexes have a different number of unpaired electrons. We rationalized the results by electronic structure calculations based on density functional theory. High-spin Mn(II) complex has trigonal-prismatic geometry with ionic metal-ligand bonding. Hund's rule of maximum multiplicity is responsible for its sextet spin-ground state. On the other hand, low-spin Fe(III) complex has octahedral coordination and strong metal-ligand covalency with delocalization of spin density toward ligands. Low-spin, doublet state is favored because of the nephelauxetic effect, i.e., smaller pairing energy in Fe(III) complex. Our results show that the difference in the electronic structure of the two complexes, i.e., different spin-ground states, directly affects these molecules' structure, magnetism, reactivity, and biological activities.

Fe(III) and Mn(II) complexes with condensation product of thiosemicarbazide and 2-acetylthiazole (HL1, (E)-2-(1-(thiazol-2-yl)ethylidene)hydrazine-1-carbothioamide) have been synthesized and characterized by single-crystal X-ray diffraction, IR spectroscopy, and elemental analysis. In both complexes, the thiosemicarbazone ligand is coordinated in deprotonated form through the NNS donor set of atoms. However, while Fe(III) complex is in the doublet ground state with distorted octahedral geometry, the coordination environment around Mn(II) is distorted trigonal-prismatic, and the sextet state is found to be the ground state. DFT calculations were performed to rationalize spin state preferences, and continuous shape measure describes the deviation from ideal six-coordinated polyhedral geometries in the ground and excited states. Antimicrobial activity (against a panel of Gram-negative and Gram-positive bacteria, two yeast, and one fungal strain), brine shrimp assay, and DPPH radical scavenging activity of both complexes were evaluated, and these results relate to the electronic structure of the complexes., Additional crystallographic and computational results, and the Cartesian coordinates of all DFT optimized structures

In this paper, we report the synthesis, characterization, and X-ray structure analysis of one octahedral Ni(II) complex, [Ni(HL1 )2](BF4)2*H2O, formed by coordination of two ligands with NNS donor atom sets (HL1 ligand, (E)-2-(1-(thiazol-2-yl)ethylidene)hydrazine-1-carbothioamide), and Ni(III) complex, [Ni(L2 )(N3)3], formed by coordination of one hydrazone ligand coordinated through NNO donor set and three azide anions (HL2Cl ligand, (E)−1-(2-oxo-2-(2-(1-(pyridin-2- yl)ethylidene)hydrazinyl)ethyl)pyridin-1-ium chloride), complemented by DFT calculations. To the best of our knowledge this is the first Ni(III) complex obtained under ambient conditions., 1. Experimental section. 2. Single crystal X-ray diffraction study. 3. Computational details. 4. Additional details

Crystal data for complex 2.

Crystal data for complex 1.

In this paper, the previously synthesized Cu(II) complex ([CuL1(N3) (CH3OH)]BF4) with N,N,N-trimethyl-2-oxo-2-(2-(1-(thiazol-2-yl)ethylidene)hydrazinyl)ethan-1-aminium chloride, has been characterized and its biological activity has been studied in detail. The Cu(II) complex consists of ligand coordinated in a deprotonated, formally neutral zwitter-ionic form, via NNO atoms, one azido ligand and one methanol molecule. The Cu(II) complex was selected due to results of the cytotoxic activity, the brine shrimp test and DPPH radical scavenging activity, which were previously performed. The effects of Cu(II) complex on cell cycle phase distribution of cervical adenocarcinoma HeLa cells were investigated in order to examine the mechanisms of its anticancer activity. The measurement of intracellular ROS levels in HeLa and HaCaT cell lines were evaluated in order to explore their possible generation and the role in cytotoxic activity. The possible anti-invasive and anti-angiogenic properties of Cu(II) complex were evaluated. DNA binding experiments, including fluorescence displacement study and DNA cleavage experiments, were performed in order to obtain information on the type of DNA-metal complex interactions. © 2022 Serbian Chemical Society. All rights reserved.

Selected bond lengths (Å) and angles (°) of complexes 1 and 2. Comparison of Co-Nthiazole, Co-Nimine and Co-Sthiolate bond lengths (Å) in octahedral Co(III)-N4S2 complexes with thiosemicarbazone based ligands. Comparison of Co-Npy, Co-Nimine, Co-Nazide and Co-Oenolate bond lengths (Å) in octahedral Co(III)N4O2–Co(III)N2O(N3)3 complexes with hydrazone and azide ligands.Hydrogen-bond parameters for complex 1.Intermolecular p×××p interaction parameters for complex 2. Hydrogen-bond parameters for complex 2.Crystal packing of 1 showing self-assembled complex cations within a layer parallel with the (001) lattice plane by means of intermolecular N–H×××N and N–H×××S hydrogen bonds and (b) Intermolecular p×××p interactions between thiazole rings.Crystal packing of 2 showing 2D assembly parallel with the (10-1) lattice plane generated by intermolecular p×××p interactions and C–H×××N hydrogen bonds.Cartesian coordinates of all DFT optimized structures

Two Co(III) complexes with condensation product of thiosemicarbazide and 2-acetylthiazole (HL1 ligand, (E)-2-(1-(thiazol-2-yl)ethylidene)hydrazine-1-carbothioamide) and the condensation product of 2-acetylpyridine and Girard's P reagent (HL2Cl ligand, (E)-1-(2-oxo-2-(2-(1-(pyridin-2-yl)ethylidene)hydrazinyl)ethyl)pyridin-1-ium chloride) have been synthesized and characterized based on the results of single-crystal X-ray diffraction, NMR and IR spectroscopy and elemental analysis. Cobalt(III) complex with HL1 ligand, [Co(L1)2]BF4⋅H2O (1), is bis octahedral complex in which two deprotonated ligand molecules coordinate in a mer arrangement through two NNS sets of donor atoms. In cobalt(III) complex with HL2Cl, [Co(L2)(N3)3] (2), the ligand is coordinated in deprotonated, formally neutral, form to Co(III) ion in tridentate fashion through NNO set of donor atoms, and the other three coordination sites of a monokis octahedron are occupied by meridionally coordinated azide anions. DFT calculations were performed to elucidate coordination preferences of these ligands toward Co(III) ion.

Two Co(III) complexes [Co(L1)2]BF4·H2O (1) and [Co(L2)(N3)3] (2) with condensation product of thiosemicarbazide and 2-acetylthiazole (HL1) and the condensation product of 2-acetylpyridine and Girard’s P reagent (HL2Cl) and Co(BF4)2·6H2O have been synthesized. Complexes were characterized by elemental analysis, IR and NMR spectroscopy and X-ray crystallographic analysis. DFT calculations revealed the thermodynamical stability of obtained complexes., Kompleks [Co(L1)2]BF4·H2O (1) dobijen je u reakciji Co(BF4)2·6H2O sa kondenzacionim proizvodom tiosemikarbazida i 2-acetiltiazola (HL1), dok je kompleks [Co(L2)(N3)3] (2) dobijen u reakciji iste soli sa kondenzacionim proizvodom 2-acetilpiridina i Žirarovog P reagensa (HL2Cl). Oba kompleksa su okarakterisana elementalnom analizom, IC i NMR spektroskopijom i rendgenskom strukturnom analizom. DFT proračunima određena je termodinamička stabilnost kompleksa.

The HL ligand was synthesized in the reaction of thiosemicarbazide and 2-acetylthiazole in molar ratio 1:1 in water, with 3 drops of 2M HCl. Complex [Fe(L)2]BF4·H2O (1) was synthesized in the reaction of ligand and Fe(BF4)6·6H2O in MeOH, after complete dissolution of Fe(BF4)2·6H2O in the reaction mixture, NaN3 was added. In the reaction of ligand (HL), MnCl2·4H2O and NaN3, in molar rotio 1 : 1 : 4, Mn(II) complex (2) was obtained. Complexes 1 and 2 were characterized by elemental analysis, IR and UV/Vis spectroscopy and X-ray crystallographic analysis. Both complexes 1 and 2 with HL ligand are bis octahedral complexes in which two deprotonated ligand molecules coordinate in a mer arrangement through two NNS sets of donor atoms, through thiazole and imine nitrogens and thioenolate sulfur., Ligand (HL) sintetisan je u reakciji tiosemikarbazida i 2-acetiltiazola u molarnom odnosu 1 : 1 u vodi, u kiseloj sredini. Kompleks [Fe(L)2]BF4·H2O (1) dobijen je u reakciji liganda i Fe(BF4)2·6H2O u metanolu i nakon potpunog rastvaranja Fe(II) soli dodat je NaN3 u višku (1 : 1 : 4). U reakciji liganda (HL), MnCl2·4H2O i NaN3 u molarnom odnosu 1 : 1 : 4, dobijen je kompleks Mn(II), [Mn(L)2] (2). Kompleksi 1 i 2 okarakterisani su elementalnom analizom, IC spektroskopijom, UV/Vis spektroskopijom i rendgenskom strukturnom analizom. Kod oba kompleksa 1 i 2 dolazi do forimiranja bis oktaedarske geometrije tako što se za centralni metalni jon koordinuju dva deprotonovana liganda preko dva NNS donorska seta atoma u mer okruženju. Do koordinacije liganda za centralni metalni jon, kako Fe(III), tako i Mn(II), dolazi preko dva azota, od kojih jedan potiče iz tiazola, a drugi iz iminske grupe, kao i preko sumpora iz tioenolatne grupe.

The HLCl ligand with metal salts Cu(BF4)2‧6H2O / MnCl2‧4H2O / Zn(BF4)2‧6H2O and NaN3, in methanol form mononuclear penta-coordinated complexes [CuL(N3)(CH3OH)]BF4 (1) and [ZnL(N3)2] (2) and binuclear [Mn2L2(µ-1,1-N3)2(N3)2]⋅2CH3OH (3) complex. Complexes 1, 2 and 3 were characterized by elemental analysis, IR spectroscopy, single-crystal X-ray diffraction, and DFT calculations., U reakciji liganda HLCl sa solima metala Cu(BF4)2‧6H2O / MnCl2‧4H2O / Zn(BF4)2‧6H2O i NaN3 u metanolu, dobijeni su mononuklearni kompleksi koordinacionog broja pet: [CuL(N3)(CH3OH)]BF4 (1) i [ZnL(N3)2] (2) i dinuklearni kompleks [Mn2L2(µ-1,1-N3)2(N3)2]⋅2CH3OH (3). Kompleksi 1, 2 i 3 okarakterisani su elementalnom analizom, IC spektroskopijom, rendgenskom stukturnom analizom i DFT proračunima.

In this paper, the previously synthesized Cu(II) complex ([CuL1(N3) (CH3OH)]BF4) with N,N,N-trimethyl-2-oxo-2-(2-(1-(thiazol-2-yl)ethylidene)hydrazinyl)ethan-1-aminium chloride, has been characterized and its biological activity has been studied in detail. The Cu(II) complex consists of ligand coordinated in a deprotonated, formally neutral zwitter-ionic form, via NNO atoms, one azido ligand and one methanol molecule. The Cu(II) complex was selected due to results of the cytotoxic activity, the brine shrimp test and DPPH radical scavenging activity, which were previously performed. The effects of Cu(II) complex on cell cycle phase distribution of cervical adenocarcinoma HeLa cells were investigated in order to examine the mechanisms of its anticancer activity. The measurement of intracellular ROS levels in HeLa and HaCaT cell lines were evaluated in order to explore their possible generation and the role in cytotoxic activity. The possible anti-invasive and anti-angiogenic properties of Cu(II) complex were evaluated. DNA binding experiments, including fluorescence displacement study and DNA cleavage experiments, were performed in order to obtain information on the type of DNA-metal complex interactions. © 2022 Serbian Chemical Society. All rights reserved.

Two Co(III) complexes were synthesized and characterized by SCXRD, elemental analysis, IR, NMR and UV/Vis spectroscopy. DFT calculations were performed to elucidate the structures of Co(III) complexes in solution.

In this paper, the previously synthesized Cu(II) complex ([CuL1(N3) (CH3OH)]BF4) with N,N,N-trimethyl-2-oxo-2-(2-(1-(thiazol-2-yl)ethylidene)hydrazinyl)ethan-1-aminium chloride, has been characterized and its biological activity has been studied in detail. The Cu(II) complex consists of ligand coordinated in a deprotonated, formally neutral zwitter-ionic form, via NNO atoms, one azido ligand and one methanol molecule. The Cu(II) complex was selected due to results of the cytotoxic activity, the brine shrimp test and DPPH radical scavenging activity, which were previously performed. The effects of Cu(II) complex on cell cycle phase distribution of cervical adenocarcinoma HeLa cells were investigated in order to examine the mechanisms of its anticancer activity. The measurement of intracellular ROS levels in HeLa and HaCaT cell lines were evaluated in order to explore their possible generation and the role in cytotoxic activity. The possible anti-invasive and anti-angiogenic properties of Cu(II) complex were evaluated. DNA binding experiments, including fluorescence displacement study and DNA cleavage experiments, were performed in order to obtain information on the type of DNA-metal complex interactions. © 2022 Serbian Chemical Society. All rights reserved.

The ligand (HL) was synthetized by the reaction of 2-acetylthiazole and thiosemicarbazide in molar ratio 1:1 in water. In the reaction of ligand (HL) and nickel(II) tetrafluoroborate hexahydrate [Ni(HL)2](BF4)2 complex was obtained. The Ni(II) ion has octahedral coordination geometry. The tridentate ligand (HL) is coordinated to the nickel ion with a NNS set of donor atoms forming two five- -membered chelate rings. The ligand (HL) and the [Ni(HL)2](BF4)2 complex were characterized by elemental analysis, IR and UV/Vis spectroscopy and the structure of the complex was defined by X-ray analysis.

The ligand ([HL]Cl) was synthetized by the reaction of 2-acetylpyridine and Girard's P reagent in molar ratio 1:1 in ethanol. In the reaction of ligand ([HL]Cl), nickel(II) tetrafluoroborate hexahydrate and sodium azide [Ni(HL)(N3)3] complex was obtained. The Ni(II) ion has a distorted octahedral coordination geometry. The tridentate ligand (HL) is coordinated to the nickel ion with an NNO set of donor atoms forming two five-membered chelate rings and the other three coordination sites are supplemented by azido ligands. The ligand (HL) and the [Ni(HL)(N3)3] complex were characterized by elemental analysis, IR and UV/Vis spectroscopy and structure of the complex was defined by X-ray analysis.

We have synthesized and characterized Co(II) (1), Zn(II) (2), Fe(III) (3) and Cu(II) (4) complexes of 2,2'‐[2,6‐pyridinediylbis(ethylidyne‐1‐hydrazinyl‐2‐ylidene)]bis[N,N,N‐trimethyl‐2‐oxoethanaminium] dichloride (H2LCl2) by NMR, IR, and X‐Band EPR spectroscopy, respectively, as well as by single‐crystal X‐ray structural analysis. H2LCl2 belongs to the class of diacetylpyridine bis(hydrazone) ligands and bears two positively charged quaternary ammonium functionalities. The complexes 1–3 possess a pentagonal‐bipyramidal geometry, whereas 4 has square‐pyramidal geometry. Redox reactivity and SOD activity of the complexes was studied by means of electrochemical measurements in aqueous‐buffer and DMF or DMSO solutions, respectively, as well as by stopped‐flow measurements. Complexes 1–3 do not have SOD activity, whereas 4 exhibits a high catalytic rate constant for the superoxide dismutation, kcat = 1.73 × 107 m–1 s–1 (in MOPS buffer solution of pH = 7.4). The results were discussed in terms of complex redox potentials, electrostatic interactions and their spatial distribution, kinetic lability of metal centers, and stability of peroxo intermediates, respectively.

The impact of ionizing radiation on microorganisms such as microalgae is a topic of increasing importance for understanding the dynamics of aquatic ecosystems in response to environmental radiation, and for the development of efficient approaches for bioremediation of mining and nuclear power plants wastewaters. Currently, nothing is known about the effects of ionizing radiation on the microalgal cell wall, which represents the first line of defence against chemical and physical environmental stresses. Using various microscopy, spectroscopy and biochemical techniques we show that the unicellular alga Chlorella sorokiniana elicits a fast response to ionizing radiation. Within one day after irradiation with doses of 1–5 Gy, the fibrilar layer of the cell wall became thicker, the fraction of uronic acids was higher, and the capacity to remove the main reactive product of water radiolysis increased. In addition, the isolated cell wall fraction showed significant binding capacity for Cu2+, Mn2+, and Cr3+. The irradiation further increased the binding capacity for Cu2+, which appears to be mainly bound to glucosamine moieties within a chitosan-like polymer in the outer rigid layer of the wall. These results imply that the cell wall represents a dynamic structure that is involved in the protective response of microalgae to ionizing radiation. It appears that microalgae may exhibit a significant control of metal mobility in aquatic ecosystems via biosorption by the cell wall matrix.

The impact of ionizing radiation on microorganisms such as microalgae is a topic of increasing importance for understanding the dynamics of aquatic ecosystems in response to environmental radiation, and for the development of efficient approaches for bioremediation of mining and nuclear power plants wastewaters. Currently, nothing is known about the effects of ionizing radiation on the microalgal cell wall, which represents the first line of defence against chemical and physical environmental stresses. Using various microscopy, spectroscopy and biochemical techniques we show that the unicellular alga Chlorella sorokiniana elicits a fast response to ionizing radiation. Within one day after irradiation with doses of 1-5 Gy, the fibrilar layer of the cell wall became thicker, the fraction of uronic acids was higher, and the capacity to remove the main reactive product of water radiolysis increased. In addition, the isolated cell wall fraction showed significant binding capacity for Cu2+, Mn2+, and Cr3+. The irradiation further increased the binding capacity for Cu2+, which appears to be mainly bound to glucosamine moieties within a chitosan-like polymer in the outer rigid layer of the wall. These results imply that the cell wall represents a dynamic structure that is involved in the protective response of microalgae to ionizing radiation. It appears that microalgae may exhibit a significant control of metal mobility in aquatic ecosystems via biosorption by the cell wall matrix.