Reciprocating thermal behavior and thermometry studies of Tb3+- and Gd3+-oxamato single-ion magnets Cleber R. Araujo Junior, Luana M. Murad, Rafael V. Perrella, Willian X. C. Oliveira, Carlos B. Pinheiro, Thais F. Ramos, Patrícia S. O. Patricio, Emerson F. Pedroso, Wallace C. Nunes, Pablo R. T. Ribeiro, Diego Muraca, Fernando Fabris, Marcelo Knobel, Fernando A. Sigoli, Cynthia L. M. Pereira Inorganic Chemistry Frontiers, 2025 Thermostable lanthanide(iii) single-ion magnets enabling quantum information processing technologies and photonics.
Isostructural Oxamate Complexes with Visible Luminescence (Eu3+) and Field-Induced Single-Molecule Magnet (Nd3+) Emilay B. T. Diogo, Eufrânio N. da Silva Júnior, Willian X. C. Oliveira, Humberto O. Stumpf, Fernando Fabris, Adriele A. de Almeida, Marcelo Knobel, Fabio F. Ferreira, Wallace C. Nunes, Emerson F. Pedroso, Miguel Julve, Cynthia L. M. Pereira Chemistry an Asian Journal, 2024 The search for new metal‐organic compounds as candidates for quantum information processing technologies is in the spotlight. Several metal ions and organic linkers have been used to obtain such compounds. Herein, we describe the synthesis, crystal structures, and cryomagnetic properties of two air‐stable isostructural neodymium(III) and europium(III) one‐dimensional (1D) coordination polymers of formula [Nd(Hmpa)3(DMSO)2]n (1) and [Eu(Hmpa)3(DMSO)2]n (2) [Hmpa=N‐(4‐methylphenyl)oxamate, and DMSO=dimethylsulfoxide]. These complexes were prepared by reacting n‐Bu4N(Hmpa) proligand [n‐Bu4N+=tetra‐n‐butylammonium] and the correspondent LnCl3 ⋅ 6H2O salt (Ln=Nd or Eu) in the open air and mild conditions. The crystal structures of 1 and 2 reveal the Ln3+ ion surrounded by two DMSO molecules and three oxamate ligands, one of them connecting to adjacent mononuclear entities through carboxylate bridges featuring a homometallic chain, while the other two establishing double N−H ⋅ ⋅ ⋅ O hydrogen bonds among adjacent polymers to give a resultant supramolecular 2D network. Cryomagnetic measurements in the static (dc) and dynamic current (ac) regimes reveal that 1 behaves as a field‐induced single‐molecule magnet below 8.8 K. A photoluminescence study shows that Hmpa ligands efficiently sensitize the luminescence of Eu3+ complex in the visible region in the solid state at room temperature.
Metallacrown of CeIIICuII5: Synthesis, Structural Characterization and Insights for Nanoparticles † Jésio D. Tempesta, Fábio Faria Paiva, Leonildo A. Ferreira, Rafaela M. R. da Silva, Luckerman D. G. Botelho, Iara M. L. Rosa, Caio Cesar Candido, Angelo Marcio Gomes, Wallace C. Nunes, Guilherme P. Guedes, Maria Vanda Marinho Magnetochemistry, 2024 The heterobimetallic 15-MC-5 metallacrown of formula [CeCu5(5mpzHA)5(NO3)(H2O)7]·2NO3·7H2O, designated MC-Ce, was synthesized using 5-methyl-2-pyrazinehydroxamic acid (5mpzHA) as a linker, reacting with CeIII and CuII salts under mild conditions. Single-crystal X-ray diffraction analysis reveals a crown-like [Cu5Ce(5mpzHA)5] core, characteristic of a 15-MC-5 system, with five CuII atoms at the rim of the crown and the CeIII ion occupying the dome of the crown, with water molecules, oxygen atoms and one nitrate anion filling the nine-coordination sphere around the CeIII ion, which exhibits a distorted spherical tricapped trigonal prism geometry. The thermogravimetric analysis evidences successive mass losses due to the removal of water molecules and decomposition of the structure after 217 °C, whereas the PXRD analysis of the thermal decomposition residue reveals the presence of copper and copper/cerium oxide particles. These nanocomposite materials were also synthesized using the metallacrown MC-Ce under a hydrothermal method in the presence of multi-walled carbon nanotubes (MWCNTs), affording insights that this metallacrown can act as a source precursor for the synthesis of these mixed cerium/copper oxide nanomaterials. The experimental χMT value in MC-Ce at room temperature is 3.175 cm3 mol−1 K, which is higher than the calculated one for one magnetically isolated CeIII plus five CuII ions, probably due to the antiferromagnetic interactions among CuII ions within the metallacrown hoop plus the thermal depopulation of JZ sublevels of CeIII ground state (5/2), which exhibit a small splitting under the anisotropic ligand field effects. The χMT decreases continuously until it reaches the value of 0.80 cm3 mol−1 K at 10 K, reinforcing the presence of intramolecular antiferromagnetic interactions.
Calixarene-like Lanthanide Single-Ion Magnets Based on NdIII, GdIII, TbIII and DyIII Oxamato Complexes † Tamyris T. da Cunha, João Honorato de Araujo-Neto, Meiry E. Alvarenga, Felipe Terra Martins, Emerson F. Pedroso, Davor L. Mariano, Wallace C. Nunes, Nicolás Moliner, Francesc Lloret, Miguel Julve, Cynthia L. M. Pereira Magnetochemistry, 2024 In this work, we describe the synthesis, crystal structures and magnetic properties of four air-stable mononuclear lanthanide(III) complexes with the N-(2,4,6-trimethylphenyl)oxamate (Htmpa) of formula: n-Bu4N[Nd(Htmpa)4(H2O)]·4H2O (1), n-Bu4N[Gd(Htmpa)4(H2O)]·3DMSO·2H2O (2), n-Bu4N[Tb(Htmpa)4(H2O)]·3DMSO·1H2O (3) and n-Bu4N[Dy(Htmpa)4(H2O)]·3DMSO·2H2O (4) (n-Bu4N+ = n-tetrabutylammonium; DMSO = dimethylsulfoxide). Their crystal structures reveal the occurrence of calixarene-type monoanionic species containing all-cis-disposed Htmpa ligands and one water molecule coordinated with the respective LnIII ion (Ln = Nd, Gd, Tb and Dy), featuring a nine-coordinated environment with muffin (MFF-9) (1) or spherical-capped square antiprism (CSAPR-9) (2–4) geometry. The major difference between their crystal structures is related to the nature of crystallization solvent molecules, either water (1) or both DMSO and water (2–4). The intermolecular hydrogen bonds among the self-complementary Htmpa ligands in all four compounds mediated a 2 D supramolecular network in the solid state. Direct-current (dc) magnetic properties for 1–4 show typical behavior for the ground state terms of the LnIII ions [4I9/2 (Nd); 8S7/2(Gd), 7F6 (Tb), 6H15/2 (Dy)]. Alternating-current (ac) magnetic measurements reveal the presence of slow magnetic relaxation without the presence of a dc field only for 4. In contrast, field-induced slow magnetic relaxation behavior was found in complexes 1, 2 and 3.
Crystal structure and cryomagnetic study of a mononuclear erbium(III) oxamate inclusion complex Cleber R. Araujo Junior, Willian X. C. Oliveira, Carlos B. Pinheiro, Emerson F. Pedroso, Wallace C. Nunes, Adriele A. de Almeida, Marcelo Knobel, Miguel Julve, Cynthia L. M. Pereira Acta Crystallographica Section C Structural Chemistry, 2024 The synthesis, crystal structure and magnetic properties of an oxamate-containing erbium(III) complex, namely, tetrabutylammonium aqua[N-(2,4,6-trimethylphenyl)oxamato]erbium(III)–dimethyl sulfoxide–water (1/3/1.5), (C16H36N)[Er(C11H12NO3)4(H2O)]·3C2H6OS·1.5H2O or n-Bu4N[Er(Htmpa)4(H2O)]·3DMSO·1.5H2O (1), are reported. The crystal structure of 1 reveals the occurrence of an erbium(III) ion, which is surrounded by four N-phenyl-substituted oxamate ligands and one water molecule in a nine-coordinated environment, together with one tetrabutylammonium cation acting as a counter-ion, and one water and three dimethyl sulfoxide (DMSO) molecules of crystallization. Variable-temperature static (dc) and dynamic (ac) magnetic measurements were carried out for this mononuclear complex, revealing that it behaves as a field-induced single-ion magnet (SIM) below 5.0 K.
Photoluminescence and magnetic properties of isostructural europium(iii), gadolinium(iii) and terbium(iii) oxamate-based coordination polymers Cleverton O. C. da Silveira, Willian X. C. Oliveira, Eufrânio N. da Silva Júnior, Meiry E. Alvarenga, Felipe T. Martins, Claudia C. Gatto, Carlos B. Pinheiro, Emerson F. Pedroso, Júlia P. O. Silva, Lippy F. Marques, Moliria V. Santos, Francisco R. Torres, Rividy Euclides, Ricardo O. Freire, Wallace C. Nunes, Adriele A. de Almeida, Marcelo Knobel, Cynthia L. M. Pereira Dalton Transactions, 2024 In this contribution, we present a series of new lanthanide–oxamate coordination polymers as suitable candidates for light conversion molecular devices and molecular qubits for quantum computing.
Exploring morphological variation in bismuth ferrite nanostructures by pulsed laser deposition: synthesis, structural and electrochemical properties Diana M A García, Rodrigo D Santos, Liying Liu, Wallace C Nunes Nanotechnology, 2024 Structural and electrochemical properties of bismuth ferrite nanostructures produced by pulsed laser deposition with various morphologies are reported. The nanostructures are also explored as electrode materials for high-performance supercapacitors. Scanning electron microscopy images revealed that various bismuth ferrite morphologies were produced by varying the background pressure (10−6, 0.01, 0.10, 0.25, 0.50, 1.0, 2.0 and 4.0 Torr) in the deposition chamber and submitting them to a thermal treatment after deposition at 500 ◦C. The as-deposited bismuth ferrite nanostructures range from very compact thin-film (10−6, 0.01, 0.10 Torr), to clustered nanoparticles (0.25, 0.50, 1.0 Torr), to very dispersed arrangement of nanoparticles (2.0 and 4.0 Torr). The electrochemical characteristic of the electrodes was investigated through cyclic voltammetry process. The increase in the specific surface area of the nanostructures as background pressure in the chamber increases does not lead to an increase in interfacial capacitance. This is likely due to the wakening of electrical contact between nanoparticles with increasing porosity of the nanostructures. The thermal treatment increased the contact between nanoparticles, which caused an increase in the interfacial capacitance of the nanostructure deposited under high background pressure in the chamber.
Intensity and lifetime ratiometric luminescent thermometer based on a Tb(iii) coordination polymer Augusto Iwashita Costa, Rafaela M. R. da Silva, Luckerman D. G. Botelho, Sergio F. N. Coelho, Fernando A. Sigoli, João Honorato, Javier Ellena, Felipe T. Martins, Angelo M. Gomes, Wallace C. Nunes, Francesc Lloret, Miguel Julve, Maria Vanda Marinho Dalton Transactions, 2024 A 3D coordination polymer of Tb(iii) of formula [Tb(bttb)0.5(2,5-pzdc)0.5]n, where two polycarboxylate ligands act as linkers, exhibits a maximum relative sensitivity of 0.76% K−1 at 295 K.
Building-up host-guest helicate motifs and chains: a magneto-structural study of new field-induced cobalt-based single-ion magnets Nathália R. de Campos, Cintia A. Simosono, Iara M. Landre Rosa, Rafaela M. R. da Silva, Antônio C. Doriguetto, Walace D. do Pim, Tatiana R. Gomes Simões, Ana Karoline S. M. Valdo, Felipe T. Martins, Charlie V. Sarmiento, Wallace C. Nunes, Guilherme P. Guedes, Emerson F. Pedroso, Cynthia L. M. Pereira, Humberto O. Stumpf, Francesc Lloret, Miguel Julve, Maria Vanda Marinho Dalton Transactions, 2021
A pH-triggered bistable copper(ii) metallacycle as a reversible emulsion switch for biphasic processes Walace D. do Pim, Willian X. C. Oliveira, Marcos A. Ribeiro, Érica N. de Faria, Ivo F. Teixeira, Humberto O. Stumpf, Rochel M. Lago, Cynthia L. M. Pereira, Carlos B. Pinheiro, João C. D. Figueiredo-Júnior, Wallace C. Nunes, Patterson P. de Souza, Emerson F. Pedroso, María Castellano, Joan Cano, Miguel Julve Chemical Communications, 2013
NiO nanoparticles dispersed in mesoporous silica glass Nathália M. Carneiro, Wallace C. Nunes, Rui P. Borges, Margarida Godinho, Luis E. Fernandez-Outon, Waldemar A. A. Macedo, Italo O. Mazali Journal of Physical Chemistry C, 2010
Ion beam synthesis of Mn/Sb clusters in silicon M Steinert, W Wesch, A Undisz, M Rettenmayr, W C Nunes, R P Borges, M Godinho, R M Rubinger, M C Carmo, N A Sobolev Journal of Physics D Applied Physics, 2009
Exchange bias in Fe/EuTe(111) bilayers W. A. A. Macedo, M. D. Martins, M. J. M. Pires, R. B. Oliveira, C. J. S. M. Pombo, W. C. Nunes, M. Knobel, P. H. O. Rappl, P. Motisuke Journal of Applied Physics, 2007
