DFT computations combined with semiempirical modeling of variations with temperature of spectroscopic and magnetic properties of Gd3+-doped PbTiO3

The rare-earth or 3d transition metal dopants in perovskites have potential to induce interesting features, thus opening opportunities for investigations and applications. Hence, understanding some features, i.e., defect structure, site of incorporation, valence state, and mechanism of charge compensation, in a wide range of temperature is crucial for their technological applications. A comprehensive understanding of the mechanism of structural changes in PbTiO₃ doped with trivalent rare-earths is significant for their potential applications in photonics. To unravel the structural changes, we utilize the density functional theory (DFT) to optimize structural data, which then serve as input for the semiempirical superposition model (SPM) analysis of spectroscopic and magnetic properties of Gd³⁺-doped PbTiO₃. We compute the formation energies of the doped compounds with and without O-vacancy to determine the stable composition. Analysis of the Bader electron charges computed using DFT plus quantum theory of atoms in molecules enables elucidating the effects of the Gd dopant and O-vacancy on the ionic and covalent bonds and, thereby, chemical stability of the compositions. To explain and corroborate the zero-field splitting parameters (ZFSPs) measured by EMR and the lattice parameter changes obtained from XRD, we employ SPM. The optimized structures obtained from ab initio computations for various structural models of Gd³⁺ doped PbTiO₃ are utilized as input data for SPM calculations of ZFPs. This enables theoretical analysis of variations of ZFSPs from 5 to 780 K. The results were fine-tuned by matching with available experimental EMR data for Gd³⁺ probes in PbTiO₃ nanoparticles. Modeling has been carried out considering several possible structural models and the role of an O-vacancy around Gd³⁺ centers. The results show that the two-fold modeling approach, combining DFT and SPM, provides a reliable description of experimental data. Comparative analysis indicates that the Ti-site is less favorable for being replaced by Gd³⁺ with/without O-vacancy. This analysis confirms the plausibility of the Pb²⁺ site for Gd³⁺ dopants and sheds light on the changes of crystal structure during the phase transitions occurring in PbTiO₃ with decreasing temperature.

SMM behaviour of heterometallic dinuclear CuIILnIII (Ln = Tb and Dy) complexes derived from N2O3 donor unsymmetrical ligands

Four heterometallic dinuclear Cu^IILn^III (Ln = Tb and Dy) complexes derived from two different N₂O₃ donor unsymmetrical Schiff base ligands exhibit SMM behaviour.

Ln-MOFs using a compartmental ligand with a unique combination of hard–soft terminals and their magnetic, gas adsorption and luminescence properties

The present work is part of our ongoing quest for developing multifunctional lanthanide–organic hybrid materials using non-conventional soft N-rich pyridyl–pyrazole-based ligands.

Solvent-induced formation of two gadolinium clusters demonstrating strong magnetocaloric effects and ferroelectric properties

Large magnetocaloric effects and ferroelectric properties were demonstrated in two gadolinium clusters obtained via solvent modulation.

A series of new octanuclear Ln8 clusters: magnetic studies reveal a significant cryogenic magnetocaloric effect and slow magnetic relaxation

A series of new octanuclear Ln₈ clusters. Magnetically, Gd₈ exhibited a significant magnetocaloric effect and a magnetic entropy change is 32.49 J K⁻¹ kg⁻¹ for a field of 7 T at 2 K, while Dy₈ exhibited a frequency dependent slow relaxation of magnetization at a zero applied direct current magnetic field.

Field Induced Slow Magnetic Relaxation in a Non Kramers Tb(III) Based Single Chain Magnet

Herein, we report a novel Tb(III) single chain magnet with the chemical formulae [Tb(μ-OH2)(phen)(μ-OH)(nb)2]n by using 4-nitrobenzoic acid (Hnb) and 1,10-phenanthroline (phen) as ligand system. The single-crystal X-ray diffraction reveals that 4-nitrobenzoic acid acts as a monodentate ligand, water and hydroxyl ions are the bridging ligand and the phen serves as a bidentate chelating ligand. The static magnetic susceptibility measurement (from 2 K to 300 K) shows ferromagnetic interaction at very low temperature (below 6 K). The alternating current (AC) susceptibility data of the complex show temperature and frequency dependence under an applied 2000 Oe DC (direct current) field. The phen moiety behaves as an antenna and enables the complex to show the green light fluorescence emission by absorption-energy transfer-emission mechanism. To calculate the exchange interaction, broken symmetry density functional theory (BS-DFT) calculations have been performed on a model compound which also reveals weak ferromagnetic interaction. Ab initio calculations reveals the anisotropic nature (gz = 15.8, gy, gy = 0) of the metal centre and the quasi doublet nature of ground state with small energy gap and that is well separated from the next excited energy state.

3D isomorphous lanthanide coordination polymers displaying magnetic refrigeration, slow magnetic relaxation and tunable proton conduction

Four lanthanide 3D coordination frameworks with 1D hydrophilic channels along the crystallographic c direction have been investigated for their proton conduction and magnetic properties.

Magnetorefrigeration capability of a gadolinium(iii) coordination polymer containing trimesic acid: a correlation between the isothermal magnetic entropy change and the gadolinium content

A general correlation for Gd(iii) complexes showing the magnetocaloric effect was proposed.

A series of six-membered lanthanide rings based on 2,2-bis(hydroxymethyl)-2,2′,2″-nitrilotriethanol: synthesis, crystal structures and magnetic properties

A series of six-membered ring cyclic lanthanide(iii) clusters have been constructed by utilizing the pentol ligand.

3D oxalato-bridged lanthanide(iii) MOFs with magnetocaloric, magnetic and photoluminescence properties

Four isostructural 3D lanthanide(iii) metal–organic frameworks with the general formula (H₆edte)_0.5[Ln^III(ox)₂(H₂O)] (Ln = Gd (1), Tb (2), Dy (3) and Ho (4); H₄edte = N,N,N′,N′-tetrakis(2-hydroxyethyl)ethylenediamine) and ox = oxalate have been synthesized from oxalate.

Coordination-Cluster-Based Molecular Magnetic Refrigerants

Coordination polymers serving as molecular magnetic refrigerants have been attracting great interest. In particular, coordination cluster compounds that demonstrate their apparent advantages on cryogenic magnetic refrigerants have attracted more attention in the last five years. Herein, we mainly focus on depicting aspects of syntheses, structures, and magnetothermal properties of coordination clusters that serve as magnetic refrigerants on account of the magnetocaloric effect. The documented molecular magnetic refrigerants are classified into two primary categories according to the types of metal centers, namely, homo- and heterometallic clusters. Every section is further divided into several subgroups based on the metal nuclearity and their dimensionalities, including discrete molecular clusters and those with extended structures constructed from molecular clusters. The objective is to present a rough overview of recent progress in coordination-cluster-based molecular magnetic refrigerants and provide a tutorial for researchers who are interested in the field.

A family of dinuclear lanthanide(III) complexes from the use of a tridentate Schiff base

The use of N-salicylidene-o-aminophenol (H2saph) in 4f-metal chemistry has led to the isolation of seven new isostructural lanthanide(iii) [Ln(III)] complexes. More specifically the Ln(NO3)3·xH2O/H2saph/Et3N (1 : 1 : 1) reaction mixtures in DMF/MeCN gave complexes [Ln2(NO3)2(saph)2(DMF)4] (Ln = Sm (); Eu (); Gd (); Tb (); Dy (); Ho (); Er ()) in good yields (∼65%). The structures of the isomorphous complexes and were solved by single-crystal X-ray crystallography; the other complexes are proposed to be isostructural with and based on elemental analyses, IR spectra and powder XRD patterns. The two Ln(III) atoms in the centrosymmetric molecules of and are doubly bridged by the deprotonated iminophenolato oxygen atoms of two nearly planar η(1):η(1):η(2):μ saph(2-) ligands. The imino nitrogen and five terminal oxygen atoms (the salicylaldiminate, two from one bidentate chelating nitrato group and two from two DMF ligands) complete square antiprismatic coordination at each metal centre. The IR spectra of the complexes are discussed in terms of the coordination modes of the ligands present in the complexes. Solid-state emission studies for all display identical ligand-based photoluminescence. Dc magnetic susceptibility studies in the 2-300 K range reveal the presence of a weak, intramolecular antiferromagnetic exchange interaction (J = -0.19(1) cm(-1) based on the spin Hamiltonian H = -J(ŜGd·ŜGd')) for and probably ferromagnetic exchange interaction within the molecules of and . Ac magnetic susceptibility measurements in zero dc field show temperature- and frequency-dependent out-of-phase signals with two well defined, thermally-activated processes for , suggesting potential single-molecule magnetism character. The Ueff value is 17.4 cm(-1) for the higher temperature process and 16.2 cm(-1) for the lower temperature one. The combination of photoluminescence and single-molecule behaviour in the Dy complex is critically discussed.

Pentanuclear [2.2] spirocyclic lanthanide(iii) complexes: slow magnetic relaxation of the DyIII analogue

A series of [2.2] spirocyclic complexes [Ln₅(LH)₄(η¹-Piv)(η²-Piv)₃(μ₂–η² η¹Piv)₂(H₂O)]·Cl (Ln = Dy^III, Tb^III and Ho^III) were synthesized. Magnetic analysis reveals that the Dy^III analogue showed slow relaxation of magnetization.

Concomitant spin-canted antiferromagnetic ordering and proton conduction in homometallic and homoleptic coordination polymers

Two oxonate based 1D zig-zag coordination polymers with Fe^II and Co^II are reported. These complexes are the first oxonate based systems to exhibit spin canted antiferromagnetic ordering at low temperatures and good proton conduction ability at elevated temperatures and under high humidity conditions.

Nanoscopic molecular magnets

This review highlights fundamental concepts and synthetic strategies of SMMs and selected examples of 3d, 4f, 5f and mixed 3d–4f, 4d–5d and 3d–5f based SMMs are discussed.

A family of Fe3+ based double-stranded helicates showing a magnetocaloric effect, and Rhodamine B dye and DNA binding activities

A series of Fe³⁺ based double-stranded helicates unveil a significant magnetocaloric effect as well as binding activities with Rhodamine B dye and CT-DNA.

Influence of the coordination environment on slow magnetic relaxation and photoluminescence behavior in two mononuclear dysprosium(iii) based single molecule magnets

Two luminescent mononuclear Dy(iii) based complexes with SMM behaviour have been reported. The SMM behaviours differ due to the slight variation of local symmetry around the Dy(iii) centers and photoluminescence study showed quantum yields of 0.98 and 1.44%.

Modulating the magnetic properties by structural modification in a family of Co-Ln (Ln = Gd, Dy) molecular aggregates

Two types of 3d–4f cages are reported where the Gd analogues show significant magnetic refrigeration and the Dy containing compounds display SMM behaviour.

Synthesis, crystal structure and study of magnetocaloric effect and single molecular magnetic behaviour in discrete lanthanide complexes

Hydrazone based four lanthanide complexes were synthesized where two gadolinium complexes show significant magnetocaloric effect and dysprosium analogues show SMM behavior.