Complex Ions Research Articles

Tridentate Nitrogen Ligand as a Tool for the Construction of Well-Defined Rare Earth Trichloride Complexes.

LnCl3(THF)3 (Ln = Y, La ÷ Nd, Sm ÷ Lu) readily react with the tridentate 1,3,5-trimethyl-1,3,5-triazacyclohexane (Me3tach) ligand to form mono- or binuclear lanthanide trichloride complexes, depending on the stoichiometry of the reaction and the ionic radius of the metal: mononuclear pseudosandwich [LnCl3(Me3tach)2], (Ln = Y, La ÷ Ho) or binuclear complexes [Ln2Cl6(Me3tach)3], or [LnCl3(Me3tach)(THF)]2 (Ln = Sm, Tb). Detailed analysis of the NMR data of [LnCl3(Me3tach)2] complexes with paramagnetic lanthanide ions showed that their structures remained unchanged in the toluene solution. A series of isomorphous complexes [LnCl3(Me3tach)(Py)2] (Ln = La, Sm, Tb, Er, Lu; Py = pyridine) have been obtained by the recrystallization of either mononuclear or binuclear complexes from pyridine. Complexes of terbium and europium ions with the Me3tach ligand exhibit relatively high quantum yields of metal-centered luminescence (0.39 and 0.32, respectively).

Ultratough Epoxy Resin Based on an Ionic Complex from Phytic Acid

Ultratough Epoxy Resin Based on an Ionic Complex from Phytic Acid

Radiolabelled 177 Lu-Bispidine-Trastuzumab for Targeting Human Epidermal Growth Factor Receptor 2 Positive Cancers.

Radioimmunotherapy (RIT) is a promising alternative to conventional treatment options. Here, we present experimental work on the synthesis, radiochemistry, and in vivo performance of a lanthanoid-selective nonadentate bispidine ligand suitable for 177 Lu3+ ion complexation. The ligand (bisp,1) was derivatised with a photoactivatable aryl azide (ArN3 ) group as a bioconjugation handle for light-induced labelling of proteins. Quantitative radiosynthesis of [177 Lu]Lu-1+ was accomplished in 10 minutes at 40 °C. Subsequent incubation of [177 Lu]Lu-1+ with trastuzumab, followed by irradiation with light at 365 nm for 15 min, at room temperature and pH 8.0-8.3, gave the radiolabelled mAb, [177 Lu]Lu-1-azepin-trastuzumab ([177 Lu]Lu-1-mAb) in a decay-corrected radiochemical yield of 14 %, and radiochemical purity (RCP)>90 %. Stability studies and cellular binding assays in vitro using the SK-OV-3 human ovarian cancer cells confirmed that [177 Lu]Lu-1-mAb remained biological active and displayed specific binding to HER2/neu. Experiments in immunocompromised female athymic nude mice bearing subcutaneous xenograft models of SK-OV-3 tumours revealed significantly higher tumour uptake in the normal group compared with the control block group (29.8±11.4 %ID g-1 vs. 14.8±6.1 %ID g-1 , respectively; P-value=0.037). The data indicate that bispidine-based ligand systems are suitable starting points for constructing novel, high-denticity chelators for specific complexation of larger radiotheranostic metal ion nuclides.

Transition Metal Ion FRET-Based Probe to Study Cu(II)-Mediated Amyloid-β Ligand Binding.

Recent therapeutic strategies suggest that small peptides can act as aggregation inhibitors of monomeric amyloid-β (Αβ) by inducing structural rearrangements upon complexation. However, characterizing the binding events in such dynamic and transient noncovalent complexes, especially in the presence of natively occurring metal ions, remains a challenge. Here, we deploy a combined transition metal ion Förster resonance energy transfer (tmFRET) and native ion mobility-mass spectrometry (IM-MS) approach to characterize the structure of mass- and charge-selected Aβ complexes with Cu(II) ions (a quencher) and a potential aggregation inhibitor, a small neuropeptide named leucine enkephalin (LE). We show conformational changes of monomeric Αβ species upon Cu(II)-binding, indicating an uncoiled N-terminus and a close interaction between the C-terminus and the central hydrophobic region. Furthermore, we introduce LE labeled at the N-terminus with a metal-chelating agent, nitrilotriacetic acid (NTA). This allows us to employ tmFRET to probe the binding even in low-abundance and transient Aβ-inhibitor-metal ion complexes. Complementary intramolecular distance and global shape information from tmFRET and native IM-MS, respectively, confirmed Cu(II) displacement toward the N-terminus of Αβ, which discloses the binding region and the inhibitor's orientation.

Phase tree, analysis of crystallizing phases and description of chemical interaction in the three-component reciprocal system Ca,Ba| |F,Cl

The paper analyzes the crystallizing phases in the ternary reciprocal system Ca,Ba | | F,Cl, describes the chemical interaction of ion exchange reactions and complexation reactions. The system is partitioned into simplices using graph theory. A tree of phases of the system has been constructed, on the basis of which a prediction of the number and composition of crystallizing phases in stable elements has been made. A 3D model of the phase complex of the Ca,Ba | | F,Cl system was built using the KOMPAS 3D v21 software. On the stable CaF2–BaCl2 diagonal, the presence of a quasi-binary eutectic and the stability of the crystallizing phases were confirmed by thermogravimetry and XRD methods.

Resourcization of Argillaceous Limestone with Mn3O4 Modification for Efficient Adsorption of Lead, Copper, and Nickel.

Argillaceous limestone (AL) is comprised of carbonate minerals and clay minerals and is widely distributed throughout the Earth's crust. However, owing to its low surface area and poorly active sites, AL has been largely neglected. Herein, manganic manganous oxide (Mn3O4) was used to modify AL by an in-situ deposition strategy through manganese chloride and alkali stepwise treatment to improve the surface area of AL and enable its utilization as an efficient adsorbent for heavy metals removal. The surface area and cation exchange capacity (CEC) were enhanced from 3.49 to 24.5 m2/g and 5.87 to 31.5 cmoL(+)/kg with modification, respectively. The maximum adsorption capacities of lead (Pb2+), copper (Cu2+), and nickel (Ni2+) ions on Mn3O4-modified argillaceous limestone (Mn3O4-AL) in mono-metal systems were 148.73, 41.30, and 60.87 mg/g, respectively. In addition, the adsorption selectivity in multi-metal systems was Pb2+ > Cu2+ > Ni2+ in order. The adsorption process conforms to the pseudo-second-order model. In the multi-metal system, the adsorption reaches equilibrium at about 360 min. The adsorption mechanisms may involve ion exchange, precipitation, electrostatic interaction, and complexation by hydroxyl groups. These results demonstrate that Mn3O4 modification realized argillaceous limestone resourcization as an ideal adsorbent. Mn3O4-modified argillaceous limestone was promising for heavy metal-polluted water and soil treatment.

1,1ʹ-Dimethyl-4,4ʹ-bipyridinium as a multivalent structure-directing counterion to anionic uranyl ion polycarboxylate complexes

Seven uranyl ion complexes with polycarboxylates have been synthesized under solvo-hydrothermal conditions and in the presence of 1,1ʹ-dimethyl-4,4ʹ-bipyridinium (Me2bipy2+) as structure-directing counterion. Two complexes were obtained with phthalate (pht2–), [Me2bipy]2[(UO2)4(pht)4(O)2] (1), which is a discrete, bis(μ3-oxo-bridged) tetranuclear species, and {[Me2bipy][(UO2)3(pht)4(H2O)]}n (2), which crystallizes as a monoperiodic coordination polymer. The complex obtained with citric acid (H4cit), {[Me2bipy][UO2(Hcit)]2·H2O}n (3), assumes a well-known monoperiodic form. {[Me2bipy][(UO2)2(Hthftc)2]}n (4), obtained from tetrahydrofurantetracarboxylic acid (H4thftc), is also a monoperiodic polymer further assembled into layers through hydrogen bonding, the packing defining channels containing columns of stacked counterions. The previously reported {[Me2bipy][(UO2)2(tdc)3]}n (5), where tdc2– is 2,5-thiophenedicarboxylate, is a diperiodic hcb network, with the counterions crossing the hexanuclear rings. One experiment with pimelate (pim2–) gave the two complexes {[Me2bipy][(UO2)2(pim)3]}n (6) and {[Me2bipy][(UO2)4(pim)5(DMA)2]}n (7) (DMA = N,N-dimethylacetamide). Both 6 and 7 are diperiodic assemblies, but while 6 has the KIa topology previously found in other uranyl ion complexes with elongated dicarboxylate ligands, 7 is a very intricate and thick assembly with a packing displaying interdigitation. The weak interactions formed by the counterions are discussed through examination of Hirshfeld surfaces.

Rapid monitoring of heavy metal-ammonia complexes in solutions by UV–vis/ATR-FTIR spectroscopy and chemometric models

Ammonia can form stable chemical complexes with heavy metal ions, which significantly affect the treatment efficiency of these wastewaters. Thus, accurately determining the concentration of heavy metal ammonia complex ions is crucial to understanding the complex decomposition mechanism. The current study predicted the composition of copper ammonia solution through thermodynamic calculations. The mid-infrared first derivative spectra obtained from density functional theory (DFT) calculation and measurements of the simulated solutions were compared, which indicated that [Cu(NH3)4]2+ was the primary form of complexes in solution. The acquired FTIR spectra and UV–vis spectra demonstrated a strong correlation with the [Cu(NH3)4]2+ concentrations; whereas a principal component regression (PCR) model was implemented for concentration computation. The UV–vis-PCR model was found to be a fast and accurate method for quantification of copper-ammonia complex concentration, and its detection limit and quantification limit could reach 5 mg·L−1 and 10 mg·L−1, respectively, in the 5–200 mg·L−1 range. This study established qualitative and quantitative methods for analyzing copper ammonia complex in water, which provided the feasibility for rapid real-time monitoring of copper ammonia complex.

Acidification is required for calcium and magnesium concentration measurements in equine urine

BackgroundAcidification of equine urine to promote dissociation of ion complexes is a common practice for urine ion concentration measurements. The objective of this study was to evaluate the effect of acidification and storage after acidification on calcium (Ca), magnesium (Mg) and phosphate (P) concentrations and on fractional excretion (FE) of these electrolytes. Thirty-two fresh equine urine samples were analysed between December 2016 and July 2020. Complete urinalysis (stick and sediment) was performed on all samples. Ca, Mg, P and creatinine concentrations were measured in supernatant of centrifuged native urine, urine directly centrifuged after acidification and urine centrifuged 1 hour after acidification. Urine was acidified with hydrochloric acid to reach a pH of 1–2. Ca, Mg, P and creatinine concentrations were also measured in blood plasma, and fractional excretion of each electrolyte was calculated. Equality of medians was tested with Friedman tests and Bland-Altman bias plots were used to show the agreement between conditions.ResultsAcidification had a statistically significant effect on Ca and Mg concentrations, FECa and FEMg. Bland-Altman plot revealed a strong positive proportional bias between Ca concentration in native and acidified urine with a mean bias of 17.6 mmol/l. For Mg concentration, the difference between native and acidified urine was small with a mean bias of 1.8 mmol/l. The increase in FECa was clinically relevant. Storage of acidified urine had no effect on any of the measured ion concentrations. All P concentrations in native urine samples were below the detection limit of the assay and statistical analysis and calculation of FEP was not possible.ConclusionsUrine acidification is essential for accurate measurement of Ca and Mg concentrations and therefore FE calculations in equine urine. Storage time of 1 hour after acidification does not significantly change Ca and Mg concentrations.

Theoretical study of the influence of electron push or pull bipyridine ligands on the electronic structure of Eu3+ ibuprofenate complexes

In this work, we showed the influence of dissubstituted bipyridine ligands with electron push or pull groups in the structural and electronic properties of the Eu3+ ibuprofenate complexes. QTAIM-DFT analyzes performed for the sixteen complexes demonstrated that the interaction between the 6,6′-X-bpy ligands and the Eu3+ ion is strongly weakened when X = –OCH3 (complex 10) and –NO2 (complex 16) due to steric hindrances and a decrease in ligand basicity. The Gibbs free energy of the formation of these complexes is less favored around 27 kcal mol−1 compared to complex 3 (X = 5,5′-NH2-bpy), which is the most thermodynamically stable structure. The calculated absorption bands in the ultraviolet region revealed that bpy ligands containing strongly electron donating groups shift the maximum absorption wavelength towards the near visible region. These results suggest that the studied Ln3+ ion complexes may be used in molecular devices with optoelectronic applications in the visible region.

Novel Model for Predicting the Electrical Conductivity of Multisalt Electrolyte Solutions.

This study presents a novel model to predict the electrical conductivity of multisalt electrolyte solutions by incorporating corrections to the ideal behavior due to relaxation and electrophoretic effects. The performance of the model is evaluated by comparing its predictions with the experimental data of 24 multisalt aqueous solutions. The comparison reveals good agreement for solutions with an ionic strength below 1 mol/L without adjusting any parameter to fit to the experimental data. However, the model tends to overestimate the molar conductivity at higher ionic strengths. The discrepancy is attributed to the neglect of the solvent structure and the formation of ion pairs. It has been speculated how the accuracy of the developed model could be improved in relation to these limitations. Furthermore, the performance of the model is rigorously tested in systems with ion complex formation. It has been demonstrated that when the distribution of ion complexes is calculated from a thermodynamic model and then used to predict the electrical conductivity with the developed model, a satisfactory level of accuracy is attained for these systems.

An ultrasensitive 4-aminophenol electrochemical sensors based on zinc and nitrogen-doped γ-cyclodextrin composites

4-Aminophenol (4-AP) is an environmental pollutant that is harmful to aquatic organisms and can cause long-term adverse effects in the aquatic environment. Herein, a Zn,N-γ-CD/GCE sensing platform was constructed by utilizing the complexation of Zn ions with γ-cyclodextrin (γ-CD), along with the composite of N-doped γ-cyclodextrin (N-γ-CD) and ZnCl2, for the detection of 4-AP. The presence of pore structures and hydrogen bonding groups in N-γ-CD enables effective capture of the target analyte through host–guest interactions, thereby enhancing the detection efficiency. The doping of Zn metal significantly improves the sensitivity of the sensing platform. After optimization, the detection limit of the Zn,N-γ-CD/GCE sensor was as low as 29.1 nM. Moreover, the sensor exhibits reliable repeatability, reproducibility, and stability. The practical feasibility of detecting 4-AP in real samples using this sensor demonstrated a recovery rate of 94.3 %–105.5 %, providing a new method for the accurate detection of 4-AP.

Deciphering the Origin of Interface‐Induced High Li and Na Ion Conductivity in Nanocomposite Solid Electrolytes Using X‐Ray Raman Spectroscopy

AbstractSolid‐state electrolytes (SSEs) with high ionic conductivities are crucial for safer and high‐capacity batteries. Interface effects in nanocomposites of SSEs and insulators can lead to profound increases in conductivity. Understanding the composition of the interface is crucial for tuning the conductivity of composite solid electrolytes. Herein, X‐ray Raman Scattering (XRS) spectroscopy is used for the first time to unravel the nature of the interface effects responsible for conductivity enhancements in nanocomposites of complex hydride‐based electrolytes (LiBH4, NaBH4, and NaNH2) and oxides. XRS probe of the Li, Na, and B local environments reveals that the interface consists of highly distorted/defected and structurally distinct phase(s) compared to the original compounds. Interestingly, nanocomposites with higher concentrations of the interface compounds exhibit higher conductivities. Clear differences are observed in the interface composition of SiO2‐ and Al2O3‐based nanocomposites, attributed to differences in the reactivity of their surface groups. These results demonstrate that interfacial reactions play a dominant role in conductivity enhancement in composite solid electrolytes. This work showcases the potential of XRS in investigating interface interactions, providing valuable insights into the often complex ion conductor/insulator interfaces, especially for systems containing light elements such as Li, B, and Na present in most SSEs and batteries.

Zein/polyvinyl alcohol‐based electrospun nanofibrous films reinforced with nano‐hydroxyapatite for efficient Cu(II) adsorption

AbstractTo solve the problem of the presence of heavy metals in water causing water pollution, the biodegradable film based on zein/polyvinyl alcohol (PVA) with the incorporation of nano‐hydroxyapatite (nHAP) was fabricated through an electrospinning technique. The copper ion was taken as the representative of heavy metal ions in this study. The result showed that the incorporated nHAP nanoparticles were dispersed within the zein/PVA matrix, and strong hydrogen bonding interactions were formed between the filler and matrix, improving the hydrophobicity of the nanofibrous films and maintaining thermal stability. The adsorption mechanism was analyzed by fitting the adsorption process with pseudo‐first‐order model and pseudo‐second‐order model. Based on the ion exchange effect, electrostatic interaction, and complexation, the adsorption capacities of nanofibrous films for Cu(II) were significantly increased after adding nHAP. When the nHAP content was 20 wt.%, the Cu(II) adsorption capacity reached up to 23.86 mg/g, and the adsorption efficiency was 13.94% higher than that of neat zein/PVA nanofibers. This work suggests the potential of the electrospun zein/PVA/nHAP nanofibrous films as desirable eco‐friendly materials in metal removal applications.

An approach to determine nickel in aqueous systems through complexation with a Schiff base based on high‐performance liquid chromatography coupled with photodiode array detector

AbstractThis study presents a new and rapid analytical high‐performance liquid chromatography coupled with a photodiode array detector method for determining nickel ion (Ni2+) complex with Schiff base (Z)‐1‐(thiophen‐2‐yl‐methyleneamino) propane‐2‐ol easily. The influence of pH, surfactant, and effect of mobile phase on the formation of the Ni‐(Z)‐1‐(thiophen‐2‐yl‐methyleneamino)propane‐2‐ol complex was studied and optimized. The results showed that the acidic condition (pH = 5) favors the complexation most. Triton X‐100 neutral surfactant was used for dissolving the Ni–complex synthesized. A mobile phase ratio of methanol:acetonitrile:water 70:20:10, v/v/v was taken as optimum. This approach allowed the analysis of Ni2+ ion with the limit of detection of 0.0349 ng/mL over the linear range of (0.1–250 ng/mL) and a relative standard deviation of < 2%. The developed method exhibited remarkable extraction recoveries for Ni2+ in various real water samples (tap water; 98.0%–99.8% and river water; 97.0%–98.7%) and alloys with recoveries of (nichrome; 85.2% and chromel; 88.4%). Moreover, this protocol was also applied for the quantitation of Ni2+ in real sewage samples at a concentration level of 0.256 ng/mL. The outcomes of the present work successfully revealed the apparent superiority of Schiff base (Z)‐1‐(thiophen‐2‐yl‐methyleneamino) propane‐2‐ol toward the practical removal of target Ni2+ under real‐world conditions.

Fabrication, characterization, and application of pea protein isolate-polyphenol-iron complexes with antioxidant and antibacterial activity

Plant proteins are becoming increasingly popular as functional ingredients in foods because of their health, sustainability, and environmental benefits. The functional performance of plant proteins can often be improved by combining them with other food ingredients. For instance, they can be combined with polyphenols and metal ions to form surface active protein-polyphenol-iron complexes with biological activity. In this study, ternary complexes of pea protein isolate (PPI), epigallocatechin-3-gallate (EGCG) and iron (Fe3+) was prepared using a simple molecular self-assembly method. The formation mechanism, characteristics, and functional properties of these complexes were then characterized. Our results showed that PPI, EGCG, and Fe3+ could spontaneously combine to form nano-sheet networks held together by hydrogen bonds, phenolic hydroxyl coordination bonds, and electrostatic interactions. The addition of Fe3+ increased the fraction of disordered secondary structures, reduced the thermal denaturation temperature, reduced the surface hydrophobicity, increased the particle size, and altered the surface potential of the proteins in a dose dependent manner. Optimizing the EGCG-to-Fe3+ ratio in the complexes (1:2 w/w) led to the formation of protein composites with improved surface, antioxidant, and antibacterial activities. This study provided valuable insights into the interaction mechanisms of proteins, polyphenols, and metal ions in ternary complexes. These complexes may be used as multifunctional ingredients in plant-based foods because of their beneficial antioxidant, antimicrobial, nutritional, and emulsification properties.

Structures and stability of I2 and ICl complexes with pyridine: Ab initio and DFT study.

Theoretical investigation of thermodynamic stability and bonding features of possible isomers of the molecular and ionic complexes of pyridine with molecular iodine and iodine monochloride IX (X = I,Cl) is presented. M06-2X DFT functional is found to provide bond distances and dissociation energies which are close to those obtained at high-level ab initio CCSD(T)/aug-cc-pvtz//CCSD/aug-cc-pvtz benchmark computations for the most stable isomers, formed via donation of a lone pair of nitrogen atom of pyridine to the iodine atom. These isomers are by 23-33 kJ mol-1 (in case of I2) and by 39-56 kJ mol-1 (in case of ICl) more stable than other molecular complexes. T-shaped π-σ* bonded isomers turn out to be energetically comparable with van der Waals bound compounds. Among the ionic isomers, structures featuring [IPy2]+ cation with I3 - or ICl2 - counterions are more stable. Oligomerization favors ionic isomers starting from the tetrameric clusters of the composition (IX)4Py4.

Approaching 100% Comprehensive Utilization Rate of Ultra‐Stable Zn Metal Anodes by Constructing Chitosan‐Based Homologous Gel/Solid Synergistic Interface

AbstractAqueous Zn–metal batteries are considered promising candidates for next‐generation energy storage. However, low zinc utilization rate (ZUR) and limited cycle life are still hinder its commercial application because of severe parasitic side effects. Herein, inspired by the wound healing process, an innovative electrode recovery technology is developed to improve the comprehensive ZUR and prolong the cycling life through repetitive rejuvenation of zinc anode by designing chitosan‐based homologous gel/solid synergistic electrolyte. The designed synergistic electrolyte, consisting of protonated chitosan gel electrolyte and Zn‐chitosan solid electrolyte, exhibits superior zinc ion diffusion capability and low free‐water activity, leading to dendrite‐free Zn deposition and HER inhibition. Moreover, through proton neutralization and zinc ion complexation, the formulated electrolyte can implement the rejuvenation of zinc anode by smoothing interfacial defects and eliminating parasitic byproducts. Consequently, the gel/solid synergistic electrolyte displays reversible Zn plating/stripping chemistry for 4000 cycles with high average Coulombic efficiency (99.8%) and realizes comprehensive ZUR of 97.4% through four iterations of electrode recover under extreme conditions (20 mA cm−2, 31.5% Zn depth of discharge), noticeably higher than zinc electrode with no recover (11.8%). Furthermore, the superiority of customized synergistic electrolyte is further demonstrated by coupling with I2 cathode and achieving impressive 36 000 stable cycles.

Substituted fullerenes as a promising capping ligand towards stabilization of exohedral Dy(III) based single-ion magnets: a theoretical study.

Organometallic dysprosocenium-based molecular magnets are the forefront runners in offering giant magnetic anisotropy and blocking temperatures close to the boiling point of liquid nitrogen. Attaining linearity in the organometallic dysprosocenium complexes is the key to generating giant magnetic anisotropy and blocking barriers. In the present study, we have unravelled the coordination ability of the substituted fullerene (C55X5)- (where X = CCH3, B, and N) generated by fencing around the five-membered ring of fullerene towards stabilizing a new family of exohedral dysprosium organometallic complexes showcasing giant magnetic anisotropy and blockade barriers. Eight exohedral mononuclear dysprosium organometallic complexes, namely [Dy(η5-C55X5)(η4-C4H4)] (1), [Dy(η5-C55X5)(η5-Cp)]+ (2), [Dy(η5-C55X5)(η5-Cp*)]+ (3), [Dy(η5-C55X5)(η6-C6H6)]2+ (4), [Dy(η5-C55X5)(η8-C8H8)] (5), [Dy(η5-C55X5)2]+ (6) (where X = CCH3), [Dy(η5-C55B5)2]+ (7) and [Dy(η5-C55N5)2]+ (8), were studied using scalar relativistic density functional theory (SR-DFT) and the complete active space self-consistent field (CASSCF) methodology to shed light on the structure, stability, bonding and single-ion magnetic properties. SR-DFT calculations predict complexes 1-8 to be highly stable, with a strictly linear geometry around the Dy(III) ion in complexes 6-8. Energy Decomposition Analysis (EDA) predicts the following order for interaction energy (ΔEint value): 5 > 1 > 2 ≈ 3 > 6 > 7 > 8 > 4, with sizable 4f-ligand covalency in all the complexes. CASSCF calculations on complexes 1-8 predict stabilization of mJ |±15/2〉 as the ground state for all the complexes except for 5, with the following trend in the Ucal values: 6 (1573 cm-1) ≈ 3 (1569 cm-1) > 1 (1538 cm-1) > 8 (1347 cm-1) > 2 (1305 cm-1) > 7 (1284 cm-1) > 4 (1125 cm-1) > 5 (108 cm-1). Ab initio ligand field theory (AILFT) analysis provides a rationale for Ucal ordering, where π-type 4f-ligand interactions in complexes 1-4 and 6-8 offer giant barrier height while the large (C8H8)2- rings generate δ-type interaction in 5, which diminishes the axiality in the ligand field. Our detailed finding suggests that the exohedral organometallic dysprosocenium complexes are more linear compared to bent [DyCp*2]+ cations and display a giant barrier height exceeding 1500 cm-1 with negligible quantum tunnelling of magnetization (QTM) - a new approach to design highly anisotropic dysprosium organometallic complexes.

Theoretical exploration of single-molecule magnetic and single-molecule toroic behaviors in peroxide-bridged double-triangular {MII3LnIII3} (M = Ni, Cu and Zn; Ln = Gd, Tb and Dy) complexes.

Detailed state-of-the-art ab initio and density functional theory (DFT) calculations have been undertaken to understand both Single-Molecule Magnetic (SMM) and Single-Molecule Toroic (SMT) behaviors of fascinating 3d-4f {M3Ln3} triangular complexes having the molecular formula [MII3LnIII3(O2)L3(PyCO2)3](OH)2(ClO4)2·8H2O (with M = Zn; Ln = Dy (1), Tb (2) & Gd (3) and M = Cu; Ln = Dy (4), Tb (5) & Gd (6)) and [Ni3Ln3(H2O)3(mpko)9(O2)(NO3)3](ClO4)·3CH3OH·3CH3CN (Ln = Dy (7), Tb (8), and Gd (9)) [mpkoH = 1-(pyrazin-2-yl)ethanone oxime]. All these complexes possess a peroxide ligand that bridges the {LnIII3} triangle in a μ3-η3:η3 fashion and the oxygen atoms/oxime of co-ligands that connect each MII ion to the {LnIII3} triangle. Through our computational studies, we tried to find the key role of the peroxide bridge and how it affects the SMM and SMT behavior of these complexes. Primarily, ab initio Complete Active Space Self-Consistent Field (CASSCF) SINGLE_ANISO + RASSI-SO + POLY_ANISO calculations were performed on 1, 2, 4, 5, 7, and 8 to study the anisotropic behavior of each Ln(III) ion, to derive the magnetic relaxation mechanism and to calculate the LnIII-LnIII and CuII/NiII-LnIII magnetic coupling constants. DFT calculations were also performed to validate these exchange interactions (J) by computing the GdIII-GdIII and CuII/NiII-GdIII interactions in 3, 6, and 9. Our calculations explained the experimental magnetic relaxation processes and the magnetic exchange interactions for all the complexes, which also strongly imply that the peroxide bridge plays a role in the SMM behavior observed in these systems. On the other hand, this peroxide bridge does not support the SMT behavior. To investigate the effect of bridging ions in {M3Ln3} systems, we modeled a {ZnII3DyIII3} complex (1a) with a hydroxide ion replacing the bridged peroxide ion in complex 1 and considered a hydroxide-bridged {CoIII3DyIII3} complex (10) having the formula [Co3Dy3(OH)4(OOCCMe3)6(teaH)3(H2O)3](NO3)2·H2O. We discovered that as compared to the LoProp charges of the peroxide ion, the greater negative charges on the bridging hydroxide ion reduce quantum tunneling of magnetization (QTM) effects, enabling more desirable SMM characteristics and also leading to good SMT behavior.