FeIII Ions Research Articles

Energy transfer-mediated multiphoton synergistic excitation for selective C(sp3)–H functionalization with coordination polymer

Activation and selective oxidation of inert C(sp3)–H bonds remain one of the most challenging tasks in current synthetic chemistry due to the inherent inertness of C(sp3)–H bonds. In this study, inspired by natural monooxygenases, we developed a coordination polymer with naphthalenediimide (NDI)-based ligands and binuclear iron nodes. The mixed-valence FeIIIFeII species and chlorine radicals (Cl•) are generated via ligand-to-metal charge transfer (LMCT) between FeIII and chlorine ions. These Cl• radicals abstract a hydrogen atom from the inert C(sp3)–H bond of alkanes via hydrogen atom transfer (HAT). In addition, NDI converts oxygen to 1O2 via energy transfer (EnT), which then coordinates to FeII, forming an FeIV = O intermediate for the selective oxidation of C(sp3)–H bonds. This synthetic platform, which combines photoinduced EnT, LMCT and HAT, provides a EnT-mediated parallel multiphoton excitation strategy with kinetic synergy effect for selective C(sp3)–H oxidation under mild conditions and a blueprint for designing coordination polymer-based photocatalysts for C(sp3)–H bond oxidation.

Binuclear Coordination Assemblies of Metal Tetraphenylporphyrins (M = Mn, Fe, and In) with Anionic Thioindigo Bridges as Promising Magnetic Systems with Tunable Properties.

A series of hybrids comprising two metal (Mn, Fe, and In) tetraphenylporphyrins axially substituted with anionic bidentate trans-thioindigo ligands (TI) were obtained. Substitution of the axial chloride anion by an oxygen atom of the dye forms short M-O bonds. Crystalline binuclear assemblies (TI•-)·{[MnIITPP]0·[MnIIITPP]+}·xC6H4Cl2 (x = 2 for 1 or 1 for 2) and (TI2-){[MIIITPP]+}2·xC6H4Cl2 (M = Fe and x = 2 for 3, M = In and x = 1 for 4) were synthesized. The thioindigo (TI2-) dianion and metal (FeIII and InIII) atoms in TPPs maintain their initial charge states during the formation of 3 and 4, allowing the separation of paramagnetic FeIII or diamagnetic InIII ions by a diamagnetic TI2- bridge. Strong antiferromagnetic coupling is observed between FeIII (S = 5/2) centers in complex 3. Partial reduction of MnIII to MnII occurs upon the formation of 1 and 2, leading to assemblies containing three paramagnetic centers: MnII (S = 5/2), MnIII (S = 2), and TI•- radical anion (S = 1/2). Orthogonal arrangement of TPP and TI molecules in 1 provides strong ferromagnetic coupling. Weak antiferromagnetic coupling is realized in 2 due to the rotation of the TI bridge.

Heavy metal ions in polluted water removable by synthesising a new compounds for dithiocarbamate derivatives

Metal ion poisoning in water and industrial effluents threatens ecosystems and human health. The development of efficient metal ion removal technologies has garnered attention in recent years. This work synthesizes and characterizes dithiocarbamate complexes as metal ion scavengers. Used to make dithiocarbamate ligands. Different metal salts were added to carbon disulfide and the proper amines to initiate substitution reactions. The complexes were characterized using FTIR, UV-Vis, mass spectroscopy, 13C-, 1H-NMR, magnetic susceptibility, melting point, and electrical conductivity molar EC. Data from spectroscopy and analysis indicate the development of two-type macrocyclic complexes with the formula [M(L)]2, where M = FeII, CoII, and ZnII ions. Tetrahedral geometries around the metal core and the second general formula [M(L)(H2O)2]2, where M = MnII, NiII, CuII, suggested octahedral structures. Heavy water pollution has been removed using this essential ligand. Metal ion scavenging of 96–98% was possible with the produced dithiocarbamate complexes. This work developed unique and efficient strategies for metal contamination removal from aquatic settings, promising environmental remediation and human health protection. Optimizing synthesis conditions and scaling up operations are needed to fully use these compounds in real-world applications. KEY WORDS: Dithiocarbamate ligand, Transition metal complexes, Spectral characterization, Coordination chemistry, Dithiocarbamate complexes, Scavenger heavy metal ions Bull. Chem. Soc. Ethiop. 2024, 38(6), 1583-1593. DOI: https://dx.doi.org/10.4314/bcse.v38i6.7

Enhanced chemotherapy response in hepatocellular carcinoma: synergistic effects of miR-122 and doxorubicin co-delivery system inducing apoptosis and DNA damage

BackgroundCancer cells can resist chemotherapy through various mechanisms, diminishing treatment outcomes. Research had indicated that combining miR-122 with doxorubicin (DOX) can improve hepatocellular carcinoma (HCC) therapy.ResultsTo explore this, we created a one-pot co-delivery system, Fe-miR-122/DOX, by coordinating miR-122, DOX, and FeII ions into nanoparticles. These nanoparticles display uniform particle sizes, well-defined morphology, and exceptional colloidal stability in 10% FBS and 20% FBS solution over 24 h. When the ratio of DOX to miR-122 was set at 20:1, the loading efficiency of both drugs reached 54.7% and 55.5%, respectively. Cell experiments confirmed that Fe-miR-122/DOX efficiently delivers both miR-122 and DOX, enabling cytoplasmic delivery through lysosomal escape, facilitated by the positive charge of the nanoparticles. Functionally, miR-122 increases intracellular accumulation of DOX by downregulating P-glycoprotein (P-gp) expression, and it promotes apoptosis by downregulating B-cell lymphoma 2 (Bcl-2), which leads to the upregulation of Caspase-3. Additionally, Fe-miR-122/DOX disrupts cIAPs-mediated anti-apoptotic signals, downregulates PARP-1 expression, hinders DNA repair, promotes DNA fragmentation, enhances caspase-3 expression, and triggers programmed cell death, synergistically enhancing its antitumor efficacy. This synergistic mechanism disrupts DNA repair, amplifying DNA damage and apoptosis. Our cytotoxicity and apoptosis assays (with a HepG2 cell apoptosis rate of 85.98%) demonstrated the potent antitumor capability of Fe-miR-122/DOX.ConclusionsThis innovative system has demonstrated good biocompatibility and has the potential to transform HCC therapy. Future research could focus on optimizing the co-delivery system and assessing its efficacy in clinical trials.

Mössbauer and EPR detection of iron trafficking kinetics and possibly labile iron pools in whole Saccharomyces cerevisiae cells

The kinetics of iron trafficking in whole respiring Saccharomyces cerevisiae cells were investigated using Mössbauer and EPR spectroscopies. The Mössbauer-active isotope 57Fe was added to cells growing under iron-limited conditions; cells were analyzed at different times post iron addition. Spectroscopic changes suggested that the added 57Fe initially entered the labile iron pool, and then distributed to vacuoles and mitochondria. The first spectroscopic feature observed, ∼3min after adding 57Fe plus a 5 to 15min processing dead time, was a quadrupole doublet typical of nonheme high-spin FeII. This feature likely arose from labile FeII pools in the cell. At later times (15-150min), magnetic features due to S=5/2 FeIII developed; these likely arose from FeIII in vacuoles. Corresponding EPR spectra were dominated by a g=4.3 signal from the S=5/2 FeIII ions that increased in intensity over time. Developing at a similar rate was a quadrupole doublet typical of S=0 [Fe4S4]2+ clusters and low-spin FeII hemes; such centers are mainly in mitochondria, cytosol, and nuclei. Development of these features was simulated using a published mathematical model, and simulations compared qualitatively well with observations. In the five sets of experiments presented, all spectroscopic features developed within the doubling time of the cells, implying that the detected iron trafficking species are physiologically relevant. These spectroscopy-based experiments allow the endogenous labile iron pool within growing cells to be detected without damaging or altering the pool, as definitely occurs using chelator-probe detection and possibly occurs using chromatographic separations.

Modulating the isomerization of bpp-modified azoheteroarene by transition metal ions coordination

A new photoswitchable azoheteroarene L was design and synthesized by replacing one of the phenyl rings of azobenzene moiety with a 2,6-di[pyrazol-1-yl]pyridine(bpp) unit. The assembly of L with transition metal ions results in the formation of three metal complexes, namely, M(L)2(OTf)2 (M=ZnII, FeII and CoII). These complexes are fully characterized by ESI-TOF-MS, UV–vis spectrum, 1H NMR spectrum and single-crystal X-ray diffraction. Upon irradiation with 380 nm light, L exhibits excellent E to Z photoisomerization in solution, achieving up to 82 % Z-configuration with a thermotropic isomerization half-life time of 301 days. After coordination with ZnII, FeII and CoII, the photoisomerization properties of L were significantly varied. Coordinating with the ZnII ion, the conversion of Z-L slightly decreased from 82 % to 77 %. However, this coordination significantly extends thermal isomerization half-life time to 564 days, resulting in a 1.9-fold enhancement compared to free Z-L. In contrast, the coordination with open-shell transition metal ions FeII and CoII noticeably inhibits the formation of Z-L and only yields E-L isomers. Moreover, the spin-crossover behavior of Fe(E-L)2(OTf)2 was also investigated. The analysis of variable temperature NMR indicates that Fe(E-L)2(OTf)2 shows a spin transition temperature of 265 K in solution. This work provides valuable insights into tunning conformational transitions of azoheteroarene molecules.

An intelligent and self-assembled nanoscale metal organic framework (99mTC-DOX loaded Fe3O4@FeIII-tannic acid) for tumor targeted chemo/chemodynamic theranostics

BackgroundRecent advances in clinical transformation research have focused on chemodynamic theranostics as an emerging strategy for tackling cancer. Nevertheless, its effectiveness is hampered by the tumor's glutathione antioxidant effect, poor acidic tumor microenvironment (TME) and inadequate endogenous H2O2. Hence, we designed an activatable theranostics (99mTc-DOX loaded AA-Fe3O4@FeIII-TA) that effectively boost the catalytic efficiency of the Fenton-reaction-induced ROS production and augment the chemotherapeutic efficacy combined with diagnostic action.ResultsA cross-linked matrix of tannic acid-ferric salt (FeIII-TA) as a pH-responsive shell onto ascorbic acid-decorated iron-oxide nanoparticles (AA-Fe3O4NPs) was prepared demonstrating a metal–organic- framework (MOF) nanostructure, followed by loading of 99mTc-labelled DOX. The platform (99mTc-DOX loaded AA-Fe3O4@FeIII-TA) displayed suitable physical–chemical properties, including 69.8 nm particle size, 94.8 nm hydrodynamic size, − 21 mV zeta potential, effective FeIII-TA shell crosslinking onto AA-Fe3O4NPs and 94% loading efficiency for 99mTc-DOX. The results of the in-vitro release investigations showed that the platform exhibited a pH-dependent release manner with 98.3% of the 99mTc-DOX being released at pH 5 (simulating the tumor’s pH) and only 10% being released at the physiological pH (pH 7.4). This indicates that there was negligible payload leakage into the systemic circulation during the platform's passive accumulation inside tumor. Due to the acidic TME nature, the MOF shell might be degraded releasing free FeIII, TA and a sustained release of 99mTc-DOX. Besides its chemotherapeutic impact and capacity to raise intracellular H2O2 content, the released 99mTc-DOX might be used as SPECT imaging tracer for concurrent tumor diagnosis. Furthermore, the mild acidity of the tumor may be overcome by the released TA, which might raise the acidification level of cancer cells. The released FeIII, TA and the endogenous GSH could engage in a redox reaction that depletes GSH and reduces FeIII to FeII ions which subsequently catalyze the elevated concentration of H2O2 to reactive •OH via Fenton-like reaction, increasing the effectiveness of chemodynamic therapy. Moreover, the in-vivo evaluation in tumor-bearing mice showed significant radioactivity accumulation in the tumor lesion (16.8%ID/g at 1 h post-injection) with a potential target/non-target ratio of 8.ConclusionsThe 99mTc-DOX loaded AA-Fe3O4@FeIII-TA could be introduced as an effective chemo/chemodynamic theranostics.Graphical

Synthesis, Characterization, and Application of a Polyoxometalates‐Based CuII Complex for Efficient Catalytic Oxidation and Electrochemical Detection

AbstractThe development of eco‐friendly, high‐efficiency polyoxometalates (POMs) catalysts is vital for advancing catalytic oxidation and electrochemical detection in environmental protection. Herein, a POM‐based CuII‐containing complex with the molecular formula [H(4‐AP)]8[Cu2(H2O)4(P2Mo5O23)2]·8H2O (1) (4‐AP = 4‐aminopyridine) is synthesized using the hydrothermal method, and the crystal structure is determined by single X‐ray diffraction (SXRD), infrared (IR) spectroscopy, and powder X‐ray diffraction (PXRD). Structurally, complex 1 exhibits a one dimension (1D) chain arrangement, composed of CuII ions and Strandberg‐type (P2Mo5O23)6− anionic clusters. These 1D chains are further interconnected through [H(4‐AP)]+ ligands, resulting in the formation of a two dimension (2D) supramolecular network. Complex 1 serves as an outstanding heterogeneous catalyst for the oxidation of methyl phenyl sulfide (MPS), demonstrating a remarkable conversion rate of 99% for MPS and a selectivity of 98% toward methyl phenyl sulfoxide (MPSO). In addition to its catalytic capabilities, complex 1 is also employed in the electrochemical detection of FeIII and CrVI ions, with low limits of detection (LODs) at 4.92 µm for FeIII and 7.82 µM for CrVI.

54 K Spin Transition Temperature Shift in a Fe6L4 Octahedral Cage Induced by Optimal Fitted Multiple Guests.

Spin-crossover (SCO) coordination cages are at the forefront of research for their potential in crafting next-generation molecular devices. However, due to the scarcity of SCO hosts and their own limited cavities, the interplay between the SCO host and the multiple guests binding has remained elusive. In this contribution, we present a family of pseudo-octahedral coordination cages (M6L4, M = ZnII, CoII, FeII, and NiII) assembled from a tritopic tridentate ligand L with metal ions. The utilization of FeII ion leads to the successful creation of the Fe6L4-type SCO cage. Host-guest studies of these M6L4 cages reveal their capacity to encapsulate four adamantine-based guests. Notably, the spin transition temperature T1/2 of Fe6L4 is dependent on the multiple guests encapsulated. The inclusion of adamantine yields an unprecedented T1/2 shift of 54 K, a record shift in guest-mediated SCO coordination cages to date. This drastic shift is ascribed to the synergistic effect of multiple guests coupled with their optimal fit within the host. Through a straightforward thermodynamic cycle, the binding affinities of the high-spin (HS) and low-spin (LS) states are separated from their apparent binding constant. This result indicates that the LS state has a stronger binding affinity for the multiple guests than the HS state. Exploring the SCO thermodynamics of host-guest complexes allows us to examine the optimal fit of multiple guests to the host cavity. This study reveals that the T1/2 of the SCO host can be manipulated by the encapsulation of multiple guests, and the SCO cage is an ideal candidate for determining the multiple guest fit.

Detection of Microorganisms Using Artificial Siderophore-FeIII Complex-Modified Substrates.

Four FeIII complexes of typical artificial siderophore ligands containing catecholate and/or hydroxamate groups of tricatecholate, biscatecholate-monohydroxamate, monocatecholate-bishydroxamate, and trihydroxamate type artificial siderophores (K3[FeIIILC3], K2[FeIIILC2H1], K[FeIIILC1H2], and [FeIIILH3]) were modified on Au substrate surfaces. Their abilities to adsorb microorganisms were investigated using scanning electron microscopy, quartz crystal microbalance, and AC impedance methods. The artificial siderophore-iron complexes modified on Au substrates (FeLC3/Au, FeLC2H1/Au, FeLC1H2/Au, and FeLH3/Au) showed the selective immobilization behavior for various microorganisms, depending on the structural features of the artificial siderophores (the number of catecholate and hydroxamate arms). Their specificities corresponded well with the structural characteristics of natural siderophores released by microorganisms and used for FeIII ion uptake. These findings suggest that they were generated via specific interactions between the artificial siderophore-FeIII complexes and the receptors on microorganism surfaces. Our observations revealed that the FeL/Au systems may be potentially used as effective microbe-capturing probes that can enable rapid and simple detection and identification of various microorganisms.

Single-molecule magnet behavior in heterometallic decanuclear [Ln2Fe8] (Ln = Y, Dy, Ho, Tb, Gd) coordination clusters.

Five decanuclear lanthanide-iron clusters, formulated as [Ln2Fe8(hmp)10(μ2-OH)4(μ3-OH)2(μ4-O)4(H2O)6]·6ClO4·xH2O (x ≈ 8, Ln = Y for 1; x ≈ 6, Ln = Dy for 2; x ≈ 6, Ln = Ho for 3; x ≈ 7, Ln = Tb for 4; x ≈ 7, Ln = Gd for 5, Hhmp = 2-(hydroxymethyl)pyridine), have been synthesized and structurally characterized. Single-crystal structural analysis reveals that the cluster consists of six face-sharing defective cubane units. Dynamic magnetic investigations indicated that cluster 2 exhibits single-molecule magnet behavior under a zero dc field eliciting an effective energy barrier of Ueff = 17.76 K and a pre-exponential factor of τ0 = 7.93 × 10-8 s. Investigation of the performance of a series of FeIII-DyIII SMMs indicates that the relatively low energy barrier in 2 is associated with the weak ferromagnetic coupling between FeIII and DyIII ions, while the strength of ferromagnetic interaction in these clusters is mainly related to the bond distances between DyIII and O atoms coordinated to FeIII ions. Clusters 3 and 4 exhibit similar dual relaxation pathways under their respective optimal external applied dc field, where the direct relaxation process occurs in the low-frequency area, which impedes the extraction of the Ueff, while the secondary relaxation process appears at a higher frequency, which is probably a connection with intermolecularly driven relaxation. Our findings offer a magneto-structural correlation model for further investigating the single-molecule magnet behavior in lanthanide-iron systems.

An electrically conducting 3D coronene-based metal-organic framework.

A novel cubic mesoporous metal-organic framework (MOF), consisting of hexahydroxy-cata-hexabenzocoronene (c-HBC) and FeIII ions is presented. The highly crystalline and porous MOF features broad optical absorption over the whole visible and near infrared spectral regions. An electrical conductivity of 10-4 S cm-1 was measured on a pressed pellet.

Hysteretic spin crossover in a Hofmann-type metal–organic framework constructed from a [MoIII(CN)7]4− unit

A unique 3D Hofmann-type framework containing [MoIII(CN)7]4− unit and FeII ion was synthesized and characterized. This compound exhibits an abrupt and hysteretic one-step SCO as well as ferrimagnetic ordering below about 65 K.

Effects of mono- or di-fluoro-substitution on spin crossover behavior in a pair of Schiff base-like FeII-coordination polymers.

Spin crossover (SCO) has long been a hot topic in the field of molecular magnetism owing to its unique bistability character. Rational control of thermal hysteresis and transition temperature (T1/2) is crucial for their practical applications, which rely on precise manipulation of the substituents of SCO coordinating ligands and molecular packing interactions. In this study, we designed two different bridging ligands (2-FDPB: 4,4'-(2-fluoro-1,4-phenylene)dipyridine; 2,3-FDPB: 4,4'-(2,3-difluoro-1,4-phenylene)dipyridine) featuring one and two fluoro substitution on the central benzene ring and applied a Schiff base-like equatorial tetradentate ligand {diethyl(E,E)-2,2'-[4,5-difluoro-1,2-phenyl-bis(iminomethylidyne)]bis(3-oxobutanoate)-(2-)-N,N',O3,O3'} (H2L) to coordinate with the FeII ion. Two FeII-coordination chain polymers [FeII(L)(2,3-FDPB)]·0.25CH2Cl2 (1) and [FeII(L)(2-FDPB)]·0.5CH3OH (2) were obtained. 1 crystallizes in the monoclinic P21/n space group with only one FeII center, while 2 crystallizes in the triclinic P1̄ space group with two independent FeII centers. Unlike the identical 2D layer stacking in 1, 2 exhibited alternating stacking of the extending 2D layers and meshed chains. Magnetic measurements revealed the typical thermally induced spin crossover behavior (SCO): 1 exhibited a 41 K-wide thermal hysteresis with transition temperatures of T1/2↑ = 245 K and T1/2↓ = 204 K, while 2 showed a higher transition temperature (T1/2 = 330 K) with no thermal hysteresis. Magneto-structural correlation studies suggest that the electron-withdrawing effect present in the fluoro substituents does not have a significant impact on the SCO behaviors. Despite the fluoro substituents having a similar atomic radius of hydrogen atoms, variations in the number of these substituents can alter the crystallization behavior of these complexes, which in turn affects the solvents, molecular stacking patterns, and intermolecular interactions, ultimately influencing the SCO behaviors.

Fe3O4@C Magnetite Nanocomposite: An Artificial Peroxidase Nanozyme for Development of A Colorimetric Glucose Biosensor

The horseradish peroxidase (HRP), a natural enzyme, consists of a FeIII ion which plays the role as an active center the enzyme, wherein, the binding of H2O2 to the FeIII...

Water stable colloidal PVP coated spin crossover nanoparticles.

Stable aqueous dispersions of spin-crossover (SCO) doped [FeII(Htrz)2(trz)](BF4) nanoparticles (NPs) were prepared by using water-soluble polyvinylpyrrolidone (PVP) as protecting polymer. The metal or ligand substitution percentage regulated the ultra-small size and morphology of the NPs. At the same time, the colloidal dispersions showed a complete conversion of the LS state to the HS state of the FeII ion.

Optimization of the Extraction Process of Bioactive Compounds from Zingiber officinale Roscoe, Evaluation of Acetylcholinesterase Enzyme Inhibition and Cytotoxic Activity of the Free and Encapsulated Extract

The present study optimized the extraction process of bioactive compounds present in ginger (Zingiber officinale) dried at 80 °C, using ethanol:water 70:30 (v/v) as solvent. The extracts were evaluated for antioxidant activity by the 2,2’-azino-bis(3-ethylbenzothiazoline6-sulfonic acid (ABTS) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical reduction methods and by the chelating activity of FeII ions. It was found that the extraction condition with a temperature of 60 °C and an extraction time of 12 h showed better responses to the tests. Then, the characterization of the compounds was carried out by mass spectrometry and thermal analysis (thermogravimetric (TG), differential thermal analysis (DTA), and differential scanning calorimetry (DSC)), identifying that the main compounds of ginger were gingerols and shogaols, being confirmed by the intensities and characteristics of the thermal graphs. The inhibition of the enzyme acetylcholinesterase (AChE) was evaluated using the Ellman test, which did not show an inhibitory action. Regarding cytotoxic activity, the free extract and encapsulated in liposomes were tested, showing antiproliferative effect at different concentrations for human kidney tumor cells (786-0), liver cells (HUH7.5), and Macaca mullata normal kidney cells (LLC-MK2). Given the results obtained, ginger presents itself as a renewable source of bioactive compounds and can be indicated for applications in the pharmaceutical industry

Controlling the symmetry of hexamonodentate 3d-transition metal complexes through symmetry propagation from high-symmetry Ti-Mo and Zr-Mo clusters via hydrogen-bonding interactions.

The symmetry of one of the simplest hexamonodentate complexes, [M(H2O)6]2+ (M = Fe, Co, Ni, and Zn), was controlled by tuning interactions in the second coordination sphere. Highly symmetric Ti-Mo or Zr-Mo cluster cations acted as symmetry templates, imposing a crystallographic trigonal coordination geometry in the hexamonodentate complexes through intermolecular hydrogen-bonding interactions. Magnetic measurements revealed that the ideal trigonal symmetry results in weak spin-orbit coupling for high-spin FeII complexes, despite the T-term ground state in the octahedral geometry. In contrast, high-spin CoII analogues with the T-term ground state exhibited strong spin-orbit coupling. DFT studies supported that a d6 FeII ion in the D3 symmetry has a 5A1 ground state while a d7 CoII in the same symmetry has a 4E ground state. Single-ion magnet behavior was observed in the CoII complexes. These results demonstrate that incorporating a diamagnetic, highly symmetric cluster enables precise symmetry control in single-ion magnets containing only monodentate ligands.

The Synthesis and Crystal Structures of New One- and Two-Dimensional Fe(II) Coordination Polymers Using Imidazole Derivatives

We studied the synthesis and crystal structures of a new two-dimensional (2D) coordination polymer, {FeII(1-Ethyl-imidazole)2[NiII(CN)4]}n (1), and one-dimensional (1D) coordination polymers, {FeII(1-benzyl-imidazole)4[NiII(CN)4]}n (2) and {FeII(1-Allyl-imidazole)4[NiII(CN)4]}n (3). Compound 1 has a 2D sheet structure, which is a traditional Hofmann-like structure. In compound 1, an octahedral FeII ion is coordinated with the nitrogen atoms of the [NiII(CN)4] planar unit at equatorial positions and monodentate imidazole derivatives at axial positions. The layers construct a parallel stacking array. Compounds 2 and 3 have a 1D chain structure. In compounds 2 and 3, the FeIIN6 coordination environment is formed with four imidazole ligands and two [NiII(CN)4]2− metalloligands. In the [NiII(CN)4]2− unit, two CN substituents act as bidentate ligands that form infinite –Ni–C–N–Fe–N–C–Ni– chains. Herein, we discuss the systematic design of polymeric dimensionality.

Crystal structure of bis-{3-(3,4-di-meth-oxy-phen-yl)-5-[6-(pyrazol-1-yl)pyridin-2-yl]-1,2,4-triazol-3-ato}iron(II)-methanol-chloro-form (1/2/2).

The unit cell of the title compound, [Fe(C18H15N6O2)2]·2CH3OH·2CHCl3, consists of a charge-neutral complex mol-ecule, two methanol and two chloro-form mol-ecules. In the complex, the two tridentate 2-(5-(3,4-di-meth-oxy-phen-yl)-1,2,4-triazol-3-yl)-6-(pyrazol-1-yl)pyridine ligands coordinate to the central FeII ion through the N atoms of the pyrazole, pyridine and triazole groups, forming a pseudo-octa-hedral coordination sphere. Neighbouring tapered mol-ecules are linked through weak C-H(pz)⋯π(ph) inter-actions into one-dimensional chains, which are joined into two-dimensional layers through weak C-H⋯N/C/O inter-actions. Furthermore, the layers stack in a three-dimensional network linked by weak inter-layer C-H⋯π inter-actions of the meth-oxy and phenyl groups. The inter-molecular contacts were qu-anti-fied using Hirshfeld surface analysis and two-dimensional fingerprint plots, revealing the relative contributions of the contacts to the crystal packing to be H⋯H 32.0%, H⋯C/C⋯H 26.3%, H⋯N/N⋯H 13.8%, and H⋯O/O⋯H 7.5%. The average Fe-N bond distance is 2.185 Å, indicating the high-spin state of the FeII ion. Energy framework analysis at the HF/3-21 G theory level was performed to qu-antify the inter-action energies in the crystal structure.