Symmetric Ligand Research Articles

Nickel(II), copper(II) and zinc(II) complexes containing symmetrical Tetradentate Schiff base ligand derived from 3,5-diiodosalicylaldehyde: Synthesis, characterization, crystal structure and antimicrobial activity

Novel transition metal complexes of nickel(II), copper(II) and zinc(II) with a symmetrical tetradentate Schiff base, obtained by condensation of 1,3-diaminopropane and 3,5-diiodosalicylaldehyde, N,N′-bis(3,5-diiodosalicylaldehyde)-1,3-diaminoporpane (H2L), have been prepared and characterized by elemental (CHN), FT-IR, UV–Vis and 1H NMR spectroscopic techniques. Out of these, copper (Cu(L)) and zinc (Zn(L)) complexes were isolated in the form of single crystals and characterized by single-crystal X-ray diffraction studies. In the Cu(L) complex, the geometry was found to be slightly distorted square planar, whereas the Zn(L) complex adapted slightly distorted octahedral geometry due to the attachment of two pyridine rings. The antibacterial screening of the prepared compounds was carried out by taking two Gram-positive (Staphylococcus aureus and Bacillus cereus) and two Gram-negative (Escherichia coli and Pseudomonas aeruginosa) bacterial strains. The appearance of zones of inhibition clearly depicted that the complexes have more retardation potential as compared to the Schiff base ligand.

Exploring the synthesis and characterization of fac-Re(CO)3L complexes using diethylenetriamine derivative functionalized at the central nitrogen

The aim of this research is to develop new rhenium complexes with favorable bio-distribution properties which can be used as radiometal complexes or for conjugation with biomolecules for the development of targeted radiolabelled biopharmaceuticals. Two metals of interest utilized in radiopharmaceuticals are technetium and rhenium, both of which share similar chemical and structural properties. The coordination chemistry of these metals is highly dependent upon ligands that are structurally and chemically robust among other factors. The synthesis of new symmetrical tridentate ligands and ligand conjugation methods will expand the likelihood of developing suitable fac-[Re(CO)3L]n compounds with promising biomedical properties and were consequently the subject of this investigation. In order to accomplish this, the design, synthesis, characterization and X-ray structure of new water-soluble rhenium complexes for assessing metal binding to biomolecules were investigated. Three diethylenetriamine (dien) derivatives, 2-(bis(2-aminoethyl)amino)-N-(2-oxo-4-(trifluoromethyl)-2H-chromen-7-yl)acetamide (atfcdien, 3), 2-(bis(2-aminoethyl)amino)-N-(3,5-bis(trifluoromethyl)benzyl)acetamide (tfmedien, 6), and N-benzyl-2-(bis(2-aminomethyl)amino)acetamide (badien, 9) and their rhenium complexes were synthesized. 1H NMR spectroscopy, mass spectrometry and X-ray crystallography techniques were employed to characterize the ligands and their rhenium complexes [Re(CO)3atfcdien]Br (10), [Re(CO)3tfmedien]Br (11) and [Re(CO)3badien]Br (12). 1H NMR studies were conducted to examine chelated Re complexes revealed a consistent downfield shift of the CH signal of the dien moiety for all three new ligands.

A novel benzimidazole based cadmium (II) dinuclear complex as bioactive material with different coordination number and their interactions with BSA and HSA: Synthesis, characterization and docking studies

A novel dinuclear cadmium (II) complex [Cd2(H4PDTB)(η (Schenk et al., 2012 [1])-NO3)2(η (Mitic et al., 2006 [2])-NO3)2H2O]·3H2O having symmetrical ligand N,N,N′,N′-tetrakis-(1H-benzimidazol-2ylmethyl)propane-1,3-diamine (H4PDTB) having N6 donor set was synthesized. It was thoroughly characterized by different spectroscopic and elemental analysis. Single crystals of the dinuclear metal complex were grown and the structure of the complex was authenticated by X-ray crystal structure determination. The structural investigations revealed that the two metal centres rest in remarkably different coordination environments. The dinuclear complex comprised of two crystallographically unique metal centres exhibiting coordination number asymmetry despite symmetric nature of the H4PDTB ligand. The ancillary nitrato-ligand also exhibited dual binding behaviour towards cadmium (II) centres. It coordinated to the first metal centre (Cd1) only in monodentate fashion whereas it exhibited only bidentate binding mode with second metal centre (Cd2). The dinuclear cadmium (II) complex presented in this report sets the first example of coordination number asymmetric metal complex bearing symmetric ligand without any endogenous bridge to date. Photoluminescence properties of the ligand and the dinuclear metal complex were investigated in the solution state and enhancement in emission intensity was observed after complexation. Furthermore, binding of the synthesized complex to bovine serum albumin (BSA) and human serum albumin (HSA) was studied using computational tools.

Revisiting Dinuclear Ruthenium Water Oxidation Catalysts: Effect of Bridging Ligand Architecture on Catalytic Activity.

An attractive catalytic pathway for the conversion of water to oxygen would involve two metal oxide centers combining in a constructive sense to make O═O. This prospect makes the study of certain dinuclear transition metal complexes particularly attractive. In this work, we describe the design and synthesis of two symmetrical bis-tridentate polypyridine ligands 6 and 12 that bind two RuII centers at a separation of 3.6 Å in 7 and 5.7 Å in 13. In the presence of CeIV at pH = 1, these systems oxidize water with the system having the more proximal metals being more reactive. In the case of the more proximal metal centers, the bridging ligand is a 3,6-disubstituted pyridazine which, under the influence of CeIV, cleaves into two [Ru(bpc)(pic)2CH3CN]+ fragments (14) which then function as the actual catalyst (bpc = 2,2'-bipyridine-6-carboxylate, pic = 4-methylpyridine). The second dinuclear catalyst contains a central pyrimidine ring which is less sensitive to oxidative decay and hence less reactive. Caution is advised in the use of CeIV as a sacrificial electron acceptor due to unexpected oxidative decay of the catalyst.

MOFs assembled from C3 symmetric ligands: structure, iodine capture and role as bifunctional catalysts towards the oxidation-Knoevenagel cascade reaction.

Three new NiII/CoII-metal organic frameworks were self-assembled by the reaction of C3 symmetric 1,3,5-tribenzoic acid (H3BTC) and 2,4,6-tris(4-pyridyl)-1,3,5-triazine (4-TPT) ligands and NiII/CoII salts under solvothermal conditions. Isomorphous MOF1 and MOF2 exhibit a 3D pillar-layer framework based on binuclear M2(OH)(COO)2 units connected by tritopic BTC3- and 4-TPT ligands with a novel (3,5)-connected topology net. MOF3 displays a 3-fold interpenetrated 3D network exhibiting a (3,4)-connected topology net. The porous MOF3 can reversibly take up I2. The activated MOFs contain both Lewis acid (NiII center) and basic (uncoordinated pyridyl or carboxylic groups) sites, and act as bifunctional acid-base catalysts. The catalytic measurements demonstrate that the activated MOF3 exhibits good activities for benzyl alcohol oxidation and the Knoevenagel reaction and can be recycled and reused for at least four cycles without losing its structural integrity and high catalytic activity. Thus, the catalytic properties for the oxidation-Knoevenagel cascade reaction have also been studied.

Two Cu(II) and Co(II) Coordination Polymers: Important Values on Colon Cancer Patients by Reducing Insulin Resistance.

In the current study, via utilizing H5L (H5L = 2,4-di(3',5'-dicarboxylphenyl)benzoic acid), the symmetrical rigid polycarboxylic acid ligand with V-shape geometry, two new coordination polymers containing Cu(II) and Co(II) have been produced, and their chemical formulae respectively are {[Co5(L)2(H2O)12]·6H2O} n (1) and {[H2N(Me)2][Cu2(L)(H2O)]·DMF·H2O} n (2), leading to a variety kinds of coordination patterns of H5L and multifunctional skeletons. Their inhibitory activity on the insulin resistance of colon cancer patients was assessed. In addition, the detailed mechanism of the compound was also investigated. Firstly, the detection of enzyme-linked immunosorbent assay was carried out and the Tumor Necrosis Factor-α (TNF-α) level and the Interleukin-1β (IL-1β) level was detected. Then, the glucose concentration was determined with blood glucose meter. Next, the insulin receptor expression levels of β cells were determined with the real time reverse transcription-polymerase chain reaction assay. Ultimately, the cytotoxicity of compounds 1 and 2 was determined with Cell Counting Kit-8 assay.

Syntheses, Structures, Magnetic Properties and Antibacterial Activities of Two Copper(II) Azido Complexes with Varied Nuclearities Containing Symmetrical 1,3-Diammine as Chelator

Two copper(II) azido complexes of the types mononuclear [Cu(TMEDA)2(N3)2] (1) and dinuclear [Cu(TMEDA)(μ1,1-N3)(N3)]2 (2) [TMEDA = trimethylenediamine; N3 – = azide ion] have been synthesized and characterized. X-ray structural analysis revealed that each copper(II) center in complex 1 adopts a distorted octahedron geometry with a CuN6 chromophore ligated through four N atoms of two different symmetrical TMEDA ligands as bidentate chelator and two N atoms of two terminal azides. In complex 2, each copper(II) center adopts a distorted square pyramidal geometry with a CuN5 chromophore ligated through two N atoms of TMEDA as bidentate chelator and two N atoms of two different azides as μ1,1-N3 bridging mode and one N atom of terminal azide ion. The two copper centers are connected through double μ1,1-N3 bridges affording a dinuclear structure with Cu···Cu separation 3.327(2) Å. In crystalline state, mononuclear units in complex 1 are associated through intermolecular N-H···N and C-H···N hydrogen bonds to form a 2D sheet structure viewed along crystallographic b-axis, whereas dinuclear entities in complex 2 are propagated through intermolecular N-H···N and C-H···N hydrogen bonds to form a 3D network structure viewed along crystallographic a-axis. The Variable-temperature magnetic susceptibility measurement evidenced a dominant antiferromagnetic interaction between the metal centers through μ1,1-azide bridges in complex 2 with J = − 0.40 cm-1. The antibacterial activities of the complexes have also been studied.

Luminescence tuning and sensing properties of stable 2D lanthanide metal–organic frameworks built with symmetrical flexible tricarboxylic acid ligands containing ether oxygen bonds

New Ln-MOFs were yielded by a flexible ligand and lanthanide ions. The colors can be regulated by adjusting the molar ratios of Eu3+/Tb3+, showing promising applications in NB sensing, tunable photoluminescence and pH sensing.

A novel tetranuclear nickel(II) salamo-based complex adopting two open cubic structures: synthesis, chracterization, DFT calculation, Hirshfeld analysis, and fluorescent properties

A novel tetranuclear Ni(II) complex [Ni4(L)2(N3)4Cl(MeOH)3]·CH3COCH3 is synthesized via a symmetrical salamo-based ligand H2L, NiCl2·6H2O, and NaN3. The structure is characte­rized by elemental analyses, IR and UV-Vis spectroscopy, and X-ray diffraction analysis. The X-ray crystal analysis shows that Ni(II) atoms in the Ni(II) complex have distorted octahedral geometries. It is the key factor that the ligand containing 3-position methoxy groups gives rise to the formation of the tetranuclear Ni(II) complex. When NO3– anions are used to bridge two Ni2 atoms, there are two symmetrical open cubic structures. The Ni(II) complex forms a 3D supramolecular structure through intermolecular hydrogen bond interactions. Using the Hirshfeld surface to clarify interactions between the molecules, the percentages of C—H/H—C, O—H/H—O, and H—H/H—H contacts are calculated as 19.0 %, 15.3 %, and 54.0 %, respectively. Density functional theory (DFT) studies show that the stability of the Ni(II) complex is much higher than that of H2L. The calculation of the fluorescence titration experiment can give K = 1.05·108 M–1, which further proves the stability of the Ni(II) complex.

C1-Symmetric PNP Ligands for Manganese-Catalyzed Enantioselective Hydrogenation of Ketones: Reaction Scope and Enantioinduction Model

A family of ferrocene-based chiral PNP ligands is reported. These tridentate ligands were successfully applied in Mn-catalyzed asymmetric hydrogenation of ketones, giving high enantioselectivities ...

A New Class of C2 -Symmetric Chiral Cyclopentadienyl Ligand Derived from Ferrocene Scaffold: Design, Synthesis and Application.

A new class of C2 -symmetric, chiral cyclopentadienyl ligand based on planar chiral ferrocene backbone was developed. A series of its corresponding rhodium(I), iridium(I), and ruthenium(II) complexes were prepared as well. In addition, the rhodium(I) complexes were evaluated in the asymmetric catalytic intramolecular amidoarylation of olefin-tethered benzamides via C-H activation.

Highly Conductive Cobalt Perthiolated Coronene Complex for Efficient Hydrogen Evolution.

Metal-bis(dithiolene) is one of the most promising structures showing redox activity, excellent electron transport and magnetic properties as well as catalytic activities. Perthiolated coronene (PTC), an emerging highly symmetric ligand containing the smallest graphene nanoplate was employed to manufacture a hybrid material with fused metal-bis(dithiolene) and graphene nanoplate, and it has been demonstrated as an efficient strategy for the construction of multifunctional materials recently. Herein, Co-PTC, a 2D MOF containing Co-bis(dithiolene) and coronene units is prepared via a homogeneous reaction for the first time as powder samples, which are bar-shaped microparticles composed of nanosheets. A neutral formula of [Co3 (C24 S12 )]n is verified for Co-PTC. Co-PTC plays an ultrahigh conductivity of approximately 45 S cm-1 at room temperature as compressed samples, which is among the highest value ever reported for the compressed powder samples of conducting MOFs. Moreover, Co-PTC exhibits good electrocatalytic performance in the hydrogen evolution reaction (HER) with a Tafel slope of 189 mV decade-1 and an operating overpotential of 227 mV at 10 mA cm-1 with pH=0, as well as a remarkable stability in the extremely acidic aqueous solutions, which is the best hydrogen evolution properties among metal-organic compounds.

Synthesis, structure and properties of a novel self-assembled tetranuclear copper(II) complex derived from carboxylate-based multidentate ligand

A novel tetranuclear copper(II) complex, [Cu(H2O)5][Cu4(cpdp)2(adip)]ClBr∙2CH3OH·8H2O (1) of carboxylate-based symmetrical multidentate ligand, H3cpdp [H3cpdp = N,N'-Bis[2-carboxybenzomethyl]-N,N'-Bis[2-pyridylmethyl]-1,3-diaminopropan-2-ol; adip = adipate], has been synthesized and fully characterized. Complex 1 has been synthesized by carrying out reaction of ligand H3cpdp with stoichiometric amounts of CuCl2·2H2O/Na2(CH2CH2COO)2 in methanol-water in the presence of NaOH at room temperature. The solid state structure of 1 consists of a [Cu4(µ4-adip)] core unit which is held together by two multidentate bridging ligands, cpdp3−. In fact, complex 1 can be viewed as a “dimer-of-dimers” generated by self-assembly of two [Cu2(cpdp)]+ units exclusively bridged by one adipate group in a μ4:η1:η1:η1:η1 fashion. Variable-temperature (2–300 K) magnetic susceptibility measurements disclose the presence of antiferromagnetic interactions among the copper(II) ions. Thermal behaviour of 1 has been investigated by thermogravimetric analysis specifying that the complex is stable up to ∼200 °C.

Conversion from Heterometallic to Homometallic Metal-Organic Frameworks.

Two new heterometallic metal-organic frameworks (MOFs), LnZnTPO 1 and 2, and two homometallic MOFs, LnTPO 3 and 4 (Ln=Eu for 1 and 3, and Tb for 2 and 4; H3 TPO=tris(4-carboxyphenyl)phosphine oxide) were synthesized, and their structures and properties were analyzed. They were prepared by solvothermal reaction of the C3 -symmetric ligand H3 TPO with the corresponding metal ion(s) (a mixture of Ln3+ and Zn2+ for 1 and 2, and Ln3+ alone for 3 and 4). Single-crystal XRD (SXRD) analysis revealed that 1 and 3 are isostructural to 2 and 4, respectively. TGA showed that the framework is thermally stable up to about 400 °C for 1 and 2, and about 450 °C for 3 and 4. PXRD analysis showed their pore-structure distortions without noticeable framework-structure changes during drying processes. The shapes of gas sorption isotherms for 1 and 3 are almost identical to those for 2 and 4, respectively. Solvothermal immersion of 1 and 2 in Tb3+ and Eu3+ solutions resulted in the framework metal-ion exchange affording 4 and 3, respectively, as confirmed by photoluminescence (PL), PXRD, IR, inductively coupled plasma atomic emission spectroscopy (ICP-AES), and energy-dispersive X-ray (EDX) analyses.

Synthesis and Biological Studies on Dinuclear Gold(I) Complexes with Di-(N-Heterocyclic Carbene) Ligands Functionalized with Carbohydrates.

The design of novel metal complexes with N-heterocyclic carbene (NHC) ligands that display biological activity is an active research field in organometallic chemistry. One of the possible approaches consists of the use of NHC ligands functionalized with a carbohydrate moiety. Two novel Au(I)–Au(I) dinuclear complexes were synthesized; they present a neutral structure with one bridging diNHC ligand, having one or both heterocyclic rings decorated with a carbohydrate functionality. With the symmetric diNHC ligand, the dicationic dinuclear complex bearing two bridging diNHC ligands was also synthesized. The study was completed by analyzing the antiproliferative properties of these complexes, which were compared to the activity displayed by similar mononuclear Au(I) complexes and by the analogous bimetallic Au(I)–Au(I) complex not functionalized with carbohydrates.

An investigation of comparative substitution behavior of bifunctional trans‐platinum(II) complexes with symmetric and asymmetric alkylamine ligands

AbstractThis study was undertaken to investigate the comparative substitution behavior of mononuclear trans‐platinum(II) complexes with symmetric and asymmetric amine ligands. The rate of substitution of the aqua moeities from the complexes trans‐[Pt(NH3)2(H2O)2](ClO4)2 (tPt), trans‐[Pt(NH3)(NH2C2H5)(H2O)2](ClO4)2 (tPt2H2O), trans‐[Pt(NH3)(NH2C3H7)(H2O)2](ClO4)2 (tPt3H2O), [trans‐Pt(OH2)2(NH2CH3)2](ClO4)2 (tPtM), and [trans‐Pt(OH2)2{NH2CH(CH3)2}2](ClO4)2 (tPtR), by three nucleophiles, namely thiourea (TU), 1,3‐dimethylthiourea (DMTU), and 1,1,3,3‐tetramethylthiourea (TMTU) was studied under pseudo–first‐order conditions as a function of concentration and temperature by stopped‐flow spectrophotometry. All the substitution reactions of each of the trans‐platinum(II) complexes proceeds by a stepwise mechanism involving rate‐determining substitution of the first aqua ligand followed by a fast second substitution step, without any intermediates formed. The reactions were second order overall (rate = kobs[complex] where kobs = k2[nucleophile]), first order in both [complex] and [nucleophile]. The reactivity of the complexes was essentially governed by both steric and electronic factors. Comparing the second‐order rate constants for the substitution reactions of the mononuclear diaqua trans‐platinum(II) complexes with the thiourea‐based nucleophiles, the observed trend follows: tPt > tPt2H2O > tPtM > tPt3H2O > tPtR. This reactivity trend is consistent with the pKa values obtained for the first deprotonation step. The reactivity of the nucleophiles with the complexes decreases with an increase in steric demand in the following order: TU > DMTU > TMTU. The low positive values of activation enthalpy and large negative values of activation entropy indicate an associative mechanism of substitution in all the complexes. The computational modeling using density functional theory calculations was employed to provide theoretical interpretation of kinetic data.

Lanthanide complexes based on a C3 symmetric tripodal ligand and potential application as fluorescent probe of Fe3+

Based on a novel C3 symmetric tripodal ligand 1,1′,1′′-[(2,4,6-trimethyl-1,3,5-benzenetriyl)tris(methylene)]tris[2(1H)-pyridinone], eight isostructural lanthanide coordination complexes have been constructed. The one-dimensional ladder-like chain structures in these complexes are packed together through the interaction of hydrogen bonding and π-π stacking, leading to the formation of a three-dimensional structure with one-dimensional channels. A systematic study on Ln-O bond lengths in this family of complexes revealed that Ln-O distances exhibited a trend according to the lanthanide contraction. And the torsion angles that define the ligand conformation are different for the pyridone groups on distinct side of the plane of the central phenyl ring. Selected complex from the family shows highly selective and sensitive fluorescence quenching by Fe3+ ion, which is not affected by other common metal ions. The Stern–Volmer curve regarding the fluorescence quenching of Fe3+ toward the complex exhibits perfect linearity for a variety of concentrations, demonstrating the complex to be a good candidate as highly selective, efficient, and quantitative fluorescent probe for Fe3+.

A One-Step Preparation of Tetradentate Ligands with Nitrogen and Phosphorus Donors by Reductive Amination and Representative Iron Complexes.

The synthesis and use of the first examples of unsymmetrical, mixed phosphine donor tripodal NPP2' ligands N(CH2CH2PR2)2(CH2CH2PPh2) are presented. The ligands are synthesized via a convenient, one pot reductive amination using 2-(diphenylphosphino)ethylamine and various substituted phosphonium dimers in order to introduce mixed phosphine donors substituted with P/P', those being Ph/Cy (2), Ph/iPr (3), Ph/iBu (4), Ph/o-Tol (5), and Ph/p-Tol (6). Additionally, we have developed the first known synthesis of a symmetrical tripodal NP3 ligand N(CH2CH2PiBu2)3 using bench safe ammonium acetate as the lone nitrogen source (7). This new protocol eliminates the use of extremely dangerous nitrogen mustard reagents typically required to synthesize NP3 ligands. Some of these tetradentate ligands and also P2NN' ligands N(CH2-o-C5H4N)(CH2CH2PR2)2 (P2NN'-Cy, R = Cy; P2NN'-Ph, R = Ph) prepared by reductive amination using 2-picolylamine are used in the synthesis and reactions of iron complexes. FeCl2(P2NN'-Cy) (8) undergoes single halide abstraction with NaBPh4 to give the trigonal bipyramidal complex [FeCl(P2NN'-Cy)][BPh4] (9). Upon exposure to CO(g), complex 9 readily coordinates CO giving [FeCl(P2NN'-Cy)(CO)][BPh4] (10), and further treatment with an excess of NaBH4 results in formation of the hydride complex [Fe(H)(P2NN'-Cy)(CO)][BPh4] (11). Our previously reported complex FeCl2(P2NN'-Ph) undergoes double halide abstraction with NaBPh4 in the presence of the coordinating solvent to give [Fe(NCMe)2(P2NN'-Ph)][BPh4]2 (12). Ligand 3 can be coordinated to FeCl2, and upon sequential halide abstraction, treatment with NaBH4, and exposure to an atmosphere of dinitrogen, the dinitrogen hydride complex [Fe(H)(NPP2'-iPr)(N2)][BPh4] (13) is isolated. Our symmetrical NP3 ligand 7 can also be coordinated to FeCl2 and, upon exposure to an atmosphere of CO(g), selectively forms [FeCl(NP3)(CO)][BPh4] (14) after salt metathesis with NaBPh4. Complex 14 can be treated with an excess of NaBH4 to give the hydride complex [Fe(H)(NP3)(CO)][BPh4] (15), which can further be deprotonated/reduced to the Fe(0) complex Fe(NP3)(CO) (16) upon treatment with an excess of KH.

STRUCTURALLY CHARACTERIZED SELF-ASSEMBLED HETEROBIMETALLIC Ni(II)–Eu(III)-SALAMO-BIPYRIDINE COORDINATION POLYMER: SYNTHESIS, PHOTOPHYSICAL AND ANTIMICROBIAL PROPERTIES

An independent self-assembling heterobimetallic [Ni(II)–Eu(III)] salamo-like coordination polymer, $$^1_\infty$$ [Ni(L)Eu(NO3)3(4,4′-bipy)], is synthesized by the one-pot reaction of a symmetrical salamo-like hexadentate ligand (H2L = 6,6′-dimethoxy-2,2′-[1,2-ethylenedioxybis(nitrilomethylidyne)]diphenol), Ni(OAc)2·4H2O, Eu(NO3)3·6H2O, and 4,4′-bipy. The coordination polymer is obtained by the reaction in the 1:1:1:1 ratio and characterized by elemental analyses, IR and UV-Vis absorption spectra, and single crystal X-ray diffraction. The newly synthesized polymer is constructed from heterobimetallic [Ni(II)(L)Eu(III)] units connected by the 4,4′-bipy exodentate ligand bearing N donor atoms. Meanwhile, the hydrogen bonding, π⋯π stacking and C–H⋯π interactions play an important role in the structure of the coordination polymer. In terms of the antibacterial activity, the polymer dissolved in DMF has a good antibacterial effect on Staphylococcus aureus.

Rational design of 2D organic magnets with giant magnetic anisotropy based on two-coordinate 5d transition metals

As a new class of single-molecule magnets, two-coordinate complexes of open-shell transition metals are comparatively rare and have attracted interest due to their high degree of coordinative unsaturation. However, the dynamic distortion associated with the low coordination number of the metal center hinders the applications of high-density information storage, quantum computing, and spintronics. Here, we propose a series of stable 2D metal–organic frameworks constructed by ideal (1, 3, 5)-benzenetricarbonitrile (TCB) molecules and 5d transition metals (Hf, Ta, W, Re, Os, and Ir) with a highly symmetrical ligand field and rigid π conjugated framework. Among them, TCB-Re exhibits intrinsic ferromagnetic ordering with a considerably large magnetic anisotropic energy (MAE) of 19 meV/atom and high Curie temperature (TC) of 613 K. Under biaxial strain, diverse magnetic states (such as ferromagnetic, paramagnetic, and antiferromagnetic states) can be achieved in TCB-Re by the complicated competition between the in-plane d–px/y–d and out-of-plane d–pz–d superexchange interactions. At a small compressive strain of 0.5%, the MAE for perpendicular magnetization increases substantially to 120 meV/atom; meanwhile, the magnetization and TC above room temperature are well retained. Our results not only extend two-coordinate transition metal complexes to continuous 2D organic magnets but also demonstrate an effective method of strain engineering for manipulating the spin state and MAE.