A tetracobalt(II) cluster with a two vertex truncated dicubane topology endogenously supported by carboxylate-based (2-pyridyl)methylamine ligands: magneto-structural and DFT studies

A reaction between CoCl2 and L3-(CO2-)2 (2 : 1 stoichiometry) in CH3OH affords a discrete complex [CoII4-{L3-(CO2-)2}2(μ3-OCH3)2(CH3OH)2(H2O)2Cl2] (1) [L3-(CO2-)2 = 3-[N-{2-(pyridin-2-yl)methyl}amino]-bis(propionate)]. The structure of 1 reveals two terminal mononuclear CoII{L3-(CO2-)2}Cl units connected by a dimeric CoII2(μ3-OCH3)2(CH3OH)2(H2O) unit present in the centre through two methoxo (μ3-OCH3)- and two carboxylate (μ-1,1-OCO-) bridges affording a tetranuclear coordination cluster of Co(II) with a defective dicubane topology. In 1, Co1 (terminal) has distorted octahedral CoIIN2O3Cl and the central Co2 has CoIIO6 coordination. Such coordination arrangements afford the observed topology. Variable-temperature magnetic studies reveal anti-ferromagnetic coupling in 1. Three magnetic exchange interactions (one anti-ferromagnetic and two ferromagnetic: J1 = +3.3 cm-1 (Co⋯Co 3.176 Å; μ-1,1-OCO- and μ3-OCH3 bridges), J2 = -2.5 cm-1 (Co⋯Co 3.228 Å; μ-1-OCO- and μ3-OCH3 bridges) and J3 = +10.6 cm-1 (Co⋯Co 3.084 Å; two μ3-OCH3 bridges)) have been identified, with the inclusion of the orbital reduction parameter (α = Aκ = 1.38), spin-orbit coupling (λ = -158 cm-1) and axial distortion (energy gap Δ = -975 cm-1 between singlet and doublet levels), rationalized by density functional theory (DFT) calculations.

Heterobimetallic cyanide-bridged FeIII(μ-CN)MII complexes (M = Mn and Cu): synthesis, structure and magnetism

Systematic magneto-structural studies reveal ‘[FeIII(Tp)(CN)2(μ-CN)MnIICl(L1/L2)]′ (both antiferromagnetic) and [FeIII(Tp)(CN)2(μ-CN)CuII(L1/L2)]+′(L1 ferro- and L2 antiferromagnetic).

Dimeric Mn(ii), Co(ii), Ni(ii) and Cu(ii) complexes of a common carboxylate-appended (2-pyridyl)alkylamine ligand: structure, magnetism and DFT study

Weak anti- (1) and ferro-magnetic (2–4) interactions are observed in [MII2(L3)2(S)2]2+ (Mn 1, Co 2, Ni 3) (S = MeOH) and Cu 4 (S = none).

Self-assembly of a nonanuclear NiII cluster via atmospheric CO2 fixation: synthesis, structure, collision-induced dissociation mass spectrometry and magnetic property

A novel nonanuclear nickel(ii) cluster identified as [Ni9(OH)6(CO3)2(ba)8(Hdmpz)6(DMF)2]·EtOH·2DMF (SD/Ni9a, Hba = benzoic acid, Hdmpz = 3,5-dimethyl-1H-pyrazole) is successfully constructed from mixed ligands. The single-crystal X-ray diffraction (SCXRD) structural analysis confirms the composition and reveals the "drum-like" inner core structure surrounded by ba- and DMF. Six Hdmpz ligands in their neutral form further sandwich the "drum" up and down, and is hydrogen bonded with two carbonate anions that are derived from the atmospheric CO2 with the help of Et3N. Electrospray ionization mass spectrometry (ESI-MS) reveals that the SD/Ni9a maintains an intact core in the solution with a slight exchange of outer ligands. Detailed collision-induced dissociation (CID) experiments reveal the collision energy (CE)-promoted ligand loss and exchange between ba- and Hdmpz. Furthermore, the magnetic study shows that there is no interaction between the Ni centers at room temperature, whereas the ferromagnetic coupling between the Ni centers is found with an S = 3 spin ground state of the cluster at low temperature. Moreover, the UV-vis spectrum and the photocurrent response measurements show its good optical properties with an indirect bandgap of about 2.35 eV and fast current response upon visible light irradiation.

Ionic strength effect on regulating the synthetic assembly of polyoxometalate clusters with slow magnetic relaxation behavior

Three novel polyoxometalate (POM) clusters of K10Na10[Dy3(H2O)6Ni(H2O)(W3O11)(B-α-SbW9O33)3]·(H2O)45 (1), (NH4)5K4Na8[Dy3(H2O)6SbV(H2O)(W3O11)(B-α-SbW9O33)3]·(H2O)50 (2), and (NH4)9Na[Ni2(H2O)6(WO2)2(B-β-SbW9O33)2]·(H2O)24 (3) were successfully obtained using the same precursor under different ionic strength conditions. Structural analysis showed that compounds 1-3 possess discrepant structural characteristics in 1 M KCl, 1 M NH4Cl, and saturated NH4Cl, respectively. Among them, 2 is the first reported lanthanide cluster including both Sb3+ and Sb5+ in POM derivatives. Furthermore, the analysis of ac magnetic data proved that 1 and 2 embodied dramatic field-induced slow magnetic relaxation, and the effective barrier of 2 was estimated as Ueff/KB = 21.10 K based on the Orbach process. It was found that the structure and magnetic properties of POM materials can be regulated using an effective and satisfactory ionic strength-controlled strategy.

Four 3D coordination polymers based on layers with single syn-anti carboxylate bridges: synthesis, structures, and magnetic properties

Four novel coordination polymers (CPs) based on a new 4-(3,5-dicarboxylphenyl) picolinic acid ligands (H₃L), [M₃(L)₂(H₂O)₆]·4H₂O (M₃ = Mn₃, 1; Co₃, 2; Ni₃, 3, Co_1.01Ni_1.99, 4), have been hydrothermally synthesized, and structurally and magnetically characterized. In these isomorphous CPs, octahedrally coordinated metal ions are linked by the single syn–anti carboxylate bridge (μ-COO) to give linear trinuclear motifs. The motifs are connected through the other single syn–anti carboxylate bridge (μ-COO) to give a 2D (4,4) layer, and the layers are interlinked by the L ligands into 3D frameworks. Magnetic measurement indicates that antiferromagnetic interactions between metal ions are mediated through the single syn–anti carboxylate bridges in 1 and 2, while the same carboxylate bridges in 3 transmit ferromagnetic couplings. The bimetallic CP 4 shows interesting complicated magnetic behaviors due to the competition effect of Co(ii) and Ni(ii) ions.

Four 3D carboxylate-bridged metal(II) compounds were prepared. Mn(II) and Co(II) compounds show AFM interactions, while FM coupling is found in Ni(II) compound. The bimetallic shows interesting competition effect of FM and AFM interactions.

Stabilization of Ni2+ dimers in hexacyano Mo6 cluster-based Prussian blue derivatives: experimental and theoretical investigations of magnetic properties

Herein, two new octahedral molybdenum cyanide cluster compounds, namely [{Ni(NH₃)₆}₄{Ni₂(NH₃)₈}₁][Mo₆Br₆Q₂(CN)₆]₃·12H₂O, Q = S (1) and Se (2), have been synthesized as single crystals by slow diffusion of a solution of nickel chloride into aqueous ammonia solutions of a K₂Cs₂[Mo₆Br₆Q₂(CN)₆] molybdenum cyanide cluster-based compound. Both 1 and 2 were structurally characterized by single-crystal X-ray diffraction. They are isostructural and crystallize in the cubic system (Im3[combining macron]m (no. 229); Z = 2, a = 18.147(1) Å, and V = 5976(1) ų and a = 18.188(2) Å and V = 6016(2) ų for 1 and 2, respectively). 1 and 2 are based on the association of [Mo₆Brⁱ₆Qⁱ₂(CN)^a₆]^4- (Q = S, Se) cluster anions with Ni²⁺ dimer-based cubic [Ni₂(NH₃)₈]⁴⁺ and octahedral [Ni(NH₃)₆]²⁺ cations. The structure is based on 2-fold interpenetrated [{Ni(NH₃)₆}₄{Ni₂(NH₃)₈}₁][Mo₆Br₆Q₂(CN)₆]₃ frameworks related to each other by [½, ½, ½] translation. The unit cell is based on a body-centered cubic framework of cubic [Ni₂(NH₃)₈]⁴⁺. The [Mo₆Brⁱ₆Qⁱ₂(CN)^a₆]^4- (Q = S, Se) cluster units are located in the middle of the edges and at the center of the faces of the cell. The [{Ni(NH₃)₆}]²⁺ cations are located at the center of the cubes of the a/2 edge. The dimers [Ni₂(NH₃)₈]⁴⁺ are stabilized by hydrogen bonds between the cyanide ligands of the cluster unit and the hydrogen atoms of the ammonia molecules. Both compounds exhibit a weak antiferromagnetic coupling within the [Ni₂(NH₃)₈]⁴⁺ dimer entities at low temperatures together with a paramagnetic behavior originating from the cations of the octahedral [{Ni(NH₃)₆}]²⁺ complexes.

Long-range magnetic ordering in a metal-organic framework based on octanuclear nickel(ii) clusters

A novel three-dimensional metal-organic framework [Ni₃(BTC)₂(bpp)₂(H₂O)]·3H₂O (1) based on mixed ligands H₃BTC (1,2,4-benzenetricarboxylic acid) and bpp (1,3-bis(4-pyridyl)propane) was obtained under hydrothermal conditions. Crystal structure analysis reveals that 1 is a framework based on cage-like Ni₈(COO)₁₂ units. Furthermore, long-range magnetic ordering is observed at low temperature.

An unusual zig-zag 1D copper(ii) coordination polymer displaying magnetic phase transition

A new Cu(ii)-based 1D chain was prepared and its magnetic behaviour was investigated, which indicated a magnetic phase transition below 25 K as well as long-range magnetic ordering.