From Bowls to Capsules: Assembly of Hexanuclear NiII Rings Tailored by Alkali Cations

An anionic hexanuclear Ni^II metallamacrocycle with endo and exo linking sites has been employed as a building block to generate a series of capsules and bowls of nanometric size. The supramolecular arrangement of the {Ni₆} rings was tailored by the size of the alkali cations, showing the transition from {Ni₆-M₂-Ni₆} capsules (M=Li^I and Na^I) to {Ni₆-M} bowls (M=K^I and Cs^I). The alkyl co-cations are determinant to stabilize the assemblies by means of CH⋅⋅⋅π interactions on the exo side of the metallamacrocycles. The effect on the topology of the supramolecular assemblies of the cation size, cation charge, Et₃NH⁺ or Me₄N⁺ counter cations has been analyzed. Magnetic measurements reveal the presence of ferromagnetic and antiferromagnetic interactions inside the rings that allow a S=0 ground state.     

Linear Copper Complex Arrays as Versatile Molecular Strings: Syntheses,Structures, Luminescence,and Magnetism

The defined linear arrangement of metal atoms in discrete coordination complexes or polymers is still one of the most intriguing challenges in synthetic chemistry. These chain arrangements are of fundamental importance, because of their potential applications as molecular wires and single molecule magnets (SMM) in microelectronic devices on a molecular scale. Oligonuclear Group 11 metal complexes with suitable bridging ligands, specifically those that are based on copper as the first choice of a cheap precursor coinage metal, are of particular interest in this regard. This is due to the superior luminescence properties of these linear clusters that often show d¹⁰⋅⋅⋅d¹⁰ interactions in their molecular structures. The combination of Cu^I with heavier coinage metal ions results in tunable emissive arrays that are also stimuli-responsive. Thus, both linear multinuclear Cu^I and linear heteropolymetallic Cu^I/Ag^I as well as Cu^I/Au^I clusters are excellent candidates for applications in molecular/organic light-emitting devices (OLEDs). Alternatively, paramagnetic multinuclear cupric arrays are prominent as potential molecular wires with enhanced magnetic properties through multiple coupled d⁹ centers. This Review covers the whole range of linear multinuclear assemblies of cuprous and cupric ions in complexes and coordination polymers, their syntheses, photophysical behavior, and magnetic properties. Moreover, recent advances in the rapidly progressing field of hetero-Cu^I/Ag^I and Cu^I/Au^I molecular strings are also discussed.     

A cubane-type nickel single-molecule magnet with exchange-biased quantum tunneling of magnetization

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Synthesis,crystal structure and magnetic properties of diaquabis(2,6‐diamino‐7H‐purin‐1‐ium‐κN9)bis(4,4′‐oxydibenzoato‐κO)cobalt(II) dihydrate

The title mononuclear Co^II complex, [Co(C₅H₇N₆)₂(C₁₄H₈O₅)₂(H₂O)₂]·2H₂O, has been synthesized and its crystal structure determined by X‐ray diffraction. The complex crystallizes in the triclinic space group P, with one formula unit per cell (Z = 1 and Z′ = ). It consists of a mononuclear unit with the Co^II ion on an inversion centre coordinated by two 2,6‐diamino‐7H‐purin‐1‐ium cations, two 4,4′‐oxydibenzoate anions (in a nonbridging κO‐monodentate coordination mode, which is less common for the anion in its Co^II complexes) and two water molecules, defining an octahedral environment around the metal atom. There is a rich assortment of nonbonding interactions, among which a strong N⁺—H…O⁻ bridge, with a short N…O distance of 2.5272 (18) Å, stands out, with the H atom ostensibly displaced away from its expected position at the donor side, towards the acceptor. The complex molecules assemble into a three‐dimensional hydrogen‐bonded network. A variable‐temperature magnetic study between 2 and 300 K reveals an orbital contribution to the magnetic moment and a weak antiferromagnetic interaction between Co^II centres as the temperature decreases. The model leads to the following values: A (crystal field strength) = 1.81, λ (spin‐orbit coupling) = −59.9 cm⁻¹, g (Landé factor) = 2.58 and zJ (exchange coupling) = −0.5 cm⁻¹.     

A Redox‐Active Bridging Ligand to Promote Spin Delocalization,High‐Spin Complexes,and Magnetic Multi‐Switchability

A dinuclear Co^II complex, [Co₂(tphz)(tpy)₂]ⁿ⁺ (n=4, 3 or 2; tphz: tetrapyridophenazine; tpy: terpyridine), has been assembled using the redox‐active and strongly complexing tphz bridging ligand. The magnetic properties of this complex can be tuned from spin‐crossover with T_1/2≈470 K for the pristine compound (n=4) to single‐molecule magnet with an S_T=5/2 spin ground state when once reduced (n=3) to finally a diamagnetic species when twice reduced (n=2). The two successive and reversible reductions are concomitant with an increase of the spin delocalization within the complex, promoting remarkably large magnetic exchange couplings and high‐spin species even at room temperature.     

Two Diammonium Copper Azides with Similar Layerlike Magnetic Substructures Made of Chains of Serially Connected Cu6 Rings Show Cation‐Modulated Magnetism

We present here the first examples of Cu–azide compounds synthesized by using protonated diamine ions as cationic templates: (dmenH₂)[Cu₆(N₃)₁₄] and (trimenH₂)[Cu₆(N₃)₁₄] (dmenH₂²⁺: N,N′‐dimethylethylenediammonium; trimenH₂²⁺: N,N,N′‐trimethylethylenediammonium). Both compounds possess a similar, rarely observed anionic Cu–azide layer, which consists of [Cu₆(N₃)₁₄^2?]_n anionic chains linked by asymmetric end‐to‐end azido bridges. The chain, in turn, is made up of elongated Cu₆ rings, with double and single end‐on azido linkages between the square‐planar Cu²⁺ sites within the ring and double end‐on azido bridges serially connecting the rings. The molecular geometry results in ferromagnetic interactions within the Cu–azide layer in both compounds. The interlayer separations are determined by the cations, with the shortest interlayer Cu???Cu separations being 8.016 Å for the dmenH₂²⁺ compound and 9.106 Å for the trimenH₂²⁺ compound. These different interlayer separations tune the magnetic properties of the two materials. The dmenH₂²⁺ compound displays long‐range antiferromagnetic ordering at lowtemperature and short‐range ferromagnetic interaction at high temperature, while only short‐range ferromagnetism was observed in the trimenH₂²⁺compound at 2–300 K.     

密度泛函理论在分子磁学中的应用——混合价三核锰配合物磁性的理论研究

在对混合价化合物分类的基础上, 将双核耦合模型推广到三核磁耦合体系, 重点研究定域与离域两类混合价化合物的磁学性质. 以混合价三核锰为例, 应用密度泛函理论方法计算了定域与离域 [Mn3O(O2CH)6L3]z+(L=pyridine; z=0)化合物的电子结构, 得到与实验可比较的磁耦合常数J. 结果表明, 密度泛函理论(DFT)结合对称性破损(BS)方法可用于此三核混合价体系; 对于完全离域的混合价Mn3Ⅱ,Ⅲ,Ⅲ体系, 必须考虑电子的离域作用对磁耦合的影响, 其Hamiltonian量应该包含双交换参数B. 为便于比较, 同时计算了等价三核锰化合物[Mn3O(O2CH)6L3]z+(L=pyridine; z=1)的磁学性质.