Three heterometallic lanthanide–titanium oxo clusters (LnTOCs) formulated as Eu2Ti4(μ3-O)4(tbba)12(acac)2 (Eu2Ti4, 1, Hacac = acetylacetone), Eu5Ti4(μ3-O)6(tbba)20(Htbba)(THF)2 (Eu5Ti4, 2), and Eu8Ti10(μ3-O)14(Ac)2(tbba)34(H2O)4(THF)2(Htbba)2 (Eu8Ti10, 3) were prepared through the reactions of 4-tert-butylbenzoate (Htbba), rare-earth salts, and Ti(OiPr)4. The solution luminescence investigation discovered a size-dependent quantum yield phenomenon in solution. A solid-state luminescence study showed that these three LnTOCs display temperature-dependent photoluminescent properties. Interestingly, the Eu5Ti4 cluster exhibited the highest quantum yield of 94.9% in the solid state among the reported 3d–4f clusters.

We report two nonanuclear lanthanide complexes, [Ln9(μ4-O)(μ3-OH)8(LH)4(OAc)4(H2O)12]·5ClO4·24H2O (Ln = Gd, 1; Dy, 2), where LH2– is the doubly deprotonated chiral ligand Chromogen I (2-acetamido-2,3-dideoxy-D-erythro-hex-2-enofuranose), one of the many products from the dehydration of N-acetyl-D-glucosamine (GlcNAc). Mass spectroscopic studies established the solution stability of these clusters. Through hydrogen bonding, the cluster complex self-organizes into a nanostructured 54-metal cagelike assembly featuring six of its units occupying the vertices of an octahedron. Free Chromogen I can be obtained in pure form and high yield by a straightforward workup of the cluster complex. This is the first report of dehydrating GlcNAc without the need of a catalyst or forcing conditions.

Three homometallic high-nuclearity clusters, formulated as [(CO3)2@Ln37(LH3)8(CH3COO)21(CO3)12(μ3-OH)41(μ2-H2O)5(H2O)40]·(ClO4)21·(H2O)100 (abbreviated as Ln37, Ln = Gd (1); Tb (2); Eu (3), LH3 = 1,2,3-cyclohexanetriol) and featuring a double cage-like structure, were obtained through the reaction of 1,2,3-cyclohexanetriol, acetate ligand, and Ln(ClO4)3. The largest odd-numbered lanthanide cluster Gd37 exhibits an entropy change (−ΔSm) of 38.7 J kg–1 K–1.

We report the synthesis and photoelectrochemical activity of three lanthanide–titanium oxo clusters (LTOCs), formulated as [Ln8Ti10(μ3-O)14(tbba)34(Ac)2(H2O)4(THF)2]·2Htbba [Ln = Eu (1), Sm (2), and Gd (3); Htbba = 4-tert-butylbenzoic acid; Ac– = acetate]. These stable compounds are efficient catalysts of photoelectrochemical water oxidation with high turnover numbers (7581.0 for 1, 5172.4 for 2, and 5413.0 for 3) and high turnover frequencies (2527.0 for 1, 1724.1 for 2, and 1804.0 for 3). The differences in the photoelectrochemical activity among these three compounds may be related to the differences in their band gaps. This work shows that the heterometallic LTOCs provide a tunable platform for the design of highly effective water oxidation catalysts.

AbstractThe structural phase transition compound {[(CH3)2CHCH2]2NH2}•[CF3COO] (1) has been synthesized based on the diisobutylamine and trifluoroacetic acid. The DSC data reveal that 1 undergoes a phase transition at 277 K (Tc). When one chlorine atom replaces one fluorine atom on trifluoroacetate anion, three order-disorder phase transitions at 251 K (T1), 282 K (T2) and 290 K could be achieved owing to a stepwise release of rotation motions of the anion and cation in {[(CH3)2CHCH2]2NH2}•[CF2ClCOO] (2). Based on the variable temperature crystal structures, the phase transition in compound 1 is triggered by the rotation of three fluorine atoms on the trifluoroacetate anion synchronized with the motions of the methyl groups on the diisobutylammonium cation. However, in compound 2, the phase transitions can be realized by a sequence of motions of both the anion and cation. Besides, the dielectric- temperature dependences were investigated in order to prove this regulation process. All of this investigation will be beneficial to design and synthesis of the novel phase transition materials and molecular dielectric materials on purpose.

•Ionic liquid incorporated within MOF exhibit a fast-ionconductor.•EMIMCl was introduced into the pores of UiO-67(Zr) MOF.•It shows high ionic conductivity (1.67 × 10− 3 S·cm− 1 at 200 °C).•It can work at high-temperature and humidity-independent condition.IL@MOF (IL = ionic liquid; MOF = metal organic framework) as a new type hybrid ionic conductor has attracted research interest. Ionic liquids incorporated within MOFs not only promote the ionic conductivity of ILs, but also mediate the working temperature. In our report, 1-Ethyl-3-methylimidazolium Chloride (EMIMCl) was introduced into the pores of UiO-67(Zr) MOF by taking simple strategy basing on capillary action through specific grinding and diffusing in heating process. The working temperature of EMIMCl@UiO-67 is up to 200 °C. And it shows high ionic conductivity (1.67 × 10− 3 S·cm− 1 at 200 °C). The activation energy was estimated to be 0.37 eV. It is noteworthy that the hybrid material can be regarded as a fast-ion conductor based on the value of high conduction and low Ea. The high-temperature and humidity-independent ion conduction as well as low activation energy make this material potentially useful for electrochemical devices.EMIMCl@UiO-67 as a new hybrid humidity-independent fast-ion conductor could work in high temperature up to 200 °C.Download high-res image (111KB)Download full-size image

A series of heterometallic 3d–4f compounds, formulated as [Ln2Ni2(dcta)2(H2O)8(NO3)2]·8H2O (Ln = Nd (1); Ln = Dy (2)); {[DyNi(dcta)(H2O)6]·Cl·(H2O)2}n (3); {[LnNi(dcta)(H2O)6]·(ClO4)·(H2O)3}n (Ln = La (4); Ln = Nd (5)); {[Gd12Ni12(dcta)12(H2O)24]·[Ni(H2O)6]3·(ClO4)18·(H2O)80}n (6) and {[La12Ni12(dcta)12(H2O)60]·[Ni(H2O)6]3·(ClO4)18·(H2O)30}n (7), (H4dcta = trans-1,2-diaminocyclohexane-N,N,N′,N′-tetraacetic acid), have been obtained through a metalloligand strategy. Structural analysis reveals that [Ni(dcta)]2− acts as a bidentate metalloligand in 1–3, tridentate metalloligand in 4 and 5, and tetradentate metalloligand in 6 and 7. These compounds can be divided into four types according to the dimensionality of the structures. Compounds 1 and 2 are 0D tetranuclear clusters comprised of symmetric [LnNi(dcta)]2 12-membered rings, compound 3 is a 1D chain which is reinforced by hydrogen bonds. Compounds 4 and 5 possess an infinite 2D layer structure with a 63-hcb topology, and compounds 6 and 7 are two 3D frameworks constructed by face-sharing Keplerate-type metal–organic polyhedra. It is interesting that different anions lead to different topology structures. The magnetic properties and thermal stabilities of them are also studied.

A supramolecular compound [C6H11NH3]+[CF3COO]− was synthesized. Investigation on the structure of 1 at different temperatures reveals that it is the disorder of the anions that plays a key role in thermal energy storage. Studies on the thermal and physical properties of 1 indicate that utilization of the sensible heat in 1 can significantly enhance its ability to store thermal energy.

Two high-nuclearity 3d–4f clusters Ln24Zn4 (Ln = Gd and Sm) featuring four Ln6 octahedra encapsulating a Zn4 tetrahedron were obtained through the self-assembly of Zn(OAc)2 and Ln(ClO4)3. Quantum Monte Carlo (QMC) simulations show the antiferromagnetic coupling between Gd3+ ions. Studies of the magnetocaloric effect (MCE) show that the Gd24Zn4 cluster exhibits the entropy change (−ΔSm) of 31.4 J kg−1 K−1.

Magnetocaloric effect (MCE) and thermal conductivity of two gadolinium hydroxides, Gd(OH)3 (1) and Gd2O(OH)4(H2O)2 (2), are investigated. Magnetic studies indicate that both 1 and 2 exhibit antiferromagnetic interaction, and the MCE values for 1 and 2 at 2 K and ΔH = 7 T are 62.00 J kg−1 K−1 and 59.09 J kg−1 K−1, respectively. Investigation of their thermal conductivity reveals that the thermal conductivity for 1 is significantly better than that for 2.

Two enantiomorphic 3D lanthanide coordination polymers of {[Dy5(L)4(H2O)10][Dy(H2O)7][Na(H2O)5]}·(ClO4)7·(H2O)15 (1a for R and 1b for S) with chiral helical chains were synthesized based on an achiral ligand N-(2-hydroxyethyl)ethylenediamine-N,N′,N′-triacetic acid (H3L) and Dy(ClO4)3. Crystal analysis revealed that 1a and 1b were crystallized in chiral space groups P4132 and P4332, respectively. The absolute configurations of the two structures were evidenced by vibrational circular dichroism (VCD) spectra with one single crystal sample.

The hydrolysis of Ln(ClO4)3 in the presence of acetate leads to the assembly of the three largest known lanthanide-exclusive cluster complexes, [Nd104(ClO4)6(CH3COO)60(μ3-OH)168(μ4-O)30(H2O)112]·(ClO4)18·(CH3CH2OH)8·xH2O (1, x ≈ 158) and [Ln104(ClO4)6(CH3COO)56(μ3-OH)168(μ4-O)30(H2O)112]·(ClO4)22·(CH3CH2OH)2·xH2O (2, Ln = Nd; 3, Ln = Gd; x ≈ 140). The structure of the common 104-lanthanide core, abbreviated as Ln8@Ln48@Ln24@Ln24, features a four-shell arrangement of the metal atoms contained in an innermost cube (a Platonic solid) and, moving outward, three Archimedean solids: a truncated cuboctahedron, a truncated octahedron, and a rhombicuboctahedron. The magnetic entropy change of ΔSm = 46.9 J kg–1 K–1 at 2 K for ΔH = 7 T in the case of the Gd104 cluster is the largest among previously known lanthanide-exclusive cluster compounds.

Three polynuclear lanthanide clusters: (NH4)2[Dy6Mo4O12(rac-L3−)4(OOCCH3)8]·4CH3OH·6H2O (I), (Et3NH)2[Dy6Mo4O12(rac-L3−)4(OOCCH3)8]·18H2O (II), and (Me4N)2[Dy6Mo4O12(rac-L3−)4(OOCCH3)8]·CH3OH·14H2O (III) (H3L = (E)-2-((2,3-dihydroxypropylimino)methyl)-phenol) were synthesized. Single-crystal analysis reveals that cluster I crystallized in the centrosymmetric space group (P42/n), while clusters II and II crystallized in the chiral space group (P3121 or P3221), and cluster I can be transformed into clusters II and III, when Et3NH+ and Me4N+, respectively, are used to replace NH4+. Investigation on the solid-state vibrational circular dichroism (VCD) spectra shows that the clusters II and III are homochiral crystallization. Powder X-ray diffraction study demonstrates that the transformation between chiral and achiral clusters is reversible.

Two heterometallic cage-like Dy24M2 (M = Ni, Mn) cluster compounds have been synthesized through self-assembly of the metal ions and myo-inositol ligand templated by three ClO4− anions.

Three heterometallic cluster complexes {Ln12Mo4} featuring an Ln12 core of a distorted truncated tetrahedron were synthesized with the assistance of four MoO42− anions as ancillary ligands. Magnetic studies of the {Gd12Mo4} cluster revealed a large magnetocaloric effect due to the presence of the large number of weakly coupled Gd(III) ions.

A discrete dihalide–decahydrate cluster of [X2(H2O)10]2– has been observed in a solid-state structure of {[Na2(H2O)6(H2O@TMEQ[6])]·2(C6H5NO3)}X2(H2O)10} (TMEQ[6] = α,α′,δ,δ′-tetramethylcucurbit[6]uril; X = Cl (1), Br (2)). Its structure can be viewed as a connection of two [X(H2O)3]− clusters with a uudd water tetramer through hydrogen-bonding interactions.

Three isomorphic decanuclear heterometallic 3d–4f Ln2Cu8 clusters, formulated as [Ln2Cu8(μ2-OH)2(μ3-OH)2(ClO4)2(HTMHSA)4(H2O)10]·15H2O (Ln = La (1, La2Cu8); Ln = Gd (2, Gd2Cu8); Ln = Dy (3, Dy2Cu8), H5TMHSA = 3-[N-tris(hydroxymethyl)methylamino]-2-hydroxyprop-anesulfonic acid), were obtained through the reaction of H5TMHSA, Ln(ClO4)3, and Cu(NO3)2·3H2O. The present three Ln2Cu8 compounds are rare examples of alkylsulfonate-based polynuclear 3d–4f clusters. Magnetic studies indicate that the cluster La2Cu8 exhibits antiferromagnetic behavior, Gd2Cu8 displays ferromagnetic behavior and a large magnetocaloric effect at low temperature, while Dy2Cu8 shows slow magnetic relaxation.

Dielectric anisotropy of anilinium perchlorate is investigated at various temperatures. Crystal structures at different temperatures reveal that significant dielectric change between low and high dielectric states is closely related to the disorder of the anilinium cation and perchlorate anion at high dielectric state; meanwhile, the conductivity after phase transition also contributes a lot to the high dielectric state.

Four 52-metal-ion 3d–4f cluster complexes featuring a common core of Ln42M10 (Ln = Gd3+, Dy3+; M = Co2+/3+, Ni2+) were obtained through self-assembly of the metal ions templated by mixed anions (ClO4– and CO32–). Magnetic studies revealed that the Gd42Co10 and Gd42Ni10 clusters exhibit the largest magnetocaloric effect (MCE) among any known 3d–4f complexes. Replacement of Gd3+ ions with anisotropic Dy3+ ions caused significant changes in the magnetic behavior of the clusters; both Dy42Co10 and Dy42Ni10 displayed slow relaxation of the magnetization.

Proton transport along different axes in an organic–inorganic compound [(C6H10N2)2(SO4)2·3H2O]n (1) was investigated, revealing that proton transport is not only influenced by the structure of the proton transport pathway, but also by the order–disorder extent of proton carriers.

A pentanuclear dysprosium cluster, [Dy5(μ3–OH)6(Acc)6(H2O)10]·Cl9·24H2O (1), has been synthesized through the reaction of 1-amino-cyclohexanel-carboxylic acid (Acc) and DyCl3·5H2O. Crystal structural analysis reveals that the metal core of cluster 1 shows an unprecedented trigonal bipyramidal (TBP) geometry. Magnetic studies indicate that the Dy5 cluster exhibits slow magnetic relaxation.

Two homochiral coordination polymers, namely, [YbIII3MnIII6(L)6(μ2-OMe)6(isonicotinate)2(HOMe)2][YbIII3MnIII6(L)6(μ2-OMe)6(isonicotinate)2(HOMe)4](NO3)2·6MeOH·12H2O (5) (H3L = (S,E)-4-(2-hydroxybenzylideneamino)-2-hydroxybutanoic acid) and [YbIII3MnIII6Na(L)6(μ2-OMe)6(OOCH)3]I·17H2O (6), have been constructed by utilizing a stable enantiopure [YbIII3MnIII6(L)6(μ2-OMe)6]3+ (Yb3Mn6) cluster as a precursor.

An undeca-nuclear nickel substituted POM, namely [Ni(H2O)6][Ni11(PW9O34)2(IDA)3(en)2(Hen)2(OH)6]·(H2O)7·(H2en)2 (1) (en = 1,2-ethylenediamine, H2IDA = iminodiacetic acid), was synthesized through hydrothermal reaction of Na6PW9O34, en, H2IDA and NiCl2·6H2O. Single-crystal structure reveals that 1 can be viewed as Ni6PW9 and Ni5PW9 units linked by a μ3-O bridge and two IDA2− ligands. Magnetic investigation indicates the presence of dominantly ferrimagnetic interactions within the Ni11 core. Electrochemistry study shows that 1 displays a stable and reproducible voltammetric graph.

The dielectric properties of water confined in nanochannels of a cucurbit[8]uril-based supramolecular architecture containing water and hydrated copper(II) ions were investigated in the frequency range of 102 to 5 × 107 Hz at various temperatures around room temperature. Two relaxation processes were revealed and studied. The low-frequency dispersion described by the fractional power law is related to the relaxation of hopping charge carriers. The second orientational polarization contribution follows the Kohlrausch–Williams–Watts relaxation law with the characteristic relaxation time almost independent of temperature and gives rise to an exceptionally large static dielectric constant (∼500). The data suggest the existence of a third relaxation process with the characteristic frequency significantly larger than the measurement frequencies used in this work.

A 3D metal–organic framework, featuring three kinds of cation channels, was obtained through an ionothermal reaction. Investigation on its temperature-dependent conductivity indicates the contribution of order and disorder of the Emim+ (Emim+ = 1-ethyl-3-methyl imidazolium bromide) in the channel to its conductivity.

Four lanthanide-based metal–organic frameworks, [Emim][Ln1.5(2,5-tdc)2]Cl1.5−xBrx (Ln = Nd 1, Eu 2) and [Emim][Ln(2,5-tdc)2] (Ln = Nd 3, Eu 4) (2,5-tdc = thiophene-2,5-dicarboxylate, Emim = 1-methyl-3-ethylimidazolium), were synthesized under ionothermal conditions. Compounds 1 and 2 crystallize in the polar space groupP21212, while 3 and 4 crystallize in the central symmetry space groupP21/c. Luminescence studies revealed a significantly higher quantum yield of 4 than that of 2, with similar lifetimes. It is clear that the coordination of the halide ions has profound effects on the structures and properties of these lanthanide-based metal–organic frameworks.

Two three-dimensional 2p−3d−4f heterometallic frameworks featuring a nanosized Ln6Cu24Na12 (Ln = Gd, Dy) cluster as a node have been obtained under microwave irradiation conditions through the reaction of H2ANMA (H2ANMA = l-alanine-N-monoacetic acid), Cu(NO3)2, and Ln(NO3)3 (Ln = Gd for 1, Dy for 2) with NaOH in deionized water. Investigations on the magnetic properties show that 1 exhibits ferrimagnetic behavior. The electrical conductivity measurements reveal that 1 behaves as a proton conductor.

A series of dinuclear, trinuclear and tetranuclear lanthanide complexes, formulated as [Nd2(Acc)6(H2O)4]3 [Nd2(Acc)6(H2O)6]·Cl24·8H2O (1), [Dy2(Acc)4(H2O)8]·Cl6·5.89H2O (2), [Ln3(Acc)10(H2O)6]·(ClO4)9·4H2O (Ln = La, (3); Nd, (4)) and [Ln4(μ3-OH)4(Acc)6(H2O)7(ClO4)] ·(ClO4)7·11H2O (Ln = Dy, (5); Yb, (6)), have been synthesized through the reaction of 1-amino cyclohexanel-carboxylic acid (Acc) and LnCl3/Ln(ClO4)3. Crystal structure analysis reveals that complexes 1 and 2 show dinuclear lanthanide cluster, complexes 3 and 4 have three lanthanide ions with a linear arrangement, while complexes 5 and 6 exhibit a cubane-like [Ln4(μ3-OH)4]8+ (Ln = Dy and Yb) cluster core. Their structural variations are attributed to the effect of anions and lanthanide contraction. Magnetic studies indicate that the Dy2 and Dy4 clusters exhibit slow relaxation of magnetization.

Three metal–organic frameworks, [M3(ip)4][EMIm]2 (M = Co 1, Ni 2, Mn 3, H2ip = isophthalic acid, EMIm = 1-ethyl-3-methyl imidazolium) were prepared from an ionic liquid medium. All the compounds feature the same (424)(64) topology based on linear trinuclear clusters as eight-connected nodes. Compounds 1 and 2 are isostructural, while compound 3 exhibits a different structure due to the slight difference in the arrangement of M3(OOCR)8 SBUs. Magnetic property measurements reveal that all the compounds display anti-ferromagnetic coupling, where compounds 2 and 3 show isotropic exchange interactions of −0.10 cm−1 for 2 and −1.6 cm−1 for 3. Investigation of the thermal diffusivity shows that the thermal diffusivity of 1 is higher than that of 3, while that of 3 is higher than that of 2.

Three enantiopure isostructural sandwich-type clusters, LnIII3MnIII6 (Ln = Dy (1), Tb (2) and Gd (3)) have been synthesized through reactions of a chiral Schiff-base ligand ((S,E)-4-(2-hydroxybenzylideneamino)-2-hydroxybutanoic acid, H3L) with manganese and lanthanide ions, showing intramolecular antiferromagnetic interaction.

The discovery of fullerenes in 1985 opened a new chapter in the chemistry of highly symmetric molecules. Fullerene-like metal clusters, characterized by (multi)shell-like structures, are one rapidly developing class of molecules that share this shape. In addition to creating aesthetically pleasing molecular structures, the ordered arrangement of metal atoms within such frameworks provides the opportunity to develop materials with properties not readily achieved in corresponding mononuclear or lower-nuclearity complexes. In this Account, we survey the great variety of fullerene-like metal-containing clusters with an emphasis on their synthetic and structural chemistry, a first step in the discussion of this fascinating field of cluster chemistry. We group the compounds of interest into three categories based on the atomic composition of the cluster core: those with formal metal−metal bonding, those characterized by ligand participation, and those supported by polyoxometalate building blocks. The number of clusters in the first group, containing metal−metal bonds, is relatively small. However, because of the unique and complex bonding scenarios observed for some of these species, these metalloid clusters present a number of research questions with significant ramifications. Because these cores contain molecular clusters of precious metals at the nanoscale, they offer an opportunity to study chemical properties at size ranges from the molecular to nanoscale and to gain insights into the electronic structures and properties of nanomaterials of similar chemical compositions. Clusters of the second type, whose core structures are facilitated by ligand participation, could aid in the development of functional materials. Of particular interest are the magnetic clusters containing both transition and lanthanide elements. A series of such heterometallic clusters that we prepared demonstrates diverse magnetic properties including antiferromagnetism, ferrimagnetism, and ferromagnetism. Considering the diversity of their composition, their distinct electronic structures, and the disparate coordination behaviors of the different metal elements, these materials suggest abundant opportunities for designing multifunctional materials with varied structures. The third type of clusters that we discuss are based on polyoxometalates, in particular those containing pentagonal units. However, unlike in fullerene chemistry, which does not allow the use of discrete pentagonal building blocks, the metal oxide-based pentagonal units can be used as fundamental building blocks for constructing various Keplerate structures. These structures also have a variety of functions, including intriguing magnetic properties in some cases. Coupled with different linking groups, such pentagonal units can be used for the assembly of a large number of spherical molecules whose properties can be tuned and optimized. Although this Account focuses on the topological aspects of fullerene-like metal clusters, we hope that this topical review will stimulate more efforts in the exploratory synthesis of new fullerene-like clusters. More importantly, we hope that further study of the bonding interactions and properties of these molecules will lead to the development of new functional materials.

Three sandwich-type silicotungstates, formulated as [Cu4(H2O)2(SiW9O34)2]·12NH4·22H2O (1), [Cu4(H2O)2(SiW9O34)2]·12NH4·11H2O (2) and {[Cu(NH3)4]2[Cu(H2O)4][Cu4(H2O)2(SiW9O34)2]} 2[Cu(NH3)4(H2O)]·2NH4·6H2O (3), were synthesized by microwave irradiation and hydrothermal reaction. Crystal structural analysis reveals that 1–3 possess the same dimeric polyoxoanions [Cu2SiW9O34(H2O)]212− featuring tetranuclear copper(II) clusters. Magnetic studies indicate that the Cu4 clusters exhibit ferromagnetic coupling interactions. Investigation on their catalytic activity for the oxidation of ethylbenzene suggests that catalytic activity of 1–3 is closely related to the acidity of complexes and the existence of unsaturated coordination sites in the complex.

A series of lanthanide coordination polymers have been synthesized through the hydrothermal reaction of 2,5-piperazinedione-1,4-diacetic acid (H2PODC) and Ln(NO3)3 (Ln = La, 1; Pr, 2; Sm, 3; Ho, 4 and Er, 5). Crystal structure analysis reveals that their structural variations are attributed to the effect of lanthanide contraction.

Crystal engineering is the rational design and assembly of solid-state structures with desired properties via the manipulation of intermolecular interactions, hydrogen bonding and metal–ligand complexation in particular. The heart of crystal engineering is to control the ordering of the building blocks, be they molecular or ionic, toward a specific disposition in the solid state. The relatively weak strength of intermolecular forces with respect to chemical bonding renders the assembly of supramolecular constructs sensitive to external physical and chemical stimuli, with pH condition of the reaction mixture being arguably the most prominent and extensively observed. Using selected examples of constructing metal–organic architectures from recent literature, the influences of pH on the specific ligand forms, the generation and metal coordination of hydroxo ligands, ligand transformation promoted by pH condition changes, pH-dependent kinetics of crystallization of a number of metal–organic architectures are discussed. Current status of this particular areas of research in supramolecular chemistry and materials are assessed and personal perspectives as to toward what directions should this chemistry head are elaborated.

A nanosized heterometallic cluster containing 60 La(III) and 76 Ni(II) ions, which are arranged into a four-shell, nest-like framework structure, was obtained by the hydrolytic reaction of the mixed La(NO3)3–Ni(NO3)2 system using iminodiacetate as an ancillary ligand to control the hydrolysis.

The anisotropy of polarization in a 1D copper(II)-based coordinationpolymer was investigated experimentally and theoretically for the first time, revealing that the origin of the ferroelectricity and its anisotropic nature are closely related to the coordination geometry of the metal ion and the packing mode of the coordinationpolymer.

Polynuclear lanthanide hydroxide complexes featuring the cubane-like [Ln4(μ3-OH)4]8+ [Ln = Eu(III), Gd(III)] cluster core have been synthesized by controlled hydrolysis of the lanthanide ions using nicotinic acid as the ancillary ligand. The synthetic procedure has been found to significantly influence the nature of the resulting cluster species. In a one-pot synthesis, adjusting the pH of the reaction mixture containing Ln(ClO4)3 and nicotinic acid afforded tetranuclear complexes of the general formula [Ln4(μ3-OH)4(Hnic)5(H2O)12](ClO4)8 with the [Ln4(μ3-OH)4]8+ (Ln = Eu, Gd) cluster core encapsulated by zwitterionic nicotinate ligands. In stark contrast, mixing aqueous solutions of Ln(ClO4)3 and nicotinic acid whose pH had been preadjusted produced assemblies composed of two of the cubane-like cluster cores that are related by a crystallographic inversion center and are doubly bridged by nicotinate ligands using both the carboxylate group and pyridyl N atom for coordination. The influences of pH conditions and synthetic procedures on the identity of the resulting cluster species are discussed, so is the structural relevance of the low-pH complexes to their cluster analogues obtained under higher-pH conditions.

A La(III)–Co(II) heterometallic framework and a La(III)-based anionic layered architecture were prepared under ionothermal conditions.

The reaction of cucurbit[6]uril with Cu(NO3)2 and CuCl2, respectively, generates a 1D zigzag chain of {[Cu(H2O)4(cucurbit[6]uril)]·(NO3)2·(H2O)8}n and a 1D tubular structure of {[Cu(H2O)2(Cl)2(cucurbit[6]uril)]1/3·(H2O)3}n, showing clearly how to control the reversible and mutual interconnections between ligand and metal ion under the guide of coordination chemistry.

A cage-shaped 3d–4f heterometallic ferromagnetic cluster, consisting of six Ni(II) and three La(III) ions, was synthesized by microwave irradiation. The magnetic susceptibilities of the cluster were fitted with the help of the program MAGPACK, revealing that the magnetic exchange in the cluster is closely related to the coordination mode and spatial distribution between the metal ions.

The reaction of iminodiacetic acid with Ln2O3 (Ln = Dy, Ho, Er, Yb) under hydrothermal conditions generate a series of 3D lanthanide-based coordination polymers, in which, the iminodiacetic acid (IDA) was transformed into a 2,5-diketopiperazine-1,4-diacetate.

Four Keggin-based coordination polymers, namely, {[Cu2(4,4′-bpy)(4,4′-Hbpy)4(H2O)4](SiW12O40)2(H2O)4}n (1), {[Cu2(4,4′-bpy)(4,4′-Hbpy)6(SiW12O40)3](4,4′-Hbpy)2(H2O)7}n (2), {[Cu2(μ2-H2O)2(4,4′-bpy)3(SiW12O40)](H2O)6}n (3) and {[Cu2(μ2-OH)(4,4′-bpy)3(SiW12O40)(H2O)] [Cu2(μ2-O)(4,4′-bpy)4(H2O)2]0.5·(H2O)3}n (4) (4,4′-bpy = 4,4′-bipyridine) were prepared through the hydrothermal reaction of silicotungstic acid, copper(II) nitrate and 4,4′-bipyridine under different pH conditions. Coordination polymers 1 and 2, which exhibit 0D and 1D structures respectively, were prepared at pH = 3.5. At pH = 5.5, a 2D coordination polymer 3 was obtained. Increasing the pH of the reaction to 8.5 led to a 3D coordination polymer 4. The structural diversities of 1–4 reveal that the pH value of the reaction plays a key role in the assembly of POM-based coordination polymers. Investigation of the catalytic properties of 1–4 for the oxidation of ethylbenzene indicates that the catalytic activity of the coordination polymers is closely related to the protonated extent of 4,4′-bpy in the coordination polymers.

Dual shell-like nanoscopic magnetic clusters featuring a polynuclear nickel(II) framework encapsulating that of lanthanide ions (Ln = La, Pr, and Nd) were synthesized using Ni(NO3)2·6H2O, Ln(NO3)3·6H2O, and iminodiacetic acid (IDA) under hydrothermal conditions. Structurally established by crystallographic studies, these clusters are [La20Ni30(IDA)30(CO3)6(NO3)6(OH)30(H2O)12](CO3)6·72H2O (1), [Ln20Ni21(C4H5NO4)21(OH)24(C2H2O3)6(C2O4)3(NO3)9(H2O)12](NO3)9·nH2O [C2H2O3 is the alkoxide form of glycolate; Ln = Pr (2), n = 42; Nd (3), n = 50], and {[La4Ni5Na(IDA)5(CO3)(NO3)4(OH)5(H2O)5][CO3]·10H2O}∞ (4). Carbonate, oxalate, and glycolate are products of hydrothermal decomposition of IDA. Compositions of these compounds were confirmed by satisfactory elemental analyses. It has been found that the cluster structure is dependent on the identity of the lanthanide ion as well as the starting Ln/Ni/IDA ratio. The cationic cluster of 1 features a core of the Keplerate type with an outer icosidodecahedron of NiII ions encaging a dodecahedral kernel of LaIII. Clusters 2 and 3, distinctly different from 1, are isostructural, possessing a core of an outer shell of 21 NiII ions encapsulating an inner shell of 20 LnIII ions. Complex 4 is a three-dimensional assembly of cluster building blocks connected by units of Na(NO3)/La(NO3)3; the structure of the building block resembles closely that of 1, with a hydrated LaIII ion internalized in the decanuclear cage being an extra feature. Magnetic studies indicated ferromagnetic interactions in 1, while overall antiferromagnetic interactions were revealed for 2 and 3. The polymeric, three-dimensional cluster network 4 displayed interesting ferrimagnetic interactions.

Hydrothermal reaction of La(NO3)3, NaHCO3 and H3L (H3L = pyrazole-3,5-dicarboxylic acid) gives a 3D metal–organic framework with a dynamic porous property.

Two supramolecular architectures were assembled from the supermolecular building blocks of calixarenes and cucurbiturils through noncovalent binding. They not only exhibit an intriguing topology but also show clearly the role of hydrophobic−hydrophobic and hydrophilic−hydrophilic interactions in directing the supramolecular assembly.

Two high-nuclearity 3d–4f clusters Ln24Zn4 (Ln = Gd and Sm) featuring four Ln6 octahedra encapsulating a Zn4 tetrahedron were obtained through the self-assembly of Zn(OAc)2 and Ln(ClO4)3. Quantum Monte Carlo (QMC) simulations show the antiferromagnetic coupling between Gd3+ ions. Studies of the magnetocaloric effect (MCE) show that the Gd24Zn4 cluster exhibits the entropy change (−ΔSm) of 31.4 J kg−1 K−1.

Three polynuclear lanthanide clusters: (NH4)2[Dy6Mo4O12(rac-L3−)4(OOCCH3)8]·4CH3OH·6H2O (I), (Et3NH)2[Dy6Mo4O12(rac-L3−)4(OOCCH3)8]·18H2O (II), and (Me4N)2[Dy6Mo4O12(rac-L3−)4(OOCCH3)8]·CH3OH·14H2O (III) (H3L = (E)-2-((2,3-dihydroxypropylimino)methyl)-phenol) were synthesized. Single-crystal analysis reveals that cluster I crystallized in the centrosymmetric space group (P42/n), while clusters II and II crystallized in the chiral space group (P3121 or P3221), and cluster I can be transformed into clusters II and III, when Et3NH+ and Me4N+, respectively, are used to replace NH4+. Investigation on the solid-state vibrational circular dichroism (VCD) spectra shows that the clusters II and III are homochiral crystallization. Powder X-ray diffraction study demonstrates that the transformation between chiral and achiral clusters is reversible.

Three heterometallic cluster complexes {Ln12Mo4} featuring an Ln12 core of a distorted truncated tetrahedron were synthesized with the assistance of four MoO42− anions as ancillary ligands. Magnetic studies of the {Gd12Mo4} cluster revealed a large magnetocaloric effect due to the presence of the large number of weakly coupled Gd(III) ions.

The anisotropy of polarization in a 1D copper(II)-based coordinationpolymer was investigated experimentally and theoretically for the first time, revealing that the origin of the ferroelectricity and its anisotropic nature are closely related to the coordination geometry of the metal ion and the packing mode of the coordinationpolymer.

A nanosized heterometallic cluster containing 60 La(III) and 76 Ni(II) ions, which are arranged into a four-shell, nest-like framework structure, was obtained by the hydrolytic reaction of the mixed La(NO3)3–Ni(NO3)2 system using iminodiacetate as an ancillary ligand to control the hydrolysis.

The reaction of cucurbit[6]uril with Cu(NO3)2 and CuCl2, respectively, generates a 1D zigzag chain of {[Cu(H2O)4(cucurbit[6]uril)]·(NO3)2·(H2O)8}n and a 1D tubular structure of {[Cu(H2O)2(Cl)2(cucurbit[6]uril)]1/3·(H2O)3}n, showing clearly how to control the reversible and mutual interconnections between ligand and metal ion under the guide of coordination chemistry.

Two one-dimensional acetate chains, GdIII–MnII (1) and GdIII–CoII (2), have been prepared. Magnetic investigations indicate that the magnetic entropy changes (−ΔSm) in 1 have maximum values of 38.70 J kg−1 K−1 at ΔH = 7 T and 31.08 J kg−1 K−1 at ΔH = 3 T, while these in 2 have maximum values of 35.18 J kg−1 K−1 at ΔH = 7 T and 28.67 J kg−1 K−1 at ΔH = 3 T.

A supramolecular compound [C6H11NH3]+[CF3COO]− was synthesized. Investigation on the structure of 1 at different temperatures reveals that it is the disorder of the anions that plays a key role in thermal energy storage. Studies on the thermal and physical properties of 1 indicate that utilization of the sensible heat in 1 can significantly enhance its ability to store thermal energy.

Hydrothermal reaction of La(NO3)3, NaHCO3 and H3L (H3L = pyrazole-3,5-dicarboxylic acid) gives a 3D metal–organic framework with a dynamic porous property.

Four Keggin-based coordination polymers, namely, {[Cu2(4,4′-bpy)(4,4′-Hbpy)4(H2O)4](SiW12O40)2(H2O)4}n (1), {[Cu2(4,4′-bpy)(4,4′-Hbpy)6(SiW12O40)3](4,4′-Hbpy)2(H2O)7}n (2), {[Cu2(μ2-H2O)2(4,4′-bpy)3(SiW12O40)](H2O)6}n (3) and {[Cu2(μ2-OH)(4,4′-bpy)3(SiW12O40)(H2O)] [Cu2(μ2-O)(4,4′-bpy)4(H2O)2]0.5·(H2O)3}n (4) (4,4′-bpy = 4,4′-bipyridine) were prepared through the hydrothermal reaction of silicotungstic acid, copper(II) nitrate and 4,4′-bipyridine under different pH conditions. Coordination polymers 1 and 2, which exhibit 0D and 1D structures respectively, were prepared at pH = 3.5. At pH = 5.5, a 2D coordination polymer 3 was obtained. Increasing the pH of the reaction to 8.5 led to a 3D coordination polymer 4. The structural diversities of 1–4 reveal that the pH value of the reaction plays a key role in the assembly of POM-based coordination polymers. Investigation of the catalytic properties of 1–4 for the oxidation of ethylbenzene indicates that the catalytic activity of the coordination polymers is closely related to the protonated extent of 4,4′-bpy in the coordination polymers.

The reaction of iminodiacetic acid with Ln2O3 (Ln = Dy, Ho, Er, Yb) under hydrothermal conditions generate a series of 3D lanthanide-based coordination polymers, in which, the iminodiacetic acid (IDA) was transformed into a 2,5-diketopiperazine-1,4-diacetate.

Three sandwich-type silicotungstates, formulated as [Cu4(H2O)2(SiW9O34)2]·12NH4·22H2O (1), [Cu4(H2O)2(SiW9O34)2]·12NH4·11H2O (2) and {[Cu(NH3)4]2[Cu(H2O)4][Cu4(H2O)2(SiW9O34)2]} 2[Cu(NH3)4(H2O)]·2NH4·6H2O (3), were synthesized by microwave irradiation and hydrothermal reaction. Crystal structural analysis reveals that 1–3 possess the same dimeric polyoxoanions [Cu2SiW9O34(H2O)]212− featuring tetranuclear copper(II) clusters. Magnetic studies indicate that the Cu4 clusters exhibit ferromagnetic coupling interactions. Investigation on their catalytic activity for the oxidation of ethylbenzene suggests that catalytic activity of 1–3 is closely related to the acidity of complexes and the existence of unsaturated coordination sites in the complex.

A cage-shaped 3d–4f heterometallic ferromagnetic cluster, consisting of six Ni(II) and three La(III) ions, was synthesized by microwave irradiation. The magnetic susceptibilities of the cluster were fitted with the help of the program MAGPACK, revealing that the magnetic exchange in the cluster is closely related to the coordination mode and spatial distribution between the metal ions.

Three metal–organic frameworks, [M3(ip)4][EMIm]2 (M = Co 1, Ni 2, Mn 3, H2ip = isophthalic acid, EMIm = 1-ethyl-3-methyl imidazolium) were prepared from an ionic liquid medium. All the compounds feature the same (424)(64) topology based on linear trinuclear clusters as eight-connected nodes. Compounds 1 and 2 are isostructural, while compound 3 exhibits a different structure due to the slight difference in the arrangement of M3(OOCR)8 SBUs. Magnetic property measurements reveal that all the compounds display anti-ferromagnetic coupling, where compounds 2 and 3 show isotropic exchange interactions of −0.10 cm−1 for 2 and −1.6 cm−1 for 3. Investigation of the thermal diffusivity shows that the thermal diffusivity of 1 is higher than that of 3, while that of 3 is higher than that of 2.

Three enantiopure isostructural sandwich-type clusters, LnIII3MnIII6 (Ln = Dy (1), Tb (2) and Gd (3)) have been synthesized through reactions of a chiral Schiff-base ligand ((S,E)-4-(2-hydroxybenzylideneamino)-2-hydroxybutanoic acid, H3L) with manganese and lanthanide ions, showing intramolecular antiferromagnetic interaction.

Two homochiral coordination polymers, namely, [YbIII3MnIII6(L)6(μ2-OMe)6(isonicotinate)2(HOMe)2][YbIII3MnIII6(L)6(μ2-OMe)6(isonicotinate)2(HOMe)4](NO3)2·6MeOH·12H2O (5) (H3L = (S,E)-4-(2-hydroxybenzylideneamino)-2-hydroxybutanoic acid) and [YbIII3MnIII6Na(L)6(μ2-OMe)6(OOCH)3]I·17H2O (6), have been constructed by utilizing a stable enantiopure [YbIII3MnIII6(L)6(μ2-OMe)6]3+ (Yb3Mn6) cluster as a precursor.

An undeca-nuclear nickel substituted POM, namely [Ni(H2O)6][Ni11(PW9O34)2(IDA)3(en)2(Hen)2(OH)6]·(H2O)7·(H2en)2 (1) (en = 1,2-ethylenediamine, H2IDA = iminodiacetic acid), was synthesized through hydrothermal reaction of Na6PW9O34, en, H2IDA and NiCl2·6H2O. Single-crystal structure reveals that 1 can be viewed as Ni6PW9 and Ni5PW9 units linked by a μ3-O bridge and two IDA2− ligands. Magnetic investigation indicates the presence of dominantly ferrimagnetic interactions within the Ni11 core. Electrochemistry study shows that 1 displays a stable and reproducible voltammetric graph.

Two enantiomorphic 3D lanthanide coordination polymers of {[Dy5(L)4(H2O)10][Dy(H2O)7][Na(H2O)5]}·(ClO4)7·(H2O)15 (1a for R and 1b for S) with chiral helical chains were synthesized based on an achiral ligand N-(2-hydroxyethyl)ethylenediamine-N,N′,N′-triacetic acid (H3L) and Dy(ClO4)3. Crystal analysis revealed that 1a and 1b were crystallized in chiral space groups P4132 and P4332, respectively. The absolute configurations of the two structures were evidenced by vibrational circular dichroism (VCD) spectra with one single crystal sample.

A 3D metal–organic framework, featuring three kinds of cation channels, was obtained through an ionothermal reaction. Investigation on its temperature-dependent conductivity indicates the contribution of order and disorder of the Emim+ (Emim+ = 1-ethyl-3-methyl imidazolium bromide) in the channel to its conductivity.

Four lanthanide-based metal–organic frameworks, [Emim][Ln1.5(2,5-tdc)2]Cl1.5−xBrx (Ln = Nd 1, Eu 2) and [Emim][Ln(2,5-tdc)2] (Ln = Nd 3, Eu 4) (2,5-tdc = thiophene-2,5-dicarboxylate, Emim = 1-methyl-3-ethylimidazolium), were synthesized under ionothermal conditions. Compounds 1 and 2 crystallize in the polar space groupP21212, while 3 and 4 crystallize in the central symmetry space groupP21/c. Luminescence studies revealed a significantly higher quantum yield of 4 than that of 2, with similar lifetimes. It is clear that the coordination of the halide ions has profound effects on the structures and properties of these lanthanide-based metal–organic frameworks.

Proton transport along different axes in an organic–inorganic compound [(C6H10N2)2(SO4)2·3H2O]n (1) was investigated, revealing that proton transport is not only influenced by the structure of the proton transport pathway, but also by the order–disorder extent of proton carriers.

Magnetocaloric effect (MCE) and thermal conductivity of two gadolinium hydroxides, Gd(OH)3 (1) and Gd2O(OH)4(H2O)2 (2), are investigated. Magnetic studies indicate that both 1 and 2 exhibit antiferromagnetic interaction, and the MCE values for 1 and 2 at 2 K and ΔH = 7 T are 62.00 J kg−1 K−1 and 59.09 J kg−1 K−1, respectively. Investigation of their thermal conductivity reveals that the thermal conductivity for 1 is significantly better than that for 2.