Controlled Synthesis of Heterotrimetallic Single‐Chain Magnets from Anisotropic High‐Spin 3 d–4 f Nodes and Paramagnetic Spacers

By using the node‐and‐spacer approach in suitable solvents, four new heterotrimetallic 1D chain‐like compounds (that is, containing 3d–3d′–4f metal ions), {[Ni(L)Ln(NO₃)₂(H₂O)Fe(Tp*)(CN)₃] ? 2 CH₃CN ? CH₃OH}_n (H₂L=N,N′‐bis(3‐methoxysalicylidene)‐1,3‐diaminopropane, Tp*=hydridotris(3,5‐dimethylpyrazol‐1‐yl)borate; Ln=Gd ( 1 ), Dy ( 2 ), Tb ( 3 ), Nd ( 4 )), have been synthesized and structurally characterized. All of these compounds are made up of a neutral cyanide‐ and phenolate‐bridged heterotrimetallic chain, with a {? Fe? C?N? Ni(? O? Ln)? N?C? }_n repeat unit. Within these chains, each [(Tp*)Fe(CN)₃]^? entity binds to the Ni^II ion of the [Ni(L)Ln(NO₃)₂(H₂O)]⁺ motif through two of its three cyanide groups in a cis mode, whereas each [Ni(L)Ln(NO₃)₂(H₂O)]⁺ unit is linked to two [(Tp*)Fe(CN)₃]^? ions through the Ni^II ion in a trans mode. In the [Ni(L)Ln(NO₃)₂(H₂O)]⁺ unit, the Ni^II and Ln^III ions are bridged to one other through two phenolic oxygen atoms of the ligand (L). Compounds 1 – 4 are rare examples of 1D cyanide‐ and phenolate‐bridged 3d–3d′–4f helical chain compounds. As expected, strong ferromagnetic interactions are observed between neighboring Fe^III and Ni^II ions through a cyanide bridge and between neighboring Ni^II and Ln^III (except for Nd^III) ions through two phenolate bridges. Further magnetic studies show that all of these compounds exhibit single‐chain magnetic behavior. Compound 2 exhibits the highest effective energy barrier (58.2 K) for the reversal of magnetization in 3d/4d/5d–4f heterotrimetallic single‐chain magnets.     

Two Oxime‐Based {LnIII3NiII3} Clusters with Triangular {Ln3(μ3‐Ο2)}7+ Core: Solvothermal Syntheses,Crystal Structures,and Magnetic Properties

Two isostructural heterometallic complexes, {[Dy₃Ni₃(H₂O)₃(mpko)₉(O₂)(NO₃)₃](ClO₄) · 3CH₃OH · 3CH₃CN} ( 1 ) and {[Gd₃Ni₃(H₂O)₃(mpko)₉(O₂)(NO₃)₃](NO₃) · 10.75CH₃OH} ( 2 ) [mpkoH = 1‐(pyrazin‐2‐yl)ethanone oxime], were solvothermally synthesized by varying lanthanide ions with different magnetic anisotropy. Structural analyses revealed that both complexes contain a peroxide anion‐aggregated triangular {Ln₃(μ₃‐Ο₂)}⁷⁺ core, which is surrounded by three Ni^II octahedra through threefold oxime linkages into a heterometallic hexanuclear cluster. Apparent antiferromagnetic interactions are observed between the adjacent spin carriers of 1 and 2 with the coupling constant J_{Ln ··· Ni} ≈ 12J_{Ln ··· Ln}. Additionally, 1 with highly anisotropic Dy^III site shows slow magnetization relaxation under zero dc field and 2 constructed from isotropic Gd^III ion displays significant cryogenic magnetocaloric effect with a maximum entropy change of 24.8 J · kg^–1 · K^–1 at 3.0 K and 70 kOe.     

Solvent‐Mediated Transformation from Achiral to Chiral Nickel(II) Metal–Organic Frameworks and Reassembly in Solution

Reactions of 5‐nitroisophthalic acid (NO₂‐H₂ip), 1,4‐bis(imidazol‐1′‐yl)butane (bimb), and Ni(NO₃)₂ ? 6 H₂O gave rise to four metal–organic frameworks (MOFs), [Ni₂(NO₂‐ip)₂(bimb)_1.5]_n ( 1 ), [Ni₄(NO₂‐ip)₃(bimb)₂(OH)₂(H₂O)]_n ? (CH₃CH₂OH)_{0.5 n} ( 2 ), [Ni(NO₂‐ip)(bimb)_1.5(H₂O)]_n ? (H₂O)_n ? (CH₃CH₂OH)_{0.5 n} ( 3 ), and [Ni(NO₂‐ip) (bimb)(μ‐H₂O)]_n ? (H₂O)_n ( 4 ). The metal/ligand ratio, pH value, and solvent exerted a subtle but crucial influence on the formation of complexes 1 – 4 , which possess different visual color and crystal structures. Complex 1 exhibits a twofold interpenetrating 3D pillared bilayer framework composed of binuclear and mononuclear Ni^II units, whereas complex 2 is a 3D chiral network that consists of asymmetric tetranuclear Ni^II units. Complexes 3 and 4 are 3D layer‐pillared frameworks that consist of mononuclear Ni^II ions and a 3D six‐connected network of μ‐water‐bridged dinuclear Ni^II units, respectively. Interestingly, achiral 4 can be transformed into chiral 2 by using a solvent‐mediated single‐crystal‐to‐single‐crystal process without any chiral auxiliary. Magnetic analyses of 2 and 4 show the occurrence of antiferromagnetic interactions. Complex 3 is difficult to obtain directly as a single solid phase, but it can be homogeneously formed by solvent‐mediated transformations from 1 , 2 , and 4 .     

Heterotrimetallic Coordination Polymers: {CuIILnIIIFeIII} Chains and {NiIILnIIIFeIII} Layers: Synthesis,Crystal Structures,and Magnetic Properties

The use of the [Fe^III(AA)(CN)₄]^? complex anion as metalloligand towards the preformed [Cu^II(valpn)Ln^III]³⁺ or [Ni^II(valpn)Ln^III]³⁺ heterometallic complex cations (AA=2,2′‐bipyridine (bipy) and 1,10‐phenathroline (phen); H₂valpn=1,3‐propanediyl‐bis(2‐iminomethylene‐6‐methoxyphenol)) allowed the preparation of two families of heterotrimetallic complexes: three isostructural 1D coordination polymers of general formula {[Cu^II(valpn)Ln^III(H₂O)₃(μ‐NC)₂Fe^III(phen)(CN)₂ {(μ‐NC)Fe^III(phen)(CN)₃}]NO₃ ? 7 H₂O}_n (Ln=Gd ( 1 ), Tb ( 2 ), and Dy ( 3 )) and the trinuclear complex [Cu^II(valpn)La^III(OH₂)₃(O₂NO)(μ‐NC)Fe^III(phen)(CN)₃] ? NO₃ ? H₂O ? CH₃CN ( 4 ) were obtained with the [Cu^II(valpn)Ln^III]³⁺ assembling unit, whereas three isostructural heterotrimetallic 2D networks, {[Ni^II(valpn)Ln^III(ONO₂)₂(H₂O)(μ‐NC)₃Fe^III(bipy)(CN)] ? 2 H₂O ? 2 CH₃CN}_n (Ln=Gd ( 5 ), Tb ( 6 ), and Dy ( 7 )) resulted with the related [Ni^II(valpn)Ln^III]³⁺ precursor. The crystal structure of compound 4 consists of discrete heterotrimetallic complex cations, [Cu^II(valpn)La^III(OH₂)₃(O₂NO)(μ‐NC)Fe^III(phen)(CN)₃]⁺, nitrate counterions, and non‐coordinate water and acetonitrile molecules. The heteroleptic {Fe^III(bipy)(CN)₄} moiety in 5 – 7 acts as a tris‐monodentate ligand towards three {Ni^II(valpn)Ln^III} binuclear nodes leading to heterotrimetallic 2D networks. The ferromagnetic interaction through the diphenoxo bridge in the Cu^II?Ln^III ( 1 – 3 ) and Ni^II?Ln^III ( 5 – 7 ) units, as well as through the single cyanide bridge between the Fe^III and either Ni^II ( 5 – 7 ) or Cu^II ( 4 ) account for the overall ferromagnetic behavior observed in 1 – 7 . DFT‐type calculations were performed to substantiate the magnetic interactions in 1 , 4 , and 5 . Interestingly, compound 6 exhibits slow relaxation of the magnetization with maxima of the out‐of‐phase ac signals below 4.0 K in the lack of a dc field, the values of the pre‐exponential factor (τ_o) and energy barrier (E_a) through the Arrhenius equation being 2.0×10^?12 s and 29.1 cm^?1, respectively. In the case of 7 , the ferromagnetic interactions through the double phenoxo (Ni^II–Dy^III) and single cyanide (Fe^III–Ni^II) pathways are masked by the depopulation of the Stark levels of the Dy^III ion, this feature most likely accounting for the continuous decrease of χ_M T upon cooling observed for this last compound.     

Two Lanthanide(III) Complexes based on the Schiff Base N,N′‐Bis(salicylidene)‐1,5‐diamino‐3‐oxapentane: Synthesis,Characterization, DNA‐binding Properties,and Antioxidation

The Schiff base N,N′‐bis(salicylidene)‐1,5‐diamino‐3‐oxapentane (H₂L) and its lanthanide(III) complexes, PrL(NO₃)(DMF)(H₂O) ( 1 ) and Ho₂L₂(NO₃)₂ · 2H₂O ( 2 ), were synthesized and characterized by physicochemical and spectroscopic methods. Single crystal X‐ray structure analysis revealed that complex 1 is a discrete mononuclear species. The Pr^III ion is nine‐coordinate, forming a distorted capped square antiprismatic arrangement. Complex 2 is a centrosymmetric dinuclear neutral entity in which the Ho^III ion is eight‐coordinate with distorted square antiprismatic arrangement. The DNA‐binding properties of H₂L and its Ln^III complexes were investigated by spectrophotometric methods and viscosity measurements. The results suggest that the ligand H₂L and its Ln^III complexes both connect to DNA in a groove binding mode; the complexes bind more strongly to DNA than the ligand. Moreover, the antioxidant activities of the Ln^III complexes were in vitro determined by superoxide and hydroxyl radical scavenging methods, which indicate that complexes 1 and 2 have OH ^· and O₂^{– ·} radical scavenging activity.     

Aquachlorobis[4,4,5,5‐tetramethyl‐2‐(2‐pyridyl)‐4,5‐dihydro‐1H‐imidazol‐1‐oxyl 3‐oxide‐κ2O1,N2]nickel(II) nitrate methanol disolvate monohydrate

The title complex, [NiCl(C₁₂H₁₆N₃O₂)₂(H₂O)]NO₃·2CH₄O·H₂O, was obtained from a methano­lic solution of Ni(NO₃)₂·6H₂O, 2‐pyridyl nitro­nyl nitro­xide (2‐NITpy) and (NEt₄)₂[CoCl₄]. The equatorial coordination sites of the octahedral Ni^II centre are occupied by two chelating radical ligands, with the axial positions occupied by the Cl^? and water ligands. The H₂O—Ni—Cl axis of the complex lies along a crystallographic twofold axis, so that only half the cation is present in the asymmetric unit. The Ni—Cl bond length [2.3614 (17) Å] is significantly shorter than distances typical of octahedral Ni^II centres [2.441 (5) Å]. However, with only one nitrate anion per formula unit, the oxidation state of the metal must be assigned as Ni^II. The 2‐NITpy ligands bend away from the equatorial plane, forming a hydro­phobic region around the Cl atoms. Conversely, the ligated water mol­ecule forms moderately strong hydrogen bonds with the disordered methanol solvent mol­ecules, which in turn form interactions with the water of crystallization and the disordered nitrate anion. These interactions combine to give hydro­philic regions throughout the crystal structure.     

2‐Amino‐5‐(2‐pyridyl)‐thiadiazole as Bidentate Ligand

The amino substituted bidentate chelating ligand 2‐amino‐5‐(2‐pyridyl)‐1,3,4‐thiadiazole (H₂ L ) was used to prepare 3:1‐type coordination compounds of iron(II), cobalt(II) and nickel(II). In the iron(II) perchlorate complex [Fe^II(H₂ L )₃](ClO₄)₂·0.6MeOH·0.9H₂O a 1:1 mixture of mer and fac isomers is present whereas [Fe^II(H₂ L )₃](BF₄)₂·MeOH·H₂O, [Co^II(H₂ L )₃](ClO₄)₂·2H₂O and [Ni^II(H₂ L )₃](ClO₄)₂·MeOH·H₂O feature merely mer derivatives. Moessbauer spectroscopy and variable temperature magnetic measurements revealed the [Fe^II(H₂ L )₃]²⁺ complex core to exist in the low‐spin state, whereas the [Co^II(H₂ L )₃]²⁺ complex core resides in its high‐spin state, even at very low temperatures.     

Synthesis and characterization of two novel bimetallic macrocyclic complexes generated from 1,2,4‐triazole‐containing semi‐rigid ligands and M(NO3)2 units (M = Ni and Zn)

Bimetallic macrocyclic complexes have attracted the attention of chemists and various organic ligands have been used as molecular building blocks, but supramolecular complexes based on semi‐rigid organic ligands containing 1,2,4‐triazole have remained rare until recently. It is easier to obtain novel topologies by making use of asymmetric semi‐rigid ligands in the self‐assembly process than by making use of rigid ligands. A new semi‐rigid ligand, 3‐[(pyridin‐4‐ylmethyl)sulfanyl]‐5‐(quinolin‐2‐yl)‐4H‐1,2,4‐triazol‐4‐amine (L), has been synthesized and used to generate two novel bimetallic macrocycle complexes, namely bis{μ‐3‐[(pyridin‐4‐ylmethyl)sulfanyl]‐5‐(quinolin‐2‐yl)‐4H‐1,2,4‐triazol‐4‐amine}bis[(methanol‐κO)(nitrato‐κ²O,O′)nickel(II)] dinitrate, [Ni₂(NO₃)₂(C₁₇H₁₄N₆S)₂(CH₃OH)₂](NO₃)₂, (I), and bis{μ‐3‐[(pyridin‐4‐ylmethyl)sulfanyl]‐5‐(quinolin‐2‐yl)‐4H‐1,2,4‐triazol‐4‐amine}bis[(methanol‐κO)(nitrato‐κ²O,O′)zinc(II)] dinitrate, [Zn₂(NO₃)₂(C₁₇H₁₄N₆S)₂(CH₃OH)₂](NO₃)₂, (II), by solution reactions with the inorganic salts M(NO₃)₂ (M = Ni and Zn, respectively) in mixed solvents. In (I), two Ni^II cations with the same coordination environment are linked by L ligands through Ni—N bonds to form a bimetallic ring. Compound (I) is extended into a two‐dimensional network in the crystallographic ac plane via N—H…O, O—H…N and O—H…O hydrogen bonds, and neighbouring two‐dimensional planes are parallel and form a three‐dimensional structure via π–π stacking. Compound (II) contains two bimetallic rings with the same coordination environment of the Zn^II cations. The Zn^II cations are bridged by L ligands through Zn—N bonds to form the bimetallic rings. One type of bimetallic ring constructs a one‐dimensional nanotube via O—H…O and N—H…O hydrogen bonds along the crystallographic a direction, and the other constructs zero‐dimensional molecular cages via O—H…O and N—H…O hydrogen bonds. They are interlinked into a two‐dimensional network in the ac plane through extensive N—H…O hydrogen bonds, and a three‐dimensional supramolecular architecture is formed via π–π interactions between the centroids of the benzene rings of the quinoline ring systems.     

The Building Block [FeIII(pzphen)(CN)4]– and its Lanthanide Complexes: Synthesis,Crystal Structure,and Magnetic Properties

The cyanide building block [Fe^III(pzphen)(CN)₄]^– and its four lanthanide complexes [{Fe^III(pzphen)(CN)₄}₂Ln^III(H₂O)₅(DMF)₃] · (NO₃) · 2(H₂O) · (CH₃CN) [Ln = Nd ( 1 ), Sm ( 2 ), DMF = dimethyl formamide] and [{Fe^III(pzphen)(CN)₄}₂Ln^III(NO₃)(H₂O)₂(DMF)₂](CH₃CN) [Ln = Gd ( 3 ), Dy ( 4 )] were synthesized and structurally characterized by single‐crystal X‐ray diffraction. Compounds 1 and 2 are ionic salts with two [Fe^III(pzphen)(CN)₄]^– cations and one Ln^III ion, but compounds 3 and 4 are cyano‐bridged Fe^III‐Ln^III heterometallic 3d‐4f complexes exhibiting a trinuclear structure in the same conditions. Magnetic studies show that compound 3 is antiferromagnetic between the central Fe^III and Gd^III atoms. Furthermore, the trinuclear cyano‐bridged Fe^III₂Dy^III compound 4 displays no single‐molecular magnets (SMMs) behavior by the alternating current magnetic susceptibility measurements.     

Synthesis,Crystal Structure,Fluorescent and Antioxidation Properties of Cerium(III) and Europium(III) Complexes with Bis(3‐methoxysalicylidene)‐3‐oxapentane‐1,5‐diamine

Two aliphatic ether Schiff base lanthanide complexes (Ln = Eu, Ce) with bis(3‐methoxysalicylidene)‐3‐oxapentane‐1,5‐diamine (Bod), were synthesized and characterized by physicochemical and spectroscopic methods. [Eu(Bod)(NO₃)₃] ( 1 ) is a discrete mononuclear species and [Ce(Bod)(NO₃)₃DMF]_∞ ( 2 ) exhibits an inorganic coordination polymer. In the two complexes, the metal ions both are ten‐coordinated and the geometric structure around the Ln^III atom can be described as distorted hexadecahedron. Under excitation at room temperature, the red shift in the fluorescence band of the ligand in the complexes compared with that of the free ligand can be attributed to coordination of the rare earth ions to the ligand. Moreover, the antioxidant activities of the two complexes were investigated. The results demonstrated that the complexes have better scavenging activity than both the ligand and the usual antioxidants on the hydroxyl and superoxide radicals.     

Cerium‐Complex‐Catalyzed Oxidation of Arylmethanols under Atmospheric Pressure of Dioxygen and Its Mechanism through a Side‐On μ‐Peroxo Dicerium(IV) Complex

A new Ce^IV complex [Ce{NH(CH₂CH₂N=CHC₆H₂‐3,5‐(tBu)₂‐2‐O)₂}(NO₃)₂] ( 1 ), bearing a dianionic pentadentate ligand with an N₃O₂ donor set, has been prepared by treating (NH₄)₂Ce(NO₃)₆ with the sodium salt of ligand L1 . Complex 1 in the presence of TEMPO and 4 Å molecular sieves (MS4 A) has been found to serve as a catalyst for the oxidation of arylmethanols using dioxygen as an oxidant. We propose an oxidation mechanism based on the isolation and reactivity study of a trivalent cerium complex [Ce{NH(CH₂CH₂N=CHC₆H₂‐3,5‐(tBu)₂‐2‐O)₂}(NO₃)(THF)] ( 2 ), its side‐on μ‐O₂ adduct [Ce{NH(CH₂CH₂N=CHC₆H₂‐3,5‐(tBu)₂‐2‐O)₂}(NO₃)]₂(μ‐η²:η²‐O₂) ( 3 ), and the hydroxo‐bridged Ce^IV complex [Ce{NH(CH₂CH₂N=CHC₆H₂‐3,5‐(tBu)₂‐2‐O)₂}(NO₃)]₂(μ‐OH)₂ ( 4 ) as key intermediates during the catalytic cycle. Complex 2 was synthesized by reduction of 1 with 2,5‐dimethyl‐1,4‐bis(trimethylsilyl)‐1,4‐diazacyclohexadiene. Bubbling O₂ into a solution of 2 resulted in formation of the peroxo complex 3 . This provides the first direct evidence for cerium‐catalyzed oxidation of alcohols under an O₂ atmosphere.     

A 2D coordination polymer assembled from a nickel(II) tetraazamacrocyclic cation and 4,4′‐(dimethylsilanediyl)diphthalate(3–) linker

The preformed nickel(II) complex of the 14‐membered macrocyclic ligand 1,4,8,11‐tetraazacyclotetradecane (cyclam, L), when treated with 4,4′‐(dimethylsilanediyl)diphthalic acid (H₄A) in a DMF/H₂O mixture (4:1 v/v) under heating, leads to [Ni(L)]₃(HA)₂·3DMF ( I·DMF ). Redissolution of this compound in a DMF/H₂O/MeOH mixture (4:1:30 v/v/v) with mild acidification under gentle heating results in the formation of a similar compound but containing water and methanol molecules of crystallization, [Ni(L)]₃(HA)₂·5H₂O·2MeOH ( II·H₂O ). At lower temperature and concentration of reactants and longer reaction time, single crystals of composition {[{Ni(L)}₃(HA)₂]·4CH₃OH}_n ( II·MeOH ) were isolated. Single‐crystal X‐ray diffraction analysis of this compound, which, according to PXRD is isostructural with II·H₂O but different from I·DMF , revealed its two‐dimensional (2D) polymeric structure, i.e. poly[[bis{μ₃‐4‐[(4‐carboxy‐3‐carboxylatophenyl)dimethylsilyl]benzene‐1,2‐dicarboxylato‐κ³O¹:O²:O^3′}tris(1,4,8,11‐tetraazacyclotetradecane‐κ⁴N)trinickel(II)] methanol tetrasolvate], {[Ni₃(C₁₈H₁₃O₈Si)₂(C₁₀H₂₄N₄)₃]·4CH₃OH}_n. It is built up of the monoprotonated tricarboxylate HA^3? ligand coordinated in a monodentate manner in the axial positions of two crystallographically independent Ni^II cations, one of which is located on a crystallographic inversion centre. Both metal ions adopt a slightly tetragonally elongated trans‐N₄O₂ octahedral geometry. The compound has a lamellar structure with polymeric layers oriented parallel to the (10) plane, which are in turn linked via hydrogen bonds involving protonated carboxylic acid groups of the ligand. Bulk compounds I·DMF and II·H₂O were characterized by FT–IR and diffuse reflectance spectroscopy and thermogravimetry, which provide evidence of their structural differences.     

Three Novel 1‐H‐Benzimidazole‐5‐Carboxylate‐Based Nickel(II)/Cobalt(II) Coordination Polymers: Synthesis,Crystal Structures,Luminescent, and Magnetic Properties

Three 1H‐benzimidazole‐5‐carboxylate (Hbic^–)‐based coordination polymers, {[Ni(H₂O)(Hbic)₂] · 2H₂O}_n ( 1 ), {[Ni(H₂O)₂(Hbic)₂] · 3H₂O}_n ( 2 ), and {[Co₂(H₂O)₄(Hbic)₄] · 4DMF · 3H₂O}_n ( 3 ) were obtained by reactions of the ligand H₂bic and Ni^II or Co^II salts in the presence of different structure directing molecules. They were structurally characterized by single‐crystal X‐ray diffraction, IR spectra, elemental analysis, thermal stability, luminescent, and magnetic measurements. Structural analysis suggests that the three polymers exhibit a 2D (4, 4) layer for 1 and 1D linear double chains for both 2 and 3 due to the variable binding modes and the specific spatial orientation of the Hbic^– ligand towards the different paramagnetic metal ions, which were further aggregated into different 3D supramolecular architectures by popular hydrogen‐bonding interactions. Weak and comparable antiferromagnetic couplings mediating by Hbic^– bridge are observed between the neighboring spin carriers for 2 and 3 , respectively. Additionally, complexes 1 – 3 also display different luminescence emissions at room temperature due to the ligand‐to‐metal charge transfer.     

Hydrothermal Synthesis,Structure, Magnetic,and Photoluminescent Properties of a Heterometallic Cobalt(II)/Cerium(III) Coordination Compound with the Ligand Pyrazine 2, 3‐di­carboxylic Acid

Hydrothermal reaction of the metalloligand {[Co(Pzdc)₂] · 2H₂O}_n ( 1 ) with Ce(NO₃)₃ · 6H₂O yields a heterometallic 3d‐4f coordination compound {[Ce₂Co(Pzdc)₄(H₂O)₆] · 2H₂O}_n ( 2 ) (H₂Pzdc = pyrazine 2, 3‐dicarboxylic acid). X‐ray structure determination, IR spectroscopy, elemental analysis, thermogravimetric analysis, and magnetic property for the targets are presented. Compound 1 affords one‐dimensional double zigzag chains. Compound 2 features a three‐dimensional Co^II–Ce^III herringbone structure, in which the slightly deformational 1 and central Ce^III atoms are linked by Pzdc^2– spacers, and is further analyzed with {4.6₂}₂{4₂.6₂.8₂}{6₃}₂{6₅.8}₂ topology symbol. Magnetic property analysis reveals that the antiferromagnetic interactions occur in compound 2 due to a long‐range superexchange pathway between adjacent magnetic centers. In addition, the solid state photoluminescence of 2 was investigated.     

Pt2II and Pt2III dimers containing a Pt2(2,2′‐bipyridine)2(μ‐N,N‐dimethyl­guanidinato)2 unit

The syntheses and crystal structures of the title Pt₂^II and Pt₂^III dimers doubly bridged with N,N‐dimethyl­guanidinate ligands, namely bis­(μ‐N,N‐dimethyl­guanidinato)bis­[(2,2′‐bipyridine)platinum(II)](Pt—Pt) bis­(hexa­fluoro­phosphate) acetonitrile disolvate, [Pt₂^II(C₃H₈N₃)₂(C₁₀H₈N₂)₂](PF₆)₂·2CH₃CN, (I), and guanidinium bis­(μ‐N,N‐dimethyl­guanidinato)bis­[(2,2′‐bipyridine)sulfatoplatinum(III)](Pt—Pt) bis­(hexa­fluoro­phosphate) nitrate hexa­hydrate, (C₃H₁₀N₃)[Pt^III₂(C₃H₈N₃)₂(SO₄)₂(C₁₀H₈N₂)₂]NO₃·6H₂O, (II), are reported. The oxidation of the Pt₂^II dimer into the Pt₂^III dimer results in a marked shortening of the Pt—Pt distance from 2.8512 (6) to 2.5656 (4) Å. The change is mainly compensated for by the change in the dihedral angle between the two Pt coordination planes upon oxidation, from 21.9 (2) to 16.9 (3)°. We attribute the relatively strong one‐dimensional stack of dimers achieved in the Pt₂^II compound in part to the strong Pt^II⋯C(bpy) associations (bpy is 2,2′‐bipyridine) in the crystal structure [Pt⋯C = 3.416 (10) and 3.361 (12) Å].     

Two Heterometallic–Organic Frameworks Composed of Iron(III)‐Salen‐Based Ligands and d10 Metals: Gas Sorption and Visible‐Light Photocatalytic Degradation of 2‐Chlorophenol

Two examples of heterometallic–organic frameworks (HMOFs) composed of dicarboxyl‐functionalized Fe^III‐salen complexes and d¹⁰ metals (Zn, Cd), [Zn₂(Fe‐L)₂(μ₂‐O)(H₂O)₂] ? 4 DMF ? 4 H₂O ( 1 ) and [Cd₂(Fe‐L)₂(μ₂‐O)(H₂O)₂] ? 2 DMF ? H₂O ( 2 ) (H₄L=1,2‐cyclohexanediamino‐N,N′‐bis(3‐methyl‐5‐carboxysalicylidene), have been synthesized and structurally characterized. In 1 and 2 , each square‐pyramidal Fe^III atom is embedded in the [N₂O₂] pocket of an L^4? anion, and these units are further bridged by a μ₂‐O anion to give an (Fe‐L)₂(μ₂‐O) dimer. The two carboxylate groups of each L^4? anion bridge Zn^II or Cd^II atoms to afford a 3D porous HMOF. The gas sorption and magnetic properties of 1 and 2 have been studied. Remarkably, 1 and 2 show activity for the photocatalytic degradation of 2‐chlorophenol (2‐CP) under visible‐light irradiation, which, to the best of our knowledge, is the first time that this has been observed for Fe^III‐salen‐based HMOFs.     

Syntheses,Structures and Characterization of Four Metal‐Organic Frameworks constructed by 2,2′,6,6′‐Tetramethoxy‐4,4′‐biphenyldicarboxylic Acid

Four metal‐organic frameworks (MOFs), {[Mn_3.5L(OH)(HCOO)₄(DMF)] · H₂O} ( 1 ), {[In_2.5L₂O(OH)_1.5(H₂O)₂] · DMF · CH₃CN · 2H₂O} ( 2 ), {[Pb₄L₃O(DMA)] · CH₃CN} ( 3 ), and {[LaL(NO₃)(DMF)₂] · 2H₂O} ( 4 ) were synthesized by utilizing the ligand 2,2′,6,6′‐tetramethoxy‐4,4′‐biphenyldicarboxylic acid (H₂L) via solvothermal methods. All MOFs were characterized by single‐crystal X‐ray diffraction, powder X‐ray diffraction, thermogravimetric analysis, and infrared spectroscopy. In 1 , the Mn²⁺ ions are interconnected by formic groups in situ produced via DMF decomposition to form a rare 2D macrocyclic plane, which is further linked by L^2– to construct the final 3D network. In 2 , 1D zip‐like infinite chain is formed and then interconnected to build the 3D framework. In 3 , a [Pb₆(μ₄‐O)₂(O₂C)₁₀(DMA)₂] cluster with a centrosymmetric [Pb₆(μ₄‐O)₂]⁸⁺ octahedral core is formed in the 3D structure. In 4 , the La³⁺ ions are connected with each other through carboxylate groups of L^2– to generate 1D zigzag chain, which is further linked by L^2– to construct a 3D network with sra topology. Solid photoluminescence properties of 3 and 4 were also investigated.     

Controllable Syntheses of Porous Metal–Organic Frameworks: Encapsulation of LnIII Cations for Tunable Luminescence and Small Drug Molecules for Efficient Delivery

Two porous metal–organic frameworks (MOFs), [Zn₃(L)(H₂O)₂] ? 3 DMF ? 7 H₂O ( MOF‐1 ) and [(CH₃)₂NH₂]₆[Ni₃(L)₂(H₂O)₆] ? 3 DMF ? 15 H₂O ( MOF‐2 ), were synthesized solvothermally (H₆L=1,2,3,4,5,6‐hexakis(3‐carboxyphenyloxymethylene)benzene). In MOF ‐ 1 , neighboring Zn^II trimers are linked by the backbones of L ligands to form a fascinating 3D six‐connected framework with the point symbol (4¹².6³) (4¹².6³). In MOF‐2 , eight L ligands bridge six Ni^II atoms to generate a rhombic‐dodecahedral [Ni₆L₈] cage. Each cage is surrounded by eight adjacent ones through sharing of carboxylate groups to yield an unusual 3D porous framework. Encapsulation of Ln^III cations for tunable luminescence and small drug molecules for efficient delivery were investigated in detail for MOF‐1 .     

Porous Metal‐organic Framework based on Strip‐shaped Manganese(II) Chains: Synthesis,Structure, and Magnetic Properties

The Mn^II‐based porous metal‐organic framework, [Mn₃(btca)₂(HCOO)(μ₃‐OH)(H₂O)₂] · 2DMF ( 1 ) (H₂btca = benzotriazole‐5‐carboxylate acid), was prepared by the solvothermal reaction of Mn(CH₃COO)₂ · 4H₂O and H₂btca, which was characterized by infrared spectroscopy, thermogravimetric analyses, and X‐ray crystallographic study. 1 exhibits 3D framework with 1D rectangle channels constructed by the strip‐shaped chains containing [Mn₅(μ₃‐OH)₂(btca)₄]^– pentaclusters subunits. Furthermore, the magnetic measures show that 1 exhibits weak ferromagnetic behavior at low temperature.     

Two different one‐dimensional supramolecular chains formed from the reaction of 2‐[1‐(pyridin‐4‐ylmethyl)‐1H‐benzimidazol‐2‐yl]quinoline with two different precursors,Co(NO3)2 and CoCl2

Two different one‐dimensional supramolecular chains with Co^II cations have been synthesized based on the semi‐rigid ligand 2‐[1‐(pyridin‐4‐ylmethyl)‐1H‐benzimidazol‐2‐yl]quinoline (L), obtained by condensation of 2‐(1H‐benzimidazol‐2‐yl)quinoline and 4‐(chloromethyl)pyridine hydrochloride. Starting from different Co^II salts, two new compounds have been obtained, viz. catena‐poly[[[dinitratocobalt(II)]‐μ‐2‐[1‐(pyridin‐4‐ylmethyl)‐1H‐benzimidazol‐2‐yl]quinoline] dichloromethane monosolvate acetonitrile monosolvate], {[Co(NO₃)₂(C₂₂H₁₆N₄)]·CH₂Cl₂·CH₃CN}_n, (I) and catena‐poly[[[dichloridocobalt(II)]‐μ‐2‐[1‐(pyridin‐4‐ylmethyl)‐1H‐benzimidazol‐2‐yl]quinoline] methanol disolvate], {[CoCl₂(C₂₂H₁₆N₄)]·2CH₃OH}_n, (II). In (I), the Co^II centres lie in a distorted octahedral [CoN₃O₃] coordination environment. {Co(NO₃)₂L}_n units form one‐dimensional helical chains, where the L ligand has different directions of twist. The helical chains stack together via interchain π–π interactions to form a two‐dimensional sheet, and another type of π–π interaction further connects neighbouring sheets into a three‐dimensional framework with hexagonal channels, in which the acetonitrile molecules and disordered dichloromethane molecules are located. In (II), the Co^II centres lie in a distorted trigonal–bipyramidal [CoCl₂N₃] coordination environment. {CoCl₂L}_n units form one‐dimensional chains. The chains interact via C—H...π and C—H...Cl interactions. The result is that two‐dimensional sheets are generated, which are further linked into a three‐dimensional framework via interlayer C—H...Cl interactions. When viewed down the crystallographic b axis, the methanol solvent molecules are located in an orderly manner in wave‐like channels.