Investigation of the zinc(II) acetylacetonate/benzotriazole reaction system in the presence of bridging N,N′-ligands: Pentanuclear, enneanuclear and polymeric complexes

The reaction of Zn(acac)₂ with btaH (1,2,3-benzotriazole) in dmf yielded the pentanuclear complex [Zn₅(bta)₆(acac)₄(dmf)]·dmf (1·dmf). In the presence of pyrazine, the pentanuclear [Zn₅(bta)₆(acac)₄(dmf)]·3.7dmf (2·3.7dmf) and enneanuclear [Zn₉(bta)₁₂(acac)₆]·6dmf (3·6dmf) complexes were formed, whereas in the presence of 4,4′-bpy the 1D coordination polymer [Zn(acac)₂(4,4′-bpy)]_n (4) was isolated. The molecular structures of 1·dmf and 2·3.7dmf reveal that the [Zn₅] clusters consist of four Zn^II ions which span the corners of a tetrahedron and the fifth resides at its centre. The molecular structure of 3·6dmf reveals that the [Zn₉] clusters consist of two corner sharing tetrahedra and the structure can be described as the addition of two [Zn₅] clusters of 1·dmf and/or 2·3.7dmf followed by the simultaneous abstraction of [Zn(acac)₂] and dmf molecules; this alternative was accomplished by recrystallization of 1·dmf from dmf which yielded 3·6dmf. Each of the μ₃-κN:κN′:κN′′ benzotriazolate ligands in 1·dmf, 2·3.7dmf and 3·6dmf spans an edge of the tetrahedron. The molecular structure of 4 reveals mononuclear [Zn(acac)₂] units bridged via 4,4′-bpy molecules to 1D coordination polymer. Characteristic IR bands of the four complexes are discussed in terms of the coordination modes of the ligands and known structures.     

Silver(I)-organic networks constructed with flexible silver-ethynide supramolecular synthon o-, m-, p-Cl–C6H5OCH2CC⊃Agn (n = 4, 5)

A series of five silver coordination polymers [(AgL1)·(AgCF₃COO)₅·(H₂O)₃] (1), [(AgL1)₂·(AgCF₃COO)₁₁·(H₂O)₆] (2), [(AgL2)·(AgCF₃COO)₃·(H₂O)] (3), [(AgL3)·(AgCF₃COO)₄·(CH₃CN)₂] (4), and [(AgL3)·(AgCF₃COO)₇·(CH₃CN)₂·(H₂O)₂] (5) have been constructed from three flexible anionic ligands HL1, HL2, and HL3 (HL1 = 1-chloro-2-(prop-2-ynyloxy)benzene, HL2 = 1-chloro-3-(prop-2-ynyloxy)benzene, HL3 = 1-chloro-4-(prop-2-ynyloxy)benzene). In these compounds, the invariable appearance of the μ₄- and μ₅-ligation modes of the ethynide moiety affirms the general utility of the flexible silver-ethynide supramolecular synthon o-, m-, p-Cl?C₆H₅OCH₂CC?Ag_n (n = 4, 5) in coordination network assembly. Among them, Ag?Cl interaction plays a vital role in assembling the supramolecular structures in complexes 1?3.     

Cross-linking nanostructured spherical capsules as building units by crystal engineering: related chemistry

The compound [Mo₇₂Fe₃₀O₂₅₂(CH₃COO)₁₀{Mo₂O₇(H₂O)}{H₂Mo₂O₈(H₂O)}₃ (H₂O)₉₁]·ca. 140 H₂O 3≡3a·ca. 140 H₂O, an important educt for an unusual solid state reaction, can now be obtained easily by reacting (NH₄)₄₂[{Mo^V₂O₄(CH₃COO)}₃₀{(Mo)Mo₅O₂₁(H₂O)₆}₁₂]·10 CH₃COONH₄·ca. 300 H₂O 1 with FeCl₃·6 H₂O in water. Interestingly, the freshly precipitated crystals of 3 contain discrete spherical clusters of the type {Mo^VI₇₂Fe^III₃₀} with as yet unprecedented 30×5 unpaired electrons (S=150/2 at room temperature). Upon drying 3, its cluster units 3a get covalently linked to form layers in a step by step solid state reaction, according to the scheme described below, resulting finally in the crystalline reaction product [H₄Mo₇₂Fe₃₀O₂₅₄(CH₃COO)₁₀{Mo₂O₇(H₂O)}{H₂Mo₂O₈(H₂O)}₃(H₂O)₈₇]·ca. 80 H₂O 44a·ca. 80 H₂O. The linking process at the Fe sites follows the well known inorganic condensation process leading to Fe^III polycations in aqueous solution according to the scheme Fe(OH₂)+(H₂O)Fe Fe(OH)+(H₂O)Fe Fe–O–Fe and thus is based on a type of crystal engineering with nanostructured spherical building blocks. This process does not allow chaotic characteristics in contrast to the mentioned polycation formation. Careful investigation leads to the identification of an intermediate 5 containing clusters 5a — with the same cluster composition as 3a and 4a — in the closest possible non-covalent contact. The related materials are of tremendous interest for magnetochemistry (nano-magneto-technology).

     

Synthesis,structure and magnetic properties of the pentanuclear complex [Fe<Subscript>2</Subscript>(CN)<Subscript>12</Subscript>Ni<Subscript>3</Subscript>(L)<Subscript>6</Subscript>]·27H<Subscript>2</Subscript>O,where L is nitronyl nitroxide

We succeeded in synthesizing a new high-spin complex [Fe₂(CN)₁₂Ni₃(L)₆]·27H₂O, where L is stable nitroxide 2-(imidazol-4-yl)-4,4,5,5-tetramethyl-2-imidazoline-3-oxide-1-oxyl. According to X-ray diffraction data, the metal core of the pentanuclear [Fe₂(CN)₁₂Ni₃(L)₆] molecule is a trigonal bipyramid with Fe atoms occupying the axial positions and linked via CN bridges to {NiL₂} fragments laying in the equatorial plane. A peculiarity of this coordination compound is a large number of water molecules per the [Fe₂(CN)₁₂Ni₃(L)₆] pentanuclear molecule in the structure. The complex character of the μ_eff(T) dependence points to many competing channels of exchange interactions between the three types of paramagnetic centers.     

Synthesis,Structure and Properties of an Unusual 2D Network Zinc Coordination Polymer Based on Pentanuclear Zinc Cluster

An unusual zinc(II) coordination polymer [Zn₅(OH)₂(bbtz)₂(bdc)₄]_n ( 1 ) [bbtz?1,4‐bis(1,2,4‐triazol‐1‐ylmethyl)benzene, bdc?1,2‐benzenedicarboxylate] was synthesized and characterized. 1 contains an unusual 2D network based on pentanuclear zinc(II) cluster [Zn₅(OH)₂]. Two adjacent pentanuclear Zn(II) clusters are bridged by four bdc ligands and extend to form the one‐dimensional chain. The bbtz ligands further link the one‐dimensional chains, resulting in a two‐dimensional coordination network. The luminescence and thermal stability were investigated.     

Two photoluminescent pentanuclear homo- and hetero-metal complexes based on benzotriazole bridge

Two new discrete Btz-bridged pentanuclear metal complexes, [HDMF][NaHg₄(Btz)₆I₄] (1) and [Zn₅(Btz)₆(L)₃(Ac)]?·?0.5MeOH?·?0.5H₂O (2) (Btz?=?deprotonated benzotriazole, L?=?p-aminobenzoate, HDMF?=?protonated DMF, and Ac?=?acetate), were synthesized using three-layered diffusion and natural evaporation methods, respectively. In 1, the pentanuclear anion [NaHg₄(Btz)₆I₄]^? is composed of a tetrahedral arrangement of four four-coordinate Hg(II) ions centered on the six-coordinate Na(I), and thereby forming a rare Btz-bridged hetero-metal complex. Compound 2 is a neutral pentanuclear homo-metal complex, consisting of a tetrahedral arrangement of four five-coordinate Zn(II) ions centered on the fifth six-coordinate Zn(II). The thermal stabilities and solid-state photoluminescence of the two complexes have been investigated.     

Derivatives of Bis(diphenylphosphino)maleic Anhydride as Ligands in Polynuclear Gold(I) Complexes

Based on the new binuclear gold(I) complex [(AuCl)₂(L1)] (1) (L1?=?2,3-bis(diphenylphosphino)maleic anhydride) four new polynuclear compounds were synthesized by reactions of 1 with E(SiMe₃)₂ (E?=?S, Se). During the formation of these new compounds the initial ligand L1 undergoes various transformations (e.g. substitution, hydration or hydrogenation) leading to the new ligands: trans-2,3-bis(diphenylphosphino)succinic anhydride (L2), 2-diphenylphosphino-3-mercapto-maleic anhydride anion (L3), 2-diphenylphosphino-3-selenolato-maleic anhydride anion (L4) and 2,3-bis(diphenylphosphino)succinic acid (L5). In case of using the sulfur species S(SiMe₃)₂ a pentanuclear cluster, [Au₅(PPh₂)₃(L3)₂] (2), and a 24-nuclear cluster, [Au₂₄S₆(PPh₂)₄(L3)₈] (3), could be obtained. With Se(SiMe₃)₂ the binuclear complex, [(AuCl)₂(L2)] (4), and the dodecanuclear cluster, [Au₁₂Se₄(L4)₄(L5)₂] (5), were yielded.     

Pentanuclear Gold(I) Cluster with an Axially Chiral Biaryl Center: Synthesis and Chiral Transformation

We synthesized and structurally characterized a novel pentanuclear gold(I) cluster by a Ag(I)‐mediated organometallic transformation. The racemic mixture of this pentanuclear gold cluster has been successfully transformed into an enantio‐rich hexanuclear cluster compound by adding adscititious chiral species [Au₂(S‐BINAP)₂]²⁺ (S‐BINAP = (S)‐2,2’‐bis(diphenylphosphino)‐1,1’‐binaphthyl). In this process, a [AuPPh₃]⁺ species in the pentanuclear cluster is replaced by [Au₂(S‐BINAP)₂]²⁺. This strategy represents a new method for the designed construction of chiral metal clusters.     

Treatment activity of 0D/2D coordination complexes on gastric carcinoma by inhibiting the cancer cell viability

In the present study, via reaction of Ni(NO₃)₂·6H₂O with two flexible dicarboxylic ligands under the solvothermal reaction conditions, two new Ni(II)-containing coordination complexes with the chemical formulae of [Ni4(L1)₄(DMF)₄·2DMF]_n (1) and [Ni(L2)(DMF)]_n (2) (H2L1= 2,2'-(1,4-phenylenebis(methylene))bis(sulfanediyl)dinicotinic acid and H2L2 ?= ?2,2'-(1,2-phenylenebis(methylene))bis(sulfanediyl)dinicotinic acid) have been prepared. For the treatment of the gastric carcinoma, the Cell Counting Kit-8 kit was carried out for the detection of the gastric carcinoma cells viability after compound treatment. Additionally, the Annexin V-FITC/PI apoptosis assay was also conducted and the apoptosis levels of the gastric carcinoma cells were determined after compound exposure.     

Structural variations in nickel, palladium, and platinum complexes containing pyrimidyl N-heterocyclic carbene ligand

Nickel(II), palladium(II), and platinum(II) complexes of 2-(3-mesitylimidazolylidenyl)pyrimidine (L), [Ni₂(μ-Cl)₂(L)₄][Ag₂Cl₄] (3), [Ni₂(μ-I)₂(L)₄][NiI(L)₂(CH₃CN)]₂[Ag₄I₈] (4), [PdCl₂(L)] (5), [PdI₂(L)] (6), and [PtCl(L)₂][AgCl₂] (7) have been obtained from the carbene transfer reactions of [Ag(L)Cl] (2). These complexes have been fully characterized by spectroscopic methods and single-crystal X-ray structure analyses. The mono(carbene)palladium and bis(carbene)platinum complexes display normal square–planar structures. Nickel complexes 3 and 4 are rare examples of paramagnetic nickel(II) complexes of N-heterocyclic carbenes having octahedral geometry.     

Cyanide-bridged complexes based on dinuclear Cu(II)-M(II) [M = Pb and Cu] building blocks: Synthesis, crystal structures and magnetic properties

Four cyanide-bridged heterometallic complexes {[CuPb(L 1 )][Fe III (bpb)(CN) 2 ]} 2 ·(ClO 4 ) 2 ·2H 2 O·2CH 3 CN (1), {[CuPb(L 1 )] 2 [Fe II (CN) 6 ](H 2 O) 2 }·10H 2 O (2), {[Cu 2 (L 2 )][Fe III (bpb)(CN) 2 ] 2 }·2H 2 O·2CH 3 OH (3) and {[Cu 2 (L 2 )] 3 [Fe III (CN) 6 ] 2 (H 2 O) 2 }·10H 2 O (4) have been synthesized by treating K[Fe III (bpb)(CN) 2 ] [bpb 2-=1,2-bis(pyridine-2-carboxamido)benzenate] and K 3 [Fe III (CN)] 6 with dinuclear compartmental macrocyclic Schiff-base complexes [CuPb(L 1 )] (ClO 4 ) 2 or [Cu 2 (L 2 )]·(ClO 4 ) 2 , in which H 2 L 1 was derived from 2,6-diformyl-4-methyl-phenol, ethylenediamine, and diethylenetriamine in the molar ratio of 2:1:1 and H 2 L 2 from 2,6-diformyl-4-methyl-phenol and propylenediamine in the molar ratio of 1:1. Single crystal X-ray diffraction analysis reveals that compound 1 displays a cyclic hexanuclear heterotrimetallic molecular structure with alternating [FeⅢ (bpb)(CN) 2 ]- and [CuPb(L 1 )] 2+ units. Complex 2 is of a neutral dumb-bell-type pentanuclear molecular configuration consisting of one [Fe(CN)6] 4- anion sandwiched in two [CuPu(L 1 )] 2+ cations, and the pentanuclear moieties are further connected by the hydrogen bonding to give a 2D supramolecular framework. Heterobimetallic complex 3 is a tetranuclear molecule composed of a centrosymmetric [Cu 2 (L2)] 2+ segment and two terminal cyanide-containing blocks [FeⅢ (bpb)(CN)2 ]- . Octanuclear compound 4 is built from two [Fe(CN)6]3- anions sandwiched in the three [Cu 2 L 2 ] 2+ cations. Investigation of their magnetic properties reveals the overall antiferromagnetic behavior in the series of complexes except 2.     

Synthesis and X-ray diffraction study of cs3[UO2(CH3COO)3]2[UO2(CH3COO)(NCS)2(H2O)] and Cs5[UO2(CH3COO)3]3[UO2(NCS)4(H2O)] · 2H2O

Cs₃[UO₂(CH₃COO)₃]₂[UO₂(CH₃COO)(NCS)₂(H₂O)] (I) and Cs₅[UO₂(CH₃COO)₃]₃[UO₂ (NCS)₄(H₂O)] · 2H₂O (II) have been synthesized via the reaction between uranyl acetate and cesium thiocyanate in aqueous solution. According to single-crystal X-ray diffraction data, both compounds crystallize in monoclinic system with the unit cell parameters a = 18.7036(5) Å, b = 16.7787(3) Å, c = 12.9636(3) Å, β = 92.532(1)°, space group C2/c, Z = 4, R = 0.0434 (I); and a = 21.7843(3) Å, b = 24.6436(5) Å, c = 13.1942(2) Å, β = 126.482(1)°, space group Cc, Z = 4, R = 0.0273 (II). Uranium-containing structural units of compound (I) are mononuclear [UO₂(CH₃COO)₃]^? and [UO₂(CH₃COO)(NCS)₂(H₂O)]^? moieties, which correspond to the AB ₃ ⁰¹ and AB⁰¹M ₃ ¹ crystallochemical groups (A = UO ₂ ²⁺ , B⁰¹ = CH₃COO^?, M¹ = NCS^? and H₂O). The structure of compound II is built of [UO₂(CH₃COO)₃]^? and [UO₂(NCS)₄(H₂O)]^2? complexes, which belong to the AB ₃ ⁰¹ and AM ₅ ¹ crystallochemical groups, respectively. Uranium-containing complexes in both structures are linked into a framework by hydrogen bonds and electrostatic interactions with cesium cations. The IR spectra of compounds I and II agree well with X-ray diffraction data.     

Preparation and structures of copper(II) and zinc(II) complexes with 5-ferrocenylpyrimidine: Structural variation derived from flexible coordination ability of the ligand and metal ions

5-Ferrocenylpyrimidine (FcPM) reacts with dinuclear copper(II) carboxylates ([Cu₂(RCOO)₄]; R = C₆H₅, C₅H₁₁, CH₃) to produce one-dimensional coordination polymers [Cu₂(C₆H₅COO)₄(FcPM)]_n (1), [Cu₂(C₅H₁₁COO)₄(FcPM)]_n · nCH₃CN (2), and a discrete tetranuclear complex [Cu₂(CH₃COO)₄(FcPM)₂] (3). Compounds 1 and 2 show similar zigzag chain structures, comprising alternate linking of FcPM and dinuclear copper(II) units, whereas the structure of 3 corresponds to the local structural motifs of 1 and 2. Reaction of FcPM with zinc salts (ZnX₂; X = NO₃, SCN) affords zinc-centered ferrocenyl cluster complexes, [Zn(NO₃)₂(FcPM)₃] (4) and [Zn(SCN)₂(FcPM)₂] · 0.5H₂O (5), with varying M:L ratios. FcPM acts as a bidentate ligand in 1 and 2, and as a monodentate ligand in the others.     

The synthesis, structural characterization, magnetochemistry and Mössbauer spectroscopy of [Fe3LnO2(CCl3COO)8H2O(THF)3] (Ln = Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Lu and Y)

The new tetranuclear complexes [Fe₃Ln(μ₃-O)₂(CCl₃COO)₈(H₂O)(THF)₃]·THF (Ln = Ce^III (1), Pr^III (2), Nd^III (3)) and [Fe₃Ln(μ₃-O)₂(CCl₃COO)₈(H₂O)(THF)₃]·THF·C₇H₁₆ (Ln = Sm^III (4), Eu^III (5), Gd^III (6), Tb^III (7), Dy^III (8), Ho^III (9), Lu^III (10) and Y^III (11)) have been prepared. All compounds were prepared by the reaction between [Fe₂BaO(CCl₃COO)₆(THF)₆] and the corresponding Ln^III nitrate salt. The crystal structures of 1–4, 8 and 9 have been determined; these isostructural molecules have a non-planar {Fe₃Ln(μ₃-O)₂} “butterfly” core. Magnetic susceptibility measurements show dominant intramolecular antiferromagnetic exchange interactions for all the complexes. ⁵⁷Fe Mössbauer spectroscopy shows three different environments for the Fe^III metal ions, all in their high-spin state S = 5/2 (confirming that no electron transfer from Ce^III to Fe^III occurs in 1). At the time scale of the Mössbauer spectroscopy (about 10⁻⁷ s), evidence of magnetization blocking, i.e. slow relaxation of the magnetization, is observed below 3 K for 7, which was confirmed by ac susceptibility measurements.     

Construction of tetranuclear macrocycles through C-H activation and structural transformation induced by [2+2] photocycloaddition reaction

A series of binuclear complexes [{Cp*Ir(OOCCH₂COO)}₂(pyrazine)] ( 1 b ), [{Cp*Ir(OOCCH₂COO)}₂(bpy)] ( 2 b ; bpy=4,4′‐bipyridine), [{Cp*Ir(OOCCH₂COO)}₂(bpe)] ( 3 b ; bpe=trans‐1,2‐bis(4‐pyridyl)ethylene) and tetranuclear metallamacrocycles [{(Cp*Ir)₂(OOC‐C?C‐COO)(pyrazine)}₂] ( 1 c ), [{(Cp*Ir)₂(OOC‐C?C‐COO)(bpy)}₂] ( 2 c ), [{(Cp*Ir)₂(OOC‐C?C‐COO)(bpe)}₂] ( 3 c ), and [{(Cp*Ir)₂[OOC(H₃C₆)‐N?N‐(C₆H₃)COO](pyrazine)}₂] ( 1 d ), [{(Cp*Ir)₂[OOC(H₃C₆)‐N?N‐(C₆H₃)COO](bpy)}₂] ( 2 d ), [{(Cp*Ir)₂[OOC(H₃C₆)‐N?N‐(C₆H₃)COO](bpe)}₂] ( 3 d ) were formed by reactions of 1 a – 3 a {[(Cp*Ir)₂(pyrazine)Cl₂] ( 1 a ), [(Cp*Ir)₂(bpy)Cl₂] ( 2 a ), and [(Cp*Ir)₂(bpe)Cl₂] ( 3 a )} with malonic acid, fumaric acid, or H₂ADB (azobenzene‐4,4′‐chcarboxylic acid), respectively, under mild conditions. The metallamacrocycles were directly self‐assembled by activation of C? H bonds from dicarboxylic acids. Interestingly, after exposure to UV/Vis light, 3 c was converted to [2+2] cycloaddition complex 4 . The molecular structures of 2 b , 1 c , 1 d , and 4 were characterized by single‐crystal x‐ray crystallography. Nanosized tubular channels, which may play important roles for their stability, were also observed in 1 c , 1 d , and 4 . All complexes were well characterized by ¹H NMR and IR spectroscopy, as well as elemental analysis.     

Cobalt(II), nickel(II) and zinc(II) coordination compounds derived from aromatic amines

The structural and spectroscopic characterization of coordination compounds of four aromatic amines derived from benzimidazole, 2-aminobenzimidazole (L1), 1-(S-methylcarbodithioate)-2-aminobenzimidazole (L2), 2-(2-aminophenyl)-1H-benzimidazole (L3) and 6,6-dimethyl-5H-benzimidazolyl[1,2-c]quinazoline (L4) are reported. Cobalt(II) [Co(L1)₂(CH₃COO)₂] (1) and nickel(II) [Ni(L1)₂(CH₃COO)₂] (2) acetate coordination compounds of L1 are discussed. The synthesis and the X-ray crystal structure of the new 1-(S-methylcarbodithioate)-2-aminobenzimidazole (L2) is informed, together with its cobalt(II) [Co(L2)₂Cl₂] (3), [Co(L2)₂Br₂] (4) and zinc(II) [Co(L2)₂Cl₂] (5), [Zn(L2)₂Br₂] (6) coordination compounds. In these compounds the imidazolic nitrogen is coordinated to the metal center, while the ArNH₂ and the S-methylcarbodithioate groups do not participate as coordination sites. A co-crystal of L1 and L2 is analyzed. Structural analyses of the coordination compounds of L3 showed that this ligand behaves as a bidentate ligand through the aniline and the imidazole groups forming six membered rings in the cobalt(II) [Co(L3)Cl₂] (7) and zinc(II) [Zn(L3)Cl₂] (8) compounds, as well as the nickel(II) nitrate [Ni(L3)₂(H₂O)₂](NO₃)₂ (9). The quinazoline L4 was produced by insertion of one acetone molecule and water elimination in L3, its X-ray crystal diffraction analysis, as well as that of its zinc(II) coordination compound [Zn(L4)₂Cl₂] (10), are discussed.     

Lanthanide Cluster Organic Frameworks Derived from Pyridine-2,6-dicarboxylate and Oxalate: Syntheses,Structures and Luminescence

Two novel cluster organic frameworks derived from pyridine-2,6-dicarboxylate (PDA) and oxalate (ox^2?) have been hydrothermally made: [Eu₃(SO₄)(PDA)₃(ox)_0.5(H₂O)₅]·4H₂O (1) and Er(PDA)(ox)_0.5(H₂O) (2). Compound 1 possesses one-dimensional chain structure constructed from the alternate linkage of tetranuclear [Eu₄(SO₄)₂]⁸⁺ (Eu₄) and dinuclear [Eu₂(ox)]⁴⁺ (Eu₂) clusters. Compound 2 is a two-dimensional layer based on dimeric [Er₂(COO)₂]²⁺ (Er₂) cluster units. Interestingly, such layer can be intuitively viewed as the linkages of helical chains and oxalate. In these two compounds, all anions are bivalent, and the ratio of trivalent lanthanide ions to these dianions is 2:3. Furthermore, compound 1 exhibits strong red luminescence upon 276 nm excitation.     

Cluster Organic Framework Based on Er3 and Cu5 Cluster Units

A novel cluster organic framework, Er₃Cu₅I₄L₁₀(H₂O) (1, L = 4-pyridin-3-yl-benzonate), has been hydrothermally made and structurally characterized by single crystal X-ray diffraction. Structure analysis shows [Er₃(COO)₆]³⁺ (Er₃) clusters are linked by carboxylate groups generating one dimensional wave-like chain, which further extended by Cu₅I₄ ⁺ (Cu₅) clusters into three dimensional heterometallic cluster organic framework. From the perspective of topology, such framework defines a new (7,9)-connected net, considering Er₃ and Cu₅ cores as the nodes. Furthermore, the elemental analysis, powder X-ray diffraction, infrared spectra and thermogravimetric analysis are also studied.     

Hendecanuclear [Cu_6Gd_5] magnetic cooler with high molecular symmetry of D_(3h)

A new family of isostructural 3 d-4 f polymetallic complexes,formulated as [Cu_6Ln_5(μ_3OH)_9(C_4H_8O_2N)_6(C_5H_4ON)_6(H_2O)_9]·(ClO_4)_6·(H_2O)_(22)(Ln=Pr,1;Nd,2;Sm,3;Eu,4;Gd,5),was successfully isolated through the simple hydrolysis reaction of 2-aminoisobutyric acid,2-hydroxypyridine,Cu(CH_3COO)_2·H_2O,and Ln(ClO_4)_3·6 H_2O.Notably,the [Cu_6Ln_5] clusters with high molecular symmetry ofD_(3 h) are rare examples of2-aminoisobutyric acid-based 3 d-4 f clusters.The successful theoretical modeling of 5 yielded that the Gd-Gd exchange is of order 0.2 K,whereas the Gd-Cu exchange is an order of magnitude larger.Magnetization data collected for comp lex 5 yield a magnetic entropy change(-ΔSm) of 19.6 J kg ~1 K~11 at 3 K and 7 T,which may be attributed to the weak magnetic interactions between the component metal ions.     

Thermal and photochemical transformations of 2-methylthiothiophene in triosmium clusters: photoinduced migrations of MeS from carbon to metal and back again

2-Methylthiothiophene (2-MeSC₄H₃S) oxidatively adds to [Os₃(CO)₁₀(MeCN)₂] with cleavage of the C–H bond at the 3-position to give [Os₃(μ-H)(μ-MeSC₄H₂S)(CO)₁₀] 1, the X-ray structure of which shows that the MeS group is coordinated to osmium through the S atom while the thiophene ring is coordinated to osmium through the 3-carbon atom. Only one invertomer at sulfur is observed in solution and in the crystal the Me group is exo. Thermal treatment of 1 in the dark gives only one product, [Os₃(μ-H)(μ₃-MeSC₄H₂S)(CO)₉] 2 (X-ray structure), derived by loss of a CO from the Os(CO)₄ unit of 1 with concomitant η²-coordination of the thiophene ring of bridging MeSC₄H₂S at the third metal atom. Whereas thermal reaction in the dark leads only to C–H cleavage products, visible irradiation at room temperature leads to various products derived by migration of the MeS group. Thus thermal treatment of 1 in daylight for 2 h gave 2, together with an isomer 3. Cluster 2 converts at room temperature to 3 in daylight while thermal treatment of 2 in the dark (125°C) gave no reaction. Isomer 3 of [Os₃(μ-H)(μ₃-MeSC₄H₂S)(CO)₉] (X-ray structure) is closely related to 2 except that the MeS group and the Os–C σ-bond have interchanged sites at the thiophene ring between the 2- and the 3-positions. Visible irradiation of 1 at room temperature for 3 days in daylight gave further chemical change leading to two bridging thienyl clusters, [Os₃(μ-MeS)(μ-2-C₄H₂S)(CO)₁₀] 4 and [Os₃(μ-MeS)(μ₃-2-C₄H₂S)(CO)₉] 5. Cluster 5 is the ultimate product of daylight irradiation of any of the clusters 1 to 4.