Construction of Four Coordination Polymers based on 2‐[4‐(Pyridine‐4‐yl)phenyl]‐1H‐imidazole‐4,5‐dicarboxylic Acid

The imidazole‐based dicarboxylate ligand 2‐(4‐(pyridin‐4‐yl)phenyl)‐1H‐imidazole‐4,5‐dicarboxylic acid (H₃PyPhIDC), was synthesized and its coordination chemistry was studied. Solvothermal reactions of Ca^II, Mn^II, Co^II, and Ni^II ions with H₃PyPhIDC produced four coordination polymers, [Ca(μ₃‐HPyPhIDC)(H₂O)₂]_n ( 1 ), {[M₃(μ₂‐H₂PyPhIDC)₂(μ₃‐HPyPhIDC)₂₆(H₂O)₂] · 6H₂O}_n [M = Mn ( 2 ), Co ( 3 )], and {[Ni(μ₃‐HPyPhIDC)(H₂O)] · H₂O}_n ( 4 ). Compounds 1 – 4 were analyzed by IR spectroscopy, elemental analyses, and single‐crystal and powder X‐ray diffraction. Compound 1 displays a one‐dimensional (1D) infinite chain. Compounds 2 and 3 are of similar structure, showing 2D network structures with a (4,4) topology based on trinuclear clusters. Compound 4 has another type of 2D network structure with a 3‐connected (4.8²) topology. The results revealed that the structural diversity is attributed to the coordination numbers and geometries of metal ions as well as the coordination modes and conformations of H₃PyPhIDC. Moreover, the thermogravimetric analyses of all the compounds as well as luminescence properties of the H₃PyPhIDC ligand and compound 1 were also studied.     

Metal-Rich Metallaboranes: Synthesis,Structure, and Bonding of Heteronuclear Trimetallic Clusters containing (μ3-BH) Ligand

Building upon our earlier results on the chemistry of nido-1,2-[(Cp*RuH)₂B₃H₇] (Cp*=ɳ⁵-C₅Me₅) (nido- 1 ) with different transition metal carbonyls, we continued to investigate the reactivity with group 7 metal carbonyls under photolytic condition. Photolysis of nido- 1 with [Mn₂(CO)₁₀] led to the isolation of a trimetallic [(Cp*Ru)₂{Mn(CO)₃}(μ-H)(μ-CO)₃(μ₃-BH)] ( 2 ) cluster with a triply bridging borylene moiety. Cluster 2 is a rare example of a tetrahedral cluster having hydrido(hydroborylene) moiety. In an attempt to synthesize the Re analogue of 2 , a similar reaction was carried out with [Re₂(CO)₁₀] that yielded the trimetallic [(Cp*Ru)₂{Re(CO)₃}(μ-H)(μ-CO)₃(μ₃-BH)] ( 3 ) cluster having a triply bridging borylene unit. Along with 3 , a trimetallic square pyramid cluster [(Cp*Ru)₂{Re(CO)₃}(μ-H)₂(μ-CO)(μ₃,ɳ²-B₂H₅)] ( 4 ), and heterotrimetallic hydride clusters [{Cp*Ru(CO)₂}-{Re(CO)₄}₂(μ-H)] ( 5 ) and [{Cp*Ru(CO)}{Re(CO)₄}₂(μ-H)₃] ( 6 ) were isolated. Cluster 4 is a unique example of a M₂M′B₂ cluster having diboron capped Ru₂Re-triangle. The hydride clusters 5 and 6 have triangular RuRe₂ frameworks with one and three μ-Hs respectively. All the clusters have been characterized by using mass spectrometry, ¹H, ¹¹B{¹H}, ¹³C{¹H} NMR and IR spectroscopies analyses and the structures of clusters 2 – 6 have been unambiguously established by XRD analyses. Furthermore, to understand the electronic, structural, and bonding features of the synthesized metal-rich clusters, DFT calculations have been performed.     

Multidimensional Snowflake‐shaped (3, 9)‐connected Metal‐Organic Frameworks Composed of Ni3(μ3‐O) Building Blocks and Symmetry Ligand Pyridine‐3,5‐dicarboxylic Acid

A metal‐organic polymer [Ni₃(μ₃‐O)(PDB)₃]·H₂O ( 1 ) (PDB = pyridine‐3,5‐dicarboxylate), with antiferromagnetic interactions between the adjacent Ni atoms, containing trinuclear μ₃‐oxo‐bridged metal units Ni₃(μ₃‐O) have been synthesized by hydrothermal reaction of the achiral building blocks pyridine‐3,5‐dicarboxylate (3,5‐PDB) and Ni(NO₃)₂·4H₂O. Compound 1 shows a high symmetry three‐dimensional snowflake‐shaped (3, 9)‐connected topology structures in which μ₃‐oxo mixed‐valence Ni₃O(CO₂)₆ clusters act as nine‐connected nodes and PDB ligands act as three‐connected nodes.     

Hydrothermal Synthesis of Five New Coordination Polymers Based on Benzophenone‐2, 4′‐dicarboxylic Acid and N‐Donor Spacers

Five new coordination polymers, namely, [Ni₂(L)₂(4, 4′‐bipy)₃)] · H₂O]_n ( 1 ), [Ni₂(L)₂(O) (bpp)₂]_n ( 2 ), [Zn(L)(bib)_0.5]_n ( 3 ), [Zn(L)(PyBIm)]_n ( 4 ), and [Zn₃(L)₂(OH)(im)]_n ( 5 ) [H₂L = benzophenone‐2, 4′‐dicarboxylic acid, 4, 4′‐bipy = 4, 4′‐bipyridine, bpp = 1, 3‐bis(4‐pyridyl)propane, PyBIm = 2‐(4‐pyridyl)benzimidazole, and im = imidazole] were synthesized under hydrothermal conditions. Structure determination revealed that compound 1 is a 3D network and exhibits a 4‐connected metal‐organic framework with (4².6³.8) topology, whereas compounds 2 , 3 , 4 , and 5 are two‐dimensional layer structures. In compounds 2 – 4 , dinuclear metal clusters are formed through carboxylic groups. In compound 5 , trinuclear metal clusters are formed through μ₃‐OH and carboxylic groups. The carboxylic groups exhibit three coordination modes in compounds 1 – 5 : monodentately, bidentate‐chelating, and bis‐monodentately. Furthermore, the luminescent properties for compounds 3 , 4 , and 5 were investigated.     

Hydrothermal Combination of Trilacunary Dawson Phosphotungstates and Hexanickel Clusters: From an Isolated Cluster to a 3D Framework

Three novel hexa‐Ni‐substituted Dawson phosphortungstates [Ni₆(en)₃(H₂O)₆(μ₃‐OH)₃(H₃P₂W₁₅O₅₆)] ? 14 H₂O ( 1 ), [Ni(enMe)₂(H₂O)][Ni₆(enMe)₃(μ₃‐OH)₃(H₂O)₆(HP₂W₁₅O₅₆)] ? 10 H₂O ( 2 ), and [Ni(enMe)₂]₃[Ni(enMe)₂(H₂O)][Ni(enMe)(H₂O)₂][Ni₆(enMe)₃(μ₃‐OH)₃(Ac)₂(H₂O)(P₂W₁₅O₅₆)]₂ ? 6 H₂O ( 3 ) (en=ethylenediamine, enMe=1, 2‐diaminopropane, Ac=CH₃COO^?) have been made under hydrothermal conditions and were characterized by IR spectroscopy, elemental analysis, diffuse reflectance spectroscopy, thermogravimetric analysis, powder X‐ray diffraction, and single‐crystal X‐ray diffraction. The common structural features of compounds 1 – 3 contain the similar hexa‐Ni‐substituted Dawson polyoxometalate (POM) units that can be viewed as a [Ni₆(μ₃‐OH)₃]⁹⁺ cluster capping on a [P₂W₁₅O₅₆]^12? fragment. Compounds 1 and 2 are two isolated clusters, whereas compound 3 is the first 3D POM framework constructed from hexa‐Ni‐substituted Dawson POM units and Ni(enMe) complex bridges. The preparations of compounds 1 – 3 not only indicate that triangle coplanar Ni₆ clusters are very stable fragments in both trivacant Keggin and trivacant Dawson POM systems, but also offer that the hydrothermal technique can act as an effective strategy for making novel Dawson‐type high‐nuclear transition‐metal cluster substituted POMs by combination of lacunary Dawson precusors with transition‐metal cations in the tunable role of organic ligands. In addition, magnetic measurements illustrate that there exist overall ferromagnetic interactions in compound 3 .     

Replacement of carboxylate bridges in polynuclear nickel pivalates with 2-hydroxy-6-methylpyridine anions

The reaction of 2-hydroxy-6-methylpyridine (HL, 1) with nonanuclear nickel trimethyl-acetate Ni₉(OH)₆(OOCCMe₃)₁₂(HOOCCMe₃)₄ (2) in MeCN with a ratio M: L = 1: 1 under mild conditions (20 °C, 15 min) led to degradation of the metal core to form the hexanuclear complex (HL)₂(μ ₂-HL)₂Ni₆(μ₃-OH)₂(μ₂-H₂O)₂(μ-OOCCMe₃)₈(η-OOCCMe₃)₂ (3). Further heating of 3 in acetonitrile at 80 °C for 4 h afforded the (HL)Ni₆(μ ₃-OH)(μ₃,η²-L)₃(μ,η²-L)(μ₃-L)(μ ₃-OOCCMe₃)(μ-OOCCMe₃)₄(η²-OOCCMe₃) complex. The reaction with the use of a 2: 1 THF-EtOH mixture instead of acetonitrile at 50 °C gave the decanuclear complex [Ni₁₀(μ ₃-O)₂(μ₃-OH)₄(μ-OOCCMe₃)₆(μ₃,η ²-L)₆(EtOH)₆](H₂O)₂, which is also produced from compounds 1 and 2 in ethanol. The structures of the resulting complexes were established by X-ray diffraction. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 908–917, May, 2007.     

The chain-shaped coordination polymers based on the bowl-like Ln18Ni24(23.5) clusters exhibiting favorable low-field magnetocaloric effect

The design of assembling high-nuclearity transition-lanthanide (3d-4f) clusters along with excellent magnetocaloric effect (MCE) is one of the most prominent fields but is extremely challenging. Herein, two heterometallic metal coordination polymers are constructed via the “carbonate-template” method, formulated as {[Gd₁₈Ni₂₄(IDA)₂₂(CO₃)₇(μ₃-OH)₃₂(μ₂-OH)₃(H₂O)₅Cl]·Cl₈·(H₂O)₁₄}_n and {[Eu₁₈Ni_23.5(IDA)₂₂(CO₃)₇(μ₃-OH)₃₂(H₂O)₅(IN)(CH₃COO)₂(NH₂CH₂COO)Cl]·Cl₆·(H₂O)₁₇}_n [abbreviated as 1-(Gd₁₈Ni₂₄)_n and 2-(Eu₁₈Ni_23.5)_n respectively; H₂IDA = iminodiacetic acid; HIN = isonicotinic acid]. Concerning the structures, compounds 1-(Gd₁₈Ni₂₄)_n and 2-(Eu₁₈Ni_23.5)_n both feature the one-dimensional (1D) chain-like structure which is rarely reported in high-nuclearity metal complexes. Meanwhile, the large presences of Gd³⁺ ions in compound 1-(Gd₁₈Ni₂₄)_n are conducive to the fantastic MCE, and the value of −∆S_m is 35.30 J kg⁻¹ K⁻¹ at 3.0 K and ∆H = 7.0 T. And more significantly, compound 1-(Gd₁₈Ni₂₄)_n shows the large low-field magnetic entropy change (−∆S_m = 20.95 J kg⁻¹ K⁻¹ at 2.0 K and ∆H = 2.0 T) among the published 3d-4f mixed metal clusters.     

New Bimetallic Ni–Rh Carbonyl Clusters: Synthesis and X-ray Structure of the [Ni7Rh3(CO)18]3?, [Ni3Rh3(CO)13]3? and [NiRh8(CO)19]2? Cluster Anions

The reaction of the [Ni₆(CO)₁₂]²⁻ dianion with [Rh(COD)Cl]₂ (COD = cyclooctadiene) in acetone affords a mixture of bimetallic Ni–Rh clusters, mainly consisting of the new [Ni₇Rh₃(CO)₁₈]³⁻ and [Ni₈Rh(CO)₁₈]³⁻ trianions. A study of the reactivity of [Ni₇Rh₃(CO)₁₈]³⁻ led to isolation of the new [Ni₃Rh₃(CO)₁₃]³⁻ and [NiRh₈(CO)₁₉]²⁻ anions. All these new bimetallic Ni–Rh carbonyl clusters have been isolated in the solid state as tetrasubstituted ammonium salts and have been characterised by elemental analysis, X-ray diffraction studies, ESI-MS and electrochemistry. The unit cell of the [NEt₄]₃[Ni₇Rh₃(CO)₁₈] salt contains two orientationally-disordered ν₂-tetrahedral [Ni₇Rh₃(CO)₁₈]³⁻ trianions with occupancy factors of 0.75 and 0.25. Besides, their inner Ni₃Rh₃ octahedral moieties show two cis sites purely occupied by Rh atoms, two trans sites purely occupied by Ni atoms and the remaining two cis sites are disordered Ni and Rh sites with respective occupancy fraction of 0.5. At difference from the parent [Ni₇Rh₃(CO)₁₈]³⁻, the octahedral [Ni₃Rh₃(CO)₁₃]³⁻ displays an ordered distribution of Ni and Rh atoms in two staggered triangles. The [NiRh₈(CO)₁₉]²⁻ dianion adopts an isomeric metal frame with respect to that of the [PtRh₈(CO)₁₉]²⁻ congener. As a fallout of this work, new high-yield synthesis of the known [Ni₆Rh₃(CO)₁₇]³⁻ and [Ni₆Rh₅(CO)₂₁]³⁻, as well as other currently-investigated bimetallic Ni–Rh clusters have been obtained.     

A novel octanuclear nickel(II)–molybdenum(VI) heterometallic cluster based on the salicylhydroxamate ligand

Salicylhydroxamic acid (H₃shi) is known for its strong coordination ability and multiple coordination modes, and can easily coordinate to metal cations to form compounds with five‐ or six‐membered rings, as well as mono‐, di‐ and multinuclear compounds with interesting structures having potential applications in organic chemistry, coordination chemistry, and the materials and biological sciences. A novel octanuclear nickel(II)–molybdenum(VI) heterometallic cluster based on the salicylhydroxamate ligand, namely di‐μ₃‐acetato‐di‐μ₂‐acetato‐di‐μ₃‐hydroxido‐di‐μ₃‐oxido‐tetraoxidooctakis(pyridine‐κN)bis(μ₅‐salicylhydroxamato)hexanickel(II)dimolybdenum(VI) monohydrate, [Mo₂Ni₆(C₇H₄NO₃)₂(C₂H₃O₂)₄O₅(OH)₂(C₅H₅N)₈]·H₂O, (I), was synthesized by the reaction of sodium molybdate, nickel acetate and salicylhydroxamic acid in a dimethylformamide/pyridine/methanol solution at room temperature. The salicylhydroxamate(3−) (shi³⁻), acetate and oxide ligands adopt complicated coordination modes and link six Ni^II and two Mo^VI cations into the octanuclear heterometallic cluster. All of the metal cations exhibit octahedral coordination geometries and are connected to each other through the sharing of corners, edges or planes. The heterometallic clusters are further connected to form two‐dimensional supramolecular layers through weak C—H…O hydrogen bonds. Studies of the magnetic properties of the title compound reveal antiferromagnetic interactions between the Ni^II cations.     

Preparation and Characterisation of a Bis-μ-Hydroxo-NiIII2 Complex

Hydroxide-bridged high-valent oxidants have been implicated as the active oxidants in methane monooxygenases and other oxidases that employ bimetallic clusters in their active site. To understand the properties of such species, bis-μ-hydroxo-Ni^II₂ complex ( 1 ) supported by a new dicarboxamidate ligand (N,N′-bis(2,6-dimethyl-phenyl)-2,2-dimethylmalonamide) was prepared. Complex 1 contained a diamond core made up of two Ni^II ions and two bridging hydroxide ligands. Titration of the 1 e⁻ oxidant (NH₄)₂[Ce^IV(NO₃)₆] with 1 at −45 °C showed the formation of the high-valent species 2 and 3 , containing Ni^IINi^III and Ni^III₂ diamond cores, respectively, maintaining the bis-μ-hydroxide core. Both complexes were characterised using electron paramagnetic resonance, X-ray absorption, and electronic absorption spectroscopies. Density functional theory computations supported the spectroscopic assignments. Oxidation reactivity studies showed that bis-μ-hydroxide-Ni^III₂ 3 was capable of oxidizing substrates at −45 °C at rates greater than that of the most reactive bis-μ-oxo-Ni^III complexes reported to date.     

Diagnosis of magnetoresponsive aromatic and antiaromatic zones in three‐membered rings of d‐ and f‐block elements

Magnetoresponsive three‐membered rings of d‐ and f‐block elements have been thoroughly investigated with the help of electronic structure calculation methods. The magnetic response of the clusters was evaluated by the Nucleus Independent Chemical Shifts (NICS)_zz‐scan curves, which in conjunction with symmetry‐based selection rules for the most significant translationally and rotationally allowed transitions helped rationalize and predict the orbital‐type of aromaticity/antiaromaticity of the clusters. The magnetoresponsive early (Groups 3, 4, and 5) transition metal M₃ rings exhibit successive aromatic and antiaromatic zones separated by a nodal plane. The magnetoresponsive late (Groups 11 and 12) transition metal M₃ rings exhibit long‐range aromatic zone with the NICS_zz(R) values decaying rapidly and monotonically with respect to R. The magnetic response of Group 10 transition metal M₃ rings is similar to that of the early transition metal M₃ rings, but it is long‐range antiaromatic only for the [c‐Ni₃] cluster. The NICS_zz‐scan curve of the [(H_tLa)₃(μ₂‐H)₆] cluster is indicative of weak pure σ‐aromaticity due to the induced diatropic ring current from the translationally allowed a → e′ and e′ → a transitions. The aromatic–antiaromatic behavior of the [(H_tCe)₃(μ₂‐H)₆]⁺ and [(H_tTm)₃(μ₂‐H)₆]²⁻ clusters is similar to that of the early d‐block elements. The magnetic response of [(H_tYb)₃(μ₂‐H)₆]³⁻ is similar to that of [c‐Hg₃]²⁻. The [(H_tLu)₃(μ₂‐H)₆] cluster can be considered as a doubly (σ + π) aromatic system, with the σ‐aromatic component being much stronger than the π‐aromatic one. Finally, the [(X_tRe)₃(μ₂‐X)₆] and [(X_tRu)₃(μ₂‐X)₆]⁺ (X = Cl, Br, I) clusters exhibit significant aromatic character with the greatest contribution to the induced diatropic ring currents coming from π‐type transitions. © 2009 Wiley Periodicals, Inc. J Comput Chem 2010     

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 .     

Zinc(II) and Nickel(II) Complexes Based on Schiff Base Ligands: Synthesis,Crystal Structure,Luminescent and Magnetic Properties

Three new phenolate oxygen bridged transition metal complexes [Zn₃(HL¹)₃(μ₃‐CH₃O)]·(ClO₄)₂(H₂O)₃ ( 1 ), [Ni₂(HL¹)₂(μ_1,1‐N₃)(o‐vanillin)]·H₂O ( 2 ), [Ni₃(HL²)₂(PhCOO)₂(PhCOOH)₂(EtOH)₂] ( 3 ) have been synthesized by metal ions and potentially multidentate Schiff base ligands (H₂L¹ = 2‐((1‐hydroxy‐2‐methylpropan‐2‐ylimino) methyl)‐6‐methoxyphenol; H₃L² = (E)‐1‐((2‐hydroxy‐3‐methoxy‐benzylidene)amino)ethane‐1,2‐diol). All the three complexes 1 , 2 , and 3 have been characterized by elemental analysis, FT‐IR spectroscopy, and single‐crystal X‐ray diffraction studies. Crystal structures reveal that complex 1 is a trinuclear incomplete cubane‐like zinc cluster whereas complex 2 is a dinuclear nickel complex bridged by azide, and compound 3 is a trinuclear nickel complex. The luminescent property for complex 1 and magnetic behaviors for complexes 2 and 3 have been investigated.     

Structure and chromotropism properties of an unsymmetrical alkoxo-bridged nickel(II) cubane-like complex

A new tetranuclear cubane-like complex, [Ni₄(L)₄Cl₄(H₂O)₃(EtOH)]·(H₂O), has been synthesized from the reaction of a metal salt with the bidentate ligand 2-hydroxymethylpyridine (LH), and its crystal structure, spectroscopic and chromotropic properties have been studied. The complex has a [Ni₄O₄] core comprising a distorted cubane arrangement, of which four nickel(II) ions were bridged by μ₃-alkoxo moieties. Each nickel(II) was coordinated to three μ₃-alkoxo oxygens, one pyridine nitrogen and one chloride. The peripheral ligation was completed by an oxygen atom of water or ethanol ligand, which participated in intramolecular hydrogen bonding. Chromotropism properties of the complex including solvato-, thermo-, and ionochromism were investigated. The complex displayed strong ionochromism and shows high-sensitive and selective activity toward CN^? and SCN^? anions in the presence of other halides and pseudo-halides. The solvatochromic property of the complex was analyzed by a multi-parametric equation using SPSS/PC software. The stepwise multiple linear regression method demonstrated that the acceptor power of the solvent plays the most important role in the observed negative solvatochromism of the compound. It shows reversible thermochromism in solution due to loss of the weakly coordinated water and ethanol from the nickel(II) units.     

Intramolecular Cyclization of Butadiyne Functionalized Ligands coordinated to Triosmium‐Carbonyl Cluster

Reactions between diynes and [Os₃(CO)₁₁(CH₃CN)] in the presence of water give rise to the formation of intriguing hydride triosmium clusters [Os₃(μ‐H)(CO)₉{μ₃,η¹:η³:η¹‐RC₂COHC≡CR}] ( 1a – 1c ) under mild conditions in high yields. When these allylic alcohol compounds 1a – 1c are dissolved in dry polar and donor solvents, an intramolecular cyclization process takes place to give [Os₃(μ‐H)(CO)₉{μ₃,η¹:η³:η¹‐RC₂CH=COCR}] ( 2a – 2c ) in quantitative yield. The utilization of [Os₃(CO)₁₁(CH₃CN)] as starting material together with the addition of water can replace the inconvenient use of [Os₃(μ‐H)₂(CO)₁₀]. This method of synthesis provides a facile pathway for diyne cyclizations and has a clear advantage over those described to date in the literature. Additionally, the analogous cyclized mixed‐metal complex [Os₃(μ‐H)(CO)₉{μ₃,η¹:η³:η¹‐FcC₂CH=COCFc}] ( 2d ) (Fc = ferrocenyl), was synthesized in order to carry out a comparative electrochemical study with the related compounds [Os₃(CO)₁₁(μ₃‐FcC₄Fc)] ( I ) and [Os₃(CO)₁₀(μ₃‐FcC₄Fc)] ( II ), which were previously reported by R. D. Adams.     

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.     

Syntheses,Crystal Structures,and Luminescence Properties of Four Coordination Polymers Based on 1,3,5‐Tris (imidazol‐1‐yl)benzene

Based on the tripodal 1,3,5‐tris(imidazol‐1‐yl)benzene (tib) ligand, four transition metal coordination polymers, namely, {[Ni₃(tib)₂(H₂O)₁₂] · (SO₄)₃}_n ( 1 ), {[Co_1/6(tib)_1/3] · (O)_1/3}_n ( 2 ), and [M(tib)(hip)]_n (M = Mn for 3 , and M = Co for 4 ) (hip = 5‐hydroxyisophthalic acid), were synthesized through solvothermal method. Their structures were defined by single‐crystal X‐ray diffraction analyses and further characterized by elemental analyses (EA), IR spectra, powder X‐ray diffraction (PXRD), and thermogravimetric analyses (TGA). Complex 1 displays a 2D 3‐connected (6³) hcb net. Complex 2 is a 2D (3,6)‐connected (4³)₂(4⁶.6⁶.8³) kgm net. Complex 3 and 4 present similar 2D 4‐connected (4⁴.6²) sql net. Moreover, the solid state luminescence properties of complexes 1 and 3 were investigated.     

Preparation of a Lanthanide–Titanium Oxo Cluster–Polymer Composite by CuI-Catalyzed Click Chemistry

Incorporating metal clusters within the skeleton of the organic polymers through a click reaction cannot only effectively prepare cluster–polymer composites, but also effectively avoid the cluster aggregation. Herein, an azide-containing lanthanide–titanium oxo cluster of Eu₈Ti₁₀-N₃ ( Eu₈Ti₁₀-N₃ =[Eu₈Ti₁₀(μ₃-O)₁₄(H₂O)₄(OAc)₂(tbba)₃₀(paza)₄(THF)₂] ⋅ 4 THF ⋅ 8 H₂O ( 1 ), Htbba=4-tert-butylbenzoic acid, Hpaza=4-azidobenzoate, HOAc=acetic acid, THF=tetrahydrofuran) through an in situ solvothermal reaction of 4-azidobenzoic acid and 4-tert-butylbenzoic acid. Reaction of 1 with PEG ( PEG =methoxypoly(ethyleneglycol)alkyne, 2000 g mol⁻¹) through Cu^I-catalyzed click chemistry generates a lanthanide–polymer composite of Eu₈Ti₁₀-N₃@PEG ( 2 ). Investigation with IR, ¹H NMR and ICP-OES of 2 indicates that the structural integrity of 1 is maintained in 2 . Study of the luminescent properties of 1 and 2 reveals that the quantum yield of 1 itself basically remains unchanged in 2 . Significantly, the formation of 2 cannot only effectively prevent the cluster 1 from aggregation, but also greatly enhance its solubility and adhesion to the substrate. Owing to the solubility and adhesion of luminescent materials being the key to their practical application, present work is thus of great significance for the development of metal cluster–polymer composite luminescent materials.     

Ligand Symmetry Modulation for Designing a Mesoporous Metal–Organic Framework: Dual Reactivity to Transition and Lanthanide Metals for Enhanced Functionalization

A promising alternative strategy for designing mesoporous metal–organic frameworks (MOFs) has been proposed, by modifying the symmetry rather than expanding the length of organic linkers. By means of this approach, a unique MOF material based on the target [Zn₈(ad)₄] (ad=adeninate) clusters and C₃‐symmetric organic linkers can be obtained, with trigonal microporous (ca., 0.8 nm) and hexagonal mesoporous (ca., 3.0 nm) 1D channels. Moreover, the resulting 446‐MOF shows distinct reactivity to transition and lanthanide metal ions. Significantly, the transmetalation of Co^II or Ni^II on the Zn^II centers in 446‐MOF can enhance the sorption capacities of CO₂ and CH₄ (16–21 %), whereas the impregnation of Eu^III and Tb^III in the channels of 446‐MOF will result in adjustable light‐emitting behaviors.     

Molybdenum-Tungsten Mixed-Metal Trinuclear Clusters with Two Capping Oxides and Six Bridging Acetates,and Other Mixed Molybdenum-Tungsten Clusters

Abstract

Mixed molybdenum-tungsten clusters of di-, tri-, tetra- and pentavalent metal ions are reviewed. Those having strong π-accepting and/or [sgrave]-donating ligands such as CO are not included. The complexes which have been prepared by the authors' group are described in more detail. These are trinuclear complexes ([Mo_nW_3-n(μ₃-O)₂(μ-CH₃COO)₆(H₂O)₃]²⁺) with the oxidation state four and dinuclear complex ([MoW(μ-O)₂-(O)₂(μ-N, N'-edta)]^2-) with the oxidation state five. Other complexes described are dinuclear complexes of divalent metal ions (‘Mo-W quadruple bond’) and of trivalent metal ions (“Mo-W triple bond”), and trinuclear complexes with i-propoxide ligands.