Trinuclear Molecules Research Articles

Heterometallic Molecular and Ionic Isomers.

Numerous descriptions of structural isomerism in metal complexes do not list any molecular vs ionic isomers. At the same time, one of the most striking examples of structural isomerism in organic chemistry is molecular urea, which has the same atomic composition as the chemically distinct ionic ammonium cyanate. This iconic organic couple now meets its inorganic heterometallic counterpart. We introduce a new class of structural isomers, molecular vs ionic, that can be consummated in complex and coordinatively unsaturated polynuclear/heterometallic compounds. We report inorganic molecular and ionic isomers of the composition [NaCrFe (acac)3(hfac)3] (acac = acetylacetonate; hfac = hexafluoroacetylacetonate). Heterometallic molecular [CrIII(acac)3-Na-FeII(hfac)3] (1m) and ionic {[CrIII(acac)3-Na-CrIII(acac)3]+[FeII(hfac)3-Na-FeII(hfac)3]-} (1i) isomers have been isolated in pure form and characterized. While both ions are heterobimetallic trinuclear entities, the neutral counterpart is a heterotrimetallic trinuclear molecule. The two isomers exhibit distinctly different characteristics in terms of solubility, volatility, mass spectrometry ionization, and thermal behavior. Unambiguous assignment of the positions and oxidation/spin states of the Periodic Table neighbors, Fe and Cr, in both isomers have been made by a combination of characterization techniques that include synchrotron X-ray resonant diffraction, synchrotron X-ray fluorescence spectroscopy, Mössbauer spectroscopy, and DART mass spectrometry. The transformation between the two isomers that does take place in solutions of noncoordinating solvents has also been tested.

Manganese (III) Compounds Derived from R-Salicylaldoxime and 9-Anthracenecarboxylate Ligands: A Study of Their Synthesis and Structural, Magnetic, and Luminescent Properties

The reaction of Mn(II) salts in the air with different R-salicylaldehyde oximes and the sodium or cesium salts of 9-anthracenecarboxylato (9-AC) allows for the isolation of new six polynuclear compounds: [Mn3NaO(salox)3(9-AC)2(EtOH)3H2O]n·2EtOH (1), [Mn3NaO(3-Me-salox)3(9-AC)2(EtOH)3H2O]n·EtOH (2), [Mn6O2(salox)6(9-AC)2(EtOH)2(H2O)2]·3EtOH (3), [Mn3O(3-Me-salox)3(9-AC)(EtOH)3(H2O)]·1.8EtOH·3H2O (4), [Mn6O2(Me-salox)6(9-AC)2(EtOH)4(H2O)2]·0.5H2O (5), and [Mn6O2(Et-salox)6(9-AC)2(EtOH)4(H2O)2]·3EtOH (6). H2salox is a salicylaldehyde oxime, H2(3-Me-salox) is a 3-methyl-salicylaldehyde oxime, H2Me-salox is a 1-(2-hydroxyphenyl)ethan-1-one oxime and a H2-Et-salox is 1-(2-hydroxyphenyl)propan-1-one oxime. Structurally, compounds 1 and 2 consist of chains of trinuclear {MnIII3(μ3-O)(salox)3}+ units connected by Na+ ions. Compounds 3, 5, and 6 are hexanuclear units formed by two parallel trinuclear units {MnIII3(μ3-O)(salox)3}+ or {MnIII3(μ3-O)(Me-salox)3}+ planes related through an inversion center. Compound 4 consists of two isolated [Mn3O(3-Me-salox)3(9-AC)(EtOH)3(H2O)] trinuclear molecules in the unit cell showing crystallographic differences. Magnetic studies reveal a set of antiferromagnetic interactions in compounds 1 and 2 and a combination of antiferromagnetic and ferromagnetic interactions in compounds 3, 5, and 6. In all cases, the magneto-structural correlation between the intramolecular MnIII-N-O-MnIII torsion angle and the magnetic exchange within these units have been confirmed. For compounds 5 and 6, ac magnetic measurements reveal the slow relaxation of magnetization with moderate energy barriers of 19.9 cm−1 and 31.1 cm−1, respectively. Absorbance and fluorescence measurements in solution show the transitions of the 9-anthracenecarboxylate chromophore for all the compounds.

A photochromic trinuclear dysprosium(iii) single-molecule magnet with two distinct relaxation processes.

Multifunctional molecules responsive to light are highly desired as components for the construction of remotely controlled nanodevices. Here we present a DyIII single molecule magnet (SMM) comprising dithienylethene (dte) photochromic bridging ligands in the form of a pyridine (py) derivative: 1,2-bis((2-methyl-5-pyridyl)thie-3-yl)perfluorocyclo-pentene (dtepy). The title trinuclear compound {[DyIII(BHT)3]3(dtepy)2}·4C5H12 (1) was synthesized by combining the low-coordinate dysprosium complexes DyIII(BHT)3 (BHT = 2,6-di-tert-butyl-4-methylphenolate) with dtepy bridging ligands in the 'open' form using n-pentane as a completely inert solvent. The trinuclear molecule comprises two different DyIII centers due to its quasi-linear geometry: a central trigonal bipyramidal DyIII ion and two peripheral ones with an approximate trigonal pyramidal geometry. Thanks to that, 1 shows two types of SMM behavior which is slightly affected by the photoisomerization of the photochromic dtepy bridges. The impact of the photoisomerization on the magnetization dynamics was studied by means of alternating current (AC) magnetic susceptibility measurements for the 'open' and 'closed' forms of the molecules. The changes between the 'open' and 'closed' isomers were further investigated by IR and UV-vis spectroscopy, suggesting the co-existence of the ligand-related photochromism and single-molecule magnet behavior in 1. However, the powder X-ray diffraction studies indicate loss of structural order in the first photoisomerization step preventing in-depth studies.

Filling the gap with a bulky diaryl boron group: fluorinated and non-fluorinated copper pyrazolates fitted with a dimesityl boron moiety on the backbone.

Successful synthesis has been reported of 4-Mes2B-3,5-(CF3)2PzH and 4-Mes2B-3,5-(CF3)2PzH bearing sterically demanding diarylboron moieties at the pyrazole ring 4-position, and their corresponding copper(I) pyrazolate complexes. They show visible blue photoluminescence in solution. The X-ray crystal structures revealed that the fluorinated {[4-BMes2-3,5-(CF3)2Pz]Cu}3 crystallizes as discrete trinuclear molecules whereas as the non-fluorinated {[4-BMes2-3,5-(CH3)2Pz]Cu}3 forms dimers of trimers with two close inter-trimer Cu⋯Cu separations. The solid {[4-BMes2-3,5-(CF3)2Pz]Cu}3 featuring a sterically confined Cu3N6 core displays bright blue phosphorescence while {[4-BMes2-3,5-(CH3)2Pz]Cu}3, which is a dimer of a trimer, is a red phosphor at room temperature. This work illustrates the modulation of photo-physical properties of metal pyrazolates by adjusting the supporting ligand steric features and introducing secondary diarylboron luminophores. Computational analysis of the structures and photophysical properties of copper complexes are also presented.

Low-Coordinate Erbium(III) Single-Molecule Magnets with Photochromic Behavior.

The structures and magnetic properties of photoresponsive magnets can be controlled or fine-tuned by visible light irradiation, which makes them appealing as candidates for ternary memory devices: photochromic and photomagnetic at the same time. One of the strategies for photoresponsive magnetic systems is the use of photochromic/photoswitchable molecules coordinated to paramagnetic metal centers to indirectly influence their magnetic properties. Herein, we present two erbium(III)-based coordination systems: a trinuclear molecule {[ErIII(BHT)3]3(dtepy)2}.4C5H12 (1) and a 1D coordination chain {[ErIII(BHT)3(azopy)}n·2C5H12 (2), where the bridging photochromic ligands belong to the class of diarylethenes: 1,2-bis((2-methyl-5-pyridyl)thie-3-yl)perfluorocyclopentene (dtepy) and 4,4′-azopyridine (azopy), respectively (BHT = 2,6-di-tert-butyl-4-methylphenolate). Both compounds show slow dynamics of magnetization, typical for single-molecule magnets (SMMs) as revealed by alternating current (AC) magnetic susceptibility measurements. The trinuclear compound 1 also shows an immediate color change from yellow to dark blue in response to near-UV irradiation. Such behavior is typical for the photoisomerization of the open form of the ligand into its closed form. The color change can be reversed by exposing the closed form to visible light. The chain-like compound 2, on the other hand, does not show significant signs of the expected trans–cis photoisomerization of the azopyridine in response to UV irradiation and does not appear to show photoswitching behavior.

Structure and Magnetic Properties of a Trinuclear Copper(II) Complex with Bridging Carboxy-Phenyl Nitronyl Nitroxides

A new complex {(NITPBAH)2[Cu(hfac)2]3} 1 derived from carboxy-phenyl-substituted nitronyl nitroxide radical (NITPBAH) and Cu(hfac)2(H2O)2 (NITPBAH = 2-(4-carboxy-phenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, hfac = hexafuoroacetylacetonato) has been synthesized as well as characterized structurally and magnetically. The single-crystal X-ray diffraction analyses indicated that the complex {(NITPBAH)2[Cu(hfac)2]3} 1 consists of trinuclear five-spin molecule system. Each NITPBAH ligand is bound to two copper atoms with its two oxygen atoms from ONCNO group. Copper atoms display two different coordination types. The central copper atom lies on an inversion center and is six-coordinated in an elongated octahedron using two hfac molecules and two oxygen atoms of ONCNO group from two different NITPBAH ligands. Two terminal copper atoms are five-coordinated in a distorted square-pyramidal environment formed by two hfac molecules and one oxygen atom of ONCNO group from one NITPBAH ligand. The magnetic susceptibility study of the complex {(NITPBAH)2[Cu(hfac)2]3} 1 shows strong antiferromagnetic interactions between Cu(II) ion and NITPBAH radical ligand.

Engineering Heteronuclear Arrays from IrIII‐Metalloligand and CoII Showing Coexistence of Slow Magnetization Relaxation and Photoluminescence

Comprehensive SummaryThree heteronuclear IrIII‐CoII arrays, [Co(H2O)6]2[Ir(ppyCOO)(ppyCOOH)(bpy)]2[Ir(ppyCOO)2(bpy)]2(NO3)2⋅10.5H2O (2), [Co(H2O)6]{Co(H2O)4[Ir(ppyCOO)2(bpy)]2}[Ir(ppyCOO)2(bpy)]2⋅15H2O (3) and {Co(H2O)2[Ir(ppyCOO)2(bpy)]2}⋅2CH3OH⋅3H2O (4), have been synthesized by combining paramagnetic CoII ion with luminescent IrIII‐metalloligand, [Ir(ppyCOOH)2(bpy)][Ir(ppyCOO)2(bpy)]⋅5H2O (1), where ppyCOOH = 3‐(pyridin‐2‐yl)benzoic acid and bpy = 2,2'‐bipyridyl. Owing to the variable charged states of compound 1 at different pH, compounds 2 and 3 are discrete ionic complexes containing hydrated Co2+ cations and deprotonated [Ir(ppyCOO)2(bpy)]– anions as well as coexisting neutral [Ir(ppyCOO)(ppyCOOH)(bpy)] (for 2) or Co(H2O)4[Ir(ppyCOO)2(bpy)]2 trinuclear molecule (for 3). Whereas compound 4 consists of self‐assembled two‐dimensional coordination polymer with Co‐metalloligand dative bonds. The hexa‐coordinated CoII cores in all complexes display octahedral geometries with varying degrees of distortion. In a bias dc field, the ac susceptibilities for 2—4 reveal slow magnetic relaxation. Moreover, the solid‐state phosphorescence is observed for compounds 2 and 3 due to weak supramolecular interaction between CoII ion and Ir‐moiety but is severely quenched for 4, where the Co center is strongly connected to the metalloligand. To the best of our knowledge, this is the first report of Ir‐Co systems showing both slow magnetization relaxation and photoluminescence.

Three to tango requires a site-specific substitution: heterotrimetallic molecular precursors for high-voltage rechargeable batteries.

Design of heterotrimetallic molecules, especially those containing at least two different metals with close atomic numbers, radii, and the same coordination number/environment is a challenging task. This quest is greatly facilitated by having a heterobimetallic parent molecule that features multiple metal sites with only some of those displaying substitutional flexibility. Recently, a unique heterobimetallic complex LiMn2(thd)5 (thd = 2,2,6,6-tetramethyl-3,5-heptanedionate) has been introduced as a single-source precursor for the preparation of a popular spinel cathode material, LiMn2O4. Theoretical calculations convincingly predict that in the above trinuclear molecule only one of the Mn sites is sufficiently flexible to be substituted with another 3d transition metal. Following those predictions, two heterotrimetallic complexes, LiMn2-x Co x (thd)5 (x = 1 (1a) and 0.5 (1b)), that represent full and partial substitution, respectively, of Co for Mn in the parent molecule, have been synthesized. X-ray structural elucidation clearly showed that only one transition metal position in the trinuclear molecule contains Co, while the other site remains fully occupied by Mn. A number of techniques have been employed for deciphering the structure and composition of heterotrimetallic compounds. Synchrotron resonant diffraction experiments unambiguously assigned 3d transition metal positions as well as provided a precise "site-specific Mn/Co elemental analysis" in a single crystal, even in an extremely difficult case of severely disordered structure formed by the superposition of two enantiomers. DART mass spectrometry and magnetic measurements clearly confirmed the presence of heterotrimetallic species LiMnCo(thd)5 rather than a statistical mixture of two heterobimetallic LiMn2(thd)5 and LiCo2(thd)5 molecules. Heterometallic precursors 1a and 1b were found to exhibit a clean decomposition yielding phase-pure LiMnCoO4 and LiMn1.5Co0.5O4 spinels, respectively, at the relatively low temperature of 400 °C. The latter oxide represents an important "5V spinel" cathode material for the lithium ion batteries. Transmission electron microscopy confirmed a homogeneous distribution of transition metals in quaternary oxides obtained by pyrolysis of single-source precursors.

Light‐Induced Spin‐State Switching of the MoIV Centre in Trinuclear [CuII(diamine)2]2[MoIV(CN)8] Molecules

New trinuclear molecules [Cu(meen)2]2[MoIV(CN)8]·5H2O (1) and [Cu(eten)2]2[Mo(CN)8]·7H2O (2) (meen = N‐methyl‐ethylenediamine; eten = N‐ethyl‐ethylenediamine) have been prepared and characterised by X‐ray diffraction and dc magnetometry. The crystal structure of 1 and 2 consists of trinuclear Cu2Mo molecules interacting through weak semicoordination bonds and resulting in the formation of 2D and 3D supramolecular networks, respectively. In the ground state, both molecules exhibit simple paramagnetic behaviour, with very weak antiferromagnetic interaction present at low temperatures. The photomagnetic studies of 1 and 2, performed using 436 nm light, have shown a significant increase in the magnetisation upon irradiation that might be explained in terms of a singlet–triplet transition at MoIV.

Synthesis, Characterization, and DFT Investigation of a Zinc(II)–Silver(I) Bimetallic Complex, [Zn(Dmen)2{Ag(CN)2}2][Zn(Dmen)2(H2O)2]{Ag(CN)2}2 (Dmen = N,N′-Dimethylethylenediamine)

A cyanido bridged Zn(II)-Ag(I) bimetallic complex (I) has been prepared and characterized by IR spectroscopy, thermal analysis, X-ray crystallography (CIF file CCDC no. 884016) and DFT calculations. Thermal analysis shows that the composition of the compound is consistent with the proposed stoichiometry, i.e., [Zn(diamine)2{Ag(CN)2}2] · H2O. The crystal structure of complex I consists of two independent molecules; a trinuclear molecule, [Zn(Dmen)2{Ag(CN)2}2] and an ionic species, [Zn(Dmen)2-(H2O)2]{Ag(CN)2}2; the overall formula being [Zn(Dmen)2{Ag(CN)2}2][Zn(Dmen)2(H2O)2]{Ag(CN)2}2 (I) (Dmen = N,N′-dimethylethylenediamine). The structures of I and two of its analogues, [Zn(Dmen)2{Ag(CN)2}2]2 · 2H2O (II) and {[Zn(Dmen)2{Ag(CN)2}][Ag(CN)2]}2 · 2H2O (III) were predicted by DFT calculations. The DFT results reveal that the structure I is more stable in comparison to the calculated structures, II and III. The X-ray structure of I shows that the complex is also stabilized by the argentophilic interactions. The Ag···Ag interaction energy calculated at the MP2 level of theory is –4.02 kcal mol–1.

A family of silver(I) complexes built with 2-sulfoterephthalic acid monosodium salt and different aminopyridine ligands: Syntheses, structures and properties

Five Ag(I) coordination complexes, namely, [Ag6(2-stp)2(3-methyl-2-apy)3·H2O]n (1), [Ag3(2-stp)(4-methyl-2-apy)3]n (2), [Na2Ag18(2-stp)4(2-Hstp)4(5-methyl-2-apy)16 (H2O)4·11H2O]n (3), Ag3(2-stp)(6-methy-2-apy)4·H2O (4), and [Ag6(2-stp)2(6-methyl-2-apy)8(H2O)2·H2O]n (5) (2-NaH2stp = 2-sulfoterephthalic acid monosodium salt, 3-methyl-2-apy = 3-methyl-2-aminopyridine, 4-methyl-2-apy = 4-methyl-2-aminopyridine, 5-methyl-2-apy = 5-methyl-2-aminopyridine, 6-methyl-2-apy = 6-methyl-2-aminopyridine), have been synthesized and structurally characterized. Complexes 1 and 2 show two-dimensional network. In complex 3, the adjacent Ag10 units are bridged by 5-methyl-2-apy ligands to form a 2D infinite undulated sheet. Adjacent 2D sheets are linked by coordinative bonds between carboxylic oxygen atoms and Na(I) ions to form a 3D coordination polymer. Complex 4 is a 0-D discrete trinuclear molecule, and the self-complementary the OH⋯O and NH⋯O hydrogen bonds incorporating hydrogen bond motifs extend these molecules into a 2D supramolecular framework. Compound 5 exhibits 1D-chain structure. However, complex 5 shows 3D supramolecular structure results from the linkage of neighboring layers through a rich hydrogen-bonding between uncoordinated sulfonates, amino groups and coordinated carboxylates. The thermogravimetric analyses and photoluminescence of the complexes were also investigated.

Eu3+ substitutional defects and their effect on the luminescence spectral and decay dynamics of sal-type one dimensional rare earth coordination polymers and trinuclear complexes

Two series of one dimensional coordination polymers, {Na[Ln(sal)4]}n (Ln=Eu, Tb, Er, Y) and {Na[Ln(msal)4]}n (Ln=Er) and a new series of trinuclear complexes Na[Ln2(nsal)7(CH3OH)2] (Ln=Pr, Eu, Er) have been synthesized, structurally characterized and their luminescence and decay dynamical properties studied. This in order to explore the potential of sal-type ligands to yield compounds with various dimensionalities and probe the impact of defect sites on their unique photoluminescence behaviour. The Eu3+ compounds, {Na[Eu(sal)4]}n and Na[Eu2(nsal)7(CH3OH)2] are bright red luminophores having Eu3+ (5D0) emission spectra dominated by the 5D0→7F2 transition. Eu3+ substitutional defects, possibly arising from the swapping of Na+ with Eu3+ ions and the replacement of sal- with methanol, are evident from luminescence and decay dynamical data on both complexes. Decay data also indicate that energy migration on the Eu3+ sub-lattice in one dimensional chains of {Na[Eu(sal)4]}n is multidimensional and dynamic but is less efficient than energy migration in Na[Eu2(nsal)7(CH3OH)2] which features a H-bonded network of trinuclear molecules. The results of this comparative exploration of structure and luminescence can be manipulated to direct dimensionality in crystal engineering of these compounds.

Carving a 1D Co(II)-carboranylcarboxylate system by using organic solvents to create stable trinuclear molecular analogues: complete structural and magnetic studies.

This work presents a straightforward methodology to achieve small linear trinuclear molecules based on the Co(II)-carboranylcarboxylate system obtained by carving a 1D polynuclear analogous system with the use of diethylether. The reaction of the carboranylcarboxylic ligand, 1-CH3-2-CO2H-1,2-closo-C2B10H10 (LH) with different cobalt salts leads to the polynuclear compound [Co2(μ-H2O)(1-CH3-2-CO2-1,2-closo-C2B10H10)4(THF)4], and the polymeric [Co(μ-H2O)(1-CH3-2-CO2-1,2-closo-C2B10H10)2]n(H2O)n. This latter 1D chain has been obtained by an unprecedented synthetic strategy for the isolation of cobalt(ii) compounds. [Co3(μ-H2O)2(1-CH3-2-CO2-1,2-closo-C2B10H10)6(H2O)2(C4H10O)2], is formed by the dissociation of the polymeric structure that forms when a mild coordinating solvent such as diethylether is added. These compounds have been characterized by analytical and spectroscopic techniques. X-ray analysis of and revealed that presents a dinuclear structure whereas is trinuclear; in both cases a six-coordinated Co(II) compound with water molecules bridging each of the two Co(II) centres has been observed. The magnetic properties of and show a weak antiferromagnetic behaviour, respectively, between the Co(II) centres mediated by two carboxylate ligands and a molecule of water.

Mono‐Oxido‐Bridged Heterobimetallic and Heterotrimetallic Compounds Containing Titanium(IV) and Chromium(III)

AbstractA series of oxido‐bridged heterobi‐ and heterotrimetallic complexes, [(tmtaa)Ti=O→Cr(Por)Cl] and [(tmtaa)Ti=O→Cr(Por)←O=Ti(tmtaa)]+ (tmtaa = 7,16‐dihydro‐6,8,15,17‐tetramethyldibenzo[b,i][1,4,8,11]tetraazacyclotetradecine; Por = 5,10,15,20‐tetraarylporphyrin), have been synthesized. To the best of our knowledge, these complexes are the first structurally characterized examples to contain a Ti=O→Cr or Ti=O→Cr←O=Ti structural motif. Crystal structures of representative heterobimetallic compounds, including the Ti=O→Cr binuclear complex 2 and two separate trimers, [Ti=O→Cr←O=Ti]SbF6 (10) and [Ti=O→Cr←O=Ti]Cl (12), are reported. The bi‐ and trimetallic molecules have similar structural parameters, including Ti–O, Cr–O, and Ti–O–Cr bond lengths and angles with a linear Ti=O→Cr geometry. Magnetic studies showed that a high‐spin CrIII (S = 3/2) center is present in both the bi‐ and trinuclear molecules. The redox potentials for CrIV/III (ΔE = 320 mV) and Por/Por·– (ΔE = 260 mV) can be tuned by modifying the porphyrin ligand. By determining the thermodynamics and kinetics of the formation of these complexes by titration experiments and electrochemistry, it was found that the bi‐ and trimetallic species undergo isomerization in solution, allowing easy substitution of the apical chlorido ligand.

μ2-Acetato-κ(2) O:O'-(4,4'-bipyridyl-κN)tris-(diethyl di-thio-phosphato-κ(2) S,S')-μ3-sulfido-tri-μ2-sulfido-trimolybdenum(IV) diethyl ether monosolvate.

In the title compound, [Mo3(CH3COO)(C4H10O2PS2)3S4(C10H8N2)]·C4H10O, the complex mol­ecule has a trinuclear incomplete cuboidal structure which is coordinated by three kinds of ligands, namely, diethyl di­thio­phosphate, acetate and 4,4′-bipyridyl. If Mo—Mo bonds are ignored, each Mo atom can be considered as six-coordinated in a distorted octa­hedral geometry. The Mo—Mo distance of 2.6880 (5) Å for two the Mo atoms bridged by the acetate ligand is shorter than the other two Mo—Mo distances [2.7490 (5) and 2.7566 (5) Å]. One ethyl group is disordered between two conformations in a 0.65 (3):0.35 (3) ratio. In the crystal, weak C—H⋯O inter­actions link the trinuclear mol­ecules related by translation in [100] into chains. The crystal packing exhibits short inter­molecular S⋯S contacts of 3.1886 (13) Å. In other words, in this crystal packing, a supramolecular structure is constructed by the C—H⋯O and S⋯S interactions.

Crystal structure of [Pd3(μ-OH)(μ-CH3COO)5

The crystals of the [Pd3(μ-OH)(μ-CH3COO)5] complex are obtained and characterized using powder and single crystal X-ray diffraction and IR spectroscopy. The crystal structure (a = 15.6942(6) A, b = 11.7190(3) A, c = 9.7871(3) A, V = 1800.05(10) A3, space group Pna21, Z = 4) is formed from neutral trinuclear cyclic molecules of [Pd3(μ-OH)(μ-CH3COO)5], in which the OH− group, together with five CH3COO− anions, is a bridge ligand.

Three 3-amino-1,2,4-triazole-based cobalt(II) complexes incorporating with different carboxylate coligands: synthesis, crystal structures, and magnetic behavior

Three 3-amino-1,2,4-triazole (Hatz)-based paramagnetic metal complexes, {[Co2(Hatz)2(nip)2]·H2O}n (1), [Co(atz)(nb)]n (2), and {[Co3(H2O)4(Hatz)6(btc)2]·11.5H2O} (3) (nip2− = 5-nitroisophathalate, nb– = p-nitrobenzolate, and btc3– = 1,2,4-benzenetricarboxylate), were respectively prepared by introducing differently carboxylate-containing rigid coligands. All these complexes were structurally and magnetically characterized by single-crystal and powder X-ray diffractions, elemental analysis, FT-IR spectra, thermogravimetric and magnetic measurements. Complex 1 has a four-connected CdSO4-type framework with binuclear subunits periodically extended by ditopic μ-N1, N3-Hatz and carboxylate-containing linkers. Tetrahedral CoII ions in 2 are periodically interlinked into an undulated layer by anionic μ3-N1,N2,N3-atz− connectors with deprotonated nb– spacers located on the both sides. By contrast, complex 3 is a centrosymmetric trinuclear molecule aggregated by six neutral μ-N1, N3-Hatz molecules. The structural difference of 1–3 is significantly due to the flexible binding modes adopted by triazolyl and carboxylate groups. Additionally, 1 exhibits a field-induced metamagnetic transition from an antiferromagnetic ordering to a weak ferromagnetic state resulting from the magnetic competition between triazolyl and carboxylate mediators. Instead, comparable antiferromagnetic couplings transmitted by cyclic triazolyl groups are observed in the nearest neighbors of 2 and 3.

Volatile Single-Source Molecular Precursor for the Lithium Ion Battery Cathode

The first single-source molecular precursor for a lithium-manganese cathode material is reported. Heterometallic β-diketonate LiMn(2)(thd)(5) (1, thd = 2,2,6,6-tetramethyl-3,5-heptanedionate) was obtained in high yield by simple one-step solid-state reactions employing commercially available reagents. Substantial scale-up preparation of 1 was achieved using a solution approach. The crystal structure of the precursor contains discrete Li:Mn = 1:2 trinuclear molecules held together by bridging diketonate ligands. The complex is relatively stable in open air, highly volatile, and soluble in all common solvents. It was confirmed to retain its heterometallic structure in solutions of non-coordinating solvents. The heterometallic diketonate 1 was shown to exhibit clean, low-temperature decomposition in air/oxygen that results in nanosized particles of spinel-type oxide LiMn(2)O(4), one of the leading cathode materials for lithium ion batteries.

Synthesis and Crystal Structure of a Cyanido-Bridged Bimetallic Copper(II)–Silver(I) Complex of Imidazole and [Ag(CN)2]−: [Cu(Imidazole)4{Ag(CN)2}2

A cyanido-bridged Cu(II)–Ag(I) bimetallic complex, [Cu(Imidazole)4{Ag(CN)2}2] has been prepared and structurally characterized. The compound crystallizes in the orthorhombic space group Pmna. The crystal structure of the complex consists of trinuclear molecules made up of one [Cu(Imidazole)4]+2 and two [Ag(CN)2]− units. The trinuclear molecules are interlinked to each other through N–H–N and C–H–N hydrogen bonds. The Cu(II) ions are located on mirrors and assume distorted octahedral geometry with the basal plane consisting of four imidazole N-atoms.

Synthesis and structure of a zinc(II)-carboxylate trimer containing the π··· π stacking, 1,8-naphthalimide synthon: A supramolecular metal–organic framework

The reaction of the bifunctional ligand 3-(1,8-naphthalimido)propanoate ( L C2 −), which combines a 1,8-naphthalimide strong π··· π stacking synthon and a carboxylate donor group, with Zn( O 2CCH 3 ) 2(H 2O) 2 in methanol yields trimetallic Zn 3( L C2 ) 6(MeOH) 4. The solid state structure has a central zinc(II) linked to two equivalent outer zinc(II) by both μ-κ 1 and μ-κ 2 carboxylate ligands. The two equivalent five-coordinate terminal zinc centers are also bonded to a third nonbridging κ 2-carboxylate and to the oxygen atom of a methanol molecule. The central zinc(II) is six-coordinate with the four bridging carboxylate oxygen atoms forming a square planar arrangement and two trans oriented methanol molecules completing the coordination sphere. These trimers are organized into an extended structure exclusively by noncovalent interactions. Two types of strong π··· π stacking interactions between sets of three stacked naphthalimide rings from three different trinuclear molecules organize the structure into two-dimensional thick sheets. The third dimension is organized by intermolecular hydrogen bonding interactions between the methanol molecules bonded to the terminal zinc(II) and the free oxygen of the μ-κ 1-carboxylates from adjacent trimeric units. This interaction is supported by weak π··· π stacking. Overall the structure is a highly organized supramolecular metal–organic framework (SMOF) solid.