Compact Hydrogen-Bonded Self-Assembly of Ni(II)–Salen Derivative Investigated Using Scanning Tunneling Microscopy

The self-assembly of a Ni­(II)–salen-derived complex bearing benzoate groups is investigated using scanning tunneling microscopy (STM) at the solid/liquid interface. STM reveals that the molecules form a two-dimensional nanoarchitecture of close-packed hydrogen-bonded chains on graphite surface. Favorable salen chain-shaped complementarity and molecular dipolar interactions appear to be at the origin of the compact molecular chain-packing

Mononuclear Manganese(III) Complexes as Building Blocks for the Design of Trinuclear Manganese Clusters: Study of the Ligand Influence on the Magnetic Properties of the [Mn₃(μ₃-O)]⁷⁺ Core

The synthesis, crystal structure, and magnetic properties of three new manganese(III) clusters are reported, [Mn3(μ3-O)(phpzH)3(MeOH)3(OAc)] (1), [Mn3(μ3-O)(phpzMe)3(MeOH)3(OAc)]·1.5MeOH (2), and [Mn3(μ3-O)(phpzH)3(MeOH)4(N3)]·MeOH (3) (H2phpzH = 3(5)-(2-hydroxyphenyl)-pyrazole and H2phpzMe = 3(5)-(2-hydroxyphenyl)-5(3)-methylpyrazole). Complexes 1−3 consist of a triangle of manganese(III) ions with an oxido-center bridge and three ligands, phpzR2− (R = H, Me) that form a plane with the metal ions. All the complexes contain the same core with the general formula [Mn3(μ3-O)(phpzR)3]+. Methanol molecules and additional bridging ligands, that is, acetate (complexes 1 and 2) and azide (complex 3), are at the terminal positions. Temperature dependent magnetic susceptibility studies indicate the presence of predominant antiferromagnetic intramolecular interactions between manganese(III) ions in 1 and 3, while both antiferromagnetic and ferromagnetic intramolecular interactions are operative in 2

Multivariate Metal–Organic Frameworks for the Simultaneous Capture of Organic and Inorganic Contaminants from Water

We report a new water-stable multivariate (MTV) metal–organic framework (MOF) prepared by combining two different oxamide-based metalloligands derived from the natural amino acids l-serine and l-methionine. This unique material features hexagonal channels decorated with two types of flexible and functional “arms” (−CH2OH and −CH2CH2SCH3) capable of enabling, synergistically, the simultaneous and efficient removal of both inorganic (heavy metals such as Hg2+, Pb2+, and Tl+) and organic (dyes such as Pyronin Y, Auramine O, Brilliant green, and Methylene blue) contaminants, and, in addition, this MTV-MOF is completely reusable. Single-crystal X-ray diffraction measurements allowed solving the crystal structure of a host–guest adsorbate, containing both HgCl2 and Methylene blue, and offered unprecedented snapshots of this unique dual capture process. This is the very first time that a MOF can be used for the removal of all sorts of pollutants from water resources, thus opening new perspectives for this emerging type of MTV-MOF

Multivariate Metal–Organic Frameworks for the Simultaneous Capture of Organic and Inorganic Contaminants from Water

We report a new water-stable multivariate (MTV) metal–organic framework (MOF) prepared by combining two different oxamide-based metalloligands derived from the natural amino acids l-serine and l-methionine. This unique material features hexagonal channels decorated with two types of flexible and functional “arms” (−CH2OH and −CH2CH2SCH3) capable of enabling, synergistically, the simultaneous and efficient removal of both inorganic (heavy metals such as Hg2+, Pb2+, and Tl+) and organic (dyes such as Pyronin Y, Auramine O, Brilliant green, and Methylene blue) contaminants, and, in addition, this MTV-MOF is completely reusable. Single-crystal X-ray diffraction measurements allowed solving the crystal structure of a host–guest adsorbate, containing both HgCl2 and Methylene blue, and offered unprecedented snapshots of this unique dual capture process. This is the very first time that a MOF can be used for the removal of all sorts of pollutants from water resources, thus opening new perspectives for this emerging type of MTV-MOF

Multivariate Metal–Organic Frameworks for the Simultaneous Capture of Organic and Inorganic Contaminants from Water

We report a new water-stable multivariate (MTV) metal–organic framework (MOF) prepared by combining two different oxamide-based metalloligands derived from the natural amino acids l-serine and l-methionine. This unique material features hexagonal channels decorated with two types of flexible and functional “arms” (−CH2OH and −CH2CH2SCH3) capable of enabling, synergistically, the simultaneous and efficient removal of both inorganic (heavy metals such as Hg2+, Pb2+, and Tl+) and organic (dyes such as Pyronin Y, Auramine O, Brilliant green, and Methylene blue) contaminants, and, in addition, this MTV-MOF is completely reusable. Single-crystal X-ray diffraction measurements allowed solving the crystal structure of a host–guest adsorbate, containing both HgCl2 and Methylene blue, and offered unprecedented snapshots of this unique dual capture process. This is the very first time that a MOF can be used for the removal of all sorts of pollutants from water resources, thus opening new perspectives for this emerging type of MTV-MOF

Multivariate Metal–Organic Frameworks for the Simultaneous Capture of Organic and Inorganic Contaminants from Water

We report a new water-stable multivariate (MTV) metal–organic framework (MOF) prepared by combining two different oxamide-based metalloligands derived from the natural amino acids l-serine and l-methionine. This unique material features hexagonal channels decorated with two types of flexible and functional “arms” (−CH2OH and −CH2CH2SCH3) capable of enabling, synergistically, the simultaneous and efficient removal of both inorganic (heavy metals such as Hg2+, Pb2+, and Tl+) and organic (dyes such as Pyronin Y, Auramine O, Brilliant green, and Methylene blue) contaminants, and, in addition, this MTV-MOF is completely reusable. Single-crystal X-ray diffraction measurements allowed solving the crystal structure of a host–guest adsorbate, containing both HgCl2 and Methylene blue, and offered unprecedented snapshots of this unique dual capture process. This is the very first time that a MOF can be used for the removal of all sorts of pollutants from water resources, thus opening new perspectives for this emerging type of MTV-MOF

Multivariate Metal–Organic Frameworks for the Simultaneous Capture of Organic and Inorganic Contaminants from Water

We report a new water-stable multivariate (MTV) metal–organic framework (MOF) prepared by combining two different oxamide-based metalloligands derived from the natural amino acids l-serine and l-methionine. This unique material features hexagonal channels decorated with two types of flexible and functional “arms” (−CH2OH and −CH2CH2SCH3) capable of enabling, synergistically, the simultaneous and efficient removal of both inorganic (heavy metals such as Hg2+, Pb2+, and Tl+) and organic (dyes such as Pyronin Y, Auramine O, Brilliant green, and Methylene blue) contaminants, and, in addition, this MTV-MOF is completely reusable. Single-crystal X-ray diffraction measurements allowed solving the crystal structure of a host–guest adsorbate, containing both HgCl2 and Methylene blue, and offered unprecedented snapshots of this unique dual capture process. This is the very first time that a MOF can be used for the removal of all sorts of pollutants from water resources, thus opening new perspectives for this emerging type of MTV-MOF

Coligand Effects on the Field-Induced Double Slow Magnetic Relaxation in Six-Coordinate Cobalt(II) Single-Ion Magnets (SIMs) with Positive Magnetic Anisotropy

Two mononuclear cobalt­(II) compounds of formula [Co­(dmphen)2(OOCPh)]­ClO4·1/2H2O·1/2CH3OH (1) and [Co­(dmbipy)2(OOCPh)]­ClO4 (2) (dmphen = 2,9-dimethyl-1,10-phenanthroline, dmbipy = 6,6′-dimethyl-2,2′-bipyridine and HOOCPh = benzoic acid) are prepared and magnetostructurally investigated. Each cobalt­(II) ion is six-coordinate with a distorted octahedral CoN4O2 environment. The complex cations are interlinked leading to supramolecular chains (1) and pairs (2) that grow along the crystallographic c-axis with racemic mixtures of (Δ,Λ)-Co units. FIRMS allowed us to directly measure the zero-field splitting between the two lowest Kramers doublets, which led to axial anisotropy values of 58.3 cm–1 ≤ D < 60.7 cm–1 (1) and 63.8 cm–1 ≤ D –1 (2). HFEPR spectra of polycrystalline samples of 1 and 2 at low temperatures confirm the positive sign of D and provide an estimate of the E/D quotient [0.147/0.187 (1) and 0.052 (2)]. Detailed ac and dc magnetic studies reveal that 1 and 2 are new examples of field-induced single-ion magnets (SIMs) with small transversal anisotropy. CASSCF/NEVPT2 calculations support these results. Two Orbach processes or one Orbach plus a direct relaxation mechanism provide similar agreements with the nonlinear experimental Arrhenius plots at Hdc = 500 and 2500 G for 1. Two independent relaxation processes occur in 2, but in contrast to 1, an observed linear dependence of ln­(τ) vs 1/T substantiates Orbach processes against the most widely proposed Raman and direct mechanisms. The analysis of each relaxation process in 2 provided values for Ea and τ0 that are very close to those found for 1, validating the predominant role of the Orbach relaxations in both compounds and, probably, also in other cobalt­(II) SIMs. A mechanism based on a spin-phonon coupling is proposed to account for the SIM behavior in 1 and 2 with any Raman or direct processes being discarded

Manganese(III) Compounds of Phenol−Pyrazole-Based Ligands: Synthesis, Crystal Structure, Magnetic, and Thermal Properties

Reaction of H2phpzR (R = H, Me, Ph; H2phpzH = 3(5)-(2-hydroxyphenyl)pyrazole, H2phpzMe = 3(5)-(2-hydroxyphenyl)-5(3)-methylpyrazole, and H2phpzPh = 3(5)-(2-hydroxyphenyl)-5(3)-phenylpyrazole)) with MnCl2·2H2O or MnBr2·4H2O in an acetonitrile−methanol mixture and in the presence of a small quantity of triethylamine affords the compounds [Mn(HphpzR)2Cl] (R = H (1), Me (3), and Ph (5) and [Mn(HphpzR)2Br] (R = H (2), Me (4), and Ph (6)). This new family of compounds 1−6 with a library of phenol−pyrazole-based ligands was structurally characterized. All compounds are mononuclear manganese(III) coordination compounds in which the manganese(III) ion has a square-pyramidal geometry. In compounds 1−4 intermolecular hydrogen bonds are present between the N−H group of the pyrazole ring of a mononuclear entity and the halogen of a neighboring molecule, thus forming ladder-like chains. The presence of two crystallographically independent molecules in the unit cell of 5 and 6 precludes formation of 1D structure and instead gives rise to a 2D structure with the independent molecules aligned in a face-to-face manner. Low-temperature magnetization studies evidence the presence of antiferromagnetic interactions between the manganese(III) ions in all compounds. Detailed temperature-dependent susceptibility and magnetic specific heat measurements on compounds 1 and 2 show the presence of antiferromagnetic S = 2 chains, the magnetic interaction being described by the anisotropic Heisenberg model with a predominantly planar (XY) type of crystal field anisotropy. In addition, the magnetic specific heat data evidence the occurrence of long-range magnetic ordering between chains in 1 and 2 below about 1.5 K. Compounds 3−6 show weaker antiferromagnetic interactions as compared with 1 and 2

Mono- and Dinuclear Iron Complexes of Bis(1-methylimidazol-2-yl)ketone (bik): Structure, Magnetic Properties, and Catalytic Oxidation Studies

The newly synthesized dinuclear complex [FeIII2(μ-OH)2(bik)4](NO3)4 (1) (bik, bis(1-methylimidazol-2-yl)ketone) shows rather short Fe···Fe (3.0723(6) Å) and Fe–O distances (1.941(2)/1.949(2) Å) compared to other unsupported FeIII2(μ-OH)2 complexes. The bridging hydroxide groups of 1 are strongly hydrogen-bonded to a nitrate anion. The 57Fe isomer shift (δ = 0.45 mm s–1) and quadrupole splitting (ΔEQ = 0.26 mm s–1) obtained from Mössbauer spectroscopy are consistent with the presence of two identical high-spin iron(III) sites. Variable-temperature magnetic susceptibility studies revealed antiferromagnetic exchange (J = 35.9 cm–1 and H = JS1·S2) of the metal ions. The optimized DFT geometry of the cation of 1 in the gas phase agrees well with the crystal structure, but both the Fe···Fe and Fe–OH distances are overestimated (3.281 and 2.034 Å, respectively). The agreement in these parameters improves dramatically (3.074 and 1.966 Å) when the hydrogen-bonded nitrate groups are included, reducing the value calculated for J by 35%. Spontaneous reduction of 1 was observed in methanol, yielding a blue [FeII(bik)3]2+ species. Variable-temperature magnetic susceptibility measurements of [FeII(bik)3](OTf)2 (2) revealed spin-crossover behavior. Thermal hysteresis was observed with 2, due to a loss of cocrystallized solvent molecules, as monitored by thermogravimetric analysis. The hysteresis disappears once the solvent is fully depleted by thermal cycling. [FeII(bik)3](OTf)2 (2) catalyzes the oxidation of alkanes with t-BuOOH. High selectivity for tertiary C–H bond oxidation was observed with adamantane (3°/2° value of 29.6); low alcohol/ketone ratios in cyclohexane and ethylbenzene oxidation, a strong dependence of total turnover number on the presence of O2, and a low retention of configuration in cis-1,2-dimethylcyclohexane oxidation were observed. Stereoselective oxidation of olefins with dihydrogen peroxide yielding epoxides was observed under both limiting oxidant and substrate conditions