A Two-Dimensional Oxamate- and Oxalate-Bridged CuIIMnII Motif: Crystal Structure and Magnetic Properties of (Bu4N)2[Mn2{Cu(opba)}2ox]

Intensity and lifetime ratiometric luminescent thermometer based on a Tb(III) coordination polymer

A three-dimensional terbium(III) coordination polymer of formula [Tb(bttb)0.5(2,5-pzdc)0.5]n (1) [H4bttb = 1,2,4,5-tetrakis(4'-carboxyphenyl)benzene and H2-2,5-pzdc = 2,5-pyrazinedicarboxylic acid] was obtained under hydrothermal conditions. The bttb4- tetraanion in 1 adopts the bridging and chelating-bridging pseudo-oxo coordination modes while the 2,5-pzdc2- dianion exhibits a rather unusual bis-bidentate bridging pseudo-oxo coordination mode, both ligands being responsible for the stiffness of the resulting 3D structure. Solid-state photoluminescent measurements illustrate that 1 exhibits remarkable green luminescence emission, the most intense band occurring in the region of 550 nm (5D4 → 7F5) with lifetimes at the millisecond scale. Thermometric performances of 1 reveal a maximum relative sensitivity (Sm) of 0.76% K-1 at 295 K (δT = 0.05 K), constituting a TbIII ratiometric solid luminescent thermometer over the physiological temperature range. Variable-temperature static (dc) magnetic susceptibility measurements for 1 in the temperature range 2.0-300 K show the expected behavior for the depopulation of the splitted mJ levels of the 7F7 ground state of the magnetically anisotropic terbium(III) ion plus a weak antiferromagnetic interaction through the carboxylate bridges. No significant out-of-phase magnetic susceptibility signals were observed for 1 in the temperature range 2.0-10.0 K, either in the absence or presence of a static dc magnetic field.

Study of the Counter Cation Effects on the Supramolecular Structure and Electronic Properties of a Dianionic Oxamate-Based {NiII2} Helicate

Herein, we describe the synthesis, crystal structure, and electronic properties of {[K₂(dmso)(H₂O)₅][Ni₂(H₂mpba)₃]·dmso·2H₂O}_n (1) and [Ni(H₂O)₆][Ni₂(H₂mpba)₃]·3CH₃OH·4H₂O (2) [dmso = dimethyl sulfoxide; CH₃OH = methanol; and H₄mpba = 1,3-phenylenebis(oxamic acid)] bearing the [Ni₂(H₂mpba)₃]^2- helicate, hereafter referred to as {Ni^II₂}. SHAPE software calculations indicate that the coordination geometry of all the Ni^II atoms in 1 and 2 is a distorted octahedron (O_h) whereas the coordination environments for K1 and K2 atoms in 1 are Snub disphenoid J84 (D_2d) and distorted octahedron (O_h), respectively. The {Ni^II₂} helicate in 1 is connected by K⁺ counter cations yielding a 2D coordination network with sql topology. In contrast to 1, the electroneutrality of the triple-stranded [Ni₂(H₂mpba)₃] ^2- dinuclear motif in 2 is achieved by a [Ni(H₂O)₆]²⁺ complex cation, where the three neighboring {Ni^II₂} units interact in a supramolecular fashion through four R₂²(10) homosynthons yielding a 2D array. Voltammetric measurements reveal that both compounds are redox active (with the Ni^II/Ni^I pair being mediated by OH^- ions) but with differences in formal potentials that reflect changes in the energy levels of molecular orbitals. The Ni^II ions from the helicate and the counter-ion (complex cation) in 2 can be reversibly reduced, resulting in the highest faradaic current intensities. The redox reactions in 1 also occur in an alkaline medium but at higher formal potentials. The connection of the helicate with the K⁺ counter cation has an impact on the energy levels of the molecular orbitals; this experimental behavior was further supported by X-ray absorption near-edge spectroscopy (XANES) experiments and computational calculations.

Building-up host-guest helicate motifs and chains: a magneto-structural study of new field-induced cobalt-based single-ion magnets

In this work, we present the synthetic pathway, a refined structural description, complete solid-state characterization and the magnetic properties of four new cobalt(ii) compounds of formulas [Co(H₂O)₆][Co₂(H₂mpba)₃]·2H₂O·0.5dmso (1), [Co(H₂O)₆][Co₂(H₂mpba)₃]·3H₂O·0.5dpss (2), [Co₂(H₂mpba)₂(H₂O)₄]_n·4nH₂O (3), and [Co₂(H₂mpba)₂(CH₃OH)₂(H₂O)₂]_n·0.5nH₂O·2ndpss (4) [dpss = 2,2'-dipyridyldisulfide and H₄mpba = 1,3-phenylenebis(oxamic) acid], where 2 and 4 were obtained from [Co(dpss)Cl₂] (Pre-I) as the source of cobalt(ii). All four compounds are air-stable and were prepared under ambient conditions. 1 and 2 were obtained from a slow diffusion method [cobalt(ii) : H₂mpba^2- molar ratio used 1 : 1] and their structures are made up of [Co₂(H₂mpba)₃]^2- anionic helicate units and [Co(H₂O)₆]²⁺ cations, exhibiting supramolecular three-dimensional structures. Interestingly, a supramolecular honeycomb network between the helicate units interacting with each other through R₂²(10) type hydrogen bonds occurs in 2 hosting one co-crystallized dpss molecule. On the other hand, for the first time, linear (3) and zigzag (4) cobalt(ii) chains were isolated by slow evaporation of stirred solutions of mixed solvents with cobalt(ii) : H₂mpba^2- in 1 : 2 molar ratio at room temperature. Magnetic measurements of Pre-I revealed a quasi magnetically isolated S = 3/2 spin state with a significant second-order spin-orbit contribution as expected for tetrahedrally coordinated cobalt(ii) ions. The analysis of the variable temperature static (dc) magnetic susceptibility data through first- (1 and 3) and second-order spin-orbit coupling models (2 and 4) reveals the presence of magnetically non-interacting high-spin cobalt(ii) ions with easy-axis (1 and 4)/easy-plane magnetic anisotropies (2 and 4) with low rhombic distortions. Dynamic (ac) magnetic measurements for Pre-I and 1-4 below 8.0 K show that they are examples of field-induced Single-Ion Magnets (SIMs).

Dinuclear copper(ii) complexes containing oxamate and blocking ligands: crystal structure, magnetic properties, and DFT calculations

Dicopper(ii) complexes were prepared as promising platforms for the design of polynuclear systems providing an avenue toward new molecule-based materials.

On the magneto-structural role of the coordinating anion in oxamato-bridged copper(ii) derivatives

Herein we present the self-assembly of the [Cu(opba)]²⁻ and [Cu(dmphen)]²⁺ building blocks in the presence of thiocyanate (1), chloride (2), bromide (3) and dicyanamide (4) anions.

Syntheses, crystal structures, and magnetic properties of cyanide-bridged complexestrans-RuII(dppe)2(CN)2(FeIIIX3)2(X = Cl and Br)

Cyanide-bridged complexestrans-Ru^II(dppe)₂(CN)₂(Fe^IIIX₃)₂(X = Cl,2; X = Br,3) and their parenttrans-ClRu^II(dppe)₂(CN) (1) were synthesized and fully characterized. The magnetic properties of2and3have been investigated.

A heterometallic ferrimagnet based on a new TTF-bis(oxamato) ligand

An interesting heterometallic one-dimensional complex {[Cu(TTF-opba)][Mn(CH₃OH)₂]}_n based on a π-extended TTF ligand was prepared through the method of “metalloligand”. It retains the redox activity and shows ferrimagnetic behavior.

Crystal structures, topological analysis and luminescence properties of three coordination polymers based on a semi-rigid ligand and N-donor ligand linkers

Three new mixed-ligand coordination polymers have been synthesized based on 3,3′-(anthracene-9,10-diyl)diacrylate acid and different N-donor ligands. Complex 2 displays rapid and selective sensing of Fe³⁺.

Characterization of compounds derived from copper-oxamate and imidazolium by X-ray absorption and vibrational spectroscopies

In this work, compounds derived from copper-oxamate anions (ortho, meta, and para)-phenylenebis (oxamate) and imidazolium cations (1-butyl-3-methylimidazolium) were synthesized. The compounds were characterized by Raman and FTIR spectroscopies and the band assignments were supported by DFT calculations. Strong IR bands from 1610 to 1700cm(-1) dominated the spectra of the complex and can be assigned to νCO vibrations of the [Cu(opba)](2-) anions by the comparison with the DFT data. In opposition to the FTIR spectra, the main vibrational bands in the Raman spectra are observed in the 1350-1600cm(-1) range. All bands in this region are associated to the modified benzene vibrations of the copper-phenylenebis(oxamate) anions. X-ray absorption near edge (XANES) at different energies (NK and Cu L2,3 edges) was also used to probe the interionic interactions. XANES data show that anion-cation interaction in the Cu-oxamate-imidazolium changes the electronic structure around the CuN sites in the oxamate anion.