Coordination polymers of manganese(II), cobalt(II), nickel(II) and cadmium(II) decorated with rigid pyrazine-2,3-dicarboxylic acid linker: Synthesis, structural diversity, DFT study and magneto-luminescence properties

A new family of metal–organic frameworks (MOFs) named GR-MOFs with the chemical formula {[M x (BCA) y ](H2O) z (DMF) w } (x,y,z,w: 1,1,2,0; 1,1.5,0,1; 1,2,2,1; and 1,1,0,2 for GR-MOF-11 to 14, respectively) based on s-block [M: Sr (GR-MOF-11), Ba (GR-MOF-14)] and d-block [M: Y (GR-MOF-12) and Cd (GR-MOF-13)] metals together with the biquinoline ligand 2,2′-bicinchoninic acid (H2BCA) has been synthetized by a solvothermal route and fully characterized by elemental and thermogravimetric analysis, Fourier transform infrared spectroscopy, photoluminescence, particle size distribution through optical microscopy, electrophoretic mobility, and finally, X-ray single-crystal and powder diffraction. The structural characterization reveals that these 2D and 3D MOFs possess a rich variety of coordination modes that maintained the Janus-head topology on the ligand in most of the cases. The new MOFs were studied in the catalyzed cyanosilylation and hydroboration of an extensive group of aldehydes and ketones, wherein the s-block metal-based MOFs GR-MOF-11 and GR-MOF-14 provided the highest efficiency ever reported in the MOF-catalyzed cyanosilylation of carbonyl compounds by using only 0.5 mol % of catalyst loading, room temperature, and solvent-free conditions. Furthermore, the hydroboration of ketones has been reported for the first time with this type of s-block metal catalysts obtaining from moderate to good conversions.

Section: Resultssupporting

confidence: 76%

Metal–Organic Frameworks Based on a Janus-Head Biquinoline Ligand as Catalysts in the Transformation of Carbonyl Compounds into Cyanohydrins and Alcohols

Pérez

Morales-Cámara

García-Salas

et al. 2022

“…In the past decades, metal–organic frameworks (MOFs) have successfully drawn a great deal of attention due to their advantageous features such as structure diversity and tunability, open metal sites, and large surface areas. − In particular, the easy predesign and postmodification of MOFs provide access for enhancing the interactions between the host and analytes to improve sensing performance, which allows them to be widely employed for sensor design. − In addition, MOF-based sensors always have good performances in recyclable usability. , Among these luminescence MOFs, Ln-MOFs show great potential for being sensing materials because of the good luminescent nature of lanthanide nodes and the tunable antenna effect from the ligand to the lanthanide center that can be regulated through the interaction with different analytes, thus facilizing the ratiometric emission. − It should be noted that luminescence efficiency is considered one of the important parameters for sensing materials. As we know, some luminescent materials show terrible emissions at their solid state or high concentration.…”

Section: Introductionmentioning

confidence: 99%

Constructing an AIE Diphenylquinoxaline-Based Luminescent Europium-Organic Framework for Multiple Substance Sensing

Xiong

Zhang

et al. 2023

Luminescent lanthanide metal–organic frameworks (Ln-MOFs) draw great interest due to their promising luminescent properties and wide applications in sensor design. In this work, a europium-organic framework (DPQ-Eu) has been synthesized under solvothermal conditions based on the aggregation-induced emission (AIE) ligand 4, 4′-(quinoxaline-2, 3-diyl)dibenzoic acid (H2DPQ). Structural analyses show that DPQ-Eu adopts the monoclinic C2/c space group and forms a 3, 6-connected 2D porous network with a topological symbol of {42·6}2{44·69·82}. The formation of DPQ-Eu contributes an absolute quantum efficiency of 21.49% compared with that of the AIE ligand H2DPQ (0.02%) mainly due to the coordination-induced emission, providing DPQ-Eu with a great potential of being a luminescent sensor. Fluorescent investigations show that DPQ-Eu has a selective and sensitive response to Fe3+ and Hg2+ among various metal ions by ratiometric emission changes of the decreased emission at 415 nm and increased emission at 676 nm, with the detection limits of 25.99 and 39.70 nM and good reusability (5 times). The sensing behaviors probably can be ascribed to the promoted antenna effect from the ligand to the Eu(III) center by the coordination of Fe3+/Hg2+ to the quinoxaline moiety. For anion sensing, DPQ-Eu can respond to Cr2O7 2– by emission quenching at both 415 and 676 nm with a detection limit of 9.88 nM and 5 times reusability, probably associated with the energy competing absorption and reduced energy transfer from the ligand to the Eu(III) center. In addition, DPQ-Eu shows ratiometric emission changes to CN– by the emission enhancement and decrease at 415 and 676 nm, respectively, with a detection limit of 8.19 nM and five-run recycling tests, probably corresponding to the inhibition of energy transfer from the ligand to the Eu(III) center caused by the binding interactions between the CN– and Eu(III) nodes.

“…Zhang and co-workers have reported the first genuine 3d-4f cocrystal of a mononuclear Dy III complex with a square-planar Cu II complex consisting of only one reactant . In fact, the field of lanthanide coordination chemistry has gained a lot of attention because of its potential applications in catalysts, photoluminescent materials, and molecular magnetic materials. − Compounds containing lanthanide (Ln) ions are of special interest in the field of molecular magnetism because they may exhibit an extraordinary slow relaxation of magnetization behavior or single molecule/ion magnet (SMM/SIM) behavior arising from the large spin and significant magnetic anisotropy of Ln III ions. − Despite substantial progress in the field of SMMs, it is worth mentioning that QTM-induced relaxation processes are the biggest roadblock in lowering the effective energy barrier ( U eff ) of lanthanide-containing SMM complexes. ,− There are a few strategies to mitigate the QTM, such as ligand fields of high symmetries around the lanthanide ions, application of a tiny static magnetic field, dilution of such complexes in a diamagnetic matrix, or a strong superinteraction among the paramagnetic ions (3d and 4f metal ions). ,− However, a review of the literature has shown that magnetic exchange coupling resulting from 3d/4f metal ions is often weak and has a small effective energy barrier, but when paramagnetic 3d ions are replaced by diamagnetic metal ions, it may offer magnetic dilution to the system, slowing the QTM process and elevating the energy barrier. , Furthermore, recent studies revealed that the presence of diamagnetic coordinating ions in a Dy III system can alter the electron density distribution around the Dy III ion (particularly around the bridging phenoxido oxygen donor), influencing the orientation of the Dy III g tensor and therefore increasing the energy barrier. − …”

Section: Introductionmentioning

confidence: 99%

Syntheses, Structures, and Magnetic Properties of Novel [3×1 + 2×1] Pentanuclear Zinc(II)-Lanthanide(III) Cocrystal Complexes: Slow Magnetic Relaxation Behavior of the Dy(III) Analogue

Roy

Manohar

et al. 2023

A new family of 3d-4f polynuclear cocrystals [LnZn 2 L 2 (CH 3 CO 2 ) 4 ]•[Zn 2 Cl 4 L]•H 2 O [where Ln III = Gd(1), Tb(2), and Dy(3)] are synthesized by the sequential reaction of a tetradentate multisite coordinating compartmental ligand, i.e., (E)-2methoxy-6-(((pyridine-2-ylmethyl)imino)methyl)phenol, in the presence of LnCl 3 •6H 2 O and Zn(OAc) 2 •2H 2 O.The detailed studies involve mainly synthesis, structure, and magnetic properties of three isostructural cocrystals. The X-ray diffraction analysis reveals that complexes 1−3 crystallize in triclinic crystal system with the P1̅ space group. The dimeric [Zn 2 Cl 4 L] − complex appears as a cocrystal in the vicinity of the [LnZn 2 L 2 (CH 3 CO 2 ) 4 ] + crystal structure to counter balance the overall charge on the primary coordination sphere. Magnetic relaxation studies indicate that zero-field out-of-phase magnetic susceptibility signals are observed only for complex 3 (Dy III analogue) which gets well resolved in the presence of a H dc = 0.5 kOe magnetic field. The extracted effective energy barrier (U eff ) and pre-exponential factor (τ 0 ) for 3 is found to be 13.53 K and 1.78 × 10 −6 s, respectively. The appearance of single-ion magnet properties for 3 is rationalized with CASSCF/SO-RASSI/SINGLE_ANISO based ab initio calculations.