Proton -conducting lanthanide metal-organic frameworks: a multifunctional platform.

Lanthanide metal-organic frameworks (LMOFs) have established themselves as promising proton-conducting materials among all types of porous coordination polymers and covalent organic frameworks. The structural diversity of LMOFs and high oxophilicity with a high coordination number of lanthanide ions make LMOFs a standout material for proton conduction. In the last few years, ample research efforts have been devoted to designing and developing proton-conducting lanthanide metal-organic frameworks (PCLMOFs).

Levamisole Based Co(II) Single-Ion Magnet.

A new Co(II) complex, [Co(NCS)(L)] (1) has been synthesized based on levamisole (L) as a new ligand. Single-crystal X-ray diffraction analyses confirm that the Co(II) ion is having a distorted tetrahedral coordination geometry in the complex. Notably strong intramolecular S⋅⋅⋅S and S⋅⋅⋅N interactions has been confirmed by employing Quantum Theory of Atoms in Molecules (QTAIM).

Exploration of SMM behavior of Ln complexes derived from thianaphthene-2-carboxylic acid.

Two lanthanide-based dinuclear complexes [Ln(L)(DMF)(HO)] (Ln = Dy (1)/Tb (2)) derived from thianaphthene-2-carboxylic acid have been synthesized and characterized in detail. Single-crystal XRD analyses confirm that the centro-symmetric discrete dimeric structures contain eight-coordinated lanthanide centers with biaugmented trigonal prism geometry in the complexes. Magnetic studies reveal the presence of antiferromagnetic interaction as well as thermal depopulation of Stark sublevels with a decrease in temperature for both complexes, whereas prominent field-induced single-molecule magnet behavior was observed for 1.

Anion-driven structures and SMM behavior of dinuclear terbium and ytterbium complexes.

The work in this present investigation reports the syntheses, crystal structures and magnetic properties of five dinuclear lanthanide complexes having compositions [Tb2(HL)4(NO3)6] (1), [Tb2(HL)4Cl6]·2EtOH (2), [Yb2(HL)4(NO3)6] (3), [Yb2(HL)4Cl6]·2EtOH (4) and [Y2(HL)4(NO3)6] (5) with HL = 8-hydroxyquinaldine. It is evident from the crystal structures that the coordination number of trivalent lanthanide ions in compounds 1, 3 and 5 is nine, whereas that for compounds 2 and 4 is six. A dynamic magnetic study shows that both compounds 1 and 3 exhibit single-molecule-magnet (SMM) behavior while compounds 2 and 4 do not have any SMM property.

Channel-Assisted Proton Conduction Behavior in Hydroxyl-Rich Lanthanide-Based Magnetic Metal-Organic Frameworks.

Two new lanthanide-based 3D metal-organic frameworks (MOFs), {[Ln(L)(Ox)(HO)]·xHO} [Ln = Gd and x = 3 (1) and Dy and x = 1.5 (2); HL = mucic acid; OxH = oxalic acid] showing interesting magnetic properties and channel-mediated proton conduction behavior, are presented here. Single-crystal X-ray structure analysis shows that, in complex 1, the overall structure originates from the mucate-bridged gadolinium-based rectangular metallocycles.

Densely Packed Lanthanide Cubane Based 3D Metal-Organic Frameworks for Efficient Magnetic Refrigeration and Slow Magnetic Relaxation.

Two isostructural densely packed squarato-bridged lanthanide-based 3D metal-organic frameworks (MOFs) [Ln5(μ3-OH)5(μ3-O)(CO3)2(HCO2)2(C4O4)(H2O)2] [Ln = Gd (1) and Dy (2)] show giant cryogenic magnetic refrigeration (for 1) and slow magnetic relaxation (for 2). The structural analyses reveal the presence of a self-assembled crown-shaped building unit with a cubane-based rectangular moiety that leads to a special array of metal centers in 3D space in the complexes. Magnetic investigations confirm that complex 1 exhibits one of the largest cryogenic magnetocaloric effects among the molecular magnetic refrigerant materials reported so far (-ΔSm = 64.

Tetrahedral M(II) based binuclear double-stranded helicates: single-ion-magnet and fluorescence behaviour.

A rare class of dinuclear double-stranded helicates having tetrahedral metal centres with formulae [Co2(L(1))2]·2(CH3CN) (1), [Co2(L(2))2]·6(CH3CN) (2), [Zn2(L(1))2]·2(CH3CN)·(CH3OH) (3) and [Zn2(L(2))2]·4(CH3CN) (4) were synthesized and characterized. Detailed dc and ac magnetic susceptibility measurements reveal the presence of field induced slow magnetic relaxation behaviour in high spin tetrahedral Co(II) centres with an easy-plane magnetic anisotropy. Complexes 1 and 2 are the rare examples of transition metal based helicates showing such behaviour.

Proton-Conducting Magnetic Coordination Polymers.

Three isostructural lanthanide-based two- dimensional coordination polymers (CPs) {[Ln2(L)3(H2O)2]n⋅2n CH3OH)⋅2n H2O} (Ln=Gd(3+) (1), Tb(3+) (2), Dy(3+) (3); H2L=cyclobutane-1,1-dicarboxylic acid) were synthesized by using a low molecular weight dicarboxylate ligand and characterized. Single-crystal structure analysis showed that in complexes 1-3 lanthanide centers are connected by μ3-bridging cyclobutanedicarboxylate ligands along the c axis to form a rod-shaped infinite 1D coordination chain, which is further linked with nearby chains by μ4-connected cyclobutanedicarboxylate ligands to form 2D CPs in the bc plane. Viewing the packing of the complexes down the b axis reveals that the lattice methanol molecules are located in the interlayer space between the adjacent 2D layers and form H-bonds with lattice and coordinated water molecules to form 1D chains.

Highly selective detection of palladium and picric acid by a luminescent MOF: a dual functional fluorescent sensor.

A Zn(II) based luminescent metal organic framework is synthesized, which acts as a dual functional fluorescent sensor to selectively detect picric acid and palladium(II).

Concomitant spin-canted antiferromagnetic ordering and proton conduction in homometallic and homoleptic coordination polymers.

Two unprecedented oxonate based 1D coordination polymers with Fe(II) and Co(II) have been synthesized. A detailed magnetic investigation revealed that these complexes are the first oxonate based systems to exhibit spin canted antiferromagnetic ordering at low temperatures. Proton conductivity studies of the complexes showed good proton conduction ability at elevated temperatures and under high humidity conditions.

Study of proton conductivity of a 2D flexible MOF and a 1D coordination polymer at higher temperature.

We report the proton conduction properties of a 2D flexible MOF and a 1D coordination polymer having the molecular formulas {[Zn(C10H2O8)0.5(C10S2N2H8)]·5H2O]}n (1) and {[Zn(C10H2O8)0.5(C10S2N2H8)]·2H2O]}n (2), respectively.

A perception of ferro- and antiferromagnetic interactions in a two dimensional Ni(II) heterochiral coordination polymer showing unusual CO₂ uptake behavior.

We present a robust two dimensional coordination polymer, [Ni2(L)2(N(CN)2)2]n (1) (LH = 2-((1-(pyridin-2-yl)ethylimino)methyl)phenol; N(CN)2(-) = dicyanamide ion) using a chiral Schiff base (LH), which shows diastereoselectivity in the structure via a chiral self-discrimination process, ferro- and antiferromagnetic interactions among the metal centers and unusual CO2 uptake behavior as a porous framework.

Friedel-Crafts alkylations of electron-rich aromatics with 3-hydroxy-2-oxindoles: scope and limitations.

A Lewis acid-catalyzed nucleophilic addition of electron rich aromatics with 3-hydroxy-2-oxindoles 5 was developed. The reaction is believed to proceed through the 2H-indol-2-one ring system 9, which eventually reacts with various electron-rich aromatics to afford a variety of 2-oxindoles with an all-carbon quaternary center at the pseudobenzylic position (4, 8, 13, and 16) in high yields. The methodology provides an expeditious route to the tetracyclic core (3) of diazonamide (1), and azonazine (2) as well as the tricyclic core of asperazine (6a), idiospermuline (6b), and calycosidine (6c) viz.

Synthesis, crystal structure and study of magnetocaloric effect and single molecular magnetic behaviour in discrete lanthanide complexes.

The synthesis, crystal structure and magnetic properties of four polynuclear lanthanide coordination complexes having molecular formulae, [Gd3(2)(1)L(H2O)8(Cl)](Cl)4·10H2O (1), [Dy3L(2)(1)(H2O)9](Cl)5·6H2O (2) [Gd6L(2)(2)(HCO2)4(μ3-OH)4(DMF)6(H2O)2](Cl)2·4H2O (3) and [Dy6L(2)(2)(HCO2)4(μ3-OH)4(DMF)6(H2O)2](Cl)2·4H2O (4) (where H2L(1) = bis[(2-pyridyl)methylene]pyridine-2,6-dicarbohydrazide and H4L(2) = bis[2-hydroxy-benzylidene]pyridine-2,6-dicarbohydrazide) are reported. Structural investigation by X-ray crystallography reveals similar structural features for complexes 1 and 2 and they exhibit butterfly like shapes of the molecules. Non-covalent interactions between the molecules create double helical arrangements for both molecules.

Two isostructural 3D lanthanide coordination networks (Ln = Gd(3+), Dy(3+)) with squashed cuboid-type nanoscopic cages showing significant cryogenic magnetic refrigeration and slow magnetic relaxation.

Two isostructural lanthanide-based 3D coordination networks [Ln = Gd(3+) (1), Dy(3+)(2)] with densely packed distorted cuboid nanoscopic cages are reported for the first time. Magnetic characterization reveals that complex 1 shows a significant cryogenic magnetocaloric effect (-ΔSm = 44 J kg(-1) K(-1)), whereas 2 shows slow relaxation of magnetization.

Effect of ligand substituent coordination on the geometry and the electronic structure of Cu(II)-diradical complexes.

Two organic moieties, known as ligands, having -OMe and -SePh as the ortho substituent attached to the aniline moiety of the parent 2-anilino-4,6-di-tert-butylphenol ligand, were synthesized. The ligands reacted with CuCl2·2H2O in a 2:1 ratio in CH3CN in the presence of Et3N and provided the corresponding mononuclear Cu(II)-diradical complexes 1 (-OMe) and 2 (-SePh). Complex 1 was square planar, while complex 2 was in distorted square planar geometry due to the secondary coordination between the Se atom and the central Cu(II) center.

High nuclearity (octa-, dodeca-, and pentadecanuclear) metal (M = Co(II), Ni(II)) phosphonate cages: synthesis, structure, and magnetic behavior.

The synthesis, structural characterization, and magnetic property studies of five new transition metal (M = Co, Ni) phosphonate-based cages are reported. Three substituted phenyl and benzyl phosphonate ligands [RPO3H2; R1 = p-tert-butylbenzyl, R2 = p-tert-butylphenyl, R3 = 3-chlorobenzyl] were synthesized and employed to seek out high-nuclearity cages. Complexes 1-3 are quasi-isostructural and feature a dodecanuclear metal-oxo core having the general molecular formula of [M12(μ3-OH)4 (O3PR)4(O2C(t)Bu)6 (HO2C(t)Bu)6(HCO3)6] {M = Co, Ni and R = R1 for 1 (Co12), R2 for 2, 3 (Co12, Ni12)}.

A 3D iron(II)-based MOF with squashed cuboctahedral nanoscopic cages showing spin-canted long-range antiferromagnetic ordering.

The reaction of dilithium squarate with Fe(II) perchlorate led to the formation of a new Fe(II)-based 3D MOF, [Fe3(OH)3(C4O4)(C4O4)0.5]n (1), with homoleptic squashed cuboctahedral cages. Complex 1 crystallizes in the monoclinic C2/c space group.

Observation of a large magnetocaloric effect in a 2D Gd(III)-based coordination polymer.

A new 2D Gd(III)-based coordination polymer has close to the highest cryogenic magnetocaloric effect of any MOF reported so far. The experimental results reveal its structural features and magnetic properties.

Transition-metal-free synthesis of unsymmetrical diaryl chalcogenides from arenes and diaryl dichalcogenides.

A transition-metal-free synthetic method has been developed for the synthesis of unsymmetrical diaryl chalcogenides (S, Se, and Te) from diaryl dichalcogenides and arenes under oxidative conditions by using potassium persulfate at room temperature. Variously substituted arenes such as anisole, thioanisole, diphenyl ether, phenol, naphthol, di- and trimethoxy benzenes, xylene, mesitylene, N,N-dimethylaniline, bromine-substituted arenes, naphthalene, and diaryl dichalcogenides underwent carbon-chalcogen bond-forming reaction to give unsymmetrical diaryl chalcogenides in trifluoroacetic acid. To understand the mechanistic part of the reaction, a detailed in situ characterization of the intermediates has been carried out by (77)Se NMR spectroscopy by using diphenyl diselenide as the substrate.