Unusual Magnetic Behaviors and Electronic Configurations Driven by Diverse Co(II) or Mn(II) MOF Architectures

A robust 3D zinc(II)-organic framework for efficient dual detection of acetylacetone and Tb3+ ions

There has been broad attention to the recognition and detection of ions and organic small molecules due to their essential roles in environmental systems. However, dual-functional probes have seldom been developed for sensing organic constituents and lanthanide ions. A new 3D pillared Zn(ii)-organic framework [Zn3(L)(DCTP)3]n (1) (L = 1,4-di(1H-benzo[d]imidazol-2-yl)butane and H2DCTP = 2,5-dichloroterephthalic acid) was hydrothermally synthesized and structurally characterized, and features a unique 3D 4,4,4,6-connected framework containing approximately 9.99 × 9.78 Å2 cubic channels. 1 displays excellent thermal and pH stability and can act as a novel "turn-on" fluorescent probe for highly selectively sensitizing Tb3+ ions through an "antenna effect". Furthermore, 1 is a dual-response fluorescent sensor for monitoring acetylacetone and Tb3+ ions with rapid response times (within 1 min), low limits of detection (LOD) (5.02 × 10-6/1.15 × 10-8 M, separately) and great anti-interference ability and recyclability towards the analytes. The related sensing mechanisms for detecting analytes are also investigated in detail.

Tuning dimensionality between 2D and 1D MOFs by lanthanide contraction and ligand-to-metal ratio

2D/1D dimensionality tuning in LnMOFs is related to both (i) ligand-to-metal ratio and (ii) lanthanide contraction, this is only possible with Er/Tm, lighter lanthanides e.g. Pr only produced 2D MOFs, despite different ligand-to-metal ratios were used.

Metal-Organic Framework Magnets

Metal-organic frameworks represent the ultimate chemical platform on which to develop a new generation of designer magnets. In contrast to the inorganic solids that have dominated permanent magnet technology for decades, metal-organic frameworks offer numerous advantages, most notably the nearly infinite chemical space through which to synthesize predesigned and tunable structures with controllable properties. Moreover, the presence of a rigid, crystalline structure based on organic linkers enables the potential for permanent porosity and postsynthetic chemical modification of the inorganic and organic components. Despite these attributes, the realization of metal-organic magnets with high ordering temperatures represents a formidable challenge, owing largely to the typically weak magnetic exchange coupling mediated through organic linkers. Nevertheless, recent years have seen a number of exciting advances involving frameworks based on a wide range of metal ions and organic linkers. This review provides a survey of structurally characterized metal-organic frameworks that have been shown to exhibit magnetic order. Section 1 outlines the need for new magnets and the potential role of metal-organic frameworks toward that end, and it briefly introduces the classes of magnets and the experimental methods used to characterize them. Section 2 describes early milestones and key advances in metal-organic magnet research that laid the foundation for structurally characterized metal-organic framework magnets. Sections 3 and 4 then outline the literature of metal-organic framework magnets based on diamagnetic and radical organic linkers, respectively. Finally, Section 5 concludes with some potential strategies for increasing the ordering temperatures of metal-organic framework magnets while maintaining structural integrity and additional function.

Highly selective C2H2 and CO2 capture and magnetic properties of a robust Co-chain based metal–organic framework

A robust Co-MOF based on uncommon 1D alternate Co₄ chain units was synthesized, which efficiently takes up C₂H₂ and CO₂ with significant selectivity for C₂H₂ and CO₂ over CH₄, as well as shows a slow freezing process of magnetic behavior.

A thermally stable three-dimensional cobalt(II) coordination polymer based on the V-shaped ligand 4-(4-carboxyphenoxy)isophthalate

A new cobalt(II) coordination polymer (CP), poly[[bis[μ6-4-(4-carboxylatophenoxy)benzene-1,3-dicarboxylato-κ6 O 1:O 1:O 3:O 3′:O 4:O 4′]bis(1,10-phenanthroline-κ2 N,N′)tricobalt(II)] 0.72-hydrate], {[Co3(C15H7O7)2(C12H8N2)2]·0.72H2O} n , (I), is constructed from CoII ions and 4-(4-carboxyphenoxy)isophthalate (cpoia3−) and 1,10-phenanthroline (phen) ligands. Based on centrosymmetric trinuclear [Co3(phen)2(COO)6] secondary building units (SBUs), the structure of (I) is a three-dimensional CP with a (3,6)-connected net and point symbol (42.6)2(44.62.87.102). The positions of four [Co3(phen)2(COO)6] SBUs and four cpoia3− ligands reproduce a Chinese-knot-shaped arrangement along the ab plane. (I) has been characterized by single-crystal X-ray diffraction, IR spectroscopy, powder X-ray diffraction (PXRD) and thermostability analysis. It shows a good thermal stability from room temperature to 673 K. In addition, the temperature dependence of the magnetic properties was measured.

Hydroxide-bridged dicopper complexes: the influence of secondary coordination sphere on structure and catecholase activity

This work illustrates the syntheses, structures and catecholase activities of dicopper(ii) complexes having a Cu(μ-OH)Cu core encased within a secondary coordination sphere intricately created by appended heterocyclic rings.

The influence of coordination modes and active sites of a 5-(triazol-1-yl) nicotinic ligand on the assembly of diverse MOFs

Six new complexes were successfully assembled via 5-(triazol-1-yl) nicotinic acid (HL). The L⁻ ligand shows versatile coordination modes and can form various clusters in the final structures to fine-tune the properties of MOFs.

Different magnetic responses observed in Co, Co and Co-based MOFs

Four magnetic MOFs with anisotropic Co(II) ions, {[Co5(H2O)2(μ3-OH)2(atz)2(stp)2]·1.5H2O}n (1), {[Co5(H2O)2(μ3-OH)2(trz)2(stp)2]·1.3H2O}n (2), {[Co5(H2O)6(μ3-OH)2(trz)2(stp)2]·2.5CH3OH}n (3) and {[Co3(H2O)4(Hdatrz)2(stp)2]·3H2O}n (4) (stp(3-) = 2-sulfoterephthalate, trz(-) = 1,2,4-triazolate, atz(-) = 3-amino-1,2,4-triazolate and Hdatrz = 3,5-diamino-1,2,4-triazole) were solvothermally isolated by varying the substituent groups appended on the N-heterocyclic triazole and structurally and magnetically characterized. Structural analyses indicate that the former two complexes are crystallographically isostructural, exhibiting pillared-layer frameworks with mixed triazolyl and carboxylate extended Co + Co layers supported by rigid stp(3-) connectors. Complex 3 is built from butterfly-shaped Co cluster-based layers, which are interconnected with single cobalt(ii) octahedra by ditopic stp(3-) bridges. By contrast, complex 4 consists of linear {Co3(μ-N1,N4-Hdatrz)2} subunits, which are extended by 3-connected stp(3-) linkers into a stable 3D framework. Magnetically, 1 exhibits ferromagnetic ordering below 2.7 K due to the well-organized alignment of the non-compensated resultant moment from octahedra and tetrahedral cobalt(ii) carriers, while 3 is in a non-zero paramagnetic state above 2.0 K resulting from the coexistence of intermetallic ferromagnetic and antiferromagnetic interactions. The magnetic competition between weak inter-subunit antiferromagnetic interactions and the external magnetic field makes 4 behave as a field-induced metamagnet with a critical field of 27.5 kOe. These interesting magnetostructural results suggest that the anisotropy of the moment carrier and the interlayer/intersubunit separations significantly dominate the magnetic responses in extended MOFs, providing an informative platform for the further development of interesting magnetic materials, both of academic and industrial interest.

Biphenyl-2,4,6,3',5'-pentacarboxylic acid as a tecton for six new Co(II) coordination polymers: pH and N-donor ligand-dependent assemblies, structure diversities and magnetic properties

Six new Co(ii)-based mixed-ligand coordination polymers, namely, [Co2(H3bppc)2(2,2'-bpy)4]·H2O (), [Co2(Hbppc)(2,2'-bpy)2(H2O)]·H2O (), [Co(H2bppc)(H-bpp)]·2H2O (), [Co3(μ3-OH)(bppc)(dps)(CH3CH2OH)]·4H2O (), [Co2(bppc)(bib)(H2O)4]·(H2-bib)0.5·(H2O)3 (), and [Co2(Hbppc)(bix)2]·2H2O (), (H5bppc = biphenyl-2,4,6,3',5'-pentacarboxylic acid, 2,2'-bpy = 2,2'-bipyridine, bpp = 1,3-bis(4-pyridyl)propane, dps = 4,4'-sulfanediyldipyridine, bib = 1,4-bis(imidazol-1-yl)benzene, bix = 1,4-bis(imidazol-1-ylmethyl)benzene), have been obtained under solvothermal conditions. exhibits a 3D supramolecular framework based on a [Co2(H3bppc)2(2,2'-bpy)4] unit. has a (3,4)-connected dmc net with a (4·8(2))(4·8(5)) topology containing alternate binuclear metal clusters and single metal centres. shows a 3D supramolecular architecture constructed from ladder-like arrays decorated with H-bpp. exhibits a binodal (5,7)-connected 3D network based on trinuclear [Co3(μ3-OH)](5+) units with an unusual (3·4(6)·5(2)·6)(3(2)·4(6)·5(7)·6(5)·7) topology. features a (4,6)-connected 3D fsc open framework with binuclear [Co2(H2O)(COO)](3+) units as nodes, and H2-bib and water molecules located in the voids of its framework by hydrogen bonds. possesses a 3D net containing unusual 2D polyrotaxane sheets. Topological analysis reveals that has a (3,4,4)-connected 3D network with a (4·6·7(4))(4·6·7)(6·7(2)·10(2)·11) topology. The structural difference of and is due to the different pH values of the reaction system. Though complexes were synthesised under similar reaction conditions, the carboxylic groups of H5bppc were partially deprotonated in , and and fully deprotonated in and . Complexes display diverse structures depending on different N-donor ligands and the coordination modes of the multicarboxylate ligand. Variable-temperature magnetic susceptibility measurements reveal that complexes show antiferromagnetic interactions.

A copper-based layered coordination polymer: synthesis, magnetic properties and electrochemical performance in supercapacitors

A layered copper-based coordination polymer ([Cu(hmt)(tfbdc)(H₂O)], Cu-LCP) has been synthesized, which shows ferromagnetic interactions between the adjacent copper(ii) ions and an excellent capacitive performance in supercapacitors.