Metal–Metalloligand Coordination Polymer Embedding Triangular Cobalt–Oxo Clusters: Solvent- and Temperature-Induced Crystal to Crystal Transformations and Associated Magnetism

Abstract

Reaction of the metalloligand IrIII(ppy-COOH)3 and the anisotropic paramagnetic CoII ion under solvothermal conditions resulted in a metal–metalloligand coordination polymer, [CoII 3(μ3-O)­(μ-OH2)­{IrIII(ppy-COO)2(ppy-COOH)}2(H2O)4]·2DMF·xH2O (I). It consists of trimeric Co3O secondary building units (SBUs) bridged by pairs of Ir to form chains of alternate orthogonal squares. The compound undergoes two single-crystal to single-crystal transformations while retaining its general structural features. A chemical transformation occurs to give [CoII 3(μ3-O)­{IrIII(ppy-COO)2(ppy-COOH)}2(H2O)4(DMF)]·DMF·H2O (II) by soaking in acetone, where a bridging water molecule departs and the solvent DMF bonds to the vacant site of the Co center. Both I and II undergo a temperature-induced transformation to [CoII 3(μ3-O)­{IrIII(ppy-COO)2(ppy-COOH)}2(H2O)3(DMF)]·DMF (III), where one more coordinated water molecule is lost. The major difference in the three phases is in the Co coordination spheres, which have considerable consequences on the magnetism. Compound I displays paramagnetism down to 2 K, whereas II and III show weak ferromagnetism with T C values of 14 and 17 K, respectively.

Structural conversion of three copper(ii) complexes with snapshot observations based on the different crystal colours and morphology

“…The structural transformation of complexes can lead to different properties, such as colour, morphology, adsorption, chirality, luminescence and magnetism. [1][2][3][4][5][6][7][8][9][10][11][12][13] The potential application value brought by the diversity of complex structures has attracted more and more attention. 14 The structural transformation is usually characterized by small changes in the number and order of uncoordinated molecules at the molecular level, such as the addition and removal of solvents or guest molecules.…”

Engineering Heteronuclear Arrays from IrIII‐Metalloligand and CoII Showing Coexistence of Slow Magnetization Relaxation and Photoluminescence

“…[ 28‐30 ] However, assembling Ir‐Co systems with the coexistence of luminescence and slow magnetization relaxation is desirable, but difficult to achieve. As far as we are aware, there are only five Ir(III)‐ Co(II) compounds reported in the literature including two Co 3 Ir 2 cages based on Ir(ppy) 3 derivative, [ 31 ] a CoIr 2 chain compound based on Ir(ppy) 2 (H 2 dcbpy) (H 2 dcbpy = 4,4’‐dicarboxy‐2,2’‐bipyridine), [ 32 ] a Co 3 Ir 2 chain [ 33 ] and a Co 2 Ir 2 layer [ 34 ] compound based on Ir(ppy‐COOH) 3 . These compounds were either non‐emissive or with extremely low quantum yield (≤ 0.1%).…”

Cobalt(II)‐dianthracene Frameworks: Assembly, Exfoliation and Properties

“…[8][9][10][11] Among them, cobalt-based MOFs are of particular interest because cobalt ion can show multiple oxidation states, variable coordination numbers and tunable spin states that can be sensitive to environment changes. [12][13][14][15][16][17][18] For example, Dincă et al reported the reversible storage of elemental chlorine and bromine in a robust Co-azolate MOF which operated via redox mechanism. [19] Pardo and Cano et al found that single-ion magnet behavior of a 2D Co-MOF can be tuned by changing the guest aromatic molecules.…”

“…Metal‐organic frameworks (MOFs) with their structures and properties responsive to external stimuli, such as gas/guest, [1–3] pressure, [4] temperature [5] and light, [6,7] are very attractive owing to their potential applications in gas storage and separation, drug delivery, sensors, catalysis and molecular devices [8–11] . Among them, cobalt‐based MOFs are of particular interest because cobalt ion can show multiple oxidation states, variable coordination numbers and tunable spin states that can be sensitive to environment changes [12–18] . For example, Dincă et al.…”