Modulating Magnetic and Photoluminescence Properties in 2‐Aminonicotinate‐Based Bifunctional Coordination Polymers by Merging 3d Metal Ions

Abstract

Herein, the synthesisa nd study of bifunctional coordination polymers (CPs) with both magnetica nd photoluminescence properties, derivedfrom ah eterometallice nvironment, are reported.A sastarting point, three isostructural monometallicC Ps with the formula [M(m-2ani) 2 ] n (M II = Mn (1 Mn), Co (3 Co)a nd Ni (4 Ni); 2ani = 2-aminonicotinate), crystallise as chiral 2D-layered structures stacked by means of supramolecular interactions. These compounds show high thermals tabilityi nt he solid state (above3 50 8C), despite which, in aqueous solution,c ompound 1 Mn is shown to partially transform into an ovel 1D chain CP with the formula [Mn(2ani) 2 (m-H 2 O) 2 ] n (2 Mn). As tudy of the direct current (dc) magnetic properties of 1 Mn , 3 Co and 4 Ni revealsaspin-canted structure derived from antisymmetric antiferromagnetic weak exchanges along the chiral network (as confirmed by DFT calculations) and magnetic anisotropy of the ions, in such aw ay that long-range ordering is observed with variable magnitude for the spin carriers.M oreover,c ompounds 3 Co and 4 Ni show no frequency-dependent alternating current (ac)s usceptibilityc urvesu nder zero dc field;t his is characteristic behaviour of ag lassy state that may be partially supressed for 3 Co by applyinga ne xternal dc field. To overcome long-rangem agnetic ordering,C o II ions are diluted in ad iamagnetic Zn II-based matrix, which enables single-molecule magnet behaviour.I nterestingly,t his strategy allows a bifunctional Co x Zn 1Àx 2ani material, whichi si mbuedw ith a strongp hotoluminescent emitting capacity,a sc haracterised by an intenseb lue light followed by ag reen afterglow,t o be obtained.

Single-Ion Magnet and Photoluminescence Properties of Lanthanide(III) Coordination Polymers Based on Pyrimidine-4,6-Dicarboxylate

“…In the case of compound 2-Dy, two clearly distinguishable maxima can be observed in the χ" vs. T plot (Figure 8), peaking in the 2-2.6 K and 3-3.8 K temperature ranges, which may be considered as a two-step relaxation, for which they are denoted as fast (FR) and slow (SR) relaxation processes, respectively. Although the occurrence of these sorts of multiple relaxations is not completely understood and different origins have been already argued to explain it (two distinct Dy(III) ions in the network, a concomitance of singleion and extended exchange interactions, or a combination of single-ion and long-range magnetic orderings, among others) [51][52][53], the crystalline modulation exhibited by 2-Dy at low temperature (in which the structure possesses a commensurate order that accounts for a 1 × 1 × 3 supercell) may explain the occurrence of non-equivalent relaxations in neighboring Dy(III) ions. The dual relaxation is also observed in the Cole-Cole plots in the 2.4-2.8 K region (see ESI, Figure S6, where a combination of two semicircles is appreciated.…”

Multifunctional Lanthanide-Based Metal–Organic Frameworks Derived from 3-Amino-4-hydroxybenzoate: Single-Molecule Magnet Behavior, Luminescent Properties for Thermometry, and CO2 Adsorptive Capacity

“…Within this framework, the quest for multifunctional magneto-luminescent porous molecule-based materials holding a set of properties is a field of demanding interest. Many examples have been reported so far; ,,− in this regard, our research group has paid attention to the preparation of Ln–MOFs for adsorption processes and focused on designing novel multifunctional metal–organic frameworks exhibiting magnetic and luminescence properties. In this work, we report on a novel family of isostructural porous compounds formulated as {[Ln 5 L 6 (OH) 3 (DMF) 3 ]·5H 2 O} n based on a 3-amino-4-hydroxybenzoic acid ligand (H 2 L) .…”

Slow Magnetic Relaxation and Modulated Photoluminescent Emission of Coordination Polymer Based on 3-Amino-4-hydroxybenzoate Zn and Co Metal Ions

“…In addition, at the highest temperature the magnetic value is higher than the expected spin-only value (1.875 cm −3 ·mol −1 K, S = 3/2), indicating a high g value ( g > 2.0). The decrease of the χ M T at lower temperatures can be attributed to the combination of two factors: zero-field splitting of the ground state and/or antiferromagnetic exchange interactions [ 2 , 30 ]. The occurrence of a weak, but non-negligible maximum in the χ M T curve at 5.75 K seems to indicate that there is magnetic ordering in the compound, which may be attributed to a weak ferrimagnetic behaviour.…”

“…Therefore, combinations such as conductive/optical, magnetic/optical or conductive/magnetic are possible to study, giving the opportunity of analysing simultaneously the influence of one (or more) physical property present in these materials. Because of the broad spectrum that these materials can cover, several applications can be addressed with MMMs, such as separation and storage, heterogeneous catalysis, drug delivery, sensor devices and magnetic and photoluminescence, among others [ 2 , 3 , 4 , 5 , 6 , 7 , 8 ].…”

“…This magnetic behaviour derives from the slow magnetic relaxation of metal ions with an appropriate coordination shell, in this case Co II . At this point, the structural design is thus crucial so that the coordination of organic ligands not only favour the occurrence of magnetic anisotropy but also isolate the spin carriers by imposing weak or null exchange interactions in the crystal building to avoid long-range magnetic ordering phenomena, such as ferromagnetism, antiferromagnetism, and metamagnetism [ 2 , 17 ]. An alternative to avoid those undesired effects is to physically isolate (dilute) the spin carriers into a diamagnetic matrix that preserves isostructural nature, a process called magnetic dilution, in such a way that magnetic exchange interactions would be partially suppressed to give single ion magnetic properties, and hence single-ion magnets (SIMs) [ 18 ].…”