Three‐Dimensional Porous Metal–Radical Frameworks Based on Triphenylmethyl Radicals

Abstract

Lanthanide coordination polymers {[Ln(PTMTC)(EtOH)(2)H(2)O]·x H(2)O, y EtOH} [Ln=Tb (1), Gd (2), and Eu (3)] and {[Ln(αH-PTMTC)(EtOH)(2)H(2)O]·x H(2)O, y EtOH} [Ln=Tb (1'), Gd (2'), and Eu (3')] have been prepared by reacting Ln(III) ions with tricarboxylate-perchlorotriphenylmethyl/methane ligands that have a radical (PTMTC(3-)) or closed-shell (αH-PTMTC(3-)) character, respectively. X-ray diffraction analyses reveal 3D architectures that combine helical 1D channels and a fairly rare (6,3) connectivity described with the (4(2).8)·(4(4).6(2).8(5).10(4)) Schäfli symbol. Such 3D architectures make these polymers porous solids upon departure of the non-coordinated guest-solvent molecules as confirmed by the XRD structure of the guest-free [Tb(PTMTC)(EtOH)(2)H(2)O] and [Tb(αH-PTMTC)(EtOH)(2)H(2)O] materials. Accessible voids represent 40% of the cell volume. Metal-centered luminescence was observed in Tb(III) and Eu(III) coordination polymers 1' and 3', although the Ln(III)-ion luminescence was quenched when radical ligands were involved. The magnetic properties of all these compounds were investigated, and the nature of the {Ln-radical} (in 1 and 2) and the {radical-radical} exchange interactions (in 3) were assessed by comparing the behaviors for the radical-based coordination polymers 1-3 with those of the compounds with the diamagnetic ligand set. Whilst antiferromagnetic {radical-radical} interactions were found in 3, ferromagnetic {Ln-radical} interactions propagated in the 3D architectures of 1 and 2.

Magnetic functionalities in MOFs: from the framework to the pore

“…The same ligand has also been combined with lanthanoid centers, but in this case the lanthanoid-radical magnetic exchanges were weakly ferromagnetic. 53,54 A ubiquitous organic radical in the field of functional molecular materials is the radical anion tetracyanoquinodimethane (TCNQ (Fig. 16).…”

Design of multi-functional 2D open-shell organic networks with mechanically controllable properties

“…Due to the steric protection provided by the three aryl rings, TAMs display high radical stability which has allowed chemists to synthesize more than hundred TAM derivatives that have been used for different applications and as building blocks for multi-functional materials and devices. 4,5 The radical π-conjugation in TAMs is responsible for many of their key characteristics such as fluorescence, 6 enhanced electrical conductivities, 7 redox-activity 8,9 and magnetoresistance phenomena. 10 As a consequence, TAMs have been utilized for the preparation of organic magnets, 12–14 non-volatile memory devices, 8 molecular wires, 10,15 switchable surfaces, 9 dynamic-nuclear polarization components, 16 organic light emitting diodes 17 and nano-porous magnetic sensors, 18 among others.…”

Group 3 Elements and Lanthanide Metals

“…Ferromagnetic and antiferromagnetic interactions [91,92,107,[161][162][163] were reported in addition to the single-ion paramagnetic behavior and typically refer to the respective lanthanide ions. The series of Ln-MOFs {[Ln 2 (Hpimda) 2 ( 4 -C 2 O 4 )⋅2H 2 O]⋅4H 2 O} n (Hpimda = 2-propyl-1H-imidazole-4,5-dicarboxylate) is a prominent example, showing weak ferromagnetic ordering for Tb, Dy, and Ho as well as antiferromagnetic coupling for Er [91].…”