Multi-Dimensional Crystal Structures and Unique Solid-State Properties of Heterocyclic Thiazyl Radicals and Related Materials

Abstract

The crystal structures and magnetic properties of heterocyclic thiazyl radicals and related materials have been examined. TTTA (=1,3,5-trithia-2,4,6-triazapentalenyl) exhibited a first-order phase transition between a paramagnetic high-temperature (HT) phase and a diamagnetic low-temperature (LT) phase, with a wide thermal hysteresis loop over the temperature range 230-305 K. The phase control of TTTA was achieved by pressure and by light irradiation. BDTA (=1,3,2-benzodithiazolyl) also exhibited a diamagnetic-paramagnetic phase transition above room temperature. However, fresh samples always exhibited a superheating of the LT phase that resulted in a double melting (melt-recrystallization-melt process) and supercooling of the HT phase, which in turn led to an antiferromagnetic ordering at 11 K. The molecular compounds of thiazyl radicals were prepared; TTTA formed a coordination polymer structure in the TTTA Á (M ¼ Ga and Fe), exhibited ferromagnetic ordering at 7 K and ferrimagnetic ordering at 44 K after evaporation of crystal solvents. We also grew crystals of M-TTDPz (TTDPz = tetrakis(thiadiazole)porphyrazine and M ¼ H 2 , Fe, Co, Ni, Cu, and Zn) and performed their structural analyses. Their crystal structures were found to depend strongly on the central metal ion and could be classified into three forms: , , and .The electrical and magnetic properties of molecular crystals have been studied extensively in the past three decades, and various molecule-based conductors, superconductors, and magnetic materials have been synthesized to date. The research has been characterized by the enhancement of dimensionality in intermolecular interactions. The first molecular metal, TTF-TCNQ, exhibited a Peierls transition due to instability of the 1D conducting pathway formed by the -overlap.

Metal-radical coordination complexes of thiazyl and selenazyl ligands

“…As anticipated based on a simple orbital overlap model, the exchange coupling is FM. This coordination polymer provides precedent for the potential use of thiazyl radicals as paramagnetic ligands and supramolecular building blocks [24], establishing that N-coordination is possible without disruption of the thiazyl heterocycle. [88].…”

“…As recently as ten years ago, metal-thiazyl coordination chemistry was still in its infancy and progress in the area was documented in a limited number of reviews [22][23][24]. The past decade has witnessed acceleration in the growth and progress of this field, with increased diversity in designs and results.…”

Nitronyl Nitroxide Radicals Linked to Exchange‐Coupled Metal Dimers – Studies Using X‐ray Crystallography, Magnetic Susceptibility Measurements, EPR Spectroscopy, and DFT Calculations

“…When coordinated to open-shell transition metals or lanthanides, they can help to overcome the problem of diminishing exchange interaction between the metal-centered spins, which is normally encountered in systems with an extended diamagnetic ligand framework. A large number of nitroxide, nitronyl nitroxide, [1][2][3][4][5][6] semiquinonate, [7][8][9][10][11][12] verdazyl, [13][14][15][16] thiazyl, [17][18][19][20] and other radicals are known to form discrete metal complexes as well as extended 1D, 2D, and 3D structures in of an additional coordinated acetonitrile molecule. Magnetic susceptibility measurements on powdered samples revealed a dominant antiferromagnetic interaction between the metal ions.…”

Interactive Radical Dimers in Photoconductive Organic Thin Films

“…The thiazyl radical family demonstrates chemical stability and strong intermolecular interactions, and has been shown to have various interesting properties. [11][12][13][14][15][16] Since BDTDA is a so-called disjoint diradical, the molecular orbitals for the two unpaired electrons are localized on separate five-membered rings and the exchange interactions between the two radical centers are very small. [10] The crystal structure of BDTDA in fact consists of a face-to-face BDTDA dimer, which reflects the fact that the intermolecular interaction is stronger than the intramolecular interaction.…”