Dielectric behavior of manganese(III) spin-crossover complex [Mn(taa)]

Abstract

Paraelectric behavior due to a dynamic Jahn-Teller ͑JT͒ effect is reported for the manganese͑III͒ spincrossover complex ͓Mn͑taa͔͒ ͓H 3 taaϭtris"1-(2-azolyl)-2-azabuten-4Ϫyl…amine͔ in the high-spin ͑HS͒ phase above T c ϭ48 K. The dielectric constant obeys the Curie-Weiss law with an asymptotic Curie temperature 26 K, suggesting competition between a low-spin ͑LS͒ phase and a ferrodistortively ordered ͑FO͒ phase at low temperatures. A phase diagram based on a four-state Ising-Potts model incorporating both a virtual cooperative JT transition (HS↔FO) and a spin-crossover transition (HS↔LS) is proposed to elucidate the interrelation of the HS, LS, and FO phases.

Spin crossover in[MnIII(pyrol)3tren]probed by high-pressure and low-temperature x-ray diffraction

“…The two other shortest Mn...Mn intermolecular distances between neighboring complexes are also given. of the 12 cis Φ angles in the coordination sphere [9] and Θ that is defined as the sum of the deviations from 60° of the 24 possible "twist" angles [14]. …”

“…If the first goal of our study is the determination of the high pressure behavior of this compound, the investigation of the low temperature structural properties is also of great interest. First, up to now, no Mn(III) complex has been structurally characterized in both high and low spin states.. Then, recent spectroscopic measurements have evidenced the presence of a dynamic Jahn Teller distortion in the HS phase [14][15][16] and questioned the role of the vibrational modes in the SCO behavior of this compound 15 .…”

First principles calculation of a large variation in dielectric tensor through the spin crossover in the CsFe[Cr(CN)6] Prussian blue analogue

“…In conclusion, the present study computes a significantly larger variation in the dielectric parameters of the CsFe[Cr(CN) 6 ] PBA through the thermal SCO transition than has been observed in other SCO materials [36][37][38][39]. The current approach is based upon solid-state hybrid DFT calculations, and includes, we believe for the first time, a separate account of the clamped nuclei and phonon contributions to the dielectric tensors of the HS and LS states.…”

“…Secondly, SCO transitions are often accompanied by readily detectable changes in related properties of the materials, most obviously the magnetic susceptibility [18][19][20], but also, for example, the crystal and molecular structures [21][22][23][24][25], the infrared (IR), Raman and nuclear inelastic scattering vibrational spectra [26][27][28], the Mössbauer spectra [29,30], the optical excitation spectra (often leading to a color change) [31,32], the electrical conductivity [33][34][35], and, of particular relevance here, the dielectric tensor governing the polarization response of the material to applied electric fields [36][37][38][39]. The combination of molecular bistability with detectable response properties has led to suggestions that SCO materials might be applied as switching elements in next generation information processing and display technologies [6, 40,41] and in novel gas sensors [10,42].…”

Phase Transition Behavior of a Manganese(III) Spin-Crossover Complex Examined through Dielectric and Magnetic Responses

“…Spin-density profile localized on the JahnTeller stretched axis is depicted as a blue surface 19) . 18,19) . …”