Thermometric Properties of Thio/Selenocyanato-Bridged Spin-Crossover Networks

Abstract

Thermometry is a well-researched topic in materials science, but recent advances in multifunctional complexes have introduced the idea of highly sensitive and accurate contact or noncontact thermometers, which utilize the temperature-dependent evolution of physical properties. In this context, the {[Fe(μpyrazineFeHgS, and E = Se, FeHgSe) three-dimensional networks with spin-transition temperature T 1/2 = 191 K were considered promising materials. Temperature-dependent UV−visible−NIR, IR, and Raman spectra displayed a strong dependence on the peak intensities and positions with temperature. Subsequently, firstprinciples calculations for low-and high-spin states gave a thorough description of the spectroscopic properties and origins. The unique temperature-dependent variability caused by a combination of gradual spin-crossover (SCO)-active Fe centers and SCO-inactive Fe centers as a reference allowed us to prove the feasibility of the thermometric concept via the characterization of UV−vis−NIR, IR, and Raman intensity ratios. In particular, compared to UV−vis−NIR absorption thermometry, IR and Raman thermometry manifested high thermal sensitivity (S r ) with the best values of 3.2% K −1 at 182 K (FeHgS, IR), 3.1% K −1 at 131 K (FeHgSe, IR), 16.3% K −1 at 184 K (FeHgS, Raman), and 12.1% K −1 at 186 K (FeHgSe, Raman). Overall, the realization of optical and vibrational SCO thermometers has significant implications for the practical application of switchable materials and leads to the development of advanced thermometers.

Modulation on terahertz absorption properties in LnIII–[AgI(CN)2] networks

“…Particularly, molecular complexes are emerging as an appealing category of materials owing to their simple and adjustable structures and predisposition to merge various functionalities, such as magnetism, luminescence, non-linear optics, and low-frequency absorbing capability. 28–36 Moreover, the desired THz absorbing capability can be introduced by meticulously choosing building blocks and arranging them in solid-state structures. This strategic approach harnesses the inherent flexibility of molecular complexes, facilitating the deliberate engineering of materials with tailored THz characteristics.…”