Proton Conductive Luminescent Thermometer Based on Near-Infrared Emissive {YbCo₂} Molecular Nanomagnets

Abstract

Lanthanide­(III)-based coordination complexes have been explored as a source of bifunctional molecular materials combining Single-Molecule Magnet (SMM) behavior with visible-to-near-infrared photoluminescence. In pursuit of more advanced multifunctionality, the next target is to functionalize crystalline solids based on emissive molecular nanomagnets toward high proton conductivity and an efficient luminescent thermometric effect. Here, a unique multifunctional molecule-based material, (H5O2)2(H)­[YbIII(hmpa)4]­[CoIII(CN)6]2·0.2H2O (1, hmpa = hexamethylphosphoramide), composed of molecular {YbCo2}3– anions noncovalently bonded to acidic H5O2 + and H+ ions, is reported. The resulting YbIII complexes present a slow magnetic relaxation below 6 K and room temperature NIR 4f-centered photoluminescence sensitized by [Co­(CN)6]3– ions. The microporous framework, built on these emissive magnetic molecules, exhibits a high proton conductivity of the H-hopping mechanism reaching σ of 1.7 × 10–4 S·cm–1 at 97% relative humidity, which classifies 1 as a superionic conductor. Moreover, the emission pattern is strongly temperature-dependent which was utilized in achieving a highly sensitive single-center luminescent thermometer with a relative thermal sensitivity, S r > 1% K–1 in the 50–175 K range. This work shows an unprecedented combination of magnetic, optical, and electrical functionalities in a single phase working as a proton conductive NIR-emissive thermometer based on Single-Molecule Magnets.

Asymmetric Ring Opening in a Tetrazine‐Based Ligand Affords a Tetranuclear Opto‐Magnetic Ytterbium Complex

“…Recently,t wo examples of luminescent Yb-SMMsw ith built-in thermometric capability were published. [9,10] Furthermore, am olecular ferroelectric Yb 3 + complexp ossessing room temperature magnetoelectric coupling, ar arity for molecular compounds, was reported recently by Long and coworkers. [11] These studies highlight the potentialo fY b 3 + in the development of next-generation multifunctional coordination compounds.…”

“…Among the lanthanide ions explored for the preparation of luminescent Ln‐SMMs, [5–8] the late Kramers ion Yb 3+ has shown great promise. Recently, two examples of luminescent Yb‐SMMs with built‐in thermometric capability were published [9, 10] . Furthermore, a molecular ferroelectric Yb 3+ complex possessing room temperature magnetoelectric coupling, a rarity for molecular compounds, was reported recently by Long and co‐workers [11] .…”

Identical anomalous Raman relaxation exponent in a family of single ion magnets: towards reliable Raman relaxation determination?

“…The record magnetization reversal barrier obtained for Yb III -based complexes up to date is only Ueff/kB = 54 K, 14 which is surprising taking into account the first excited state lying as high as 640 K (464 cm -1 ) as obtained from the luminescence spectra. 29 Therefore, Orbach mechanism is considered as "usually inadequate" to describe magnetization dynamics of ytterbium(III) complexes 30 and Raman relaxation might be the determining factor. [29][30][31] Studying and understanding the role of Raman relaxation is crucial as it can easily limit the usability of SIMs with large Ueff at high temperatures.…”

“…29 Therefore, Orbach mechanism is considered as "usually inadequate" to describe magnetization dynamics of ytterbium(III) complexes 30 and Raman relaxation might be the determining factor. [29][30][31] Studying and understanding the role of Raman relaxation is crucial as it can easily limit the usability of SIMs with large Ueff at high temperatures. 4,32,33 Moreover, deep understanding of relaxation mechanisms for SIMs which do not possess pure mJ ground states is also important from the point of view of molecular qubit candidates design, demonstrated for several non-dysprosium complexes so far.…”

Room‐Temperature Bistability in a Ni–Fe Chain: Electron Transfer Controlled by Temperature, Pressure, Light, and Humidity

“…Molecule-based materials,p articularly CPs,a re exceptionally efficient in the development of switching characteristics,i mplemented at the molecular level, while at the same time they can accommodate aplethora of functionalities.The switchability in CPs has been achieved in many ways,f or example,b yt he use of spin-crossover (SCO) centers, [7] electron-transfer metal couples, [8] or the construction of soft crystalline frameworks. [9] In the design of such materials the bottom-up approach, based on molecular building blocks, allows the implementation of desired features.Byemploying this molecule-to-function strategy,m any switchable and multifunctional molecular materials have been obtained, such as molecular magnets, [10] single molecule magnets, [11] ionic conductors, [12] and luminescent materials. [13] Thee lectron transfer phase transition (ETPT) has been widely investigated in CN-bridged metal complexes.T he CT between the metal sites affects their electronic states,w hich entails changes in structure,c olor,a nd magnetic properties, generating as pecific and measurable response.T he most astonishing effects have been presented for afew CN-bridged metal couples such as Co II/III -Fe III/II , [8a,b] Mn II/III -Fe III/II , [14] or Co II/III -W V/IV , [15] among which the Co-Fe-based systems are the most numerous.M oreover,i nt he Co-based compounds, thermal electron-transfer-coupled spin transition (ETCST) occurs,w hich leads to magnetic bistability between the paramagnetic and diamagnetic state.C onsidering this,t he M-CN-M' systems are perfect candidates for magnetic switches driven by external stimuli.…”