Influence of ligand encapsulation on cobalt-59 chemical-shift thermometry

Abstract

This manuscript details the first investigation of ligand encapsulation on thermometry by cobalt-59 nuclear spins.

Ionic Liquids–Cobalt(II) Thermochromic Complexes: How the Structure Tunability Affects “Self-Contained” Systems

“…On this subject, Ozvat et al took advantage of the correlation between the 59 Co chemical shift and temperature to perform thermometry via magnetic resonance imaging. 55 They investigated Δδ/ΔT for nuclei of low-spin Co(III) complexes, correlating the degree of ligand encapsulation within the first coordination sphere with the amplification of temperature sensitivity.…”

Molecular Magnetic Materials Based on {CoIII(Tp*)(CN)3}− Cyanidometallate: Combined Magnetic, Structural and 59Co NMR Study

“…Indeed, according to the Curie law, the magnetization of a paramagnetic complex is inversely proportional to the temperature. Chemical shift should thus roughly follow the same trend with temperature as chemical shift can be visualised as local magnetic susceptibility [28] . Hyperfine contribution seems therefore to be responsible for the chemical shift in 3 .…”

Ligand Control of 59Co Nuclear Spin Relaxation Thermometry

“…Thus, slight temperature-dependent structural changes are expected to drive nuclear spin behaviors by manipulating the quadrupolar coupling interaction, inducing temperature dependence in the 59 Co spin-lattice and spin-spin relaxation times, T 1 and T 2 , respectively. We note that other, more common nuclear spin-based probes, e.g., 1 H, 13 C, 19 F, and 31 P, are all I = 1 / 2 , are not quadrupolar nuclei, and thus do not sense changes in temperature in this manner [13][14][15].…”

“…Inversion recovery data were acquired from 180°− τ − 90° pulse sequence experiments with 180° and 90° pulse lengths set at 22.4 and 11.2 μs, respectively. Pulse delay lengths τ were set by exponentially incremented time intervals relative to previously reported room temperature T 1 values of each compound [ 19 ]. Similarly, CPMG (Carr–Purcell–Meiboom–Gill) pulse sequence experiments were made on each sample across a temperature range of 10–60 °C in 10 °C increments [ 25 , 26 ].…”

“…Owing to the foregoing advantages, we target design strategies to control the temperature sensitivity of 59 Co nuclear spin dynamics in encapsulating ligands, which can prevent chemical decomposition in vivo, avoiding the release of toxic metal-ions [16][17][18]. Recent work by us demonstrated that the interconnected structures of encapsulating scaffolds amplify temperature sensitivity for contained 59 Co nuclei [19]. Importantly, these studies probed only temperature-driven changes in chemical shift.…”