LnDOTA puppeteering: removing the water molecule and imposing tetragonal symmetry

Abstract

Ionic strength and solid state packing effects have been used to remove the coordinated water molecule from the LnDOTA complexes, allowing to understand the magnetic anisotropy and single molecule magnet properties of these complexes.

Engineering Clock Transitions in Molecular Lanthanide Complexes

“…Consequently, the g z and A z values given in Table should be quite reliable. Importantly, the values of g z and A z are very close to the expected free-ion values of 1.25 and 810 MHz, respectively; the <2% reduction may be indicative of weak covalency (see the Supporting Information for more detailed discussion) …”

“…These are remarkably similar to those determined for the [Ho(W 5 O 18 ) 2 ] 9− complex (±23.6, ±70.9, ±118.1, ±165.4 mT), 26 indicating that the hyperfine interactions measured in magnetic field units are almost identical for the two compounds; the hyperfine parameters given in frequency units differ by about 4% (830 MHz for [Ho(W 5 O 18 ) 2 ] 9− ), potentially reflecting differences in covalency for the two compounds. 75 It should be noted that the SCT positions, B 0 SCT , and the gap, Δ, are robust parameters obtained directly from this investigation without dependence on any model. The latter is more than an order of magnitude larger than the gap for the [Ho(W 5 O 18 ) 2 ] 9− complex.…”

“…The CASSCF calculations also predict CF terms with 6 < q ≤ 12 (Supporting Information Table S3). These interactions, which are forbidden for a purely electrostatic CF, do make small but measurable contributions to the eigenvalues, suggesting some degree of covalency …”

“…Importantly, the values of g z and A z are very close to the expected free-ion values of 1.25 and 810 MHz, respectively; 72 the <2% reduction may be indicative of weak covalency (see the Supporting Information for more detailed discussion). 75 The parametrization in Table 1 gives rise to eight 116.4 ± 1.0 GHz SCTs, four on either side of zero-field, at positions B 0 SCT = ±23.5, ±70.6, ±117.6, ±164.7 mT (see Figure 3b inset). These are remarkably similar to those determined for the [Ho(W 5 O 18 ) 2 ] 9− complex (±23.6, ±70.9, ±118.1, ±165.4 mT), 26 indicating that the hyperfine interactions measured in magnetic field units are almost identical for the two compounds; the hyperfine parameters given in frequency units differ by about 4% (830 MHz for [Ho(W 5 O 18 ) 2 ] 9− ), potentially reflecting differences in covalency for the two compounds.…”

“…These interactions, which are forbidden for a purely electrostatic CF, do make small but measurable contributions to the eigenvalues, suggesting some degree of covalency. 75 Finally, we note that minor variations in the structures of 2 a and 2 b result in very significant differences in the Zeeman splitting of the two lowest-lying eigenstates at magnetic fields below 5 T (see Supporting Information Figure S2): the lowest level exhibits marked zero-field curvature for 2 a and less so for 2 b ; meanwhile, for 2 a , the second level exhibits three turning points due to the closer approach of (and interaction with) the third level, whereas such behavior is less apparent for 2 b . These differences likely explain the complex double-peaked EPR spectra observed for compound 2 and probably also the much broader line widths in comparison to 1 on account of an extreme sensitivity to minor changes in structure, i.e., disorder, which is significant in 2.…”