High-pressure, low-temperature, single-crystal neutron diffraction study of deuterated and hydrogenous ammonium hexaaquacopper(II) sulfate (Tutton's salt): a pressure-switchable Jahn-Teller distortion

Abstract

The first example of a pressure-induced Jahn-Teller distortion switch has been observed in a single-crystal time-of-flight neutron diffraction study of the Tutton salt ( N D~)~[ C U ( D Z O )~] ( S~~)~ at T = 15 K, P = 1 bar (h) and T = 15 K, P = 1.5 kbar (h). Also studied was the hydrogenous salt ( N H~)~[ C U ( H~O )~] ( S O~)~ at T = 14 K, P = 1.4 kbar (HH). The unit cell parameters are as follows: h, a = 9.451(2) (2), Z = 2, V = 674.5(2) A3, space group = P21/a. Application of 1.5 kbar of pressure to the deuterated crystal produces a decrease in the lengths of the a and b axes by 0.315(2) and 0.451(4) A, respectively, whereas the c axis increases by 0.275( 1) A. Comparison of the 4. and L~H structures shows that the long axis of the Jahn-Teller distortion has switched by 90°, Le., Cu(l)-0(7) = 2.022(2) and Cu(1)-O(8) = 2.310(2) A for 4. vs Cu(1)-0(7) = 2.290(2) and Cu(1)-O(8) = 2.014(2) A for h, so that the DH and HH structures are similar. For HH Cu(1)-0(7) = 2.272(2) and Cu(1)-O(8) = 2.005(2) A. The switching of the long axis of the Jahn-Teller distortion appears to be associated with the rotation of the ND4+ ion with a concomitant change in the hydrogen bonding of the coordinated water molecules with the S042-ions. The resulting adiabatic potential energy surfaces are calculated using tetragonal and orthorhombic strain parameters estimated from the

Studies on the spin-Hamiltonian parameters of CuN6 clusters and their tetragonal distortions due to Jahn–Teller effect for Cu2+ in trigonal M(1-propyltetrazole)6(BF4)2 (M=Zn, Fe) crystals

“…These values in order of magnitude (∼0.1Å) are the same as those found in a great number of tetragonal or approximately tetragonal Cu 2+ octahedral clusters in pure crystals [41][42][43][44], where Cu 2+ ion is a host ion rather than an impurity, and so the tetragonal elongation can be measured exactly by X-ray diffraction. So, the tetragonal elongations for CuN 6 clusters in M(ptz) 6 (BF 4 ) 2 crystals obtained above are suitable.…”

Theoretical studies of spin Hamiltonian parameters for the tetragonally elongated Cu2+ centers in ARbB4O7 (A = Li, Na, K) glasses

“…(5) may be regarded as valid in physics. The tetragonal elongation ΔZ Cu (≈6.8%, 8.9%, and 12.3%) obtained from the above calculations for Cu 2+ centers in ARbB 4 O 7 glasses is in the same order of magnitude (5%-12%) as those found for Cu 2+ ions in some pure crystals (with tetragonal or approximately tetragonal symmetry) [24][25][26] in which the Cu 2+ ions are the host ion rather than the impurity and so the tetragonal elongations of [CuO 6 ] 10− octahedra can be measured exactly by X-ray diffraction. So the relative tetragonal elongation ΔZ Cu for [CuO 6 ] 10− clusters in ARbB 4 O 7 :Cu 2+ is reasonable.…”

Bispidine Coordination Chemistry

“…With the exception of the thoroughly studied Tutton salts, where the structural variation is based on lattice effects (221), and a thorough study on a system with dynamic Jahn-Teller distortions (222), JahnTeller isomers have not been observed until recently (71,82,194,199).…”