NMR studies of thermochromic transitions in copper(II) and nickel(II) complexes with N,N-diethylethylenediamine

Abstract

The temperature dependence of the proton and 19F NMR spectra of bis(7V,/V-diethylethylenediamine)copper(II) perchlorate, bis(7V,JV-diethylethylenediamine)copper(II) tetrafluoroborate, bis(7V,jV-diethylethylenediamine)nickel(II) perchlorate, and bis(lV,7V-diethylethylenediamine)nickel(II) tetrafluoroborate were studied. The second moments of the spectra show a sharp decrease at the temperature of the thermochromic phase transition. This decrease is due to the onset of dynamic motion in the ligand molecule. A model of the motion is described, and it is used with the crystallographic data to calculate the second moments for various amplitudes of the flipping motion. No narrowing of the 19F NMR line was observed.

Calorimetric Investigation of Phase Transitions Occurring in Molecule-Based Magnets

“…This mechanism seems to be consistent with various experimental results so far available. However, the relationship between the microscopic aspects − hitherto reported and the macroscopic energetic and entropic aspects was still unclear.…”

“…This mechanism seems to be consistent with various experimental results so far available. However, the relationship between the microscopic aspects [444][445][446][447][448] hitherto reported and the macroscopic energetic and entropic aspects was still unclear. Nishimori et al measured heat capacities of [Cu(dieten) 2 ]-X 2 by adiabatic calorimetry.…”

Calorimetric investigations of phase transitions in which electrons are directly involved

“…This mechanism seems to be consistent with various experimental results so far available. However, the relationship between the microscopic aspects (116)(117)(118)(119)(120) hitherto reported and the macroscopic energetic and entropic aspects was still unclear.…”

Synthesis, thermal, spectroscopic and structural properties of di(aqua)bis(N, N′-dimethylethylenediamine-κ 2 N, N′)copper(II) acesulfamate

“…Copper(II) and nickel(II) complexes with the bidentate diamine ligand were studied extensively due to their thermochromic properties [7][8][9][10][11][12][13][14][15]. The investigations revealed that the nature of the diamine ligand and counter anion are crucial for the thermochromism.…”