Abstract
The structure determination of the title compound was undertaken as part of a project on the modification and synthesis of new spin-crossover (SCO) compounds based on octa-hedral FeII bis-(pyrazol-yl)borate complexes. In the course of these investigations, the compound [Fe(C6H8BN4)2(C12H7BrN2)] was synthesized, for which magnetic measurements revealed an incomplete spin-crossover behaviour. Crystallization of this compound from toluene led to the formation of crystals of the toluene disolvate, [Fe(C6H8N4B)2(C12H7N2Br)]·2C7H8. Its asymmetric unit comprises two discrete metal complex mol-ecules and two toluene solvent mol-ecules. One of the latter is severely disordered and its contribution to the diffracted intensities was removed using the SQUEEZE routine [Spek (2015 ▸). Acta Cryst. C71, 9-18]. In each complex mol-ecule, the FeII cation is coordinated by the two N atoms of a 5-bromo-1,10-phenanthroline ligand and by two pairs of N atoms of chelating di-hydro-bis(pyrazol-1-yl)borate ligands in the form of a slightly distorted octa-hedron. The discrete complexes are arranged in columns along the a-axis direction with the toluene solvate mol-ecules located between the columns. The 5-bromo-1,10-phenanthroline ligands of neighbouring columns are approximately parallel and are slightly shifted relative to each other, indicating π-π inter-actions.
Highlights
The structure determination of the title compound was undertaken as part of a project on the modification and synthesis of new spin-crossover (SCO) compounds based on octahedral FeII bis(pyrazolyl)borate complexes
The FeII cation is coordinated by the two N atoms of a 5-bromo-1,10-phenanthroline ligand and by two pairs of N atoms of chelating dihydrobis(pyrazol-1-yl)borate ligands in the form of a slightly distorted octahedron
Most compounds reported in the literature are based on FeII in an octahedral coordination because, in this case, a very long lifetime of the photochemically excited high-spin state is expected
Summary
Spin crossover (SCO) occurs in octahedrally coordinated transition-metal complexes with an electron configuration of 3d4–3d7 and is of extraordinary importance in coordination chemistry and the field of molecular magnetism. In our own systematic investigations we are interested how a chemical modification of such Fe organoborate complexes influences the SCO behavior in the bulk material and in thin films This includes functionalization of the neutral diimine ligand L and the pyrazole ligand in iron(II) complexes with general composition [Fe(H2B(pz)2)2(L)], which leads to characteristic changes in the spin-transition behaviour in the solid state (Naggert et al, 2015; Ossinger et al, 2019, 2020a,b). In the course of this project we became interested in the compound [Fe(H2B(pz)2)2(5-Br-phen)] (pz = pyrazole, 5-Br-phen = 5-bromo-1,10-phenanthroline) Magnetic measurements of this new complex revealed an incomplete SCO in the temperature range from 2 to 300 K with only one step during the spin transition (see Fig. S1 in the supporting information). From the observation of thermal spin-crossover in the latter (albeit in an incomplete fashion), we can conclude that the strength of the – interactions must be weaker in the ansolvate than in the solvate
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
