The influence of NCE⁻ (E = S, Se, BH₃) ligands on the temperature of spin crossover in a family of iron(ii) mononuclear complexes

Abstract

The temperature of spin crossover was systematically tuned by replacing the NCE− (E = S, Se, BH3) co-ligands in a family of mononuclear complexes.

Solvent Effects on the Structural Packing and Spin-Crossover Properties of a Mononuclear Iron(II) Complex

“…The general regularity of solvent effects (except 1·CH 3 CN ) has been established in the analogous compounds [Fe­(tpa)­(NCS) 2 ]· Solv . It should be also noted that compounds 1·CH 3 OH , 1·C 2 H 5 OH , and 1·CH 2 Cl 2 present significantly higher T c values in comparison to those of [Fe­(tpa)­(NCS) 2 ]· Solv , which can apparently be ascribed to the stronger ligand field strength of SeCN – ion. − These results reveal that the encapsulation of solvent molecules in a crystal lattice can effectively tune the structural packing modes and thus the SCO properties, which may be helpful in developing new SCO materials whose SCO behaviors can be controllably tuned by solvents.…”

Phosphine Oxide Ligand Based Tetrahedral CoII Complexes with Field‐induced Slow Magnetic Relaxation Behavior Modified by Terminal Ligands

“…On the other hand, the ligand field strength of NCS − and NCO − is also different. Terminal ligands NCO − and NCS − , as well as NCSe − are widely used in spin‐crossover (SCO) systems to tune the SCO properties because of their similar coordination characteristics and different ligand field strength . For iron complexes the ligand field strengh increases from NCO − to NCS − and then NCSe − .…”

“…[5h, n] On the other hand, the ligand field strength of NCS À and NCO À is also different.T erminal ligandsN CO À and NCS À ,a s well as NCSe À are widely used in spin-crossover (SCO) systems to tune the SCO properties because of their similar coordination characteristics and different ligand field strength. [17] For iron complexes the ligand field strenghi ncreases from NCO À to NCS À and then NCSe À .M agnetic anisotropies of tetrahedral Co II complexes are also very sensitivet ot he ligand field strengh that in many reported systems, ZFS parameters were significantly modified by substituting the terminal ligands. [5h-m] In this case, the substitution from NCS À to NCO À changes the D tensorf rom negative to positive and enhances the slow relaxation behaviours.…”

[Fe(abpt)2(NCSe)2] polymorph A: structural studies into the spin crossover behaviour

“…1 Despite having been extensively studied it still attracts significant research interest partly due to its potential for industrial applications, [2][3][4] for example in data storage devices, 5,6 molecular magnets 7 and molecular switches. 8,9 For a spin crossover compound changes in the physical environment, 10 including temperature, 11 pressure, 12,13 magnetic field or light irradiation, 14,15 can result in a reversible change in the spin state. Many of the spin crossover complexes that have been identified and studied are octahedral Fe(II) species 10,16 but spin crossover is also relatively common for other octahedral 3d 4 -3d 7 metal centres such as Fe(III) 15,17 or Co(II).…”

“…In addition, spin crossovers can be complete, partial or stepped. 24,25 Insights into spin crossover materials and their behaviour are coming from a range of techniques including magnetic data, 13,26 X-ray crystallography, 11,27 spectroscopic techniques including UV-Vis, 26,28 Resonant Ultrasound, 29 Mossbauer 11,30 and X-ray photoelectron spectroscopy. 27 Given the complexity of spin crossover behaviour, 26,31 it is important to study such systems in detail to further our understanding and allow the customised design of spin crossover materials for desired applications.…”