Complete and Versatile Post‐Synthetic Modification on Iron‐Triazole Spin Crossover Complexes: A Relevant Material Elaboration Method

Abstract

In this paper we study the post-synthetic modification (PSM) reaction on solid spin crossover (SCO) [Fe(NH 2 trz) 3 ]X 2 (X=NO 3 , OTs, Cl, SO 4 , BF 4 ) complexes with different substrates. The wide access to a diversity of functionalized complexes with imine, amide and carbamide groups from the same amino parent compound demonstrates the synthetic approach value of this method. The as-obtained post-synthetic complexes were studied by IR, solid NMR, elemental analyses, and powder X-ray diffraction, and compared to the corresponding compounds obtained by direct synthesis (DS) routes. Moreover, after digestion of the complexes obtained by PSM reactions, the free ligands were characterized by NMR in solution, which allowed us to indirectly confirm the formation of complexes we wished to synthesize. The study reveals in numerous cases that a complete post-synthetic modification is possible despite the structural cohesion that is established between the 1D coordination chains within these materials. Spin crossover properties of some complexes obtained by both methods are also reported and compared.

Post-synthetic modification mechanism for 1D spin crossover coordination polymers

“…In our previous studies, 4,9 we have demonstrated that a quantitative modification of NH 2 substituents on complexes [Fe(NH 2 trz) 3 ](X) 2 (X = NO 3 , OTs) can be achieved by PSM reactions with different substrates. Although PSM method was implemented before by Wang et al .…”

Stimuli-responsive spin crossover nanoparticles for drug delivery and DNA-binding studies

“…Coordination complexes/polymers may also act as drug delivery systems and carry a wide range of bioactive molecules or accommodate multiple functional groups. 9 SCO [Fe II (Htrz) 2 (trz)](BF 4 ) coordination NPs, which undergo a spin state change between the LS ( S = 0) and the HS ( S = 2) when exposed to external stimuli, have good dynamics as MRI contrast agents but might also be used as promising drug nanocarriers. 10,11…”

“…Coordination complexes/polymers may also act as drug delivery systems and carry a wide range of bioactive molecules or accommodate multiple functional groups. 9 SCO [Fe II (Htrz) 2 (trz)](BF 4 ) coordination NPs, which undergo a spin state change between the LS (S = 0) and the HS (S = 2) when exposed to external stimuli, have good dynamics as MRI contrast agents but might also be used as promising drug nanocarriers. 10,11 A post-synthetic modification (PSM) method has been recently used for SCO materials in order to determine potential synergetic effects between magnetic and physical/chemical properties aiming for applications mainly in the field of multi-functional materials.…”

“…10,11 A post-synthetic modification (PSM) method has been recently used for SCO materials in order to determine potential synergetic effects between magnetic and physical/chemical properties aiming for applications mainly in the field of multi-functional materials. 9 To the best of our knowledge, most of the reports of applying the PSM method have described employing post-functionalized molecules: (i) 3D-Hofmann clathrates, 12,13 (ii) a dinuclear iron(III) complex, 14 (iii) an Fe II [M IV (CN) 8 ] 4− (M = Mo, Nb) cyanido-bridged framework, 15 (iv) 1D-polymeric iron-triazole complexes [16][17][18][19][20] and (v) iron poly ( pyrazolyl)borate complexes. 21,22 This is due to the potential they provide for the successful grafting of functional groups in their primitive molecular structures.…”

Spontaneous Synthesis of [FeII(Atrz)3]SO4 and its Analogues Through Accelerated Ageing: New Insights from Small‐Scale Reactions

“…Another method currently in use for the synthesis of these materials, is post-synthetic modification of products made using the previously described methods either mechanochemically [46] or in solution. [ 48] This allows access to analogues containing different anions and variations of the triazole ligands that could not previously be synthesized ab initio, but it also adds an additional step in the synthetic process and shares the same problems as their respective parent methods. The synthetic route to these materials is particularly important considering the sensitivity of their switching properties to particle size, solvent, matrix effects and preparation techniques.…”