Magnetogenic probes that respond to chemical stimuli in an off–on mode

Abstract

International audienceProbing chemical events can be achieved by several forms of readout. Very popular among designers of responsive probes is an optical/fluorescent output, and their operation in a truly binary off–on mode is greatly desired in view of the associated maximal signal-to-background ratio and detection simplicity. Promotion of another form of physical readout, a change in the magnetization of the sample, detectable for example by Magnetic Resonance Imaging, has been hampered by the inability to propose a molecular probe that is initially silent (off). This focus article discusses a recently proposed solution that consists in the design of suitable multi-dentate ligands whose diamagnetic ferrous complexes (off) turn into paramagnetic ones (on) in aqueous solution upon modification by an external chemical stimulus

Azoimidazole functionalized Ni-porphyrins for molecular spin switching and light responsive MRI contrast agents

“…[6][7][8][9][10] However, spin switching of single molecules in solution or on surfaces at ambient temperatures is still challenging and only a few examples are known in the literature. spintronics, data storage, 3,4 switchable diamagnetic levitation 5 or responsive ("smart") contrast agents for magnetic resonance imaging (MRI).…”

Iron(II) complexes of 2,6-di(1-alkylpyrazol-3-yl)pyridine derivatives – The influence of distal substituents on the spin state of the iron centre

“…The chemistry of spin-crossover complexes [1][2][3] continues to be heavily studied, because of their potential applications as switchable components in memory and display devices [4], in nanoscience [2] and in MRI contrast agents [5]. A class of compound that has been heavily used in spin-crossover research during the past ten years are iron(II) complexes of the isomeric 2,6-di(pyrazolyl)pyridine ligands, 1-bpp and 3-bpp [6, 7].…”

Anion-dependent spin crossover in solution for an iron(ii) complex of a 1H-pyrazolyl ligand

“…2 However, while ultrafast spectroscopy in solution has elucidated the atomistic mechanism of the spin-transition event, 3 interest in solution-phase SCO has otherwise developed more slowly. 4,5 Individual examples of cooperative SCO switching in micelles, 6 a spin-state dependent MRI response from an iron complex, 7 an SCO complex that binds barbiturate in solution 8 and designs of anion-responsive SCO centre, 9,10 have all been demonstrated. These results imply the UV/vis and paramagnetic NMR changes induced by SCO could be of use for sensor applications, for example.…”