166826-92-2Relevant academic research and scientific papers
Synthesis of 4-substituted azopyridine-functionalized Ni(II)-porphyrins as molecular spin switches
Herges, Rainer,Ludwig, Jannis,Moje, Tobias,R?hricht, Fynn
, p. 2589 - 2597 (2020/11/26)
We present the synthesis and the spin switching efficiencies of Ni(II)-porphyrins substituted with azopyridines as covalently attached photoswitchable ligands. The molecules are designed in such a way that the azopyridines coordinate to the Ni ion if the azo unit is in cis configuration. For steric reasons no intramolecular coordination is possible if the azopyridine unit adopts the trans configuration. Photoisomerization of the azo unit between cis and trans is achieved upon irradiation with 505 nm (trans→cis) and 435 nm (cis→trans). Concurrently with the isomerization and coordination/decoordination, the spin state of the Ni ion switches between singlet (low-spin) and triplet (high-spin). Previous studies have shown that the spin switching efficiency is strongly dependent on the solvent and on the substituent at the 4-position of the pyridine unit. We now introduced thiol, disulfide, thioethers, nitrile and carboxylic acid groups and investigated their spin switching efficiency.
Ni(II)porphyrins as pH dependent light-driven coordination-induced spin-state switches (LD-CISSS) in aqueous solution
Dommaschk, Marcel,Gr?bner, Jens,H?vener, Jan-Bernd,Herges, Rainer,Huber, Lukas M.,Ludwig, Jannis,Peters, Morten K.
, p. 480 - 488 (2020/01/06)
A water-soluble Ni(II)-porphyrin substituted with a covalently attached azopyridine ligand was synthesized. Upon irradiation with violet and green light, the azo unit performs a reversible cis-trans isomerization. This geometry change triggers a coordinat
Photoswitchable Magnetic Resonance Imaging Contrast by Improved Light-Driven Coordination-Induced Spin State Switch
Dommaschk, Marcel,Peters, Morten,Gutzeit, Florian,Schütt, Christian,N?ther, Christian,S?nnichsen, Frank D.,Tiwari, Sanjay,Riedel, Christian,Boretius, Susann,Herges, Rainer
, p. 7552 - 7555 (2015/07/02)
We present a fully reversible and highly efficient on-off photoswitching of magnetic resonance imaging (MRI) contrast with green (500 nm) and violet-blue (435 nm) light. The contrast change is based on intramolecular light-driven coordination-induced spin state switch (LD-CISSS), performed with azopyridine-substituted Ni-porphyrins. The relaxation time of the solvent protons in 3 mM solutions of the azoporphyrins in DMSO was switched between 3.5 and 1.7 s. The relaxivity of the contrast agent changes by a factor of 6.7. No fatigue or side reaction was observed, even after >100 000 switching cycles in air at room temperature. Electron-donating substituents at the pyridine improve the LD-CISSS in two ways: better photostationary states are achieved, and intramolecular binding is enhanced.
Structural investigations of C-nitrosobenzenes. Part 2. NMR studies of monomer-dimer equilibria including restricted nitroso group rotation in monomers
Fletcher, Daniel A.,Gowenlock, Brian G.,Orrell, Keith G.
, p. 797 - 803 (2007/10/03)
Energy barriers associated with rotation of nitroso groups in monomeric nitrosobenzene and eleven monomeric substituted nitrosobenzenes in solution have been measured by total 1H NMR bandshape analysis. ΔG? (298.15 K) values for the rotations are in the range 31-41 kJ mol-1. The values for 4-substituted compounds correlate well with the Hammett σp+ parameter for the substituent. The experimental energy barrier for nitrosobenzene is compared with theoretical calculations. Monomerdimer equilibria of these compounds in solution have been investigated, with ΔH, ΔSominus; and ΔGominus; data calculated for the dissociation of both Z- and E- azodioxy dimers to monomers. Kinetic data, based on time-dependent and two-dimensional exchange spectroscopy (2D-EXSY) NMR measurements, have been obtained for the dissociation of 3-methylnitrosobenzene and 3,5-dimethylnitrosobenzene dimers. Energy profiles for the ground and transition states of both dimers and monomers (including exchange between both their rotameric forms) are discussed.
Structural investigations of C-nitrosobenzenes. Part 1. Solution state 1H NMR studies
Fletcher, Daniel A.,Gowenlock, Brian G.,Orrell, Keith G.
, p. 2201 - 2205 (2007/10/03)
Ambient and low temperature 1H NMR spectra of a wide range of 3- and 4-monosubstituted, and some di- and tri-substituted C-nitrosobenzenes have enabled -N=O substituent constants for the static and rotating ring molecules to be calculated. This has provided information on the shielding anisotropy of the N=O group which in turn leads to the firm identification of the monomeric and dimeric solution species. In all cases lowering the solution temperature enhances the relative populations of dimers to monomers, with the (Z)-azodioxy dimer being preferred over the (E)-form, irrespective of the nature of the solid state dimeric structure.
