Reversible coordination-induced spin-state switching in complexes on metal surfaces

Köbke, Alexander; Gutzeit, Florian; Röhricht, Fynn; Schlimm, Alexander; Grunwald, Jan; Tuczek, Felix; Studniarek, Michał; Longo, Danilo; Choueikani, Fadi; Otero, Edwige; Ohresser, Philippe; Rohlf, Sebastian; Johannsen, Sven; Diekmann, Florian; Jasper-Toennies, Torben; Näther, Christian; Herges, Rainer; Berndt, Richard; Gruber, Manuel

doi:10.1038/s41565-019-0594-8

Cited by 90 publications

(78 citation statements)

References 31 publications

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“…We now present a photoswitchable catalyst whose basicity is controlled by coordination/decoordination to the Ni 2+ ion in a Ni-porphyrin. So-called record player molecules, including a Ni(II)-porphyrin as the square planar base complex and azopyridines as photoswitchable axial ligands, were previously investigated for spin switching applications [13][14][15][16][17][18][19][20][21][22][23][24][25][26]. In the present study, the basicity change linked to the coordination/decoordination process is explored.…”

Section: Introductionmentioning

confidence: 99%

Azo-dimethylaminopyridine-functionalized Ni(II)-porphyrin as a photoswitchable nucleophilic catalyst

Ludwig¹,

Helberg²,

Zipse³

et al. 2020

Beilstein J. Org. Chem.

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We present the synthesis and the photochemical and catalytic switching properties of an azopyridine as a photoswitchable ligand, covalently attached to a Ni(II)-porphyrin. Upon irradiation with 530 nm (green light), the azopyridine switches to the cis configuration and coordinates with the Ni2+ ion. Light of 435 nm (violet) isomerizes the ligand back to the trans configuration, which decoordinates for steric reasons. This so-called record player design has been used previously to switch the spin state of Ni2+ between singlet and triplet. We now use the coordination/decoordination process to switch the catalytic activity of the dimethylaminopyridine (DMAP) unit. DMAP is a known catalyst in the nitroaldol (Henry) reaction. Upon coordination to the Ni2+ ion, the basicity of the pyridine lone pair is attenuated and hence the catalytic activity is reduced. Decoordination restores the catalytic activity. The rate constants in the two switching states differ by a factor of 2.2, and the catalytic switching is reversible.

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Section: Introductionmentioning

confidence: 99%

Azo-dimethylaminopyridine-functionalized Ni(II)-porphyrin as a photoswitchable nucleophilic catalyst

Ludwig¹,

Helberg²,

Zipse³

et al. 2020

Beilstein J. Org. Chem.

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“…Molecular spin switches operated with visible light in homogeneous solution [ 1 ] or on surfaces [ 2 ], hold promise for a number of hitherto unprecedented applications such as switchable contrast agents [ 3 – 7 ], switchable NMR relaxation agents [ 8 – 10 ], and building blocks for molecular spintroncis [ 11 ]. Our modular design is based on three components: a) a Ni(II)-porphyrin (square planar base complex), b) an azoaryl unit (photoswitchable ligand) and c) a molecular linker or tether (connecting the porphyrin with the switchable ligand).…”

Section: Introductionmentioning

confidence: 99%

Synthesis of 4-substituted azopyridine-functionalized Ni(II)-porphyrins as molecular spin switches

Ludwig¹,

Moje²,

Röhricht³

et al. 2020

Beilstein J. Org. Chem.

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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.

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“…[1][2][3][4][5] As one of the prototype devices, molecular spin switches, especially intrinsic spin switches, which can be switched between at least two stable spin-states by external stimuli such as temperature, 6 pressure, 7 photons, 6,8 electric fields, 9 etc., have been considered as the essential step towards the development of molecular spintronics. [10][11][12][13] Recently, several types of single-molecule prototype devices have been demonstrated, such as voltage-triggered, 14 stretching-induced 15,16 or electron injection induced [17][18][19] spin switches. However, due to the difference in spin multiplicity and vibrational levels, the phase transition of intrinsic spin switch from low-spin (LS) to high-spin (HS) is an entropy-increasing process (ΔS > 0), suggesting that the transition is temperature-dependent, and the LS state is more stable at low temperature.…”

Section: Introductionmentioning

confidence: 99%

“…The spin-states of some 3d metal ions [25][26][27] are sensitive to the coordination of the geometric structure, and thus the squar planar Ni-center diamagnetic low-spin state will be switched-on (S = 0 → S = 1) by controlling axial ligand coordination to a square pyramidal or octahedral configuration. 18,25,[28][29][30] On the other hand, previous studies have also demonstated that the charge transport through the metal porphyrin could determine the different elements and even charge states of the metal center, [31][32][33] suggesting the control of nickel porphyrin between different spin-state may offer a promising way towards single-molecule spin switches at room temperature via CISSS strategy.…”

Section: Introductionmentioning

confidence: 99%

Room-Temperature Switching of Spin-State in Single-Molecule Junctions

et al. 2020

Preprint

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The emerging of molecular spintronics offers a unique chance for the design of molecular devices with different spin-state, and the control of spin-state becomes essential for molecular spin switches. However, the intrinsic spin switching from low-spin to high-spin state is a temperature-dependent process with a small energy barrier that low temperature is required to maintain the low-spin state, and thus the room-temperature operation of single-molecule devices have not yet been achieved. Here, we investigated the single-molecule charge transport through a diamagnetic square planar nickel(II) porphyrin using the scanning tunneling microscope break-junction (STM-BJ) technique. The reversible single-molecule conductance switches are demonstrated by utilizing a coordination-induced spin-state switching to manipulate the spin state between S = 0 and S = 1 at room temperature. Furthermore, the different coordinated complexes could be distinguished from the conductance traces, which cannot be realized by the ensemble investigations such as NMR and UV-vis spectrums. The combined DFT calculations revealed that the conductance changes come from the different spin-states of the molecules varying the number of coordination ligands, suggesting coordination-induced spin-state switching provides a new way towards room-temperature molecular spintronics.

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Reversible coordination-induced spin-state switching in complexes on metal surfaces

Cited by 90 publications

References 31 publications

Azo-dimethylaminopyridine-functionalized Ni(II)-porphyrin as a photoswitchable nucleophilic catalyst

Azo-dimethylaminopyridine-functionalized Ni(II)-porphyrin as a photoswitchable nucleophilic catalyst

Synthesis of 4-substituted azopyridine-functionalized Ni(II)-porphyrins as molecular spin switches

Room-Temperature Switching of Spin-State in Single-Molecule Junctions

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