Modular Synthetic Route to Monofunctionalized Porphyrin Architectures

Heitmann, Gernot; Dommaschk, Marcel; Löw, Roland; Herges, Rainer

doi:10.1021/acs.orglett.6b02507

“…The record player molecules 1f–j ( Fig. 1 ) were synthesized by a modular approach described by Heitmann et al [ 15 ]. The boronic ester 22 was prepared according to a mixed aldehyde procedure [ 16 – 17 ] and the substituted azopyridines 14 , 18 , 20 , and 21 were attached using Suzuki conditions.…”

Section: Resultsmentioning

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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“…For the synthesis of 4-N,N-dimethylamino record player molecule 1, a modular approach described by Heitmann et al was chosen [30] since the alternative mixed aldehyde route failed for related porphyrin derivatives [17]. Ni-porphyrin precursor 3 and 4-(N,N-dimethylaminoazo)pyridine 4 were synthesized according to literature procedures [17,30].…”

Section: Synthesismentioning

confidence: 99%

“…Following the conditions for the Suzuki cross-coupling reaction published for a similar system [30], decomposition products and only 25% yield were obtained. Optimization by lowering the reaction temperature increased the yield to 91% (Scheme 1).…”

Section: Synthesismentioning

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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“…For the synthesis of 4-N,N-dimethylamino record player molecule 1, a modular approach described by Heitmann et al was chosen [30] since the alternative mixed aldehyde route failed for related porphyrin derivatives [17]. Ni-porphyrin precursor 3 and 4-N,N-dimethylaminoazopyridine 4 were synthesized according to literature procedures [30,17].…”

Section: Synthesismentioning

confidence: 99%

“…Following the conditions for the Suzuki cross coupling reaction published for a similar system [30], decomposition products and only 25 % yield were obtained.…”

Section: Synthesismentioning

confidence: 99%

Azo-dimethylaminopyridine functionalized Ni(II)-Porphyrin as a Photoswitchable Nucleophilic Catalyst

Ludwig¹,

Helberg²,

Zipse³

et al. 2020

Preprint

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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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Modular Synthetic Route to Monofunctionalized Porphyrin Architectures

Cited by 11 publications

References 41 publications

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

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

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

Azo-dimethylaminopyridine functionalized Ni(II)-Porphyrin as a Photoswitchable Nucleophilic Catalyst

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