Control of Conformation and Chirality of Nonplanar π‐Conjugated Diporphyrins Using Substituents and Axial Ligands

Ito, Satoru; Hiroto, Satoru; Ousaka, Naoki; Yashima, Eiji; Shinokubo, Hiroshi

doi:10.1002/asia.201600105

Cited by 13 publications

(7 citation statements)

References 52 publications

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“…To control the helical chirality of the hydrogen-bonding complex, we added the optically active Brønsted base 10 − to a toluene solution of N -unsubstituted DNABI 8a and monitored the reaction by CD spectroscopy (Figure ). Interestingly, clear CD signals emerged in the range of 300–650 nm, which indicates that the helicity of the twisted DNABI core was enantiomerically controlled by 10 . − On the other hand, a DMSO solution of 8a with 10 as well as a toluene solution of N -phenyl-substituted DNABI 7a with 10 exhibited no identical CD signal (Figures S43 and S44). These results suggest that the formation of a hydrogen-bonding complex involving the central NH unit of 8a is essential to induce CD signals.…”

Section: Resultsmentioning

confidence: 99%

Inserting Nitrogen: An Effective Concept To Create Nonplanar and Stimuli-Responsive Perylene Bisimide Analogues

et al. 2019

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Establishing design principles to create nonplanar π-conjugated molecules is crucial for the development of novel functional materials. Herein, we describe the synthesis and properties of dinaphtho[1,8-bc:1′,8′-ef]azepine bisimides (DNABIs). Their molecular design is conceptually based on the insertion of a nitrogen atom into a perylene bisimide core. We have synthesized several DNABI derivatives with a hydrogen atom, a primary alkyl group, or an aryl group on the central nitrogen atom. These DNABIs exhibit nonplanar conformations, flexible structural changes, and ambipolar redox activity. The steric effect around the central nitrogen atom substantially affects the overall structures and results in two different conformations: a nonsymmetric bent conformation and a symmetric twisted conformation, accompanied by a drastic change in electronic properties. Notably, the nonsymmetric DNABI undergoes unique structural changes in response to the application of an external electric field, which is due to molecular motions that are accompanied by an orientational fluctuation of the dipole moment. Furthermore, the addition of a chiral Brønsted base to N-unsubstituted DNABI affords control over the helical chirality via hydrogen-bonding interactions.

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Section: Resultsmentioning

confidence: 99%

Inserting Nitrogen: An Effective Concept To Create Nonplanar and Stimuli-Responsive Perylene Bisimide Analogues

et al. 2019

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“…These assemblies produce characteristic absorption bands in the low-energy regions of the corresponding UV-Vis and circular dichroism (CD) spectra, which are essentially shifted from absorption of the majority of analytes [23][24][25][26]. Recently, much attention has also been paid to the phenomena of supramolecular chirogenesis, where a chiral guest determines the supramolecular chirality of the entire host-guest system upon binding to an achiral host molecule [12][13][14][15]20,[23][24][25][26][27][28][29][30][31][32][33][34][35]. In the case of ethane-bridged bis(zinc porphyrin)s (bis(ZnOEP)s) (Figure 1), steric hindrance induced by coordination of a chiral guest forces the supramolecular system to adopt a screw conformation, with the chirality of a guest determining either a clockwise or anticlockwise arrangement of porphyrin units in the bis-porphyrin host [30][31][32].…”

Section: Introductionmentioning

confidence: 99%

“…In turn, this directional helicity results in induced CD in the porphyrin absorption region due to exciton coupling between the corresponding electronic transitions. This phenomenon has been successfully applied for determination of the absolute configuration of various chiral organic compounds, including amines [27,29,33], amino acid derivatives [33], alcohols [15], carboxylic acids [15], and epoxides [34]. For the zinc porphyrin-based sensing systems, amines and other basic nitrogen-containing organic compounds are particularly privileged analytes due to their strong electrostatic (Lewis acid-base) binding to zinc ion, which produces the corresponding penta-coordinated zinc porphyrin complexes in general [31,32,35].…”

Section: Introductionmentioning

confidence: 99%

Supramolecular Chirogenesis in Bis-Porphyrin: Crystallographic Structure and CD Spectra for a Complex with a Chiral Guanidine Derivative

et al. 2021

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The complexation of (3aR,7aR)-N-(3,5-bis(trifluoromethyl)phenyl)octahydro-2H-benzo[d]imidazol-2-imine (BTI), as a guest, to ethane-bridged bis(zinc octaethylporphyrin), bis(ZnOEP), as a host, has been studied by means of ultraviolet-visible (UV-Vis) and circular dichroism (CD) absorption spectroscopies, single crystal X-ray diffraction, and computational simulation. The formation of 1:2 host-guest complex was established by X-ray diffraction and UV-Vis titration studies. Two guest BTI molecules are located at the opposite sides of two porphyrin subunits of bis(ZnOEP) host, which is resting in the anti-conformation. The complexation of BTI molecules proceed via coordination of the imine nitrogens to the zinc ions of each porphyrin subunit of the host. Such supramolecular organization of the complex results in a screw arrangement of the two porphyrin subunits, inducing a strong CD signal in the Soret (B) band region. The corresponding DFT computational studies are in a good agreement with the experimental results and prove the presence of 1:2 host-guest complex as the major component in the solution (97.7%), but its optimized geometry differs from that observed in the solid-state. The UV-Vis and CD spectra simulated by using the solution-state geometry and the TD-DFT/ωB97X-D/cc-pVDZ + SMD (CH2Cl2) level of theory reproduced the experimentally obtained UV-Vis and CD spectra and confirmed the difference between the solid-state and solution structures. Moreover, it was shown that CD spectrum is very sensitive to the spatial arrangement of porphyrin subunits.

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“…Fortunately, the most common structural features can be outlined in the majority of typical chiral pollutants to simplify the problem. (1) Nitrogen-containing molecules are prevalent among pharmaceuticals and agrochemicals [20][21][22], and basic nitrogen moieties are therefore able to serve as privileged binding sites to zinc porphyrin-based sensors due to strong Zn• • • N cation-dipole interaction [23][24][25]. (2) Additional functional groups, which can act as a secondary binding site or participate in other non-covalent interactions (such as hydrogen bonding), are also common [26][27][28], along with (3) aromatic rings decorated with electron-donating/withdrawing substituents.…”

Section: Introductionmentioning

confidence: 99%

Thiourea Organocatalysts as Emerging Chiral Pollutants: En Route to Porphyrin-Based (Chir)Optical Sensing

et al. 2021

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Environmental pollution with chiral organic compounds is an emerging problem requiring innovative sensing methods. Amino-functionalized thioureas, such as 2-(dimethylamino)cyclohexyl-(3,5-bis(trifluoromethyl)phenyl)thiourea (Takemoto’s catalyst), are widely used organocatalysts with virtually unknown environmental safety data. Ecotoxicity studies based on the Vibrio fischeri luminescence inhibition test reveal significant toxicity of Takemoto’s catalyst (EC50 = 7.9 mg/L) and its NH2-substituted analog (EC50 = 7.2–7.4 mg/L). The observed toxic effect was pronounced by the influence of the trifluoromethyl moiety. En route to the porphyrin-based chemosensing of Takemoto-type thioureas, their supramolecular binding to a series of zinc porphyrins was studied with UV-Vis and circular dichroism (CD) spectroscopy, computational analysis and single crystal X-ray diffraction. The association constant values generally increased with the increasing electron-withdrawing properties of the porphyrins and electron-donating ability of the thioureas, a result of the predominant Zn⋯N cation–dipole (Lewis acid–base) interaction. The binding event induced a CD signal in the Soret band region of the porphyrin hosts—a crucial property for chirality sensing of Takemoto-type thioureas.

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Control of Conformation and Chirality of Nonplanar π‐Conjugated Diporphyrins Using Substituents and Axial Ligands

Cited by 13 publications

References 52 publications

Inserting Nitrogen: An Effective Concept To Create Nonplanar and Stimuli-Responsive Perylene Bisimide Analogues

Inserting Nitrogen: An Effective Concept To Create Nonplanar and Stimuli-Responsive Perylene Bisimide Analogues

Supramolecular Chirogenesis in Bis-Porphyrin: Crystallographic Structure and CD Spectra for a Complex with a Chiral Guanidine Derivative

Thiourea Organocatalysts as Emerging Chiral Pollutants: En Route to Porphyrin-Based (Chir)Optical Sensing

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