Modulation of transmembrane anion transport of porphyrin boxes by dynamic window size engineering

The development of synthetic transmembrane anion transport systems is of considerable interest, not only for mimicking the functions of natural transmembrane proteins but also for practical applications. We have recently reported a porous organic cage, porphyrin box (PB(8)) having multiple windows surrounded by octyl chains as an iodide selective anion channel. Herein, we report the modulation of transmembrane transport of halides (Cl-, Br-, and I-) by dynamic window size engineering of the cage with different alkyl chain lengths (hexyl PB(6), octyl PB(8) and decyl PB(10)). 'Apparent' transport rates were measured by the HPTS fluorescence assay, which shows a gradual decrease in the transport rate upon increasing the length of alkyl chains of PB. We calculate the transport rate per PB in order to make a fair comparison as the 'apparent' transport rate is proportional to the number of PBs embedded in the lipid membrane. The transport rate per PB reveals that increasing the length of the alkyl chains of PBs results in a substantial fall in the iodide transport rate while only marginally decreasing the transport rates of bromide and chloride, thereby decreasing the selectivity of iodide transport. © 2022 World Scientific Publishing Company.11Nsciescopu

Induction and Rationalization of Supramolecular Chirality in the Tweezer–Diamine Complexes: Insights from Experimental and DFT Studies

A series of supramolecular chiral 1:1 sandwich complexes (<b>1</b>_M·L and <b>2</b>_M·L) consisting of diphenylether/ethane bridged metallobisporphyrin host (<b>1</b>_M and <b>2</b>_M; M: Zn/Mg) and chiral diamine guest (L) have been presented. The host–guest complexes are compared just upon changing the metal ion (Mg vs Zn) or the bridge (highly flexible ethane vs rigid diphenylether) keeping other factors similar. The factors that would influence the chirality induction process along with their contributions toward the sign and intensity of the CD couplet of the overall complex have been analyzed. Larger CD amplitude was observed in the host–guest complex with the more flexible ethane bridge as compared to the rigid diphenylether bridged one, irrespective of the metal ion used. Also, Zn complexes have displayed larger CD amplitude because of their stronger binding with the chiral diamines. A fairly linear dependence between the binding constant (<i>K</i>) and CD amplitude has been observed. Moreover, the amplitude of the CD couplet has been correlated with the relative steric bulk of the substituent at the stereogenic center: with increasing the bulk, CD intensity gradually increases. However, large increase of steric hindrance, after a threshold value, has diminished the intensity. The observation of a weak positive CD couplet between (1<i>R</i>,2<i>R</i>)-DPEA guest and Zn-bisporphyrin hosts indicates that the clockwise-twisted (steric-controlled) conformer is more populated as compared to the anticlockwise (chirality-controlled) one. In contrast, amplitude of the positive CD couplets is larger with Mg-bisporphyrin hosts, suggesting almost exclusive contribution of the clockwise-twisted conformer guided solely by sterics. DFT calculations support the experimental observations and have displayed the possible interconversion between clockwise and anticlockwise twisted conformers just upon changing the bulk of the substituent irrespective of the nature of chirality at the stereogenic center

Induction and Rationalization of Supramolecular Chirality in the Tweezer–Diamine Complexes: Insights from Experimental and DFT Studies

A series of supramolecular chiral 1:1 sandwich complexes (<b>1</b>_M·L and <b>2</b>_M·L) consisting of diphenylether/ethane bridged metallobisporphyrin host (<b>1</b>_M and <b>2</b>_M; M: Zn/Mg) and chiral diamine guest (L) have been presented. The host–guest complexes are compared just upon changing the metal ion (Mg vs Zn) or the bridge (highly flexible ethane vs rigid diphenylether) keeping other factors similar. The factors that would influence the chirality induction process along with their contributions toward the sign and intensity of the CD couplet of the overall complex have been analyzed. Larger CD amplitude was observed in the host–guest complex with the more flexible ethane bridge as compared to the rigid diphenylether bridged one, irrespective of the metal ion used. Also, Zn complexes have displayed larger CD amplitude because of their stronger binding with the chiral diamines. A fairly linear dependence between the binding constant (<i>K</i>) and CD amplitude has been observed. Moreover, the amplitude of the CD couplet has been correlated with the relative steric bulk of the substituent at the stereogenic center: with increasing the bulk, CD intensity gradually increases. However, large increase of steric hindrance, after a threshold value, has diminished the intensity. The observation of a weak positive CD couplet between (1<i>R</i>,2<i>R</i>)-DPEA guest and Zn-bisporphyrin hosts indicates that the clockwise-twisted (steric-controlled) conformer is more populated as compared to the anticlockwise (chirality-controlled) one. In contrast, amplitude of the positive CD couplets is larger with Mg-bisporphyrin hosts, suggesting almost exclusive contribution of the clockwise-twisted conformer guided solely by sterics. DFT calculations support the experimental observations and have displayed the possible interconversion between clockwise and anticlockwise twisted conformers just upon changing the bulk of the substituent irrespective of the nature of chirality at the stereogenic center

Induction and Rationalization of Supramolecular Chirality in the Tweezer–Diamine Complexes: Insights from Experimental and DFT Studies

A series of supramolecular chiral 1:1 sandwich complexes (<b>1</b>_M·L and <b>2</b>_M·L) consisting of diphenylether/ethane bridged metallobisporphyrin host (<b>1</b>_M and <b>2</b>_M; M: Zn/Mg) and chiral diamine guest (L) have been presented. The host–guest complexes are compared just upon changing the metal ion (Mg vs Zn) or the bridge (highly flexible ethane vs rigid diphenylether) keeping other factors similar. The factors that would influence the chirality induction process along with their contributions toward the sign and intensity of the CD couplet of the overall complex have been analyzed. Larger CD amplitude was observed in the host–guest complex with the more flexible ethane bridge as compared to the rigid diphenylether bridged one, irrespective of the metal ion used. Also, Zn complexes have displayed larger CD amplitude because of their stronger binding with the chiral diamines. A fairly linear dependence between the binding constant (<i>K</i>) and CD amplitude has been observed. Moreover, the amplitude of the CD couplet has been correlated with the relative steric bulk of the substituent at the stereogenic center: with increasing the bulk, CD intensity gradually increases. However, large increase of steric hindrance, after a threshold value, has diminished the intensity. The observation of a weak positive CD couplet between (1<i>R</i>,2<i>R</i>)-DPEA guest and Zn-bisporphyrin hosts indicates that the clockwise-twisted (steric-controlled) conformer is more populated as compared to the anticlockwise (chirality-controlled) one. In contrast, amplitude of the positive CD couplets is larger with Mg-bisporphyrin hosts, suggesting almost exclusive contribution of the clockwise-twisted conformer guided solely by sterics. DFT calculations support the experimental observations and have displayed the possible interconversion between clockwise and anticlockwise twisted conformers just upon changing the bulk of the substituent irrespective of the nature of chirality at the stereogenic center

One-pot Synthesis of a Truncated Cone-shaped Porphyrin Macrocycle and Its Self-assembly into Permanent Porous Material

© 2021 Wiley-VCH GmbHHere, we report the synthesis of a truncated cone-shaped triangular porphyrinic macrocycle, P3L3, via a single step imine condensation of a cis-diaminophenylporphyrin and a bent dialdehyde-based linker as building units. X-ray diffraction analysis reveals that the truncated cone-shaped P3L3 molecules are stacked on top of each other by π⋯π and CH⋯π interactions, to form 1.7 nm wide hollow columns in the solid state. The formation of the triangular macrocycle is corroborated by quantum chemical calculations. The permanent porosity of the P3L3 crystals is demonstrated by several gas sorption experiments and powder X-ray diffraction analysis.11Nsciescopu

A Nonempirical Approach for Direct Determination of the Absolute Configuration of 1,2-Diols and Amino Alcohols Using Mg(II)bisporphyrin

We report here a simple, facile, and direct nonempirical protocol for determining the absolute stereochemistry of a variety of chiral 1,2-diols and amino alcohols at room temperature with no chemical derivatization using Mg­(II)­bisporphyrin as a host. Addition of excess substrates resulted in the formation of a 1:2 host–guest complex in which two substrates bind in an unusual <i>endo-endo</i> fashion because of interligand H-bonding within the bisporphyrin cavity leading to the formation of a unidirectional screw in the bisporphyrin moiety that allowed us an accurate absolute stereochemical determination of the chiral substrate via exciton-coupled circular dichroism (ECCD). The sign of the CD couplet has also been found to be inverted when the stereogenic center is moved by one C atom simply from the bound to an unbound functionality and thus able to discriminate between them successfully. Strong complexation of the alcoholic oxygen with Mg­(II)­bisporphyrin rigidifies the host–guest complex, which eventually enhances its ability to stereochemically differentiate the asymmetric center. The ECCD sign of a large number of substrates has followed consistent and predictable trends; thus, the system is widely applicable. Moreover, computational calculations clearly support the experimental observations along with the absolute stereochemistry of the chiral substrate

Highly Enhanced Bisignate Circular Dichroism of Ferrocene-Bridged Zn(II) Bisporphyrin <i>Tweezer</i> with Extended Chiral Substrates due to Well-Matched Host–Guest System

Four new chiral <i>tweezer-</i>diamine complexes, consisting of an achiral ferrocene-bridged Zn­(II)­bisporhyrin host (<b>1</b>) and two small diamines (1<i>R</i>,2<i>R</i>)-1,2-diphenylethylene diamine {(1<i>R</i>,2<i>R</i>)-DPEA} and (1<i>S</i>,2<i>S</i>)-1,2-cyclohexane diamine {(1<i>S</i>,2<i>S</i>)-CHDA} and two extended diamines (1<i>R</i>,2<i>R</i>)-<i>N</i>,<i>N</i>′-bis-(isonicotinoyl)-1,2-diphenylethylene diamine {(1<i>R</i>,2<i>R</i>)-DPEApy} and (1<i>S</i>,2<i>S</i>)-<i>N</i>,<i>N</i>′-bis-(isonicotinoyl)-1,2-cyclohexane diamine {(1<i>S</i>,2<i>S</i>)-CHDApy} chiral guests, are reported. Additions of (1<i>R</i>,2<i>R</i>)-DPEA and (1<i>S</i>,2<i>S</i>)-CHDA separately to <b>1</b> in dichloromethane result in the formation of 1:1 sandwich complexes <b>1·</b>DPEA_{(<i>R</i>,<i>R</i>)} and <b>1·</b>CHDA_{(<i>S</i>,<i>S</i>)}, respectively, at low guest concentration and 1:2 anti complexes <b>1·</b>(DPEA_{(<i>R</i>,<i>R</i>)})₂ and <b>1·</b>(CHDA_{(<i>S</i>,<i>S</i>)})₂, respectively, at higher guest concentration. In contrast, separate additions of (1<i>R</i>,2<i>R</i>)-DPEApy and (1<i>S</i>,2<i>S</i>)-CHDApy to <b>1</b> produce only 1:1 sandwich complexes of <b>1·</b>DPEApy_{(<i>R</i>,<i>R</i>)} and <b>1·</b>CHDApy_{(<i>S</i>,<i>S</i>)}, respectively. The binding constants at 295 K between <b>1</b> and (1<i>R</i>,2<i>R</i>)-DPEA are observed to be (4.7 ± 0.2) × 10⁴ M^–1 and (4.3 ± 0.3) × 10³ M^–1 for 1:1 sandwich and 1:2 anti form, respectively, while the respective values with (1<i>S</i>,2<i>S</i>)-CHDA are (1.5 ± 0.2) × 10⁵ M^–1 and (5.9 ± 0.3) × 10³ M^–1. However, much larger values of (2.5 ± 0.3) × 10⁵ M^–1 and (1.3 ± 0.3) × 10⁶ M^–1 have been observed with DPEApy_{(<i>R</i>,<i>R</i>)} and CHDApy_{(<i>S</i>,<i>S</i>)}, respectively, to produce the corresponding 1:1 sandwich complexes. <b>1·</b>DPEApy_{(<i>R</i>,<i>R</i>)} (<i>A</i>_cal, −1759 cm^–1 M^–1) (<i>A</i>_cal = Δε₁ – Δε₂, representing the total amplitude of the calculated circular dichroism (CD) couplets) shows ∼10-fold increase in CD amplitude compared to the values observed for <b>1·</b>DPEA_{(<i>R</i>,<i>R</i>)} (<i>A</i>_cal, +187 cm^–1 M^–1), while <b>1·</b>CHDApy_{(<i>S</i>,<i>S</i>)} (<i>A</i>_cal, +1886 cm^–1 M^–1) shows nearly 3-fold increase of the CD amplitude compared to the value observed for <b>1·</b>CHDA_{(<i>S</i>,<i>S</i>)} (<i>A</i>_cal, −785 cm^–1 M^–1) at 295 K. The <i>A</i>_cal values of −1759 cm^–1 M^–1 and +1886 cm^–1 M^–1 observed for the <b>1·</b>DPEApy_{(<i>R</i>,<i>R</i>)} and <b>1·</b>CHDApy_{(<i>S</i>,<i>S</i>)}, respectively, are extremely high. To the best of our knowledge, these are some of the largest values reported for a chirality induction process involving bisporphyrin <i>tweezer</i> receptors. The large enhancement in the CD signal intensity is due to the well complementarity size between Zn­(II)­bisporphyrin host and the extended chiral diamines guest, which results large unidirectional twisting of two porphyrin units to accommodate the guests having preorganized binding sites with minimum host–guest steric interactions. It is interesting to note that <b>1·</b>DPEA_{(<i>R</i>,<i>R</i>)} and <b>1·</b>DPEApy_{(<i>R</i>,<i>R</i>)} show CD signal opposite in sign to each other, which happens to be the case between <b>1·</b>CHDA_{(<i>S</i>,<i>S</i>)} and <b>1·</b>CHDApy_{(<i>S</i>,<i>S</i>)} also

A Nonempirical Approach for Direct Determination of the Absolute Configuration of 1,2-Diols and Amino Alcohols Using Mg(II)bisporphyrin

We report here a simple, facile, and direct nonempirical protocol for determining the absolute stereochemistry of a variety of chiral 1,2-diols and amino alcohols at room temperature with no chemical derivatization using Mg­(II)­bisporphyrin as a host. Addition of excess substrates resulted in the formation of a 1:2 host–guest complex in which two substrates bind in an unusual <i>endo-endo</i> fashion because of interligand H-bonding within the bisporphyrin cavity leading to the formation of a unidirectional screw in the bisporphyrin moiety that allowed us an accurate absolute stereochemical determination of the chiral substrate via exciton-coupled circular dichroism (ECCD). The sign of the CD couplet has also been found to be inverted when the stereogenic center is moved by one C atom simply from the bound to an unbound functionality and thus able to discriminate between them successfully. Strong complexation of the alcoholic oxygen with Mg­(II)­bisporphyrin rigidifies the host–guest complex, which eventually enhances its ability to stereochemically differentiate the asymmetric center. The ECCD sign of a large number of substrates has followed consistent and predictable trends; thus, the system is widely applicable. Moreover, computational calculations clearly support the experimental observations along with the absolute stereochemistry of the chiral substrate

A Nonempirical Approach for Direct Determination of the Absolute Configuration of 1,2-Diols and Amino Alcohols Using Mg(II)bisporphyrin

We report here a simple, facile, and direct nonempirical protocol for determining the absolute stereochemistry of a variety of chiral 1,2-diols and amino alcohols at room temperature with no chemical derivatization using Mg­(II)­bisporphyrin as a host. Addition of excess substrates resulted in the formation of a 1:2 host–guest complex in which two substrates bind in an unusual <i>endo-endo</i> fashion because of interligand H-bonding within the bisporphyrin cavity leading to the formation of a unidirectional screw in the bisporphyrin moiety that allowed us an accurate absolute stereochemical determination of the chiral substrate via exciton-coupled circular dichroism (ECCD). The sign of the CD couplet has also been found to be inverted when the stereogenic center is moved by one C atom simply from the bound to an unbound functionality and thus able to discriminate between them successfully. Strong complexation of the alcoholic oxygen with Mg­(II)­bisporphyrin rigidifies the host–guest complex, which eventually enhances its ability to stereochemically differentiate the asymmetric center. The ECCD sign of a large number of substrates has followed consistent and predictable trends; thus, the system is widely applicable. Moreover, computational calculations clearly support the experimental observations along with the absolute stereochemistry of the chiral substrate