Porphyrin Nanocrystal Synthesized via Chemical Reaction Route: pH-Sensitive Reversible Transformation between Nanocrystals and Bulk Single Crystal

Crystalline nanostructures with octahedral morphology have been prepared by self-assembling of cationic porphyrin (H₆TPyP)⁴⁺·4Cl^– produced through chemical reaction route in aqueous solution depending on the synergistic interactions among hydrogen-bonding, π–π stacking, and ion pairing. Unexpectedly, the gradual decrease in pH by the slow evaporation of solvent in the nano-octahedron aqueous suspension obtained in situ led to the selective etching of the original nanocrystal and the isolation of (H₆TPyP)⁴⁺·4Cl^– bulk single crystals in the last stage. More interestingly, the increase in pH by adding water again into this bulk single-crystal-containing system led to the regeneration of nano-octahedrons, indicating the reversible transformation between porphyrin nano-octahedrons and bulk single crystals triggered by pH. Mechanistic investigations through powder and single-crystal X-ray diffraction analyses together with the electron microscopic, in particular, HRTEM, clearly reveal that the unique surface effect and anisotropic character of the nanomaterials differing from the bulk organic materials are responsible for such pH-sensitive reversible transformation of the two crystalline materials by controlling the dissolution or aggregation of (H₆TPyP)⁴⁺·4Cl^–, which actually induces the reversible formation and breaking of the (pyridine)­N⁺–H···Cl^–···H–O­(H₂O)···H–N⁺(pyridine) hydrogen bonds among cationic porphyrin building blocks at different pH. This result, to control the crystallinity and the unprecedented reversible transformation between nanocrystal and bulk single crystals just by tuning the pH of the synthesis process, as well as the use of the peculiar nanoeffect such as surface effect to adjust the self-assembling process, provides useful a tool for the controllable synthesis of crystalline materials and is expected to be helpful for further research and application of organic nanomaterials

Porphyrin Nanocrystal Synthesized via Chemical Reaction Route: pH-Sensitive Reversible Transformation between Nanocrystals and Bulk Single Crystal

Crystalline nanostructures with octahedral morphology have been prepared by self-assembling of cationic porphyrin (H₆TPyP)⁴⁺·4Cl^– produced through chemical reaction route in aqueous solution depending on the synergistic interactions among hydrogen-bonding, π–π stacking, and ion pairing. Unexpectedly, the gradual decrease in pH by the slow evaporation of solvent in the nano-octahedron aqueous suspension obtained in situ led to the selective etching of the original nanocrystal and the isolation of (H₆TPyP)⁴⁺·4Cl^– bulk single crystals in the last stage. More interestingly, the increase in pH by adding water again into this bulk single-crystal-containing system led to the regeneration of nano-octahedrons, indicating the reversible transformation between porphyrin nano-octahedrons and bulk single crystals triggered by pH. Mechanistic investigations through powder and single-crystal X-ray diffraction analyses together with the electron microscopic, in particular, HRTEM, clearly reveal that the unique surface effect and anisotropic character of the nanomaterials differing from the bulk organic materials are responsible for such pH-sensitive reversible transformation of the two crystalline materials by controlling the dissolution or aggregation of (H₆TPyP)⁴⁺·4Cl^–, which actually induces the reversible formation and breaking of the (pyridine)­N⁺–H···Cl^–···H–O­(H₂O)···H–N⁺(pyridine) hydrogen bonds among cationic porphyrin building blocks at different pH. This result, to control the crystallinity and the unprecedented reversible transformation between nanocrystal and bulk single crystals just by tuning the pH of the synthesis process, as well as the use of the peculiar nanoeffect such as surface effect to adjust the self-assembling process, provides useful a tool for the controllable synthesis of crystalline materials and is expected to be helpful for further research and application of organic nanomaterials

Stereochemistry and Solid-State Structure of an Intrinsically Chiral <i>Meso</i>-Patterned Porphyrin: Case Study by NMR and Single-Crystal X‑ray Diffraction Analysis

A <i>C</i>₁-symmerical <i>meso</i>-substituted ABCD-type porphyrin, [5-phenyl-10-(2-hydroxynaphthyl)-15-(4-hydroxyphenyl)­porphyrinato]­zinc­(II) (<b>1</b>), has been synthesized and characterized. The molecular structure of <b>1</b> has been determined by single-crystal X-ray diffraction analysis. The complex <b>1</b> crystallizes in a triclinic system with one pair of enantiomeric molecules per unit cell. Resolution of the racemic mixture has been achieved by chiral HPLC techniques. In particular, the absolute configurations of the enantiomers have been assigned from NMR spectroscopic analysis with l-Phe-OMe as the chiral solvating agent (CSA). The assignments have also been unambiguously confirmed by single-crystal X-ray diffraction analysis. The present results suggest that the CSA–NMR anisotropy strategy is applicable for the stereochemistry determination of chiral host–guest complexes with multiple intermolecular interactions. In addition, the multiple intermolecular interactions between the enantiomerically pure porphyrin <i>S</i>-<b>1</b> and l-Phe-OMe are proved in the solid state by single-crystal X-ray diffraction analysis

Ferrocene-Decorated (Phthalocyaninato)(Porphyrinato) Double- and Triple-Decker Rare Earth Complexes: Synthesis, Structure, and Electrochemical Properties

A series of four mixed (phthalocyaninato)­(porphyrinato) rare earth double-decker complexes (<i>Pc</i>)­M­[Por­(Fc)₂] [<i>Pc</i> = phthalocyaninate; Por­(Fc)₂ = 5,15-di­(ferrocenyl)-porphyrinate; M = Eu (<b>1</b>), Y (<b>2</b>), Ho (<b>3</b>), Lu (<b>4</b>)] and their europium­(III) triple-decker counterpart (<i>Pc</i>)­Eu­(<i>Pc</i>)­Eu­[Por­(Fc)₂] (<b>5</b>), each with two ferrocenyl units at the <i>meso</i>-positions of their porphyrin ligands, have been designed and prepared. The double- and triple-decker complexes <b>1</b>–<b>5</b> were characterized by elemental analysis and various spectroscopic methods. The molecular structures of two double-deckers <b>1</b> and <b>4</b> were also determined by single-crystal X-ray diffraction analysis. Electrochemical studies of these novel sandwich complexes revealed two consecutive ferrocene-based one-electron oxidation waves, suggesting the effective electronic coupling between the two ferrocenyl units. Nevertheless, the separation between the two consecutive ferrocene-based oxidation waves increases from <b>1</b> to <b>4</b>, along with the decrease of rare earth ionic radius, indicating the effect of rare earth size on tuning the coupling between the two ferrocenyl units. Furthermore, the splitting between the two ferrocene-based one-electron oxidations for triple-decker <b>5</b> is even smaller than that for <b>1</b>, showing that the electronic interaction between the two ferrocene centers can also be tuned through changing the linking sandwich framework from double-decker to triple-decker. For further understanding of the electronic coupling between ferrocenyl groups, DFT calculation is carried out to clarify the electronic delocalization and the molecular orbital distribution in these double-decker complexes

Stereochemistry and Solid-State Structure of an Intrinsically Chiral <i>Meso</i>-Patterned Porphyrin: Case Study by NMR and Single-Crystal X‑ray Diffraction Analysis

A <i>C</i>₁-symmerical <i>meso</i>-substituted ABCD-type porphyrin, [5-phenyl-10-(2-hydroxynaphthyl)-15-(4-hydroxyphenyl)­porphyrinato]­zinc­(II) (<b>1</b>), has been synthesized and characterized. The molecular structure of <b>1</b> has been determined by single-crystal X-ray diffraction analysis. The complex <b>1</b> crystallizes in a triclinic system with one pair of enantiomeric molecules per unit cell. Resolution of the racemic mixture has been achieved by chiral HPLC techniques. In particular, the absolute configurations of the enantiomers have been assigned from NMR spectroscopic analysis with l-Phe-OMe as the chiral solvating agent (CSA). The assignments have also been unambiguously confirmed by single-crystal X-ray diffraction analysis. The present results suggest that the CSA–NMR anisotropy strategy is applicable for the stereochemistry determination of chiral host–guest complexes with multiple intermolecular interactions. In addition, the multiple intermolecular interactions between the enantiomerically pure porphyrin <i>S</i>-<b>1</b> and l-Phe-OMe are proved in the solid state by single-crystal X-ray diffraction analysis

Density Functional Theory Study on Subtriazaporphyrin Derivatives: Dipolar/Octupolar Contribution to the Second-Order Nonlinear Optical Activity

Density functional theory calculations have been carried out on the subtriazaporphyrin skeletons, an excellent prototype for investigating the dipolar/octupolar contribution to the second-order nonlinear optical (second-order NLO) activity, revealing the size effect and clarifying the nature of the limit when expanding the conjugated system is employed to improve the hyper-Rayleigh scattering response coefficient (β_HRS). The octupolar and dipolar contributions are theoretically separated, rendering it possible to control the dipolar/octupolar second-order NLO contribution ratio by changing the number and orientation of the peripheral fused benzene moieties. In addition, both the dispersion and solvent effect were also revealed to lead to the enhancement of β_HRS

Density Functional Theory Study on Subtriazaporphyrin Derivatives: Dipolar/Octupolar Contribution to the Second-Order Nonlinear Optical Activity

Density functional theory calculations have been carried out on the subtriazaporphyrin skeletons, an excellent prototype for investigating the dipolar/octupolar contribution to the second-order nonlinear optical (second-order NLO) activity, revealing the size effect and clarifying the nature of the limit when expanding the conjugated system is employed to improve the hyper-Rayleigh scattering response coefficient (β_HRS). The octupolar and dipolar contributions are theoretically separated, rendering it possible to control the dipolar/octupolar second-order NLO contribution ratio by changing the number and orientation of the peripheral fused benzene moieties. In addition, both the dispersion and solvent effect were also revealed to lead to the enhancement of β_HRS

Stereochemistry and Solid-State Structure of an Intrinsically Chiral <i>Meso</i>-Patterned Porphyrin: Case Study by NMR and Single-Crystal X‑ray Diffraction Analysis

A <i>C</i>₁-symmerical <i>meso</i>-substituted ABCD-type porphyrin, [5-phenyl-10-(2-hydroxynaphthyl)-15-(4-hydroxyphenyl)­porphyrinato]­zinc­(II) (<b>1</b>), has been synthesized and characterized. The molecular structure of <b>1</b> has been determined by single-crystal X-ray diffraction analysis. The complex <b>1</b> crystallizes in a triclinic system with one pair of enantiomeric molecules per unit cell. Resolution of the racemic mixture has been achieved by chiral HPLC techniques. In particular, the absolute configurations of the enantiomers have been assigned from NMR spectroscopic analysis with l-Phe-OMe as the chiral solvating agent (CSA). The assignments have also been unambiguously confirmed by single-crystal X-ray diffraction analysis. The present results suggest that the CSA–NMR anisotropy strategy is applicable for the stereochemistry determination of chiral host–guest complexes with multiple intermolecular interactions. In addition, the multiple intermolecular interactions between the enantiomerically pure porphyrin <i>S</i>-<b>1</b> and l-Phe-OMe are proved in the solid state by single-crystal X-ray diffraction analysis

Ferrocene-Decorated (Phthalocyaninato)(Porphyrinato) Double- and Triple-Decker Rare Earth Complexes: Synthesis, Structure, and Electrochemical Properties

A series of four mixed (phthalocyaninato)­(porphyrinato) rare earth double-decker complexes (<i>Pc</i>)­M­[Por­(Fc)₂] [<i>Pc</i> = phthalocyaninate; Por­(Fc)₂ = 5,15-di­(ferrocenyl)-porphyrinate; M = Eu (<b>1</b>), Y (<b>2</b>), Ho (<b>3</b>), Lu (<b>4</b>)] and their europium­(III) triple-decker counterpart (<i>Pc</i>)­Eu­(<i>Pc</i>)­Eu­[Por­(Fc)₂] (<b>5</b>), each with two ferrocenyl units at the <i>meso</i>-positions of their porphyrin ligands, have been designed and prepared. The double- and triple-decker complexes <b>1</b>–<b>5</b> were characterized by elemental analysis and various spectroscopic methods. The molecular structures of two double-deckers <b>1</b> and <b>4</b> were also determined by single-crystal X-ray diffraction analysis. Electrochemical studies of these novel sandwich complexes revealed two consecutive ferrocene-based one-electron oxidation waves, suggesting the effective electronic coupling between the two ferrocenyl units. Nevertheless, the separation between the two consecutive ferrocene-based oxidation waves increases from <b>1</b> to <b>4</b>, along with the decrease of rare earth ionic radius, indicating the effect of rare earth size on tuning the coupling between the two ferrocenyl units. Furthermore, the splitting between the two ferrocene-based one-electron oxidations for triple-decker <b>5</b> is even smaller than that for <b>1</b>, showing that the electronic interaction between the two ferrocene centers can also be tuned through changing the linking sandwich framework from double-decker to triple-decker. For further understanding of the electronic coupling between ferrocenyl groups, DFT calculation is carried out to clarify the electronic delocalization and the molecular orbital distribution in these double-decker complexes

Chiral Discrimination of Diamines by a Binaphthalene-Bridged Porphyrin Dimer

A pair of 1,1′-binaphthalene-bridged bisporphyrins, (<i>R</i>)- and (<i>S</i>)-<b>H1</b>, were designed to examine their chiral discrimination abilities toward a range of model diamines by using UV–vis absorption, CD, and ¹H NMR spectroscopy with the assistance of DFT molecular modeling. The spectroscopic titrations revealed that (<i>R</i>)-/(<i>S</i>)-<b>H1</b> could encapsulate (<i>R</i>)-/(<i>S</i>)-DACH and (<i>R</i>)-/(<i>S</i>)-PPDA in the chiral bisporphyrin cavities, leading to the selective formation of sandwich-type 1:1 complexes via dual Zn–N coordination interactions. In particular, the chiral recognition energy (ΔΔ<i>G</i>°) toward (<i>R</i>)-/(<i>S</i>)-DACH was evaluated to be −4.02 kJ mol^–1. The binding processes afforded sensitive CD spectral changes in response to the stereostructure of chiral diamines. Remarkable enantiodiscrimination effects were also detected in the NMR titrations of (<i>R</i>)-/(<i>S</i>)-<b>H1</b>, in which the nonequivalent chemical shift (ΔΔδ) can reach up to 0.57 ppm for (<i>R</i>)-/(<i>S</i>)-DACH. However, due to the large steric effect, another chiral diamine ((<i>R</i>)-/(<i>S</i>)-DPEA) could not be sandwiched in the chiral bisporphyrin cavity; therefore, (<i>R</i>)-/(<i>S</i>)-DPEA could hardly be discriminated by (<i>R</i>)-/(<i>S</i>)-<b>H1</b>. The present results demonstrate a chiral bisporphyrin host with integrated CD and NMR chiral sensing functions and also highlight the binding-mode-dependent character of its enantiodiscrimination performance for different chiral guests