Porphyrin Boxes

Abstract

Conspectus In order to fabricate efficient molecular photonic devices, it has been a long-held aspiration for chemists to understand and mimic natural light-harvesting complexes where a rapid and efficient transfer of excitation energy between chlorophyll pigments is observed. Synthetic porphyrins are attractive building blocks in this regard because of their rigid and planar geometry, high thermal and electronic stability, high molar extinction, small and tunable band gap, and tweakable optical as well as redox behavior. Owing to these fascinating properties, various types of porphyrin-based architectures have been reported utilizing both covalent and noncovalent approaches. However, it still remains a challenge to construct chemically robust, well-defined three-dimensional porphyrin cages which can be easily synthesized and yet suitable for useful applications both in solution as well as in solid state. Working on this idea, we recently synthesized box-shaped organic cages, which we called porphyrin boxes, by making use of dynamic covalent chemistry of imine condensation reaction between 4-connecting, square-shaped, tetraformylporphyrin and 3-connecting, triangular-shaped, triamine molecules. Various presynthetic, as well as postsynthetic modifications, can be carried out on porphyrin boxes including a variation of the alkyl chain length in their 3-connecting subunit, chemical functionalization, and metalation of the porphyrin core. This can remarkably tune their inherent properties, e.g., solubility, window size, volume, and polarity of the internal void. The porphyrin boxes can therefore be considered as a significant addition to the family of multiporphyrin-based architectures, and because of their chemical stability and shape persistency, the applications of porphyrin boxes expand beyond the photophysical properties of an artificial light-harvesting complex. Consequently, they have been exploited as porous organic cages, where their gas adsorption properties have been investigated. By incorporating them in a lipid bilayer membrane, an iodide selective synthetic ion channel has also been demonstrated. Further, we have explored electrocatalytic reduction of carbon dioxide using Fe­(III) metalated porphyrin boxes. Additionally, the precise size and ease of metalation of porphyrin boxes allowed us to utilize them as premade building blocks for creating coordination-based hierarchical superstructures. Considering these developments, it may be worth combining the photophysical properties of porphyrin with the shape-persistent porous nature of porphyrin boxes to explore other novel applications. This Account summarizes our recent work on porphyrin boxes, starting with their design, structural features, and applications in different fields. We also try to provide scientific insight into the future opportunities that these amazing boxes have in store for exploring the still uncharted challenging domains in the field of supramolecular chemistry in a confined space.

Single vs double atom catalyst for N2 activation in nitrogen reduction reaction: A DFT perspective

“…But it is challenging for large‐scale application in terms of affordable cost to create sufficient sites for the supporting TM with good uniformity and high density. Metal‐polypyridines and metalloporphyrin derivatives (Figure 1B) have a long history being widely used in organic synthesis and electrocatalyst, because of their flexible geometry and electronic tunability . However, they typically serve as molecular homogenous catalyst with poor electronic conductivity that slows down the reactivity kinetics.…”

“…However, they typically serve as molecular homogenous catalyst with poor electronic conductivity that slows down the reactivity kinetics. Moreover, it is challenging to construct chemically robust, well‐defined three‐dimensional porphyrin cages . Thus, it is highly desirable to find a supporting substrate with low/zero band gap and high metal supporting site density.…”

Host‐Guest Chemistry of Truncated Tetrahedral Imine Cages with Ammonium Ions

“…Besides the gain to fundamental understanding of cage formations, one of the main aspects was the investigation of gas sorption by porous organic cages . Despite early investigations of binding guest molecules inside the cavities of shape‐persistent organic cages, there has not too much been done in this respect in recent years, which is in contrast to the large number and variety of studied host‐guest complexes based on e. g. hydrogen bonding capsules or coordination cages .…”

Multifunctional Tubular Organic Cage‐Supported Ultrafine Palladium Nanoparticles for Sequential Catalysis

“…[1,2] In the realm of reticular chemistry,t hose new porous organic frameworks including hydrogen-bonded frameworks (HOFs) [3] and porous organic cages (POCs) [4] constructed by the self-assembly of small molecular building blocks have attracted increasing attention due to their unique advantages in solution processing and regeneration. [1,2] In the realm of reticular chemistry,t hose new porous organic frameworks including hydrogen-bonded frameworks (HOFs) [3] and porous organic cages (POCs) [4] constructed by the self-assembly of small molecular building blocks have attracted increasing attention due to their unique advantages in solution processing and regeneration.…”

“…[4] Further to functioning as adsorbents, [4] the well-defined molecular cavity endows POCs as excellent hosts to selectively accommodate various guests. [1l, 5f] In this work, am ultifunctional tubular organic cage (MTC1) with both fluorescent and photocatalytic properties (Scheme 1), has been designed, synthesized, and structurally characterized by single-crystal X-ray diffraction analysis.B y using dynamic covalent chemistry of imine bonds, [4] simple condensation of benzo[c] [1,2,5]thiadiazole derivative and cyclohexanediamine afforded MTC1. [6] Thus far, utilizing the synergistic effect of ultrafine metal NPs and organic cages to facilitate organic reactions via two different catalytically active sites has rarely been explored owing to the lack of functionality in most cage hosts.Itistherefore of significant importance to develop new functional POCs towards cage-based synergistic/sequential catalysis.…”