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Photoacoustic (PA) imaging is a novel biological imaging technique with superior depth resolution compared to fluorescence imaging. The efficacy of PA imaging depends on contrast agents that possess considerable absorbance at longer wavelengths, coupled with high permeability in biological tissue and minimal fluorescence, achieved through mitigating aggregation‐caused quenching (ACQ) that attenuates PA intensity. Despite the successful transfer of porphyrin 2 featuring amino moieties from polysaccharides to liposomes, most of 2 incorporated within λ‐carrageenan (CGN‐2 complex) remained in CGN under acidic lysosomal conditions (pH 5.0). Consequently, the CGN‐2 complex exhibited a strong PA signal under 680 nm photoirradiation in Colon26 cells owing to the ACQ of 2. Moreover, the PA intensity of the CGN‐2 complex was further enhanced under 780 nm photoirradiation owing to the increased absorbance at 780 nm facilitated by the redshift of the Q‐band at pH 5.0. [ABSTRACT FROM AUTHOR]

Crownphyrinogens and crownphyrins constitute a group of macrocycles that combine the structural facets of porphyrinoids and crown ethers. The dual‐nature cavity embedded in their molecules enables reactivity involving two structurally distinct parts of the macrocyclic ligand. Upon Ni(II) and Pd(II) insertion, coordination compounds are produced wherein the metal is incorporated into the porphyrinoid‐like pocket, resulting in monomeric or accordion‐like dimeric products, depending on the oxidation level of the macrocycle and metal cation. The reactions with Na(I) and K(I) resulted in the formation of complexes where only the crown ether segment of the molecule is involved in metal binding, yielding remarkable dimeric species. The exploitation of a crownphyrin large enough to accommodate two metal cations allowed the synthesis of an alkali/transition metal binuclear complexes wherein the macrocycle demonstrated the Janus reactivity with one cavity acting as a porphyrinoid and the other mimicking the crown ether. [ABSTRACT FROM AUTHOR]

The synthesis of [2]rotaxanes stoppered with one or two dipyrromethane groups has opened a route for the construction of mechanically interlocked molecules incorporating various porphyrinoid stations. The exploitation of those precursors allowed the creation of [3]rotaxanes and [2]catenanes based on the calix[4]phyrin motif, presenting intriguing molecular dynamics. The intrinsic flexibility of the porphyrinoid allowed the introduction of a new type of molecular motion within the rotaxanes, termed fluttering. The latter involved a bending of the axle, interconverting two angular‐shaped stereoisomers of the rotaxane through a planarised transition state. Simple chemical transformations, i.e. methylation and (de)protonation of the [3]rotaxane and [2]catenane allowed controllable transformations within the conformationally flexible calix[4]phyrin‐incorporated mechanically interlocked porphyrinoids. [ABSTRACT FROM AUTHOR]

Noncovalent cofacial porphyrin dimers have attracted interest due to their potential use as host materials or catalysts. In this study, we introduce a novel coordination‐directed cofacial porphyrin dimer from a meso‐tetraphenylporphyrin derivative modified with 2,2′‐bipyridine moieties at the meta positions of the phenyl groups. Spectroscopic investigation has shed light on the binding processes and the structure of the dimer in solution in detail. Initial Zn2+ ion binding to the porphyrin hinders the subsequent Zn2+ binding and the binding of the second porphyrin. However, once the dimer is formed, additional Zn2+ binding is notably enhanced, resulting in a pronounced S‐shaped binding curve. The detailed structure of the dimer in solution was established based on UV‐vis spectroscopy, various 1H NMR spectroscopy techniques and mass spectrometry. Simulations of ring‐current‐induced chemical shift changes provided evidence for the face‐to‐face porphyrin structure with tetrahedral coordination of the bipyridine ligands. The X‐ray single crystal structure provided conclusive evidence for the structure of the face‐to‐face dimer, which remarkably resembles the model structure from the 1H NMR simulation. The stability of the dimer structure makes it promising for further exploration of this motif in developing new supramolecular structures and for their potential applications as host compounds and catalysts. [ABSTRACT FROM AUTHOR]

The use of 2,5‐diformylpyrrole in self‐assembly reactions with diamines and Zn(II)/Cd(II) salts allowed the preparation of [2]catenane, trefoil knot, and Borromean rings. The intrinsically dynamic nature of the diiminopyrrole motif rendered all of the formed assemblies intramolecularly flexible. The presence of diiminopyrrole revealed new coordination motifs and influenced the host–guest chemistry of the systems, as illustrated by hexafluorophosphate encapsulation by Borromean rings. [ABSTRACT FROM AUTHOR]

Porphyrins and crown ether hybrids have emerged as a promising class of molecules composed of elements of a tetrapyrrole macrocycle and an oligo(ethylene glycol) segment. These hybrid systems constitute a broad group of compounds, including crowned porphyrins, crownphyrins, and calixpyrrole-crown ether systems forming Pacman complexes with transition metals. Their unique nature accustoms them as excellent ligands and hosts capable of binding guest molecules/ions, but also to undergo unusual transformations, such as metal-induced expansion/contraction. Depending on the design of the particular hybrid, they present unique features involving intriguing redox chemistry, interesting optical properties, and reactivity towards transition metals. In this perspective article, the overview of both the early designs of porphyrin-crown ether hybrids, as well as the most recent advances in the synthesis and characterisation of this remarkable group of macrocyclic systems, are addressed. The discussion covers the strategies employed in synthesising these systems, including cyclisation reactions, self-assembly, and their remarkable reactivity. The potential applications of porphyrin-crown ether hybrids are also highlighted. Moreover, the discussion identifies the challenges associated with synthesising and characterising hybrids, outlining the possible future directions.

Tetrakis(4‐aminophenyl)porphyrin (1) and tetrakis(4‐acetamidophenyl)porphyrin (2) were dissolved in water with the incorporation of a polysaccharide (λ‐carrageenan (CGN)) as a water‐solubilizing agent. Although the photodynamic activity of the CGN‐2 complex was considerably lower than that of the CGN‐1 complex, the selectivity index (SI; IC50 in a normal cell/IC50 in a cancer cell) of the CGN‐2 complex was considerably higher than that of the CGN‐1 complex. This is because the photodynamic activity of the CGN‐2 complex was significantly affected by the intracellular uptakes by the normal and cancer cells. During in vivo experiments, the CGN‐2 complex inhibited tumor growth under light irradiation with high blood retention compared with the CGN‐1 complex and Photofrin, which exhibited lower blood retention. This study showed that the photodynamic activity and SI are influenced by substituent groups of arene in the meso‐positions of porphyrin analogs. [ABSTRACT FROM AUTHOR]

Crownphyrins are hybrid macrocycles combining structural features of porphyrin and crown ethers. The molecular architecture renders them an intriguing class of hosts capable of binding neutral, and ionic guests. The presence of dynamic covalent imine linkages connecting the dipyrrin segment with the ether chain enables unusual coordination behavior of crownphyrins, as demonstrated by the formation of two classes of strikingly different complexes. The remarkable metal‐mediated expansion to the helical [2+2] macrocyclic complex is reversible. The reaction of the figure‐eight mercury(II) assembly with [2.2.2]cryptand results in ring contraction providing the metal‐free crownphyrin macrocycle. [ABSTRACT FROM AUTHOR]

This Review discusses the recent developments in the field of synthetic chemistry of PAH–porphyrin hybrids, emphasizing phenanthrene‐embedded carbaporphyrinoids and related systems. The discussion covers various aspects of phenanthriporphyrin and its derivates chemistry, including their spectroscopic features, aromaticity, core reactivity, and coordination properties. The development of expanded phenanthriporphyrinoids is outlined, followed by the presentation of related carbaporphyrinoids incorporating hydrocarbon moieties such as fluorene, biphenyl, terphenyl, and dibenzo[g,p]chrysene. The exploitation of phenanthriporphyrinoids as a unique class of ligands for organometallic chemistry is discussed, altogether with their use for the construction of conformational and stereochemical switches. The perspective for using related macrocycles as building blocks for carbaporphyrinoid cages is also outlined. [ABSTRACT FROM AUTHOR]

Electron‐donating corroles (Cor) were integrated with electron‐accepting phthalocyanines (Pc) to afford two different non‐covalent Cor ⋅ Pc systems. At the forefront was the coordination between a 10‐meso‐pyridine Cor and a ZnPc. The complexation was corroborated in a combination of NMR, absorption, and fluorescence assays, and revealed association with binding constants as high as 106 m−1. Steady‐state and time‐resolved spectroscopies evidenced that regardless of exciting Cor or Pc, the charge‐separated state evolved efficiently in both cases, followed by a slow charge‐recombination to reinstate the ground state. The introduction of non‐covalent linkages between Cor and Pc induces sizeable differences in the context of light harvesting and transfer of charges when compared with covalently linked Cor‐Pc conjugates. [ABSTRACT FROM AUTHOR]

Inspired by the rigidified architecture of 'picket‐fence' systems, we propose a strategy utilizing strain to impose intramolecular tension in already peripherally overcrowded structures leading to selective atropisomeric conversion. Employing this approach, tuneable shape‐persistent porphyrin conformations were acquired exhibiting distinctive supramolecular nanostructures based on the orientation of the peripheral groups. The intrinsic assemblies driven by non‐covalent bonding interactions form supramolecular polymers while encapsulating small molecules in parallel channels or solvent‐accessible voids. The developed molecular strain engineering methodologies combined with synthetic approaches have allowed the introduction of the pivalate units creating a highly strained molecular skeleton. Changes in the absorption spectrum indicated the presence of severe steric repulsions between the peripheral groups which were confirmed by single crystal X‐ray analysis. To release the steric strain introduced by the peripheral units, thermal equilibration strategies were used to selectively convert the most abundant atropisomer to the desirable minor one. [ABSTRACT FROM AUTHOR]

The use of secondary interactions between substrates and catalysts is a promising strategy to discover selective transition metal catalysts for atom‐economy C−H bond functionalization. The most powerful catalysts are found via trial‐and‐error screening due to the low association constants between the substrate and the catalyst in which small stereo‐electronic modifications within them can lead to very different reactivities. To circumvent these limitations and to increase the level of reactivity prediction in these important reactions, we report herein a supramolecular catalyst harnessing Zn⋅⋅⋅N interactions that binds to pyridine‐like substrates as tight as it can be found in some enzymes. The distance and spatial geometry between the active site and the substrate binding site is ideal to target unprecedented meta‐selective iridium‐catalyzed C−H bond borylations with enzymatic Michaelis–Menten kinetics, besides unique substrate selectivity and dormant reactivity patterns. [ABSTRACT FROM AUTHOR]

Traditional 'picket fence' porphyrin systems have been a topic of interest for their capacity to direct steric shielding effects selectively to one side of the macrocycle. Sterically overcrowded porphyrin systems that adopt macrocycle deformations have recently drawn attention for their applications in organocatalysis and sensing. Here we explore the combined benefits of nonplanar porphyrins and the old molecular design to bring new concepts to the playing field. The challenging ortho‐positions of meso‐phenyl residues in dodecasubstituted porphyrin systems led us to transition to less hindered para‐ and meta‐sites and develop selective demethylation based on the steric interplay. Isolation of the symmetrical target compound [2,3,7,8,12,13,17,18‐octaethyl‐5,10,15,20‐tetrakis(3,5‐dipivaloyloxyphenyl)porphyrin] was investigated under two synthetic pathways. The obtained insight was used to isolate unsymmetrical [2,3,7,8,12,13,17,18‐octaethyl‐5,10,15,20‐tetrakis(2‐nitro‐5‐pivaloyloxyphenyl)porphyrin]. Upon separation of the atropisomers, a detailed single‐crystal X‐ray crystallographic analysis highlighted intrinsic intermolecular interactions. The nonplanarity of these systems in combination with 'picket fence' motifs provides an important feature in the design of supramolecular ensembles. [ABSTRACT FROM AUTHOR]

Atropisomerism is a fundamental feature of substituted biaryls resulting from rotation around the biaryl axis. Different stereoisomers are formed due to restricted rotation about the single bond, a situation often found in substituted porphyrins. Previously NMR determination of porphyrin atropisomers proved difficult, if not almost impossible to accomplish, due to low resolution or unresolvable resonance signals that predominantly overlapped. Here, we shed some light on this fundamental issue found in porphyrinoid stereochemistry. Using benzenesulfonic acid (BSA) for host‐guest interactions and performing 1D, 2D NMR spectroscopic analyses, we were able to characterize all four rotamers of the nonplanar 5,10,15,20‐tetrakis(2‐aminophenyl)‐2,3,7,8,12,13,17,18‐octaethylporphyirin as restricted H‐bonding complexes. Additionally, X‐ray structural analysis was used to investigate aspects of the weak host–guest interactions. A detailed assignment of the chemical signals suggests charge‐assisted complexation as a key to unravel the atropisomeric enigma. From a method development perspective, symmetry operations unique to porphyrin atropisomers offer an essential handle to accurately identify the rotamers using NMR techniques only. [ABSTRACT FROM AUTHOR]

Di‐2,7‐naphthihexaphyrin(1.1.1.1.1.1), a non‐aromatic carba‐analogue of the hexaphyrin(1.1.1.1.1.1), incorporating two built‐in 2,7‐naphthylene moieties was synthesized as two separate, conformationally locked stereoisomers. Both conformers followed complex protonation pathways involving structurally different species, which can be targeted under kinetic and thermodynamic control. The neutralization of the ultimate dicationic product, accessible from both stereoisomers of the free base, allowed to realize the complex conformational switching cycle involving six structurally different species. [ABSTRACT FROM AUTHOR]

Owing to the electron‐donating and ‐accepting nature of corroles (Corr) and phthalocyanines (Pc), respectively, we designed and developed two novel covalently linked Corr‐Pc conjugates. The synthetic route allows the preparation of the target conjugates in satisfying yields. Comprehensive steady‐state absorption, fluorescence, and electrochemical assays enabled insights into energy and electron‐transfer processes upon photoexcitation. Coordinating a pyridine‐appended subphthalocyanine (SubPc) to the Pc of the conjugate sets up the ways and means to realize the first example of an array composed by three different porphyrinoids, which drives a cascade of energy and charge‐transfer processes. Importantly, the SubPc assists in stabilizing the charge‐separated state, that is, one‐electron oxidized Corr and the one electron‐reduced Pc, upon photoexcitation by means of a reductive charge transfer to the SubPc. To the best of our knowledge, this is the first case of an intramolecular oxidation of a Corr within electron‐donor–acceptor conjugates by means of just photoexcitation. Moreover, the combination of Corr, Pc, and SubPc guarantees panchromatic absorption across the visible range of the solar spectrum, with the SubPc covering the „green gap" that usually affects porphyrinoids. [ABSTRACT FROM AUTHOR]

A series of amphiphilic 5‐(cyclic‐secondary‐amine)‐10,15,20‐tris(4‐sulfonatophenyl)porphyrins, designed with the aim of using the amphiphilic porphyrin moiety for the modulation of the aggregation state of the compound by the pH of the medium, have been synthesised, and the relationship between their supramolecular behaviour in acidic aqueous media and their organocatalytic activity in Michael and aldol reactions has been investigated. In particular, we have found that the catalytic activity of the pyrrolidine moiety in an amphiphilic isoindoline–porphyrin hybrid for the aldol reaction of cyclohexanone with 4‐nitrobenzaldehyde can be selectively and reversibly switched on and off by adjusting the homogeneity of its solutions through pH variations. The catalysis of the aldol reaction by the secondary amine moiety would otherwise take place regardless of the pH of the medium. We have demonstrated that the aggregation behaviour of these amine–porphyrin hybrids can be also used for the recovery and reutilization of the catalysts. [ABSTRACT FROM AUTHOR]

In this minireview, weak interactions that occur in supramolecular polymers are discussed. Combination of weak and strong interactions plays an important role in the construction of supramolecular polymers. It is beneficial to separate the contributions of the weak interactions, as well as each solvent effect on the weak interactions. However, it is generally difficult to observe each solvent effect separately at work in each interaction. Small molecular probes are useful to estimate the contributions of the weak interaction. But, the results should be treated with caution when applied to supramolecular polymer systems. To overcome the problems, a new solvent parameter, solvation ability (SA), is introduced, which was determined on the balance point of extended and stacked forms of porphyrin-based interconvertible supramolecular polymers. [ABSTRACT FROM AUTHOR]

A stimulus‐responsive receptor 1 was designed and prepared to control the ligand‐binding ability of three active sites, two zinc tetraphenylporphyrin units (P1) and one zinc diethynyldiphenylporphyrin unit (P2), with one effector molecule 2. Bulky hexarylbenzene units were incorporated as shielding panels in the middle of the flexible side arms of 1. Spectroscopic titrations indicated that a stable supramolecular complex 1⋅2 (K1⋅2=6.7×106 m−1) was produced by the cooperative formation of multiple hydrogen and coordination bonds. As a result, the binding of a ligand to P1 was inhibited by 2 in a competitive manner. Additionally, the formation of 1⋅2 brought about conformational restriction of the side arms to cover both faces of P2 with the shielding panels. The binding constant of 4‐phenylpyridine with P2 in 1⋅2 decreased to 8.9 % of that in 1. Namely, the ligand‐binding ability of P2 was inhibited according to an allosteric mechanism. [ABSTRACT FROM AUTHOR]

Bis(imidazolylporphyrinatozinc) molecules linked through a 1,3‐butadiynylene moiety respond to the solvents they are dissolved in to afford exclusively extended (E) or stacked (S) supramolecular polymers. This system is expected to be a solvation/desolvation indicator. However, the principles underlying the solvent‐dependent formation of the two types of polymers and the mechanism of the transformation between them are unclear. The formation of the polymers is considered to depend on the two types of complementary coordination bonds that can be formed and the π–π interactions between the porphyrins. In this study, the contributions and solvent dependence of both the coordination bonds and the π–π interactions have been investigated. The results clearly indicate that the coordination bonds are weakly or little solvent‐dependent, and that the π–π interactions function effectively only in the inner porphyrins of the S‐polymer and are strongly solvent‐dependent. Thermodynamic analysis revealed that the formation of the E‐ or S‐polymer in solution is determined by the total energies and the type of solvent used. The transformation of the E‐ to S‐polymer was investigated by gel permeation chromatography. The kinetics of the transformation were also determined. The role of the terminal imidazolylporphyrinatozinc moieties was also investigated: The results indicate that the transformation from the E‐ to S‐polymer occurs by an exchange mechanism between the polymers, induced by attack of terminal free imidazolyl groups on a polymer to zinc porphyrins on other polymers. [ABSTRACT FROM AUTHOR]

Recently identified as another form of cooperativity, interannular cooperativity is rarely observed in supramolecular chemistry. A tetra‐porphyrin molecular tweezer with two bis‐porphyrin binding sites is reported that exhibits archetypal interannular cooperativity when complexing 1,4‐diazabicyclo[2.2.2]octane (DABCO). The UV/Vis titration data best supported a 1:2 plus 2:2 plus 1:4 complexation model (host:guest), giving K12=6.32×1013 m−2, K22=3.04×1020 m−3, and K14=1.92×1016 m−4 in CHCl3. The NMR titration data supported the formation of two sandwich species, including tetra‐porphyrin⋅(DABCO)2 as the major species, although there are speciation differences between UV/Vis and NMR concentrations. Using statistical analysis, interannular cooperativity (γ) for tetra‐porphyrin⋅(DABCO)2 was determined to be negative (γ=2.41×10−3), which may be explained by DABCO being too small to be optimally bound simultaneously at both bis‐porphyrin binding sites. [ABSTRACT FROM AUTHOR]

Quadrupolar interactions of porphyrin bearing two pentafluorophenylethynyl terminals (1) drove the formation of a successive one‐dimensional staircase structure, i.e. J‐aggregates, to yield millimeter‐length needles with a single‐crystalline character in methylcyclohexane solution. In contrast, π‐stacked interactions of porphyrin bearing two nonfluorinated phenyl terminals (2) formed no aggregates in solution. A spin‐cast film of 1 also showed bathochromic shift of the Soret and Q bands, indicating the formation of J‐aggregates. The molecular arrangement of the J‐aggregates was revealed by microbeam glazing‐incidence wide‐angle X‐ray diffraction (GIWAXD), and was in good agreement with the optimized structure generated by density functional theory (DFT) calculations. [ABSTRACT FROM AUTHOR]

Abstract Equilibria of methylated N-confused platform of 2- N -methyl-5,10,15,20-tetrakis-(4′-sulfophenyl)-2-aza-21-carbaporphyrin tetraanion HMeIP (PhSO 3 H) 4 platform diprotonation by perchloric acid in water, H– and J-aggregates self-assembly were investigated using synchronous UV–Vis-fluorescence-pH titration and DFT/B3LYP/6-31++G(d,p) calculations. Methylation of inverted pyrrole ring in H 2 IP (PhSO 3 −) 4 allows to fix the tautomer HMeIP (PhSO 3 −) 4 with external NH-proton. Intramolecular tightness causes formation of two bifurcated NHN IMHB between pyrrole hydrogen and pyrrolenine nitrogen of platform HMeIP (PhSO 3 −) 4. IMHB protect intramolecular centers of hydrogen bonding from intermolecular interactions. First stage of HМеIP (PhSO 3 −) 4 protonation is accompanied by bifurcated IMHB type change from NHN to HNH. On the second protonation stage IMHB are broken and intermolecular hydrogen bonds with solvent molecules are formed. Diprotonated H 3 МеIP 2+(PhSO 3 −) 4 platform is a flexible 1,3-alternate, possessed molecular and anion receptor properties. Equilibrium in the second stage of protonation in water is completely shifted to the aquacomplex, which is formed due to hydrogen and electrostatic binding of the solvent molecules at the both receptor sites. Methylation and invertion of pyrrole ring leads to HMeIP (PhSO 3 −) 4 proton affinity increasing and eliminated the phenomena of synchronous H 2 P (PhSO 3 −) 4 porphyrin platform diprotonation, which is due to more stable aquacomplex [ H 4 P 2+(PhSO 3 −) 4 ](H 2 O) 2 formation. Initial tetraanion HMeIP (PhSO 3 −) 4 and aquacomplex [ H 4 IP 2+(PhSO 3 −) 4 ](H 2 O) 2 are monomers of H- and J-aggregates self-assembly. Driving force of H-aggregates formation is the ionic self-assembly between sulfonate groups of monomers and spacer cations. J-aggregates self-assembly is due to formation of more stable anion complexes as a result of water molecules intermolecular substitution in [ H 3 MeIP 2+(PhSO 3 −) 4 ](H 2 O) 2 by monomers sulfonate groups. Protonated chitosan was used as a inducer and chiral scaffold of CW-H- and tubular CW-J-aggregates (porphyrin nanotubes) self-assembly. Parameters of CW-H- and CW- J -dimers geometry were calculated and 3D models of H-aggregates and porphyrin nanotubes were developed on their basis. Graphical abstract Unlabelled Image Highlights • IMHB protect coordination cage of inverted platform from intermolecular interactions • Interaction of sulfonate groups with background cations leads to H-aggregates self-assembly • Diprotonated platform-receptor forms aquacomplex with two water molecules • Intermolecular substitution of water molecules by sulfonate groups leads to tubular J-aggregates self-assembly • Chitosan has been used as inducer of pH – controlled homochiral H– and J-aggregates self-assembly and interconversion [ABSTRACT FROM AUTHOR]

Development of supramolecular methods to further activate a highly reactive intermediate is a fascinating strategy to create novel potent catalysts for activation of inert chemicals. Herein, a supramolecular approach to enhance the oxidizing ability of a high‐valent oxo species of a nitrido‐bridged iron porphyrinoid dimer that is a known potent molecular catalyst for light alkane oxidation is reported. For this purpose, a nitrido‐bridged dinuclear iron complex of porphyrin‐phthalocyanine heterodimer 35+, which is connected through a fourfold rotaxane, was prepared. Heterodimer 35+ catalyzed ethane oxidation in the presence of H2O2 at a relatively low temperature. The site‐selective complexation of 35+ with an additional anionic porphyrin (TPPS4−) through π–π stacking and electrostatic interactions afforded a stable 1:1 complex. It was demonstrated that the supramolecular post‐synthetic modification of 35+ enhances its catalytic activity efficiently. Moreover, supramolecular conjugates achieved higher catalytic ethane oxidation activity than nitrido‐bridged iron phthalocyanine dimer, which is the most potent iron‐oxo‐based molecular catalyst for light‐alkane oxidation reported so far. Electrochemical measurements proved that the electronic perturbation from TPPS4− to 35+ enhanced the catalytic activity. Supramolecular activation: The ethane‐oxidation ability of an oxo species of a nitrido‐bridged iron porphyrinoid dimer was significantly enhanced by site‐selective strong supramolecular complexation of a fourfold rotaxane structure with an additional porphyrin through π–π stacking and quadruple ionic interactions. [ABSTRACT FROM AUTHOR]

Compared with their purely organic counterparts, molecular switches that are based on metal ion translocations have been underexplored, and more particularly, it remains challenging to control the translocation of several particles in multisite receptors. Recently, bimetallic complexes that undergo double translocation processes have been developed with bis‐strapped porphyrin ligands. To implement a redox control for these systems, we have investigated the formation of heterobimetallic lead/thallium complexes, with thallium in the +I and +III oxidation states. Two different complexes were characterized: 1) a PbII/TlI complex, in which both metal ions interact with the N‐core on its different sides, and 2) a PbII/TlIII complex with TlIII selectively bound to the N‐core and PbII selectively bound to the strap opposite to TlIII. These two complexes undergo interconversion between their two degenerate forms (same coordination of the metal ions but on opposite sides) by different intra or intermolecular translocation pathways. In addition, conversion of the PbII/TlI complex into its PbII/TlIII counterpart was achieved by addition of a stoichiometric amount of HgII salt as a sacrificial electron acceptor. These results further contribute to the elaboration of devices that feature redox‐controlled compartmentalized double translocations. Porphyrin plays a mean pinball! By targeting new devices based on coupled translocations of metal ions, PbII/TlI and PbII/TlIII heteromultimetallic porphyrin complexes are prepared, and their metal exchange dynamics are evaluated. A unique HgII‐mediated oxidation process allows PbII/TlI‐to‐PbII/TlIII conversion, which changes the intrinsic fluxionality of the system (see picture). [ABSTRACT FROM AUTHOR]

Inspired by enzymes such as cytochrome P‐450, the study of the reactivity of metalloporphyrins continues to attract major interest in the field of homogeneous catalysis. However, little is known about benefitting from the substrate‐recognition properties of porphyrins containing additional, catalytically relevant active sites. Herein, such an approach is introduced by using supramolecular ligands derived from metalloporphyrins customized with rigid, palladium‐coordinating nitrile groups. According to different studies (NMR and UV/Vis spectroscopy, XRD, control experiments), the supramolecular ligands are able to accommodate pyridine derivatives as substrates inside the porphyrin pocket while the reactivity occurs at the peripheral side. By simply tuning a remote metal center, different binding events result in different catalyst reactivity, and this enzyme‐like feature leads to high degrees of substrate selectivity in representative palladium‐catalyzed Suzuki–Miyaura reactions. Ground control: Supramolecular catalysts based on porphyrin scaffolds with peripheral palladium ions (see figure) modulate the reactivity of structurally similar substrates by tuning the properties of the binding site (A), which is eight chemical bonds apart from the active site (Pd). [ABSTRACT FROM AUTHOR]

Supramolecular chirality is one of the most important issues in different branches of science and technology, as stereoselective molecular recognition, catalysis, and sensors. In this paper, we report on the self-assembly of amphiphilic porphyrin derivatives possessing a chiral information on the periphery of the macrocycle (i.e., D- or L-proline moieties), in the presence of chiral amines as co-solute, such as chiral benzylamine derivatives. The aggregation process, steered by hydrophobic effect, has been studied in aqueous solvent mixtures by combined spectroscopic and topographic techniques. The results obtained pointed out a dramatic effect of these ligands on the morphology and on the supramolecular chirality of the final self-assembled structures. Scanning electron microscopy topography, as well as fluorescence microscopy studies revealed the formation of rod-like structures of micrometric size, different from the fractal structures formerly observed when the self-assembly process is carried out in the absence of chiral amine co-solutes. On the other hand, comparative experiments with an achiral porphyrin analogue strongly suggested that the presence of the prolinate moiety is mandatory for the achievement of the observed highly organized suprastructures. The results obtained would be of importance for unraveling the intimate mechanisms operating in the selection of the homochirality, and for the preparation of sensitive materials for the detection of chiral analytes, with tunable stereoselectivity and morphology.

The design, synthesis, and characterization of a new multifunctional supramolecular assembly based on a photoactive glycosylated porphyrin and covalently attached monofunctionalized cucurbit[7]uril (CB7) are reported. To obtain the target supramolecular assembly, azido‐functionalized tetraphenylporphyrin (TPP) was used as a building block. TPP was first glycosylated by copper‐catalyzed azide‐alkyne cycloaddition (CuAAC) reaction, then a monopropargyloxy‐functionalized‐CB7 unit was conjugated to glycosylated TPP with a second CuAAC reaction. The host–guest chemistry of the assembly was investigated by 1H NMR experiments to establish the availability of the CB7 as a host. The imidazole‐based guest, which is known to have high affinity toward CB7, was observed to form inclusion complex with CB7. It was also demonstrated that this supramolecular assembly can serve as an efficient photosensitizer for the generation of singlet oxygen. Sugar‐coated assemblies: A new multifunctional supramolecular assembly was synthesized by clicking an azide functionalized photoactive glycosylated porphyrin with monopropargyloxy functionalized cucurbit[7]uril (CB7). This supramolecular assembly can serve as a host to bind with guests and an efficient photosensitizer for the generation of singlet oxygen (see figure). [ABSTRACT FROM AUTHOR]

The formation of chromophore arrays using a DNA templating approach leads to the creation of supramolecular assemblies, where the optical properties of the overall system can be fine‐tuned to a large extent. In particular, porphyrin derivatives have been shown to be versatile building blocks; mostly covalent chemistry was used for embedding the units into DNA strands. Self‐assembly of porphyrin modified nucleosides, on the other hand, has not been investigated as a simplified approach. We report on the synthesis of a magnesium(II) tetraaza porphine (MgTAP) coupled to deoxyuridine, and array formation on DNA templates which contain well‐defined oligo(dA) segments showing strong fluorescence enhancement which is significantly larger than that with a Zn‐porphyrin. The use of the deep‐eutectic solvent glycholine is essential for successful assembly formation. The system allows for sizing of short tandem repeat markers with multiple adenosines, thus the concept could be adaptable to in vitro forensic DNA profiling with a suitable set of different chromophores on all nucleosides. [ABSTRACT FROM AUTHOR]

Abstract: Five‐coordinated d6 metal complexes are relatively uncommon but can be useful building blocks for the construction of supramolecular assemblies. In this work we have used the strong trans effect of aryl and alkyl ligands for the synthesis of luminescent five‐coordinated organoiridium porphyrins, which are useful building blocks for the construction of metallamacrocycles and metallacages of iridium through metal–ligand interactions at the axial positions of iridium porphyrins (Ir(por)). Diverse di‐ or tritopic aryl or alkyl linkers were employed as the axial ligands to coordinate Ir(por) at an axial position to afford di‐ or trinuclear five‐coordinated [{Ir(ttp)}n(X)] (ttp=5,10,15,20‐tetrakis(p‐tolyl)porphyrinato(2−); n=2, X=diaryl; n=3, X=trialkyl). [{Ir(ttp)}n(X)] could be further coordinated with ditopic isocyanide or pyridine ligands at the other axial site of each Ir(ttp) to give unprecedented cyclic supramolecular metalloporphyrin assemblies, including tetra‐ and hexanuclear metallamacrocycles and hexanuclear metallacages. The Ir(por) metallamacrocycles and metallacages display phosphorescence in the near‐infrared region with quantum yields of around 2 % and microsecond emission lifetimes. [ABSTRACT FROM AUTHOR]

Abstract: A chiral ZnII porphyrin derivative 1 and its achiral analogue 2 were studied in the solid state. Considering the rich molecular recognition of designed metalloporphyrins 1 and 2 and their tendency to crystallize, they were recrystallized from two solvent mixtures (CH2Cl2/CH3OH and CH2Cl2/hexane). As a result, four different crystalline arrangements (1 a,b and 2 a,b, from 0D to 2D) were obtained. Solid‐state studies were performed on all the species to analyze the role played by chirality, solvent mixtures, and surfaces (mica and HOPG) in the supramolecular arrangements. By means of combinations of solvents and substrates a variety of microsized species was obtained, from vesicles to flower‐shaped arrays, including geometrical microcrystals. Overall, the results emphasize the environmental susceptibility of metalloporphyrins and how this feature must be taken into account in their design. [ABSTRACT FROM AUTHOR]

Abstract: Two unprecedented porphyrin fused nanographene molecules, 1 and 2, have been synthesized by the Scholl reaction from tailor‐made precursors based on benzo[m]tetraphene‐substituted porphyrins. The chemical structures were validated by a combination of high‐resolution matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (HR MALDI‐TOF MS), IR and Raman spectroscopy, and scanning tunnelling microscopy (STM). The UV‐vis‐near infrared absorption spectroscopy of 1 and 2 demonstrated broad and largely red‐shifted absorption spectra extending up to 1000 and 1400 nm, respectively, marking the significant extension of the π‐conjugated systems. [ABSTRACT FROM AUTHOR]

Abstract: A CoII/porphyrinate‐based macrocycle in the presence of a 3,5‐diphenylpyridine axial ligand functions as an endotopic ligand to direct the assembly of [2]rotaxanes from diazo and styrene half‐threads, by radical‐carbene‐transfer reactions, in excellent 95 % yield. The method reported herein applies the active‐metal‐template strategy to include radical‐type activation of ligands by the metal‐template ion during the organometallic process which ultimately yields the mechanical bond. A careful quantitative analysis of the product distribution afforded from the rotaxane self‐assembly reaction shows that the CoII/porphyrinate subunit is still active after formation of the mechanical bond and, upon coordination of an additional diazo half‐thread derivative, promotes a novel intercomponent C−H insertion reaction to yield a new rotaxane‐like species. This unexpected intercomponent C−H insertion illustrates the distinct reactivity brought to the CoII/porphyrinate catalyst by the mechanical bond. [ABSTRACT FROM AUTHOR]

Stimuli-responsive materials can convert between molecular scale and macroscopic scale phenomena. Two macroscopic static electricity-responsive phenomena based on nanoscale supramolecular assemblies of a zinc porphyrin derivative are presented. One example involves the movement of supramolecular assemblies in response to static electricity. The assembly of a pyridine (Py) complex of the above-mentioned derivative in cyclohexane is drawn to a positively charged material, whereas the assembly of a 3,5-dimethylpyridine complex is drawn to a negatively charged material. The second phenomenon involves the movement of a non-polar solvent in response to static electrical stimulation. A cyclohexane solution containing a small quantity of the Py-complexed assembly exhibited a strong movement response towards negatively charged materials. Based on spectroscopic measurements and electron microscope observations, it was revealed that the assembled formation generates the observed response to static electricity. [ABSTRACT FROM AUTHOR]

Unprecedented regioselectivity to the branched aldehyde product in the hydroformylation of propene was attained on embedding a rhodium complex in supramolecular assembly L2, formed by coordination-driven self-assembly of tris( meta-pyridyl)phosphine and zinc(II) porpholactone. The design of cage L2 is based on the ligand-template approach, in which the ligand acts as a template for cage formation. Previously, first-generation cage L1, in which zinc(II) porphyrin units were utilized instead of porpholactones, was reported. Binding studies demonstrate that the association constant for the formation of second-generation cage L2 is nearly an order of magnitude higher than that of L1. This strengthened binding allows cage L2 to remain intact in polar and industrially relevant solvents. As a consequence, the unprecedented regioselectivity for branched aldehyde products can be maintained in polar and coordinating solvents by using the second-generation assembly. [ABSTRACT FROM AUTHOR]

Simultaneous occurrence of energy and electron transfer events involving different acceptor sites in a newly assembled supramolecular triad comprised of covalently linked free-base porphyrin-zinc porphyrin dyad, H2P−ZnP axially coordinated to electron acceptor fullerene, has been successfully demonstrated. The dyad was connected through the β-pyrrole positions of the porphyrin macrocycle instead of the traditionally used meso-positions for better electronic communication. Interestingly, the β-pyrrole functionalization modulated the optical properties to such an extent that it was possible to almost exclusively excite the zinc porphyrin entity in the supramolecular triad. The measured binding constant for the complex with 1:1 molecular stoichiometry was in the order of 104 m−1 revealing moderately stable complex formation. An energy level diagram constructed using optical, electrochemical and computational results suggested that both the anticipated energy and electron events are thermodynamically feasible in the triad. Consequently, it was possible to demonstrate occurrence of excited state energy transfer to the covalently linked H2P, and electron transfer to the coordinated ImC60 from studies involving steady-state and time-resolved emission, and femto- and nanosecond transient absorption studies. The estimated energy transfer was around 67 % in the dyad with a rate constant of 1.1×109 s−1. In the supramolecular triad, the charge separated state was rather long-lived although it was difficult to arrive the exact lifetime of charge separated state from nanosecond transient spectral studies due to overlap of strong triplet excited signals of porphyrin in the monitoring wavelength window. Nevertheless, simultaneous occurrence of energy and electron transfer in the appropriately positioned energy and electron acceptor entities in a supramolecular triad was possible to demonstrate in the present study, a step forward to unraveling the complex photochemical events occurring in natural photosynthesis and its implications in building light energy harvesting devices. [ABSTRACT FROM AUTHOR]

Two novel stable β-tetraethylporphycenes (TEPos), namely, trans-TEPo ( 1T) and its unsymmetrical isomer cis-TEPo ( 1C), were synthesized by reductive McMurry coupling of an unsymmetrical bipyrrole dialdehyde and were isolated through recrystallization. Both isomers showed interesting photophysical properties. Their corresponding dibromo derivatives obtained through bromination of a mixture of 1C and 1T, however, could not be separated in pure form. Interestingly, they were found to form an unprecedented 2:1 supramolecular sandwich complex through π-π stacking interactions, and in addition, only strong C-H ···Br-C interactions among the oppositely oriented cis isomers led to the formation of 2D arrays in the solid state. [ABSTRACT FROM AUTHOR]

Cover Picture: Crownphyrins: Metal-Mediated Transformations of the Porphyrin-Crown Ether Hybrids (Angew. Crown Ethers, Porphyrinoids, Receptors, Self-Assembly, Supramolecular Chemistry Keywords: Crown Ethers; Porphyrinoids; Receptors; Self-Assembly; Supramolecular Chemistry EN Crown Ethers Porphyrinoids Receptors Self-Assembly Supramolecular Chemistry 1 1 1 12/01/22 20221205 NES 221205 B Crownphyrins b are macrocycles combining the structural features of porphyrin and crown ethers. [Extracted from the article]

Das Vorhandensein von Iminbindungen, die das Dipyrin-Segment mit der Etherkette verbinden, ermöglicht das ungewöhnliche Koordinationsverhalten von Crownphyrinen, wie die Bildung von zwei Klassen auffallend unterschiedlicher Komplexe zeigt, über die Bartosz Szyszko und Mitarbeiter in ihrem Forschungsartikel berichten (e202211671). Crown Ethers, Porphyrinoids, Receptors, Self-Assembly, Supramolecular Chemistry Keywords: Crown Ethers; Porphyrinoids; Receptors; Self-Assembly; Supramolecular Chemistry EN Crown Ethers Porphyrinoids Receptors Self-Assembly Supramolecular Chemistry 1 1 1 11/30/22 20221205 NES 221205 B Crownphyrine b sind Makrozyklen, die die strukturellen Merkmale von Porphyrinen und Kronenethern kombinieren. [Extracted from the article]

Doubly and quadruply quinoline-fused porphyrins were effectively synthesized through a reaction sequence consisting of Suzuki-Miyaura coupling of β-borylated porphyrins with 2-iodoaniline and subsequent Pictet-Spengler cyclization. These quinoline-fused porphyrins display red-shifted absorption bands and higher electron-accepting abilities. This synthetic protocol also allowed the synthesis of phenanthroline-fused porphyrin dimers, which bound either a NiII or ZnII cation. The resultant metal complexes displayed further red shifted absorption spectra and molecular twists to effect an almost perpendicular arrangement of the two porphyrins. [ABSTRACT FROM AUTHOR]

Urea-functionalized porphyrin catalysts containing a cavity, which are used for the processive epoxidation of polymers, are thoroughly characterized and their binding properties and other supramolecular features disclosed. Intramolecular coordination of the urea side chains to the metal center of the porphyrin moiety is unveiled through NMR, IR, UV, and fluorescence spectroscopy studies. This intramolecular coordination appears to be essential in order to facilitate catalysis in a pseudo-rotaxane fashion, i.e. by preventing the use of an excess of bulky axial ligands. The current investigation provides information on how to modulate in a dynamic fashion the catalytic activity of supramolecular systems, which is of interest for the design of increasingly efficient processive catalysts. [ABSTRACT FROM AUTHOR]

A stacked assembly composed of a porphyrin and two phthalocyanines was prepared through fourfold rotaxane formation. Two phthalocyanine molecules, bearing four 24-crown-8 units, were assembled onto a porphyrin template incorporating four sidechains with two dialkylammonium ions each through pseudorotaxane formation between crown ether units and ammonium ions. The Staudinger phosphite reaction, as the stoppering reaction, resulted in the formation of the stacked heterotrimer composed of a porphyrin and two phthalocyanines connected through a fourfold rotaxane structure. UV/Vis spectroscopic and electrochemical studies of the heterotrimer indicated that there is a significant electronic interaction between the two phthalocyanine units due to the close stacking. The electrochemical oxidation process of the stacked heterotrimer was studied by cyclic voltammetry and spectroelectrochemistry. Electron paramagnetic resonance (EPR) spectroscopy of a dinuclear CuII complex, in which two CuII phthalocyanines were assembled on a metal-free porphyrin template, revealed that two CuII phthalocyanines were located within the stacking distance, which resulted in an antiferromagnetic interaction between the two S= [ABSTRACT FROM AUTHOR]

The J aggregates of 4-sulfonatophenyl meso-substituted porphyrins are non-covalent polymers obtained by self-assembly that form nanoparticles of different morphologies. In the case of high aspect-ratio nanoparticles (bilayered ribbons and monolayered nanotubes), shear hydrodynamic forces may modify their shape and size, as observed by peak force microscopy, transmission electron microscopy of frozen solutions, small-angle X-ray scattering measurements in a disk-plate rotational cell, and cone-plate rotational viscometry. These nanoparticles either show elastic or plastic behaviour: there is plasticity in the ribbons obtained upon nanotube collapse on solid/air interfaces and in viscous concentrated nanotube solutions, whereas elasticity occurs in the case of dilute nanotube solutions. Sonication and strong shear hydrodynamic forces lead to the breaking of the monolayered nanotubes into small particles, which then associate into large colloidal particles. [ABSTRACT FROM AUTHOR]