Conspectus Porphyrin derivatives are ubiquitous in nature and have important biological roles, such as in light harvesting, oxygen transport, and catalysis. Owing to their intrinsic π-conjugated ...structure, porphyrin derivatives exhibit characteristic photophysical and electrochemical properties. In biological systems, porphyrin derivatives are associated with various protein molecules through noncovalent interactions. For example, hemoglobin, which is responsible for oxygen transport in most vertebrates, consists of four subunits of a globular protein with an iron porphyrin derivative prosthetic group. Furthermore, noncovalently arranged porphyrin derivatives are the fundamental chromophores in light-harvesting systems for photosynthesis in plants and algae. These biologically important roles originate from the functional versatility of porphyrin derivatives. Specifically, porphyrins are excellent host compounds, forming coordination complexes with various metal ions that adds functionality to the porphyrin unit, such as redox activity and additional ligand binding at the central metal ion. In addition, porphyrins are useful building blocks for functional supramolecular assemblies because of their flat and symmetrical molecular architectures, and their excellent photophysical properties are typically utilized for the fabrication of bioactive functional materials. In this Account, we summarize our endeavors over the past decade to develop functional materials based on porphyrin derivatives using bioinspired approaches. In the first section, we discuss several synthetic receptors that act as artificial allosteric host systems and can be used for the selective detection of various chemicals, such as cyanide, chloride, and amino acids. In the second section, we introduce multiporphyrin arrays as mimics of natural light-harvesting complexes. The active control of energy transfer processes by additional guest binding and the fabrication of organic photovoltaic devices using porphyrin derivatives are also introduced. In the third section, we introduce several types of porphyrin-based supramolecular assemblies. Through noncovalent interactions such as metal–ligand interaction, hydrogen bonding, and π–π interaction, porphyrin derivatives were constructed as supramolecular polymers with formation of fiber or toroidal assembly. In the last section, the application of porphyrin derivatives for biomedical nanodevice fabrication is introduced. Even though porphyrins were good candidates as photosensitizers for photodynamic therapy, they have limitations for biomedical application owing to aggregation in aqueous media. We suggested ionic dendrimer porphyrins and they showed excellent photodynamic therapy (PDT) efficacy.
Display omitted
•Porphyrin derivatives serve as fluorescent chromophores to detect chemicals.•The coordination of metal ions to the porphyrin center provides Lewis acid sites.•Porphyrin derivatives ...act as signaling units for emission or absorption changes.
Porphyrins are heterocyclic macrocycle organic compounds, composed of four modified pyrrole subunits interconnected at their α carbon atoms via methine bridges. Because of their unique properties, synthetic porphyrin derivatives are powerful tools for molecular recognition. The optical or electronic monitoring of porphyrin derivatives permits the detection of the binding of transition metals. The binding of the metal ion to the porphyrin center provides additional axial ligand binding sites, which can be utilized for molecular recognition and sensing. Because of the large extinction coefficient and emission property, porphyrin derivatives can be utilized as fluorescent chromophores for the detection of various chemicals. In this paper, important development in terms of porphyrin-based chemical probes will be reviewed. This review is divided into nine sections focusing on porphyrin-based probes for (i) cations, (ii) anions, (iii) ion pairs, (iv) volatile organic chemicals, (v) nitroaromatic compounds, (vi) gases, (vii), reactive oxygen species, (viii) chiral discrimination, and (ix) environmental change detection, respectively.
Supramolecular electronics exploits the distinctive features stemming from noncovalent interactions, guiding the self‐assembly of molecules to craft materials endowed with customized electronic ...functionalities. Hydrogen‐bonded materials, characterized by their capacity to establish dynamic and stable networks, introduce an extra dimension to the development of supramolecular electronic systems. This study presents a comparative analysis of two remarkably small semiconductors utilizing diketopyrrolopyrrole functionalized with urea units as hydrogen‐bonding motifs, strategically positioned at opposing ends of the conjugated core. We show how the subtle distinction in functionalization not only influences morphology and self‐assembly dynamics via hydrogen‐bonding and π‐π stacking formation, but also holds significant consequences for ultimate charge transport properties. Our observations into the interplay of noncovalent interactions provide valuable insights and strategic pathways for the design of novel materials with enhanced electronic characteristics.
We explore the synthesis, self‐assembly and charge transport properties of two urea‐containing single core thiophene‐capped diketopyrrolopyrrole derivatives. The subtle differences in molecular design dictate the superior electronic properties of the lactam‐functionalized analogue
A triazole-bearing strapped calix4pyrrole (
1
) was synthesized as a lithium salt selective ion pair receptor.
1
H NMR spectral studies and X-ray crystallography showed that the capture of LiCl by
1
...occurs
via
separated ion pair binding. Furthermore, lithium salts extracted by
1
could be solidified in the form of Li
2
CO
3
through CO
2
or K
2
CO
3
treatment.
A triazole-bearing strapped calix4pyrrole (
1
) was synthesized as a lithium salt selective ion pair receptor.
A series of hydroxy thiophene-conjugated benzothiazole derivatives (HTBs) was prepared to investigate their fluorescence emission behaviors and capability to selectively stain subcellular organelles ...for fluorescence imaging. The HTB derivatives exhibited excited-state intramolecular proton transfer (ESIPT) and intramolecular charge transfer (ICT) behaviors, according to their molecular structure. Subtle changes in the molecular structure of the HTB influenced its response to changes in the surrounding environment, such as the solvent polarity and/or pH. In vitro cellular imaging experiments revealed that HTBA (5-(benzodthiazol-2-yl)-2,2′-bithiophen-4-ol) could selectively stain mitochondria. In contrast, HTBB-CO2Et (ethyl 5'-(benzodthiazol-2-yl)-3′-hydroxy-2,2′-bithiophene-5-carboxylate), which contains a regioisomeric hydroxy thiophene unit with an electron-withdrawing ethyl ester group, showed the capability to stain lipid droplets (LDs) in living cells. When the hydroxyl group in HTBB-CO2Et was protected with a benzyl group, effective staining of LDs in live cells was achieved. Thus, we successfully obtained an effective fluorescent probe. Collectively, the results indicated that small structural changes resulted in substantial changes in the intracellular localization and in vitro imaging ability of the prepared compounds.
Display omitted
•Hydroxy thiophene-conjugated benzothiazole derivatives (HTBs) were synthesized.•HTBs exhibited polarity-dependent bright emission due to ESIPT and ICT.•The structural change of HTBs enabled selective staining of mitochondria and lipid droplets.
A triazole-bearing picket fence type nickel porphyrin (1) has been synthesized as a host compound for anion binding. Among the various anionic species examined, cyanide was the only one that affected ...a spectral change of 1. Moreover, 1 exhibited strong homotropic positive allosterism against cyanide binding due to an electronic effect as well as multiple hydrogen bonds formed between cyanide and the triazole groups.
A dithiophene-bearing benzothiazole derivative (DTBz) was synthesized as a moisture-sensitive fluorescent probe for the detection of water in hygroscopic solvents. In a mixture of water and organic ...solvents, such as THF, 1,4-dioxane, MeOH, and EtOH, the fluorescence intensity of DTBz showed ratiometric changes in response to the content of water in the organic solvents. Moreover, the emission color of DTBz changed drastically from blue to red, which facilitated the development of the smartphone-assisted fluorometric device using image analysis. The custom smartphone-based device allowed water detection over the range of 0–60% with a resolution of 0.1% in the range of 0–1%. The detection sensitivity was as low as 0.05%. The total assay time was estimated to be approximately 6 min. The custom device would be very useful for determining the water content of various hygroscopic organic solvents over a wide range.
Display omitted
•An efficient moisture-sensitive fluorescent probe was designed.•The probe exhibited emission change over a wide range of water contents in hygroscopic solvents.•A smartphone-based custom device was designed for simple and effective detection of water.
A hydroxythiophene-bearing benzothiazole (HB) in phosphate buffer solution showed strong yellow fluorescence emission, which selectively and sensitively decreased by addition of IO4−. The reaction ...between HB and IO4− dramatically accelerated by UV irradiation. The fluorescence emission of HB was gradually recovered upon thermal heating of the IO4−-adducted product, indicating IO4− release. Using these properties, the solution containing HB and IO4− has been used as a fluorescence-based security ink.
Display omitted
•The probe, HB, has successfully recognized IO4− in various anions, which is accelerated by UV irradiation.•The fluorescence emission of HB was recovered upon thermal heating of the IO4− adducted product.•Using the reversible properties, the solution containing HB and IO4− could be used as a fluorescence-based security ink.
Display omitted
•Because T2(OH)B showed large stokes shift through ESIPT process, it can be useful for fluorescent probe.•Owing to turn-on fluorescence emission behavior of T2(OH)B above ...physiological pHs, it was successfully applied for mitochondria of mammalian cells, as well as detected H. pylori adhered to mammalian cells.•Also, T2(OH)B displayed faster staining rates than commercially available MitoTracker red.
An hydroxythiophene-conjugated benzothiazole (T2(OH)B) was synthesized as a pH sensitive fluorescent probe. T2(OH)B displayed dual emission behavior due to the excited state intramolecular proton transfer (ESIPT) process, while the methoxy analogs, T2(OMe)B, did not. T2(OH)B showed strong fluorescence enhancement above physiological pHs. The applicability of T2(OH)B as a biological pH indicator was demonstrated by its use for staining mitochondrial compartment and H. pylori. Owing to its strong fluorescence emission with a large stokes shift and its effective response to pH, T2(OH)B serves as a platform for the design of new types of fluorescent probes.
![Strapped calix[4]pyrrole as...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/1359-7345/small "Strapped calix[4]pyrrole as a lithium salts selective receptor through separated ion-pair binding")
