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Porphyrinoids have attracted wide interest because of their vital roles in biological processes and fascinating structural and functional characters. In this work, a doubly N-confused pentapyrrane precursor N 2 C–P 5 has been synthesized with terminal pyrrole ring A and middle pyrrole C incorporated in the N-confused mode. On this basis, pentapyrrin 1 and sapphyrin 2 have been synthesized by oxidizing N 2 C–P 5 with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ). Both 1 and 2 possess a [5.5.5]-tricyclic fused ring involving pyrrole B and the neighboring confused pyrrole C. Meanwhile, the formation of 2 involves ring closure between the terminal rings A and E. Notably, 2 exists as a diradical showing a half-field signal in the electron paramagnetic resonance (EPR) spectrum and a singlet ground state with a negative singlet-triplet energy gap of −0.50 kcal/mol. Excellent thermal stability has been observed for 2 , which may be related to its large π-conjugated framework involving the fused structure. On this basis, 1 and 2 were treated with Cu(acac) 2 to afford Cu(II) complexes 3 and 4 , respectively. As a result, an acetylacetonyl moiety is attached at the terminal pyrrole ring E to afford an NNNO coordination environment for complex 3 , and the sapphyrin macrocycle of 2 has been cleaved between rings A and B to afford a fused pentapyrrin ligand, furnishing an NNNN coordination environment for complex 4 , in which a pentafluorophenyl-ketal group generated during the ring cleavage reaction is attached to ring A, and it can be hydrolyzed to the corresponding pentafluorobenzoyl substituent to afford complex 5. Compared with free bases 1 and 2 , complexes 3 − 5 show more intense low-energy near-infrared (NIR) absorption bands at ca. 791, 926 and 907 nm, respectively. This work provides an effective approach for the syntheses of linear and macrocyclic oligopyrroles with intriguing structures and properties by oxidizing oligopyrranes with precisely designed numbers and positions of N-confused pyrroles. [Display omitted] • Facile syntheses of stable N-fused sapphyrin diradical. • Cu(II) complexes of fused pentapyrrins with an acetylacetonyl, pentafluorophenyl-ketal and pentafluorobenzoyl substituent. • Tunable low-energy near-infrared (NIR) absorption bands up to 1151 nm. [ABSTRACT FROM AUTHOR]

Dye-sensitized solar cells (DSSCs) have attracted intensive attention in developing photovoltaic devices for employing solar energy. For developing panchromatic and efficient porphyrin sensitizers, it has been demonstrated to be an effective approach to introduce an electron-withdrawing benzothiadiazole unit as an extra electron acceptor. In contrast, the structurally similar benzotriazole moiety remains relatively unknown in this respect. In this work, we have synthesized a novel porphyrin dye containing an extra electron acceptor of benzotriazole. Photophysical and electrochemical investigations revealed red-shifted absorption and a narrower band gap induced by the benzotriazole unit. Thus, a reasonable efficiency of 8.39% has been achieved with a J sc of 17.00 mA cm −2 and a V oc of 712 mV. On this basis, to investigate the effect of the dihedral angle between the benzotriazole and the adjacent phenylene ring, one or two methyl groups were attached to the ortho -positions of the phenylene ring. As a result, the enlarged torsion angles induce poor electronic coupling between the LUMO of the dyes and TiO 2 , resulting in lower efficiencies of 6.61% and 3.62%, respectively. With the purpose to further improve the efficiencies, coadsorption and cosensitization approaches were employed. And the efficiencies have been successfully elevated to 9.32%, 8.49% and 7.34%, respectively. These results demonstrate the effectiveness of incorporating an auxiliary benzotriazole acceptor into porphyrin dyes on achieving extended light-harvesting wavelength ranges and illustrate the importance of avoiding severe torsion within the acceptor part of the porphyrin dyes. In contrast to the commonly used cosensitizers with absorption peaks lying in the absorption valley between the Soret band and the Q bands of porphyrin dyes (500–600 nm), the utilization of an organic dye with broad absorption in this work has been demonstrated to be effective for improving the efficiencies despite the fact that its absorption peak at 450 nm largely overlaps with the Soret band of the porphyrin dyes. These results provide an alternative approach for developing cosensitizers for porphyrin dyes. [ABSTRACT FROM AUTHOR]

Biothiols, such as cysteine (Cys), homocysteine (Hcy), and glutathione (GSH), play essential roles in many physiological and pathological processes. In this work, three porphyrin derivatives, XQ1 , XQ2 and XQ3 , were synthesized by combining the porphyrin framework with nitroethylene, bis(methoxycarbonyl)ethylene and dicyanoethylene moieties, respectively. XQ1 was almost nonfluorescent, which could be utilized as a good starting point for developing fluorescence turn-on probes. Thus, XQ1 exhibits fast fluorescence enhancement and high selectivity towards the biothiols based on the Michael addition mechanism. It also exhibits high sensitivity towards the biothiols with the detection limits of 0.65–1.1 μM. In addition, XQ1 was successfully applied to cell imaging in living A549 cells for visualizing the biothiols. The results compose a good example of designing porphyrin derivatives for detecting biothiols, with the advantages of dramatic fluorescence enhancement in the NIR wavelength range, which exhibits good cell membrane permeability and practicability in detecting both exogenous and endogenous biothiols. [ABSTRACT FROM AUTHOR]

Biothiols such as cysteine (Cys), homocysteine (Hcy), and glutathione (GSH) play vital roles in various physiological and pathological processes. In this work, a BODIPY-based fluorescent probe XCN was synthesized from multi-step reactions. We first synthesized a BODIPY derivative with a cyano and a bromine moiety attached to the 8-diphenylaminophenyl substituent of BODIPY, followed by the reaction with p -aminothiophenol under basic condition. Interestingly, compound XCN was successfully obtained with the p -aminophenylthio moiety introduced into one of the α-positions of the pyrrolic units. This reaction may compose an efficient approach for synthesizing novel BODIPY derivatives with substituents attached to the pyrrolic unit without previously brominating it. XCN can be used as a fluorescence turn-on probe to selectively detect Cys and Hcy using the cyano group as the recognition site, with the p -aminophenylthio moiety left unreacted. XCN was found to be nearly nonfluorescent, and it exhibits only slight fluorescence enhancement when treated with GSH. However, upon interaction with Cys or Hcy, the fluorescence was enhanced by 1081 and 1126 folds, respectively. In addition, XCN exhibits good selectivity and sensitivity towards Cys and Hcy over GSH and other amino acids in a wide pH range from 2 to 10 in aqueous buffers. Furthermore, XCN was successfully used for imaging biothiols in living A549 lung cancer cells. [ABSTRACT FROM AUTHOR]

The selective and sensitive detection of zinc ions has been an important research topic because of the vital role played by zinc ions in numerous physiological activities, and fluorescent probes have emerged as effective and powerful tools for zinc detection because of their simplicity andcereal-time monitoring nature. In this work, with the purpose to improve the binding affinities and sensitivities of dipyrrin based fluorescent Zn 2+ probes, strongly coordinating pyridyl moieties were introduced into dipyrrins. Aroylation of 5-pentafluorophenyl and 5-unsubstituted dipyrromethanes with picolinoyl chloride afforded two corresponding dipicolinoyl dipyrromethanes, which were further oxidized with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) to afford the expected 5-pentafluorophenyl-substituted dipicolinoyl dipyrrin and a unique unexpected dipicolinoyl dipyrrolyl ketone, respectively. Both of these compounds exhibited noticeable fluorescence “turn-on” responses specifically to Zn 2+ over other metal cations, with fluorescence enhancements of 87 fold and 119 fold, respectively. However, because of the different substituents at the 5 positions and the different conjugation frameworks, distinct Zn 2+ sensing behavior was observed. For the 5-pentafluorophenyl-substituted dipicolinoyl dipyrrin, the sensing of Zn 2+ induced a color change from light orange to pink accompanied with enhanced red fluorescence. Whereas, the sensing of Zn 2+ by the dipicolinoyl dipyrrolyl ketone induced the color change from nearly colorless to bright yellow and enhanced green fluorescence. Based on high binding affinities and the dramatic spectral responses, both of the probes exhibit high sensitivities towards Zn 2+ with detection limits of 9.8 nM and 6.3 nM, respectively. In addition, fast responses within 10 s and wide applicable pH ranges are indicative of their potential applications as promising zinc probes. Finally, the 5-pentafluorophenyl dipicolinoyl dipyrrin was successfully applied to cell imaging in Hela cells, demonstrating its practical applicability. It is noteworthy that the single crystal structure of a Zn 2+ complex of the dipicolinoyl dipyrrolyl ketone was successfully analyzed by X-ray diffraction, which revealed an interesting tetranuclear Zn 2+ coordination structure. These results provide further insights into the design of highly sensitive Zn 2+ probes by introducing pyridyl moieties into dipyrrin platforms. [ABSTRACT FROM AUTHOR]

With the purpose to develop efficient dye-sensitized solar cells (DSSCs), a series of push-pull porphyrin dyes have been designed and optimized by introducing additional electron-donating diphenylamino and electron-withdrawing benzothiadiazole moieties. Electrochemical, photophysical and photovoltaic investigations indicate that the introduction of additional donors and acceptors can effectively extend the absorption spectra, resulting in better sunlight harvesting. However, the HOMO levels of the dyes are elevated by the additional donors, resulting in decreased driving forces for dye regeneration and decreased cell efficiencies. Upon coadsorption with 5 mM chenodeoxycholic acid (CDCA), the cell efficiencies can be elevated from 1.37% - 5.01% to 1.70% - 6.97%. Furthermore, based on the subtle absorption characteristics of the porphyrin dyes, we delicately designed a cocktail co-sensitization strategy using the solutions containing two of the porphyrin dyes as well as CDCA. Finally, a high photovoltaic efficiency of 8.6% was successfully achieved at an optimized molar ratio of 10:1 for the two porphyrin dyes. [ABSTRACT FROM AUTHOR]

A bidipyrrin nickel complex was synthesized in a high yield by oxidatively coupling between the ligands in the corresponding 2:1 (L:M) type of dipyrrin nickel complex, and further demetallation afforded the free bidipyrrin ligand. Interestingly, when treating the bidipyrrin nickel complex or the free bidipyrrin with FeCl 3 in CH 2 Cl 2 /MeOH, the symmetric di- α -methoxy bidipyrrin could be synthesized in a high yield, with two methoxy groups attached to the terminal pyrrolic α -positions. Moreover, the coordination of the unsubstituted and disubstituted bidipyrrins with Zn(OAc) 2 ·2H 2 O afforded two similar M 2 L 2 type of bidipyrrin helical complexes with different ligand conformations and different Zn⋯Zn distances of 5.353 and 3.357 Å, respectively. The difference in the conformations may be related to the electrostatic repulsions between the methoxy substituents. These results indicate that the dyes based on helical bidipyrrin zinc complexes with tunable structures and photophysical properties may be developed simply by modulating the terminal α -substituents. [ABSTRACT FROM AUTHOR]

Four alkoxy-wrapped push-pull porphyrin dyes containing the phenothiazine derived donor and the ethynylbenzoic acid acceptor have been designed, synthesized and used as sensitizers for fabricating efficient dye-sensitized solar cells (DSSCs). Branched or linear alkoxy chains were introduced to the ortho -positions of the meso- phenyl moieties to suppress the dye aggregation and charge recombination. The effect of alkoxy chains were investigated in the absence and presence of an additional electron-withdrawing benzothiadiazole unit. In the former cases, almost identical photovoltaic efficiencies of ∼8.3% were achieved for both the branched and the linear alkoxy chains, while in the latter cases, the planar benzothiadiazole unit induces serious dye aggregation and charge recombination, resulting in lower efficiencies of 6.46% and 7.50% for the linear and branched chains, respectively, even though broader absorption was achieved. The relatively higher efficiency achieved for the dyes with branched chains may be related to the better effect of suppressing the dye aggregation and charge recombination. Furthermore, the coadsorption approach was employed, and a highest efficiency of 9.62% was achieved for the dye that features branched chains and the benzothiadiazole unit. These results compose a novel approach for developing efficient DSSCs by combining the coadsorbent with a porphyrin dye containing both the additional benzothiadiazole acceptor and branched alkoxy chains. [ABSTRACT FROM AUTHOR]

From the simple one-pot Vilsmeier formylation of 9-diphenylaminoanthracence, mono-, di- and tri-formyl products were successfully synthesized and the yields for the individual products can be optimized by varying the equivalents of the Vilsmeier reagent and changing the reaction temperature. The four obtained aldehydes exhibit distinct optical properties, with the emission maxima varying in a large wavelength range of 455–593 nm, despite their similar structures. The intramolecular charge transfer effect can be effectively modulated by varying the numbers and positions of the formyl groups, resulting in the observed distinct optical properties. Based on the aldehydes, the corresponding boron-dipyrromethenes were also synthesized. Similarly, the intramolecular charge transfer effect and the optical properties can be effectively modulated by the numbers and positions of the boron-dipyrromethene moieties. To further modulate the intramolecular charge transfer effect and red shift the emission, the dimethoxy-substituted 9-diphenylaminoanthracence was also used for synthesizing the corresponding aldehyde and boron-dipyrromethene. Thus, full color emissions within the wavelength range of 455–704 nm were successfully achieved based on modulating the intramolecular charge transfer. [ABSTRACT FROM AUTHOR]

A combination of aggregation-induced emission and intramolecular charge transfer was achieved by using a triphenylamine analogue and a dicyanovinyl moiety as the electron donating and accepting units, respectively. Hence, we designed and synthesized a probe with a D-π-A framework as a near-infrared fluorescence turn-on probe for biothiols (cysteine and homocysteine). Owing to the remarkable intramolecular charge transfer effect as well as intramolecular rotations associated with the donor moiety, the probe exhibits extremely weak fluorescence, which becomes a good starting point for developing fluorescence “turn-on” probes. Upon reaction with cysteine or homocysteine utilizing the dicyanovinyl moiety, the intramolecular charge transfer character was weakened, and the reacting products were observed to aggregate in aqueous solutions, resulting in the aggregation-induced emission effect with red fluorescence at 651 and 656 nm, respectively. Hence, the probe could be used as a fluorescence “turn-on” sensor for cysteine and homocysteine, with the sensing time of less than 4 min and the detection limits of 8.4 μM and 5.7 μM towards cysteine and homocysteine, respectively. The probe could distinguish cysteine and homocysteine from glutathione. The sensing mechanism was systematically investigated by employing high resolution mass spectrometry, 1 H NMR and density functional theory calculations as well as checking the solvent viscosity dependent fluorescence, and thus the nucleophilic addition products, the intramolecular charge transfer character, and the aggregation-induced emission behaviour were clearly elucidated. It is noteworthy that the low cytotoxicity, the intrinsic aggregation-induced emission nature and near-infrared emissions enable the application of the probe in living cell imaging. [ABSTRACT FROM AUTHOR]

Abstract: Four novel naphthalimide-based dyes (D-1, D-2, D-3 and D-4) were synthesized and utilized as sensitizers in dye-sensitized solar cells (DSCs), in which the triphenylamine (TPA) or indoline groups, naphthalimide unit and carboxylic group were functionalized as electron donor, acceptor and anchoring group, respectively. The naphthalimide unit was employed as the π-conjugation ring and electron acceptor for effectively realizing intramolecular charge separation in the oxidized states. In the series of dyes, the LUMO orbital is delocalized mainly on naphthalimide moieties, especially on the carbonyl group. Consequently, the LUMO electrons are isolated from the carboxyl anchoring group (-CH2CO2H) due to the presence of the methylene group, which could suppress the electron injection efficiency from the excited dyes to the TiO2 conduction band, thus leading to the inferior efficiencies of 1.10, 1.18, 2.27 and 2.70%, respectively, even though they exhibit broad spectral response and high extinction coefficients. [Copyright &y& Elsevier]

In the past decades, porphyrin analogues have attracted increasing attention in light of their unique properties and potential applications in various areas. In this work, novel nonconjugated thiophene-embedded N -confused homoporphyrins 1 and 2 as well as a fully-conjugated N -fused homoporphyrin 3 have been prepared through acid-catalyzed condensation reactions followed by oxidation. Both 1 and 2 comprise two meso-sp3-carbon atoms. However, they are insensitive to the air or common oxidants. Single crystal X-ray diffraction analysis reveals that 2 adopts a highly distorted boat-like conformation, with the NH moieties of two pyrrolic units pointing outwards and an O atom attached to the α position of the N -confused pyrrole unit. As a result, hydrogen-bonded dimers are formed through the intermolecular hydrogen bonds between the lactam-like moieties. In contrast to the highly distorted structure of 2 , N -fused homoporphyrin 3 contains a unique 5,5,5–tricyclic fused ring, and thus demonstrates a relatively coplanar conformation except one inverted pyrrole unit. Because of the different structural characters, 3 exhibits F− binding behavior distinct from that of 1 and 2. [Display omitted] • Facile syntheses of stable thiophene-embedded N -confused homoporphyrins. • Partially and completely conjugated homoporphyrins modulated by oxidants. • Tunable fluoride binding behavior based on the different structures. [ABSTRACT FROM AUTHOR]

To fabricate efficient dye-sensitized solar cells (DSSCs), three porphyrin dyes XW65 − XW67 have been designed and synthesized using a bulky triphenylamine donor. Based on our previously reported dyes with a carbazole donor, a bulky triphenylamine unit was employed as the donor to synthesize XW65 with the aim to enhance the electron donating ability and suppress dye aggregation. As a result, XW65 shows enhanced photocurrent density (J sc) and open circuit voltage (V oc), affording a high efficiency of 9.02%. On this basis, XW66 was synthesized with a methyl group introduced into the carboxyphenyl acceptor to further suppress dye aggregation and improve the V oc , achieving an enhanced efficiency of 9.23% with improved V oc of 849 mV and J sc of 14.87 mA cm−2, which can be ascribed to the further suppressed dye aggregation and enhanced adsorption amount on the TiO 2 film induced by the additional methyl group. To further improve the J sc , a benzothiadiazole (BTD) unit has been introduced as the auxiliary acceptor to afford XW67 , which exhibits a strikingly red-shifted monochromatic photon-to-electron conversion efficiency (IPCE) onset wavelength of 830 nm, obtaining the highest J sc value of 15.83 mA cm−2 among the three dyes. Consequently, despite the sacrifice of V oc caused by the severe dye aggregation associated the extended conjugation framework, XW67 exhibits the highest efficiency of 9.43%. On this basis, cosensitization with WS-5 afforded elevated efficiencies of 10.07%, 10.38% and 10.13% for XW65 − XW67 , respectively, owing to the simultaneously enhanced J sc and V oc. These results indicate that it is effective to develop efficient DSSCs based on cosensitization of optimized porphyrin dyes containing a bulky triphenylamine donor, a methyl group on the carboxyphenyl acceptor, and an auxiliary electron acceptor. Image 1 • A strikingly red-shifted monochromatic incident photon to current conversion efficiency (IPCE) onset wavelength of 830 nm. • Better suppression of dye-aggregation and by bulky substituents on the donor and a methyl group on the carboxyphenyl acceptor. • The absorption drawbacks of the porphyrin dyes compensated by a broad band of the cosensitizer. • An efficiency 10.38% achieved with synergetically enhanced V oc and J sc. [ABSTRACT FROM AUTHOR]

Direct functionalization of meso -C 6 F 5 BODIPY with various enamines and amines at the pyrrolic α -position has been achieved by reacting the BODIPY with ethylamines in acetonitrile using BPO (benzoyl peroxide) as an additive under aerobic atmosphere at room temperature. The reaction modes of the products can be effectively modulated by the substituents on the ethylamines, affording three different types of products with enamine and amine moieties regioselectively attached at the pyrrolic α position and the para -position of the meso -C 6 F 5 group. The spectroscopic properties are effectively modulated by the ICT effect from the electron-donating enamino or amino groups to the electron-withdrawing BODIPY core and the pentafluorophenyl moiety, with the absorption and emission maxima varying in the ranges of 497–602 and 535–650 nm, respectively. These results compose an efficient method for synthesizing enamine and amine functionalized BODIPYs. A novel one-step approach using ethylamines for synthesizing enamine and amine functionalized BODIPYs with tunable absorption has been developed. Image 1 • A novel approach for synthesizing enamine functionalized BODIPYs. • Various reaction modes revealed by the crystal structures. • Tunable absorption modulated by the substituents on the ethylamines. [ABSTRACT FROM AUTHOR]

Three porphyrin sensitizers XW54 – XW56 containing a carbazole donor have been designed and synthesized by introducing a benzothiadiazole (BTD) unit as the auxiliary electron acceptor to extend the absorption spectra and/or bulky dihexyloxyphenyl groups into the carbazole unit to suppress dye aggregation and improve the photovoltage (V oc). The BTD unit incorporated in XW54 obviously broadens and red-shifts the absorption threshold to ca. 700 nm, as compared with that of 650 nm observed for XW1. Thus, XW54 exhibits a much broader monochromatic photon-to-electron conversion efficiency (IPCE) spectrum with an extremely red-shifted onset wavelength of 780 nm, resulting in a photocurrent density (J sc) of 11.60 mA cm−2, higher than that of XW1. Unfortunately, the V oc value was decreased owing to the more severe dye aggregation caused by the large conjugation framework induced by the presence of the BTD unit. As a result, XW54 shows an efficiency of 6.26%, slightly higher than that of 6.11% obtained for XW1. On the other hand, with the bulky dihexyloxyphenyl donor groups introduced to XW55 , a highest V oc of 860 mV was achieved, which can be ascribed to the efficient prevention of charge recombination and suppression of dye aggregation. Thus, XW55 -based cells exhibit an improved efficiency of 6.60%. On the basis of XW54 and XW55 , two bulky dihexyloxyphenyl groups and a BTD unit were simultaneously introduced to XW56 , affording a highest efficiency of 7.03%, with the J sc and V oc values of 12.5 mA cm−2 and 785 mV, respectively. These results compose a novel approach for developing efficient dye-sensitized solar cells (DSSCs) by simultaneously introducing bulky dihexyloxyphenyl groups and a benzothiadiazole unit, which may synergistically broaden the absorption spectra and suppress the dye aggregation, resulting in improved photocurrent and photovoltage. Image 1 • Absorption of porphyrins extended by introducing an auxiliary benzothiadiazole acceptor. • Better suppression of dye-aggregation and charge recombination by bulky substituents. • With synergetically enhanced V oc and J sc , an improved efficiency 7.03% was achieved. [ABSTRACT FROM AUTHOR]