bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Scalable Fabrication of Moisture Resistant Perovksite Solar Cells
Authors: Sunkara Mahendra Kumar
Published: February 2020

Organic-inorganic halide perovskites have created a breakthrough in the field of solar cells because of their low cost, low temperature processibility and  excellent optoelectronic properties. However, the instability of  organic-inorganic halide perovskites to moisture is currently a huge challenge in the  field of  perovskite solar cells and needs to be addressed to translate the perovskite technology from the laboratory bench to large scale industrial practice.  Currently, all the lab scale perovskite cells are fabricated in controlled glove box atmosphere with less than 1 % relative humidity to prevent their deterioration under moisture.

In this work, a novel concept of protecting the perovskite using a highly conductive composite of a layered material and a hole transporting polymer is presented.1 The excellent charge transport properties of the composite coating allow the  use of thick coating on the perovskite, creating extremely high length scales for moisture diffusion through composite. The composite coating developed in our work, could be extended to lead-free organometallic perovskites that are both moisture and oxygen sensitive. In addition, we also present our results on our lamination  approach for scalable assembly perovskite electrodes.2 The deposition of gold as a counter electrode for the lab scale perovskite cells is usually performed by thermal evaporation in a bell jar evaporator. This process is time consuming, energy intensive and not viable to scale up. Our approach involving lamination of individual electrodes, enables a much facile low cost process for fabricating perovskite solar cells.

Our results and observation on polymer composites as protective coatings for perovskite and on  laminating electrodes show high promise for the  scalability and low cost fabrication of perovskite cells under atmospheric conditions  (60 -70 % relative humidity).

References

 

Rajamanickam, N., Vendra, V.K., Kumari, S., Lavery, B.W.,  Ramachandran, K., Druffel, T., Sunkara, M.K. Moisture resistant methyl ammonium lead iodide perovskite solar cells. Submitted 2014.

Vendra, V.K., Kumari, S., Lavery, B.W., Rajamanickam, N., Druffel, T., Sunkara, M.K. Atmospheric roll to roll processing in perovskite solar cells. Submitted 2014
(Invited) Visible to Near-IR Nanoplasmonics in Inorganic Nanoparticles
Authors: Teranishi Toshiharu
Published: February 2020

A very important aspect of localized surface plasmons is the localization of an enhanced electromagnetic field around the NPs with very high spatial resolution (subwavelength) as well as the generation of hot electrons [1-6]. Here I present the unique plasmonic properties of non-stoichiometric copper sulfide (Cu7S4) nanodisks in the near IR (NIR) region by changing the hole density, structural anisotropy, and assembled structure [5-8]. As an example of plasmon-induced hot electron application, the visible to near-IR plasmon-enhanced catalytic activity of Pd hexagonal nanoplates for the Suzuki coupling reactions is also presented [9].

[1] Teranishi, T. et al. J. Mater. Chem.
2011, 21, 10238-10242. (Highlight)

[2] Yang, S.; Teranishi, T.; Gwo, S. et al. Nano Lett.
2010, 10, 632-637.

[3] He, C.-L.; Teranishi, T.; Gwo, S. et al. ACS Nano
2011, 5, 8223-8229.

[4] Li, C.; Sun, L.; Sun, Y.; Teranishi, T. Chem. Mater.
2013, 25, 2580-2590.

[5] Kanehara, M.; Teranishi T. et al. J. Am. Chem. Soc.
2009, 131, 17736-17737. (Spotlight)

[6] Furube, A.; Teranishi T. et al. Angew. Chem. Int. Ed.
2012,51, 2640-2642.

[7] Kanehara, M.; Teranishi, T. et al. Chem. Eur. J.
2012, 18, 9230-9238. (Frontispiece)

[8] Chen, L.; Teranishi, T. et al., submitted.

[9] Trinh, T. T.; Teranishi, T. et al., submitted.
(Invited) Photocatalytic Conversion of CO2 By H2o As an Electron Donor over Ag/ZnGa2O4/Ga2O3
Authors: Teramura Kentaro , Wang Zheng , Hosokawa Saburo , Tanaka Tsunehiro
Published: February 2020

Many research groups have already made significant progress in the field of water splitting to produce pure H2 and O2; in contrast, studies on the photocatalytic conversion of CO2 using H2O as a reductant are very few. This is because in such systems, overall water splitting occurs together with the reduction of CO2, resulting in H2 being the main product. Thus, it is very important to control the reduction of protons in the presence of both CO2 and H2O in order to achieve the reduction of CO2 by H2O. In this study, we found that Ag/ZnGa2O4/Ga2O3 exhibits a higher conversion of CO2 as compared to several photocatalysts reported previously. CO was evolved as the main product during the photocatalytic conversion of CO2 over 1 wt% Ag/ZnGa2O4/Ga2O3 under UV irradiation. H2 was simultaneously generated as the reduction product similar to CO, although the amount of H2 evolved was tiny as compared to that of CO. Expectedly, the evolution of O2 was observed together with those of CO and H2. After 7 h of photoirradiation, we obtained 815 μmol of CO, 65.7 μmol of H2, and 479 μmol of O2. The reaction could be carried out stably over three times, indicating that Ag/ZnGa2O4/Ga2O3 is very stable in water and under photoirradiation.
(Invited) In-Situ Raman Observation of Reaction Intermediates at Plasmon-Induced Water Oxidation Processes
Authors: Suzuki Kentaro , Yasuda Satoshi , Murakoshi Kei
Published: February 2020

Efficient multi-electron transfer reaction is important target for the developments on various energy technologies in future. Plasmon-induced photochemical reaction system should be one of the choices. Although it has been demonstrated that the excitation of localized surface plasmon resonance (LSPR) at Au metal nanoparticle on metal oxide semiconductors enable efficient water oxidation even under near-infrared light illumination, mechanis. In this work, we observed plasmon-induced water oxidation process using in-situ surface enhanced Raman scattering (SERS) measurement. Size-controlled metal nanodimer arrays was fabricated on titanium dioxide single crystalline by angle-resolved nanosphere lithography. The phonon vibrations of metal oxides were observed as the intermediate of water oxidation. The formation of the intermediate at relatively negative potential is attributed to the water oxidation process via holes generated by LSPR. We concluded that novel mechanisms exist for water oxidation on plasmonic electrode, compared with that at bulk Au electrode.
(Invited) A Unique Architecture Based on 1D Semiconductor/ Reduced Graphene Oxide/ Chalcogenide with Multifunctional Properties
Authors: Subramanian Vaidyanathan
Published: February 2020

Photoelectrochemical processes involving 1D architectures are reveling interesting optical and electronic properties that can often exceed the performance of their 0D counterparts.  A unique hetero-structured optoelectronic material (HOM), consisting of a reduced graphene oxide (RGO) layer with spatially distributed CdS, suspended by zinc oxide (ZnO) nanorods, is presented. The key features of this HOM are the assembly of the components in a manner so as to realize an effective integration between the constituents and the ability to modify the electronic properties of the RGO. For the first time, the location of RGO (as a suspended layer) along with the tuning of its charge transport properties (n-/p- type) and its influence on the photo(electro)chemical processes has been examined systematically using this ZnO/RGO/CdS HOM as a case study.

The n-RGO interlayer facilitates >100% increase in the photocurrent density and 25% increase in the photodegradation of a dye, demonstrating its multifunctionality. At 3.2 mA/cm2, this HOM architecture helps to achieve the highest photocurrent density utilizing ZnO, RGO, and CdS as building blocks in any form. The work assumes significance, as (i) other one dimensional (1D) oxides/chalcogenides or 1D oxides/dyes may be designed with similar architectures, (ii) HOMs with tunable optical absorbance and charge transport properties could be realized, and (iii) related application areas (e.g., sensing or solar fuel generation) should be greatly benefited.
Plasmon Enhanced Photovoltaic Performance in Graphene Oxide-TiO2 Composite Based Dye-Sensitized Solar Cells
Authors: Agarwal Radhe , Sahoo Satyaprakash , Katiyar Ram S.
Published: February 2020

Dye sensitized solar cells (DSSCs) have engendered great research interest with promising potentials in solar cell technology for their high power conversion efficiencies. In this study, we report a plasmon enhanced reduced graphene oxide (RGO)-TiO2 nanocomposite electron injection layer towards the improved performance of DSSCs. Graphene oxide was synthesized using modified Hummer's method and further treated with hydrazine hydrate to obtain reduced graphene oxide (RGO). Structural and morphological properties of as synthesized RGO, RGO- TiO2 and RGO-TiO2-Au nanopaticle (Au NP) composites were investigated using Raman spectroscopy and ultra-high resolution transmission electron microscope (UHRTEM). Raman mapping was performed to further characterize the composite photoanodes.. Photovoltaic performance of DSSC containing composite photoanodes were studied, on keeping the RGO concentration constant and varying the Au NP concentration. A systematic increment in the short circuit current density was noticed while the open circuit voltage (VOC ~ 0.72 V) of DSSC was observed to be constant by increasing Au NP concentration up to an optimal value, probably due to the combined effect of slight rise in quasi-Fermi level and higher carrier transport rate in the resultant composite. Thus, a significant enhancement in the overall photovoltaic performance was observed in DSSCs with RGO- TiO2-Au NP composite photoanode.
Synthesis of the Soluble Precursors of Tetrabenzoporphyrins and Their Application to Organic Field Effect Transistor Based on the Solution Process
Authors: Okujima Tetsuo
Published: February 2020

Alkyl-substituted and small-ring-fused bicyclo[2.2.2]octadiene (BCOD) fused porphyrins were synthesized by tetramerization method of the corresponding BCOD-fused pyrroles, which were obtained by the Diels–Alder reaction of trans-1,2-bis(phenylsulfonyl)ethylene with the appropriate 1,3-cyclohexadienes, followed by the Barton–Zard reaction. These soluble precursors were converted into tetrabenzoporphyrin (TBP) by heating at 180–230 °C depending on the structure of BCOD moiety. Organic field effect transistors based on TBP were fabricated by thermal conversion after spin-coating of the precursors to show good carrier mobility of 10−6–100 cm2 V−1 s−1.
Porphycene-Diketopyrrolopyrrole Conjugates As p-Type Organic Solar Cell Materials
Authors: Kuzuhara Daiki , Okabe Takuya , Suzuki Mitsuharu , Aratani Naoki , Yamada Hiroko
Published: February 2020

Porphycene is a constitutional isomer of porphyrin. Porphycene has a lower LUMO level and smaller HOMO-LUMO difference than porphyrin since its molecular symmetry is lower than that of porphyrin.
1
These properties have allowed us to explore the possible applications of porphycenes in the fields of photodynamic therapy (PDT), photoinactivation of viruses and bacteria, protein mimicry, nonlinear optics, and catalysis. Recently, we have focused on the porphycene using as the semiconducting materials for organic solar cell (OSC). OSC materials require for the absorption covering the visible to NIR regions and appropriate HOMO and LUMO energy levels. In this presentation, we have designed, synthesized and properties of the porphycene–diketopyrropyrrole conjugate (Pc–DPP) though ethynyl linkages for the OSC as p-type materials. The absorption of the DPP unit appears at around 450-550 nm, while porphycene has an absorption valley around 400-550 nm. The combination of DPP and porphycene via ethynyl linkages is expected to generate absorption covering the visible to NIR regions of the spectrum. We have measured absorption spectra of Pc–­DPP and 2,7,12,17-tetrahexylporphycene (THPc) as reference compound in thin-film on glass substrate. THPc has strong Soret band at 400 nm and Q-bands around 550 to 700 nm. On the other hand, as the result of the connection with porphycene and DPP units, Pc–DPP has broad absorption covering the visible to near in-fared regions.  Based on these optical characters, we have fabricated bulk heterojunction (BHJ) OSC by solution process with Pc–DPP as a p-type material and PC61BM as an n-type material. The active layer of the mixture of Pc–DPP and PC61BM with 0.1% 1,8-diiodooctane containing chloroform was deposited on the PEDOT:PSS-treated ITO substrate by spin coating and then calcium and aluminum electrode were deposited on the active layer by vacuum process. After optimized the device conditions, we achieved the PCEs of 1.4% (J
sc = 4.88 mA cm-2, V
oc = 0.81 V and FF = 0.37). We will also report the evaluations of film structures of these devices by AFM and XRD measurements.
Efficient Combination of Porphyrins and Thiophene Derivatives for Photovoltaics
Authors: Langa Fernando , de la Cruz Pilar , Arrechea Susana , Aljarilla Ana
Published: February 2020

Mimicking the photosynthesis, where chlorophylls absorb light for energy conversion, porphyrin and their derivatives can be suited as panchromatic photosensitizers being excellent building blocks in the construction of molecular architectures for light harvesting. Thus, porphyrins are among the most significant types of sensitizers for Dye Sensitized Solar cells (DSSCs) showing record breaking performances as high as 13%. However, utilization of porphyrins as active material in solution-processed BHJ has been scarce despite the natural tendency of porphyrins to form aggregates by π-π stacking and then favour intermolecular interactions and, consequently, the efficiency of the device.

In this lecture, we will present the synthesis and characterization of novel Porphyrin derivatives where the porphyrin is covalently linked to different thiophene-based moieties. The photophysical properties of these novel conjugates, as well as their application in photovoltaic devices (DSSCs and BHJ OPVs) will also be presented.
Charge Generation, Regeneration and Recombination in Di-Chromophoric Carbazole-Thiophene-Porphyrin-Sensitised Solar Cells
Authors: Mozer Attila Janos
Published: February 2020

Porphyrins are among the best performing dyes for their application in dye-sensitized solar cells. However, light harvesting efficiencies between the Soret and Q bands of most simple porphyrins are limited, especially when thin electrodes or electrodes with low surface area are used. Filling the absorption gap is an important objective to further enhance their efficiency, in addition to extending their absorption band edge to better match the solar spectrum. 

In this work, the absorption gap between the Soret and Q bands is filled using a multi-chromophoric approach following the synthetic strategy we have developed earlier (J. Am. Chem. Soc.
2009, 131, 15621-15623; J. Mater. Chem. A
2014, 2, 16963-16977). Three new porphyrin dyes with carbazole-fused thiophene chromophores attached to the porphyrin core using a non-conjugated phenylethenyl linker are synthesised. When attached to TiO2, an almost complete filling of the absorption gap within the 450 nm to 500 nm is achieved, which leads to doubling of the short circuit current density using the Co2+ / Co3+ electrolyte. In addition, the electron lifetime has significantly improved contributing to increased power conversion efficiency of 4.7%. Particularly significant result is the nearly 100% absorbed photon to collected electron efficiency at wavelengths dominated by the side chain absorption, suggesting the promise of the multi-chromophoric dye design using the non-conjugated approach.

 Detailed transient absorption and spectro-electrochemical investigations reveal a significant acceleration of dye cation regeneration kinetics in carbazole-porphyrin dyads attached to TiO2. This is attributed to a picosecond to microsecond intramolecular hole transfer from the porphyrin cation to carbazole, followed by a fast reduction of the carbazole cation by the electron donor redox mediator dissolved in the electrolyte. Such increase of the turnover rates without affecting the final electrochemical potential of the photo-generated species is promising for a variety of photo-electrochemical energy conversion processes, including solar cells and solar fuels.
Synergistic Interaction of Phthalocyanines and Semiconductor Quantum Dots for Advanced Co-Sensitized Solar Cells
Authors: Sastre-Santos Angela , Blas-Ferrando Vicente M. , Ortiz Javier , Sánchez Rafael S. , González-Pedro Maria Victoria , Fernández-Lázaro Fernando , Mora-Seró Iván
Published: February 2020

Quantum dots (QDs) are among potential key players in the next generation of photovoltaic devices [1] due to their low-cost solution-phase processability, large absorption cross sections, a spectrally tunable absorption onset (achieved via the quantum size effect), and enhanced multiple exciton generation or carrier multiplication.[2] After the first report on a certified QD solar cell, a remarkable progress has been reached just in a couple of years obtaining certified power conversion efficiencies (PCEs) approaching 9%.[3]

On the other hand, phthalocyanines (Pcs) are outstanding dye candidates in dye sensitized solar cells (DSSCs) due to their high extinction coefficient in the infrared spectral region and to their high thermal and chemical stabilities.[4] Pcs incorporated in DSSCs have achieved PCEs as high as 6.4 %,[5] still far away of the 12.75% PCE obtained by porphyrins, their closest relatives. An elegant strategy to improve the light-harvesting ability of the Pcs is the binding, either covalent or supramolecular, to a complementary chromophore, such as QDs, able to undergo efficient electron transfer to the charge injecting system. However, the chemical combination of Pc rings to QDs has hardly been explored probably due to the difficulties to synthesize Pcs with the adequate anchoring groups.

Herein, we will report our more recent results related with the synthesis of different unsymmetrically substituted phthalocyanines containing sulphur atom (see Figure 1 as example) and the improvement in efficiency of QD solar cells through their co-sensitization with phthalocyanines.[6]

Acknowledgements. This work has been supported by the Spanish Ministerio de Economía y Competitividad, Generalitat Valenciana and the European FEDER funds (grants CTQ2011-26455, PROMETEO 2012/010 and ISIC/2012/008)

Figure 1. Chemical structure of a disulfide substituted bisphthalocyanine

Figure 1
Electroactive Porphyrinic Metal-Organic Framework Materials
Authors: Hupp Joseph T.
Published: February 2020

We have been developing porous metal-organic framework materials using metalloporphyrins as building blocks. These crystalline materials can be configured in thin-film form on conductive glass electrodes via automated electrophoretic deposition, direct solvothermal synthesis, or automated, programmable layer-by-layer synthesis. They show intriguing photophysical, photochemical, and electrochemical behavior, including long-range, directional energy (exciton) transport, redox conductivity, and electrocatalysis. A few of our newest findings will be presented.
Indium Porphyrin Frameworks: An Efficient Photocatalytic Platform for Organic Synthesis
Authors: Zhang Jian
Published: February 2020

Porphyrinic metal-organic frameworks (PMOFs) are a class of hybrid materials consisting of metal-ion clusters bound by porphyin based organic ligands.  Porphyrinic ligands are of particular interest due to their unique photo-, electro-, and catalytic properties. In addition, porphyrins offer a rare example of a four-fold axis of symmetry in organic ligands which is highly desirable for designing new MOF architectures.  Conventional porphyrin ligands for MOF synthesis contain two or four terminal carboxy groups for metal binding.  However, many of these structures require an additional “pillar” molecule  in order to form 3D porous structures, which inherently increases the complexity of the crystallization process. To overcome this, one strategy in ligand design is to maintain the high symmetry and rigidity in the organic linker, yet increase the number of carboxy binding sites, which in effect renders the porphyrinic ligand “self-pillaring.” This presentation will focus on the structural characterization of these novel porphyrinic MOF architectures. In particular, the synthesis and photocatalytic properties of a novel In-based porphyrinic MOF will be discussed in detail. The mechanistic study of the catalytic activity will also be presented.
Nanoscale Assembly & Chemical Modification of Carbon Nanotubes & Graphene
Authors: Kim Sang Ouk
Published: February 2020

Graphitic carbon nanomaterials, including fullerene, carbon nanotubes and graphene, attract enormous research attention for their outstanding material properties along with molecular scale dimension. The optimized utilization of those graphitic carbons in various application fields inevitably requires the subtle controllability of their structures and properties. In this regard, the substitutional doping of heteroelements, such as Boron or Nitrogen, into the graphitic plane offers robust and reliable solution. In this presentation, our recent research achievements associated to nanoscale molecular scale assembly of B- or N-doped graphitic carbon nanomaterials will be presented [1,2]. In our approach, graphitic carbons can be efficiently processed into various three-dimensional structures via self-assembly principles. For instance, vertical carbon nanotube forest can be grown from graphene film surface to constitute three-dimensional carbon hybrid materials [3]. Those carbon assembled structures with extremely large surface and high electro-conductivity are potentially useful for catalysis, energy storage and so on. Aqueous dispersion of graphene oxide shows liquid crystalline phase, whose spontaneous molecular ordering is useful for display or fiber spinning [4,5]. In addition, the substitutional doping of graphitic carbon with B- or N- was achieved via pre- or post-synthetic treatment. The resultant chemically modified graphitic carbons with tunable workfunction and remarkably enhanced surface activity could be employed for organic solar cells, organic light emitting diodes, nanocomposites for improved functionalities and device performances [6,7].

References

S. H. Lee, D. H. Lee, W. J. Lee and S. O. Kim, Adv. Funct. Mater. 21, 1338 (2011).

U. N. Maiti, W. J. Lee, J. M. Lee, Y. T. Oh, .J. Y. Kim, J. E. Kim, J. Shim, T. H. Han and S. O. Kim, Adv. Mater. 26, 40 (2014).

D. H. Lee, J. E. Kim, T. H. Han, J. W. Hwang, S. Jeon, S.-Y. Choi, S. H. Hong, W. J. Lee, R. S. Ruoff and S. O. Kim, Adv. Mater. 22, 1247 (2010).

J. E. Kim, T. H. Han, S. H. Lee, J. Y. Kim, C. W. Ahn, J. M. Yun and S. O. Kim, Angew. Chem. Int. Ed. 50, 3043 (2011).

J. Y. Kim and S. O. Kim, Nat. Mater. 13, 325 (2014).

L. Lu, T. Xu, W. Chen, J. M. Lee, Z. Lou, I. H. Jung, H. I. Park, S. O. Kim and L. Yu, Nano Lett. 13, 2365 (2013).

D. J. Li, U. N. Maiti, J. W. Lim, D. S. Choi, W. J. Lee, Y. T. Oh, G. Y. Lee and S. O. Kim, Nano Lett. 14, 1228 (2014).
Osmotic Pressure Effects Reveal a Specific Dehydration-Induced Hydrophobic Electron Transfer Structure Comprising Cytochrome C and Cytochrome C Oxidase
Authors: Ishimori Koichiro
Published: February 2020

In the mitochondrial respiratory chain, Cytochrome c oxidase (CcO) accepts electrons from Cytochrome c (Cyt c) to reduce molecular oxygen. Previous studies showed that the complex formation of Cyt c with CcO is characterized by the positive entropy change, suggesting the dehydration from hydrophobic residues, but no experimental evidence of such dehydration has been reported. To confirm the dehydration during the complex formation between Cyt c and CcO, we focused on the partial molar volume change of protein (ΔV
W) for the complex formation, which reflects the volume of dehydrated water molecules. ΔV
W is correlated with the osmotic pressure (π) dependence of the K
d.  

Osmotic pressure was increased by addition of sugars or polyols having no specific interactions with proteins and K
d was estimated by the Michaelis-Menten analysis of the steady state kinetics for the electron transfer from Cyt c to CcO.

As Figure 1 shows, the K
d value is decreased with increasing the osmotic pressure, corresponding to the negative ΔV
W of – 300 ± 78 mL mol-1. Assuming that the partial molar volume change of one hydrated water molecule around hydrophobic residues would be－17.5 mL mol-1, the volume change we obtained here corresponds to the dehydration of 17 ± 4 water molecules. Considering that the entropy change from the dehydration (dehydΔS) of one water molecule was estimated to be 5.5 JK-1mol-1, dehydΔS of 17 water molecules corresponds to ~90 JK-1mol-1, which is about 75% of total entropy change for the Cyt c-CcO complex formation. The dehydration is, therefore, one of the major factors to increase the entropy for the complex formation.

To identify the dehydration sites from hydrophobic residues in the interaction site for CcO on Cyt c, we mutated Ile11 or Ile81, hydrophobic amino acid residues in the interaction site for CcO [1], to Ala, an amino acid residue having a smaller side chain and less number of the hydrated water molecules. As clearly illustrated in Figure 1, the slope of the osmotic pressure dependence of K
d for the Ile mutant is less steep than that for the wild type protein. The estimated numbers of the dehydrated water molecules were reduced to 13 ± 3 and 8 ± 2 for the Ile11 and Ile81 mutants, respectively. The reduced numbers of the dehydrated water molecules in these Ile mutants indicate that the hydrated water molecules around Ile11 and Ile81 were expelled to the solvent in the complex formation between Cyt c and CcO.

In conclusion, we successfully identified that about 17 water molecules are dehydrated in the Cyt c-CcO complex formation and the primary dehydration sites are Ile11 and Ile81. Such dehydration from the hydrophobic residues can be a major factor to increase the entropy, facilitating the complex formation and the electron transfer from Cyt c to CcO.

References

[1] Sakamoto, K. et al., PNAS., 108, (2011), 12271

  
       

Figure 1
Porphyrins and Other Chromophores with Antioxidant Substituents
Authors: Hill Jonathan P. , Jin Shangbin , Labuta Jan , Ishihara Shinsuke , Ariga Katsuhiko
Published: February 2020

Oxoporphyrinogens1,2 are a class of porphyrinoid generally containing a tetrapyrrole macrocycle with oxo or oxocyclohexadienylidene groups substituted at their periphery. They are unique in that their physical structures are coupled to their electronic structures depending on the electrochemical state of the molecule. Variations in electronic conjugation over the core tetrapyrrole and substituents affect electronic absorptive properties. Using these features we have developed oxoporphyrinogens as molecular switching elements and for sensing applications involving chemical species including water and chiral compounds.3,4 Tetrapyrroles with two or four conjugating substituents as well as corroles have been prepared and investigated for their properties depending on tautomerism,5 guest binding by hydrogen bonding and structural changes due to photoredox processes. The syntheses and mechanisms of action of the switching and sensing properties will be presented and discussed. Oxoporphyrinogens were developed from a porphyrin substituted with antioxidant 2,6-di-t-butylphenol groups. We have also investigated the synthesis and properties of other similarly substituted chromophores and will discuss some of the relevant properties.6,7

References

(1) F. D’Souza, N. K. Subbaiyan, Y. Xie, J. P. Hill, K. Ariga, K. Ohkubo, S. Fukuzumi, J. Am. Chem. Soc. (2009) 131, 16138–16146. (2) J. P. Hill, I. J. Hewitt, C. E. Anson, A. K. Powell, A. L. McCarthy, P. Karr, M. Zandler, F. D’Souza, J. Org. Chem. (2004) 69, 5861–5869. (3) S. Ishihara, J. Labuta, T. Šikorský, J. V. Burda, N. Okamoto, H. Abe, K. Ariga, J. P. Hill, Chem. Commun. (2012) 48, 3933–3935 (4) A. Shundo, J. Labuta, J. P. Hill, S. Ishihara, K. Ariga, J. Am. Chem. Soc. (2009) 131, 9494–9495; J. Labuta, S. Ishihara, A. Shundo, S. Arai, S. Takeoka, K. Ariga, J. P. Hill, Chem. Eur. J. (2011) 17, 3558–3561. (5) Y. Xie, J. P. Hill, A. L. Schumacher, P. A. Karr, F. D’Souza, C. E. Anson, A. K. Powell, K. Ariga, Chem. Eur. J. 2007, 13, 9824–9833. (6) J. P. Hill, N. K. Subbaiyan, F. D’Souza, Y. Xie,
 
S. Sahu, N. M. Sanchez-Ballester, K. Ariga, Chem. Commun. (2012) 48, 3951–3953. (7) A. Jana, H. Gobeze, M. Ishida, T. Mori, K. Ariga, J. P. Hill, F. D’Souza Dalton Trans. (2014) in press, DOI: 10.1039/C4DT03157A.
New Scaffolds for the Delivery of Protease Sensitive Photosensitizer Prodrugs
Authors: Bouilloux Jordan , Sekkat Nawal , Babic Andrej , Lange Norbert
Published: February 2020

Photodynamic therapy (PDT) is a non-invasive technique for the treatment of several diseases such as microbial infections, rheumatoid arthritis, age-related macular degeneration, and cancer. However, this therapeutic approach suffers from several drawbacks associated with the administration of conventional photoactive compounds, such as skin photosensitization, unfavorable physicochemical properties, and finally low selectivity for the diseased tissue.

To improve the selectivity of conventional photosensitizers (PS) we have developed quenched PS prodrugs based on poly (L) lysine and cyclopeptidic carriers that target up-regulated proteolytic activities related to certain diseases, including cancer. These compounds are based on energy transfer between multiple copies of PSs tethered to oligomeric carriers via protease sensitive peptide linkers, thus, silencing any photodynamic activity. Proteolytic digestion of the peptide results into the release of a PS peptidyl fragment thereby restoring photodynamic activity. These conceptually new compounds act through several complementary targeting mechanisms. They 1) accumulate preferentially in pathologic tissue, 2) target pathology-related proteases, 3) are taken-up selectively by abnormal cells, and 4) being selectively irradiated in the diseased area. Using poly(L)lysine based carriers we have designed quenched PS prodrugs that effectively image and treat prostate cancer. Unfortunately, due to their undefined chemical structure these prodrugs are not suitable for clinical use.

Therefore, we have proceeded to design defined quenched PS prodrugs based on a cyclopeptidic carrier vehicle. These novel prodrugs have a constrained secondary structure with a defined molecular weight and predefined number and positions of the PS peptide conjugates. Preliminary evaluation demonstrated that these compounds show the expected tendencies, i.e. increased quenching with increasing number PSs per carrier and digestion by recombinant target proteases including, uPA, Cathepsin B and MMPs. The influence of different design parameters has been investigated in vitro and in vivo. For instance, we have shown that high molecular weight PEGylation is unfavorable for high quenching efficiencies.

Furthermore, we have characterized quenched PS prodrugs with respect to activation and phototoxicity in human cancer cell lines with special emphasis on prostate and ovarian cancer. Furthermore, preliminary optimization of pharmacokinetics and biodistribution will be carried out in the chorioallantoic membrane model inoculated with tumor spheroids.

Finally, might be possible to translate the gained knowledge into other scientific fields such as for instance the improved drug delivery of chemotherapeutics using cyclopeptidic protease sensitive carriers or the targeted imaging of GLP-1 receptors through the multimerization of targeting moieties onto the cyclopeptidic scaffold.
Origin of Reactivity Differences Between Heme and Nonheme Iron(III)-Hydroperoxo Complexes
Authors: de Visser Sam
Published: February 2020

The cytochromes P450 are important enzymes in human physiology involved in biodegradation and biosynthesis pathways in the body.1,2 They generally react with substrates in a catalytic cycle that includes two reduction and two proton transfer steps to form a high-valent iron(IV)-oxo heme cation radical species called Compound I.3 High-valent metal-oxo species are common intermediates in enzymatic processes and have been identified in heme as well as nonheme iron enzymes. Compound I is a versatile and efficient oxidant that is known to react with substrates via aliphatic hydroxylation, epoxidation, aromatic hydroxylation, alkane dehydrogenation, N-dealkylation, sulfoxidation etc. Many of these processes involve the reduction of Compound I; unfortunately, Compound I is short-lived, which makes experimental studies in the field complicated. To overcome this, we have done computational studies on enzymatic heme enzymes as well as synthetic model porphyrins and phthalocyanines with the aim to gain insight into the intricate details of the oxidant to gain insight into the electrochemistry of the active species and the catalyzed reaction mechanism. In the past, these studies assisted experimental efforts in the field and made predictions of reaction mechanisms. It was, for instance, shown that the precursor of Compound I in the catalytic cycle, namely Compound 0, is catalytically inactive for epoxidation, sulfoxidation and aromatic hydroxylation reactions. However, in a recent twist of events, our group showed that nonheme iron(III)-hydroperoxo can be catalytically active.4 To understand the difference in activity between heme and nonheme iron(III)-hydroperoxo, we studied the mechanisms of aromatic hydroxylation and haloperoxidation. These combined experimental and computational studies gave insight into the effects of axial and equatorial ligands on the chemical and catalytic properties of Compound 0 and Compound I. In addition, our studies established the effects of environmental perturbations on the properties and reactivities of Compound I, including hydrogen bonding interactions and secondary sphere amino acid interactions.

References:

P. R. Ortiz de Montellano (Ed.), Cytochrome P450: Structure, Mechanism and Biochemistry. 3rd ed.; Kluwer Academic/Plenum Publishers, New York, 2005.

K. M. Kadish, K. M. Smith, R. Guilard (Eds.), Handbook of Porphyrin Science. World Scientific Publishing Co., New Jersey, 2010.

S. P. de Visser, D. Kumar (Eds.), Iron-containing enzymes: Versatile catalysts of hydroxylation reaction in nature. RSC Publishing, Cambridge (UK), 2011.

A. S. Faponle, M. G. Quesne, C. V. Sastri, F. Banse, S. P. de Visser, Chem. Eur. J. 2014, in press.
Porphyrin-Functionalized Porous Silicon Nanoparticles for Photodynamic Therapy
Authors: Secret Emilie , Maynadier Marie , Gallud Audrey , Chaix Arnaud , Bouffard Elise , Gary-Bobo Magali , Marcotte Nathalie , Mongin Olivier , El Cheikh Khaled , Hugues Vincent , Auffan Melanie , Frochot Céline , Morère Alain , Maillard Philippe , Blanchard-Desce Mireille , Sailor M. J. , Garcia Marcel , Durand Jean-Olivier , Cunin Frederique
Published: February 2020

Nanomaterials offer the potential for minimally invasive and focal therapies to reduce side-effects associated with systemic administration of anticancer drugs. Clinical treatment involving photodynamic therapy is particularly attractive since it allows spatial and temporal control of the production of highly cytotoxic singlet oxygen and reactive oxygen species through local excitation of a photosensitizer.

Porous silicon nanoparticles (pSiNP), obtained by electrochemical etching of crystalline silicon followed by ultrasonic treatment, are particularly attractive for nanomedicine because they are bioresorbable in vivo and their degradation product, silicic acid, is non-toxic. In addition pSiNP display intrinsic optical properties (luminescence) deriving from their semi-conductive nature, very usefull for imaging.

Here we will present simple photosensitizer/pSiNP systems based on a porphyrin derivative covalently attached to the nanoparticle, and demonstrate imaging and PDT in vitro under one (OPE) and two photon excitation (TPE) conditions. We will describe the preparation of the biodegradable pSiNP, the chemical functionalization of pSiNP with the photosensitizer by the covalent anchoring of a porphyrin into the porous silicon matrix using a new type of conjugation chemistry, as well as their functionalization with cancer cell targeting species. The targeting and photodynamic efficiency of the described formulations on various cancer cell lines will be presented. We will show that both types of excitation, OPE and TPE, lead to cell death through different excitation pathways.

Emilie Secret, Marie Maynadier, Audrey Gallud, Arnaud Chaix, Elise Bouffard, Magali Gary-Bobo, Nathalie Marcotte, Olivier Mongin, Khaled El Cheikh, Vincent Hugues, Mélanie Auffan, Céline Frochot, Alain Morère, Philippe Maillard, Mireille Blanchard-Desce, Michael J. Sailor, Marcel Garcia, Jean-Olivier Durand and Frédérique Cunin,Two-Photon Excitation of Porphyrin Functionalized Porous Silicon Nanoparticles for Photodynamic Therapy Adv. Mater.,
2014, Online. DOI: 10.1002/adma.201403415.

Emilie Secret,

Marie Maynadier,

Audrey Gallud, Magali Gary-Bobo, Arnaud Chaix, Emmanuel Belamie, Philippe Maillard,

Michael J. Sailor,

 Marcel Garcia,

Jean-Olivier Durand,

Frédérique Cunin, Anionic porphyrin-grafted porous silicon nanoparticles for photodynamic therapy,Chem. Commun., 2013, 49(39), 4202-4204. DOI: 10.1039/C3CC38837A
Optoelectronic Properties of Metal-Free Binary Porphyrin Nanostructures
Authors: Mazur Ursula , Borders Bryan , Hipps K W
Published: February 2020

Nanostructures fabricated from tetrapyridylphenyl porphyrin (TPyP) and tetrasulfonatophenyl porphyrin (TSPP) in a 1:1 ratio are conducting and also photoconducting.     I-V curves for the nanorods (in a vacuum environment) were collected in the dark and with (405, 473, and 633 nm) illumination. These wavelengths fall within the absorption spectrum of the porphyrin solid and allow determination of an action spectrum.  With illumination, the nanorods show a sharp increase in conductivity followed by a slow increase in conductivity over time until a saturation photocurrent is reached. Once the light is off, the current decays slowly over time.  This is referred to as persistent photoconductivity.  The TPyP:TSPP nanorods exhibit an increase in photo-conductivity with an applied positive gate voltage and a decrease with an applied negative gate voltage, consistent with the electrons acting as the primary mobile charge carrier.  Quantification of the persistent photoconductive behavior and a model for electron transport through the nanostructures will be presented.
Heat-Treating Self-Assembled Metalloporphyrin As Electrocatalysts for Oxygen Reduction Reaction
Authors: Song Yujiang
Published: February 2020

Proton exchange membrane fuel cell (PEMFC) is a clean and efficient energy-conversion technology, which has been widely expected to replace internal combustion engine to drive future vehicles. A crucial component of PEMFC is Pt/C electrocatalysts that are composed of 2-5 nm semi-spherical Pt particles supported on carbon. However, conventional Pt/C electrocatalysts confront the high costs, limited supply, low activity, easy poisoning and poor durability, preventing PEMFC from commercialization. To resolve these issues, new generation of electrocatalysts have to be rationally designed and synthesized. This talk will focus on the creation of non-precious metal electrocatalysts by heat-treating self-assembled metalloporphyrin molecules and the electrochemical performance toward oxygen reduction reaction. This work was partially supported by the National Key Basic Research Program of China (973 Project 2012CB215500), and National Natural Science Foundation of China (NSFC 21003114, 21103163 and 21373211).

References

[1] Y. J. Song, R. M. Garcia, R. M. Dorin, H. R. Wang, Y. Qiu, J. A. Shelnutt, Angew. Chem. Int. Ed.
2006, 45, 8126.

[2] Y. J. Song, R. E. Haddad, S. L. Jia, S. Hok, M. M. Olmstead, D. J. Nurco, N. E. Schore, J. Zhang, J. G. Ma, K. M. Smith, S. Gazeau, J. Pecaut, J. C. Marchon, C. J. Medforth, J. A. Shelnutt, J. Am. Chem. Soc.
2005, 127, 1179.

[3] Y. J. Song, R. M. Garcia, R. M. Dorin, H. R. Wang, Y. Qiu, E. N. Coker, J. E. Miller, J. A. Shelnutt, Nano Lett.
2007, 7, 3650.

[4] Y. J. Song, R. M. Dorin, R. M. Garcia, Y. B. Jiang, H. R. Wang, P. Li, Y. Qiu, F. van Swol, J. E Miller, J. A. Shelnutt, J. Am. Chem. Soc.
2008, 130, 12602.

[5] Y. J. Song, M. A. Hickner, S. R. Challa, R. M. Dorin, R. M. Garcia, H. R. Wang, Y. B. Jiang, P. Li, Y. Qiu, F. van Swol, C. J. Medforth, J. E. Miller, T. Nwoga, K. Kawahara, W. Li, , J. A. Shelnutt, Nano Lett.
200
9, 9, 1534.

[6] R. M. Garcia, Y. J. Song*, R. M. Dorin, H. R. Wang, A. M. Moreno, Y. B. Jiang, Y. M. Tian, Y. Qiu, C. J. Medforth, E. N. Coker, F. van Swol, J. E. Miller, J. A. Shelnutt*, Phys. Chem. Chem. Phys,
2011, 13,4846.

[7] W. F. Si, J. Li, H. Q. Li, J. Yin, H. Xu, X. W. Guo, T. Zhang, Y. J. Song*, Nano Research
2013, 6, 720.

[8] Y. Xie, H. Q. Li, C. Z. Tang, S. S. Li, J. Li, Y. Lv, X. M. Wei, Y. J. Song*, J. Mater. Chem. A
2014, 2, 1631.

[9] Y. Xie, C. Z. Tang, Z. Q. Hao, Y. Lv, R. X. Yang, X. M. Wei, W. Q. Deng, A. J. Wang, B. L. Yi, Y. J. Song*, Faraday Discuss.
2014, DOI: 10.1039/C4FD00121D.

[10] S. S. Li, H. Q. Li, Y. S. Zhang, R. M. Garcia, J. Li, Y. Xie, J. Yin, M. R. Li, J. H. Wang, J. A. Shelnutt, T. Zhang, Y. J. Song*, J. Mater. Chem. A
2014, DOI:10.1039/c3ta10406k.
Toward True Carbaporphyrinoids - Contraction of Benziporphyrins
Authors: Szyszko Bartosz , Kupietz Kamil , Hurej Karolina , Kedzia Aneta , Latos-Grazynski Lechoslaw
Published: February 2020

A replacement of a single pyrrole of meso-tetraarylporphyrin by cyclopentadiene moiety seems to be a notion of the very first choice for the creation of meso-substituted or β-substituted 21-carbaporphyrins which ideally conserve the fundamental frame of porphyrin, seen also in 21-heteroporphyrins and in the first metallaporphyrin (21-pallada-23-tellura-porphyrin).[3] The construction of a  true carbaporphyrin requires a replacement of the imine nitrogen of pyrrolene by a trigonally hybridized methine unit or amine NH of pyrrole by a tetrahedral methylene group affording a tautomeric couple (2 and 3) which is parental for all monocarbaporphyrinoids. It remains a challenge to create 5,10,15,20-tetraaryl-21-carbaporphyrins that are potentially amenable to diverse structural modifications.The remarkable, facile contraction of p-phenylene embedded in p-benziporphyrin 1 to cyclopentadiene, mediated by transition metal cation of 2-M produced complexes of 21-carbaporphyrins 2-M or 3-M.[1,2] Thus these investigations afforded 5,10,15,20-tetraaryl- 21-carbaporphyrin - the first example of true carbaporphyrin complexes, which are firmly stabilized via coordination of trigonal (2-M) or tetrahedral (3-M) carbon donors. One can expect the true carbaporphyrins can prompt developments in carbaporphyrinoid and organometallic chemistry building on specific reactivity of cyclopentadienyl moiety. 

References

[1]  Szyszko, B.; Latos-Grazynski, L.; Szterenberg, L. Angew. Chem. Int. Ed.
2011, 50, 6587.

[2]  Szyszko, B.; Kupietz, K.; Szterenberg, L.; Latos-Grazynski, L. Chem. Eur. J.
2014, 20, 376.

[3]  Pacholska-Dudziak E.; Szczepaniak, M.; Ksiazek, A.; Latos-Grazynski, L. Angew. Chem. Int. Ed.
2013, 52, 8898.

Figure 1
Electro- and Photo-Catalytic Reduction of Small Molecules/Ions By Corrole Metal Complexes
Authors: Gross Zeev , Mahammed Atif
Published: February 2020

The scientific interest in the macrocyclic metal chelating corroles has evidenced a remarkable increase since our discovery of their first one-pot synthesis in 1999. Facile synthetic modifications that were introduced during the latest years now allow for tuning of the most fundamental properties of corroles, such as lipo-/hydro-/amphilicity, photo-excited states and their mode of decay to the ground state, and the stability/reactivity profiles of the corresponding metal complexes.

The impact of these investigations is exemplified by the introduction of corrole metal chelates as catalysts for the most important chemical reactions involved in energy-relevant processes, such as the hydrogen and oxygen evolution reactions. This presentation will focus on the largely unexplored potential of metallocorroles for the reduction of protons to hydrogen and of halides to halogens, via electrocatalysis and photocatalysis, respectively. Tuning of reactivity and redox potentials is achieved by variations introduced onto the ligand and the choice of coordinated metal ions.

REFERENCES

“Four-Electron Oxygen Reduction by Brominated Cobalt Corrole” Inorg. Chem.
2012, 51, 22-24.

“Cobalt Corrole Catalyst for Efficient Hydrogen Evolution Reaction from H2O under Ambient Conditions: Reactivity, Spectroscopy and DFT Calculations”, Inorg. Chem.
2013, 52, 3381-3387.

"The Cobalt Corrole Catalyzed Hydrogen Evolution Reaction: Surprising Electronic Effects and Characterization of Key Reaction Intermediates" Chem. Commun.
2014, 50, 2725-2727.

Figure 1
Pyrrole-Fused Azacoronenes with Various Redox States
Authors: Takase Masayoshi
Published: February 2020

Polycyclic aromatic hydrocarbons represented by hexabenzocoronenes (HBC) have attracted a great deal of attention from materials science. Among them, nitrogen-containing π-system have potential advantages since such heteroatoms can tune the electronic nature without modifying the structure. Given these expectations, we have reported a novel nitrogen-containing π-system, i.e., hexapyrrolohexaazacoronene (HPHAC). To investigate the effect of the interior nitrogen atoms, we have recently synthesized a series of pyrrole-fused azacoronenes, where some pyrrole rings of HPHAC were substituted with phenyl rings. In all cases, they showed multiple oxidation states due to the interior nitrogen atoms and various resonance forms.

The synthesis was successively performed by SNAr reaction with fluoroiodobenzenes, Suzuki-Miyaura coupling, and oxidative Scholl reaction. As characteristic features, cyclic voltammograms exhibit up to three reversible oxidation peaks having similar first two oxidation potentials and differences between second and third oxidation potentials become smaller in order of decreasing the number of pyrroles. Chemical oxidations by monitoring the absorption spectra revealed that these compounds had different electronic states in their oxidation states. Recently, we have further designed and synthesized a new family that has two carbonyl groups directly introduced to the π-system. It is expected that the resonance forms observed for the oxidation states of previous azacoronenes become possible in the neutral state. As the result, new ones exhibit significantly different physical properties.

In the presentation, synthesis and optical and electronic properties of azacoronenes will be discussed.
Structure-Dependent Reactions of Tetraphenylporphyrin with Cu(111)
Authors: Lytken Ole , Röckert Michael , Ditze Stefanie , Stark Michael , Franke Matthias , Tariq Quratulain , Marbach Hubertus , Steinrück Hans-Peter
Published: February 2020

Tetraphenylporphyrin (2HTPP) undergoes several distinct, structure-dependent reactions on Cu(111): Firstly metalation, forming copper(II)tetraphenylporphyrin (CuTPP), and subsequently dehydrogenation. Dehydrogenation takes places in two steps. In the first step the phenyl rings fuse with the pyrrole rings, flattening the molecule on the surface, and in the last step the remaining hydrogen atoms are lost producing an ill-defined, interlinked, nitrogen-doped carbon network on the surface. The rate of metalation and dehydrogenation depends strongly on coverage, with an abrupt change as the coverage is increased and the structure of the adsorbed 2HTPP layer changes. Using ultrahigh vacuum, XPS, STM and TPD (of both deuterated and undeuterated molecules) the reaction rates and the different intermediates on the surface have been investigated in the temperature range from 200-1000 K as a function of the structure of the initial 2HTPP layer.