Gema de la Torre

Covalent and noncovalent phthalocyanine-carbon nanostructure systems: synthesis, photoinduced electron transfer, and application to molecular photovoltaics

Photosynthesis is used by nature to convert light energy into chemical energy in some living systems. In such a process, a cascade of very efficient, short-range energy and electron transfer events between well-arranged, light-harvesting organic donor and acceptor pigments takes place within the photosynthetic reaction center, leading to the overall generation of chemical energy from sunlight with near quantum efficiency.1-8 During the past decade, a significant effort has been made by the scientific community toward the preparation of synthetic model compounds of natural photosynthetic systems able to convert light into other energy sources,9 probably fostered by the increasing concerns related to the utilization of fossils fuels for the production of electricity in terms of both availability and environmental issues. However, considering the structural complexity presented by the natural photosynthetic systems, much of the scientific effort has been devoted toward the preparation and study of structurally simpler systems, with the aim of reproducing some of the fundamental steps occurring in natural photosynthesis, one of the most important being the photoinduced charge separation (CS).10-12 Among the chromophores that have been used as molecular components in artificial photosynthetic systems, porphyrinoids, the ubiquitous molecular building blocks employed by nature in natural photosynthesis, have been the preferred and obvious choice, due to their intense optical absorption and rich redox chemistry.13-20 Within the large family of porphyrinoid systems, phthalocyanines (Pcs) enjoy a privileged position (Figure 1a). These chromophores, which have a two-dimensional 18-πelectron aromatic system isoelectronic with that of porphyrins (Pors), possess in fact unique physicochemical properties which render these macrocycles valuable building blocks in materials science.21-32 Pcs are thermally and chemically stable compounds which present an intense absorption in the red/near-infrared (IR) region of the solar spectrum with extinction coefficients (as high as 200 000 M-1 cm-1) and fluorescence quantum yields * To whom correspondence should be addressed. E-mail: tomas.torres@uam.es (T.T.); dirk.guldi@chemie.uni-erlangen.de (D.M.G.). † Universidad Autonoma de Madrid. ‡ Friedrich-Alexander-Universitat Erlangen-Nurnberg. § IMDEA-Nanociencia. Chem. Rev. 2010, 110, 6768–6816 6768

Phthalocyanines: old dyes, new materials. Putting color in nanotechnology

Phthalocyanines are versatile building blocks for fabricating materials at the nanometer scale. These colored macrocycles exhibit fascinating physical properties which arise from their delocalized pi-electronic structure. This article describes why these molecules are targets for different scientific purposes and technological applications.

Facile Decoration of Functionalized Single-Wall Carbon Nanotubes with Phthalocyanines via Click Chemistry

We describe the functionalization of single-wall carbon nanotubes (SWNTs) with 4-(2-trimethylsilyl)ethynylaniline and the subsequent attachment of a zinc-phthalocyanine (ZnPc) derivative using the reliable Huisgen 1,3-dipolar cycloaddition. The motivation of this study was the preparation of a nanotube-based platform which allows the facile fabrication of more complex functional nanometer-scale structures, such as a SWNT-ZnPc hybrid. The nanotube derivatives described here were fully characterized by a combination of analytical techniques such as Raman, absorption and emission spectroscopy, atomic force and scanning electron microscopy (AFM and SEM), and thermogravimetric analysis (TGA). The SWNT-ZnPc nanoconjugate was also investigated with a series of steady-state and time-resolved spectroscopy experiments, and a photoinduced communication between the two photoactive components (i.e., SWNT and ZnPc) was identified. Such beneficial features lead to monochromatic internal photoconversion efficiencies of 17.3% when the SWNT-ZnPc hybrid material was tested as photoactive material in an ITO photoanode.

Carboxyethynyl Anchoring Ligands: A Means to Improving the Efficiency of Phthalocyanine-Sensitized Solar Cells†

Keywords: conjugation ; electron transfer ; solar cells ; synthetic methods ; zinc ; Conversion Efficiency ; Porphyrin Sensitizers ; Tio2 ; Dyes Reference EPFL-ARTICLE-177266doi:10.1002/anie.201108963View record in Web of Science Record created on 2012-05-18, modified on 2016-08-09

Phthalocyanine−Pyrene Conjugates: A Powerful Approach toward Carbon Nanotube Solar Cells

In the present work, a new family of pyrene (Py)-substituted phthalocyanines (Pcs), i.e., ZnPc-Py and H(2)Pc-Py, were designed, synthesized, and probed in light of their spectroscopic properties as well as their interactions with single-wall carbon nanotubes (SWNTs). The pyrene units provide the means for non-covalent functionalization of SWNTs via π-π interactions. Such a versatile approach ensures that the electronic properties of SWNTs are not impacted by the chemical modification of the carbon skeleton. The characterization of ZnPc-Py/SWNT and H(2)Pc-Py/SWNT has been performed in suspension and in thin films by means of different spectroscopic and photoelectrochemical techniques. Transient absorption experiments reveal photoinduced electron transfer between the photoactive components. ZnPc-Py/SWNT and H(2)Pc-Py/SWNT have been integrated into photoactive electrodes, revealing stable and reproducible photocurrents with monochromatic internal photoconversion efficiency values for H(2)Pc-Py/SWNT as large as 15 and 23% without and with an applied bias of +0.1 V.

Phthalocyanines: The Need for Selective Synthetic Approaches

Recent years have witnessed increasing interest in the synthesis of low-symmetry single phthalocyanines (Pcs) since they may show, among other applications and advantages, interesting second-order nonlinear optical (NLO) properties. This potential of unsymmetrically substituted and regioisomerically pure phthalocyanines has motivated researchers in this field to develop selective methods for synthesizing macrocycles of this type. In this microreview, we focus on the approaches reported by other research groups as well as ourselves that allow the predominant or exclusive formation of the required compounds. The selective preparation of differently substituted or intrinsically unsymmetrical Pc-related systems and Pc homologues is also discussed.

A survey on the functionalization of single-walled nanotubes. The chemical attachment of phthalocyanine moieties

Single-walled nanotubes (SWNTs) covalently attached to phthalocyanine molecules through amide bonds have been prepared. A survey on the functionalization of SWNTs is also given.

Alkynyl substituted phthalocyanine derivatives as targets for optical limiting

One of the key issues in the development of efficient optical limiters is the search for appropriate materials with improved nonlinear absorption. Phthalocyanine materials are among the most promising nonlinear absorbers described in the literature. Ethynyl and butadiynyl-bridged bisphthalocyanines and related ethynyl-containing mononuclear compounds have been synthesized and experimentally studied using the z-scan technique with nanosecond pulses at 532 nm. We intend to ascertain the effect of the electronic interaction between macrocycles in the optical limiting performance of phthalocyanines.

Functional Phthalocyanines: Synthesis, Nanostructuration, and Electro-Optical Applications

This overview focuses on the design and preparation of phthalocyanines (Pcs) and covers both fundamental synthetic approaches and more applied research. Thus, different topics including, e.g., the preparation of conjugated assemblies using Pcs as synthetic building blocks, the supramolecular organization of appropriately featured Pc-molecules, and the incorporation of Pcs into dendrimers and polymers, are discussed in this chapter. The second part of the review has been devoted to more technological aspects of these compounds covering Pc-based nanostructures and Pcs as active components of functional devices.

Sterically Hindered Phthalocyanines for Dye‐Sensitized Solar Cells: Influence of the Distance between the Aromatic Core and the Anchoring Group

A new phthalocyanine (Pc) bearing bulky peripheral substituents and a carboxylic anchoring group directly attached to the macrocycle has been prepared and used as a sensitizer in DSSCs, reaching 5.57% power conversion efficiency. In addition, an enhanced performance for the TT40 dye, previously reported by us, was achieved in optimized devices, obtaining a new record efficiency with Pc-sensitized cells.