Christian G. Claessens

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.

Phthalocyanines: From outstanding electronic properties to emerging applications†

This review paper gives a brief overview on how the outstanding chemical and physical properties of phthalocyanines and phthalocyanine derivatives are being studied and employed in order to construct state-of-the-art technological devices. In a first instance, a short account on how the nature of the phthalocyanine structure and its organization in condensed phases play an important role in their conducting and ultraviolet-visible absorption properties is presented. Consequently, these basic electronic and photophysical features of phthalocyanines allow us to explain why phthalocyanine-based multicomponent covalent or noncovalent donor-acceptor systems may give rise to very interesting photophysical properties, in particular in terms of their ability to generate very long-lived photoinduced charge-separated states. A concise survey on the organization of these multifunctional systems shows how a profound understanding of the morphology at the nanometer-scale of these phthalocyanine-based molecular materials is needed in order to control their physical properties in condensed phases. All the previously mentioned chemical and physical features combined together led us to the description of the latest attempts at incorporating phthalocyanines into photovoltaic devices for solar energy conversion and onto quantum dots for photodynamic therapy or quantum computing.

Phthalocyanines and Phthalocyanine Analogues: The Quest for Applicable Optical Properties

Summary. The central subject of this article is the description of the current work of the authors in the context of the Cost Action 518, project DE-1, and the Phthalocyanines Research Training Network, both financed by the European Community. The aim of the above projects is the design, synthesis, and structural and physical characterization of molecular and polymeric materials based on phthalocyanine derivatives with particular optical properties, as well as the study of their technological applications in the sensors field.

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.

Inclusion of C60 fullerene in a M3L2 subphthalocyanine cage

A C3 symmetric subphthalocyanine (SubPc) M3L2 cage was shown to encapsulate C60 fullerene within its aromatic walls in acetone.

Synthesis, Characterization, Molecular Structure and Theoretical Studies of Axially Fluoro-Substituted Subazaporphyrins

A new and general synthetic method for the preparation of fluoro-substituted subazaporphyrins is reported that involves the treatment of the corresponding chloro- or aryloxy-substituted subazaporphyrins (SubAPs) with BF(3).OEt(2). The strategy has been applied to both subphthalocyanines (SubPcs) and subporphyrazines (SubPzs). The yields were high for the latter, although low yields were obtained for the benzo derivatives. In contrast to the corresponding chloro derivatives, fluorosubazaporphyrins are quite robust towards hydrolysis. All of the new compounds were characterized by several spectroscopic techniques, which included (1)H, (13)C, (19)F, (15)N, and (11)B NMR spectroscopy, IR spectroscopy, UV/Vis spectrophotometry, and mass spectrometry (both high and low resolution). In addition, DFT calculations provided theoretical NMR spectroscopy values that are in good agreement with the experimental ones. The high dipole moments exhibited by the fluorosubazaporphyrins as a result of the presence of a fluorine atom in an axial position are responsible for the spontaneous and singular supramolecular aggregation of the macrocycles in the crystalline state. The molecular and crystal structures of two one-dimensional fluorine SubAPs, namely, a SubPc and a SubPz, are discussed. Molecules of the same class stack in alternating configurations along the c axis, which gives rise to columns that contain large numbers of monomers. SubPz 3 c forms aggregates with the macrocycles arranged in a parallel fashion with the B-F bonds perfectly aligned within a column, whereas with SubPc 3 b the neighboring columns cause a commensurate sinusoidal distortion along the columns in the c direction, which prevents the alignment of the B-F bonds. However, the most remarkable feature, common to both crystalline architectures, is the extremely short and unusual intermolecular F...N distances of the contiguous molecules, which are shorter than the sum of the corresponding van der Waals radii. Theoretical calculations have shown that these short distances can be explained by the existence of a cooperativity effect as the number of monomers included in the cluster increases.

Subphthalocyanine enantiomers: first resolution of a C3 aromatic compound by HPLC

Abstract The constitutional isomers of chloro(2,9,16(17)triodosubphthalocianato)boron(III) have been separated by column chromatography on silica gel. Furthermore, the enantiomers of each of these C1- and C3-regioisomers have been resolved by HPLC on a chiral analytical column.

Self-assembly, host-guest chemistry, and photophysical properties of subphthalocyanine-based metallosupramolecular capsules.

Four new subphthalocyanine-based capsules have been synthesized and characterized. These supramolecular systems have been successfully employed for the encapsulation of fullerenes and probed by a wide range of characterization methods, including NMR, UV-vis and fluorescence spectroscopy, electrospray ionization mass spectrometry, and electrochemistry. Furthermore, the binding constants of the host guest complexes were estimated. Finally, the photophysical properties revealed that the subphthalocyanines undergo a transduction of singlet excited-state energy to the fullerene inside the cavity upon photoexcitation.

Accelerating charge transfer in a triphenylamine–subphthalocyanine donor–acceptor system

We have designed, synthesized and probed a dodecafluoro-subphthalocyaninato boron(III) unit, which bears a triphenylamine moiety in its axial position, as a novel electron donor-acceptor system.

Synthesis and photophysical characterization of a subphthalocyanine fused dimer–C60 dyad

Photophysical studies of a newly synthesized fused subphthalocyanine dimer-C60 revealed a complex cascade of energy transfer events to succeed the initial SubPc dimer photoexcitation.