Self-Assembly of Discrete Cyclic Nanostructures Mediated by Transition Metals

Porphyrins and phthalocyanines have outstanding chemical and thermal stability. The macrocyclic structure and chemical reactivity of tetrapyrroles offers architectural flexibility and facilitates the tailoring of chemical, physical and optoelectronic parameters. The specific optical properties of the tetrapyrrole macrocycle combined with the synthetic methodologies now available and the already available theoretical and spectroscopic knowledge on their optical behavior make porphyrins a target of choice for this area. They are versatile organic nanomaterials with a rich photochemistry and their excited state properties are easily modulated through conformational design, molecular symmetry, metal complexation, orientation and strength of the molecular dipole moment, size and degree of conjugation of the π-systems, and appropriate donor-acceptor substituents. Here we review the structural chemistry and optical properties of recently synthesized porphyrin derivatives that offer potential for nonlinear optical (NLO) applications and complement existing studies on phthalocyanines. Classes of interest include the classic A4 symmetric tetrapyrroles, while optimized systems include push-pull porphyrins, oligomeric and supramolecular self-assembled systems, films and nanoparticle systems, and highly conjugated porphyrin arrays.

Nonlinear Optical Properties of Porphyrins

Conjugated porphyrin arrays that possess delocalised electronic networks have, for the most part, been assembled by using alkene or alkyne type bridging units or by directly connecting individual porphyrin chromophores with multiple bonds to form fused porphyrin arrays. Throughout the last two decades, such conjugated porphyrin arrays have been actively explored due to their attractive electronic, optical and electrochemical properties. This review aims to cover the multitude of synthetic methodologies that have been developed for the construction of conjugated porphyrin arrays as well as to summarise their structure–property relationships and use in various applications such as near infrared (NIR) dyes, nonlinear optical materials and electron-conducting molecular wires.

Conjugated porphyrin arrays: synthesis, properties and applications for functional materials.

Building molecular wires from the colours of life: conjugated porphyrin oligomers

Molecular Rods. 1. Simple Axial Rods.

Despite their larger separation, the porphyrin groups in 1 are more strongly conjugated than in analogous compounds in which butadiyne is the bridging unit. This stronger electronic coupling in 1 results in a bathochromic shift in its absorption and emission spectra.

Enhanced Electronic Conjugation in Anthracene-Linked Porphyrins

Trotz groserer Entfernung sind die Porphyringruppen in 1 starker konjugiert als in der analogen Verbindung, in der sie nur durch eine Butadiin-Einheit verbruckt sind, was sich in einer bathochromen Verschiebung von Absorptions- und Emissionsbanden zeigt.

Juhani Huuskonen

Papers

Enhanced Electronic Conjugation in Anthracene-Linked Porphyrins

Verstärkte elektronische Konjugation in Porphyrin‐Anthracen‐Porphyrin‐Ketten

Conjugated Porphyrin Oligomers from Monomer to Hexamer