Ivana Radivojevic

Self-Organized Porphyrinic Materials

The self-assembly and self-organization of porphyrins and related macrocycles enables the bottom-up fabrication of photonic materials for fundamental studies of the photophysics of these materials and for diverse applications. This rapidly developing field encompasses a broad range of disciplines including molecular design and synthesis, materials formation and characterization, and the design and evaluation of devices. Since the self-assembly of porphyrins by electrostatic interactions in the late 1980s to the present, there has been an ever increasing degree of sophistication in the design of porphyrins that self-assemble into discrete arrays or self-organize into polymeric systems. These strategies exploit ionic interactions, hydrogen bonding, coordination chemistry, and dispersion forces to form supramolecular systems with varying degrees of hierarchical order. This review concentrates on the methods to form supramolecular porphyrinic systems by intermolecular interactions other than coordination chemistry, the characterization and properties of these photonic materials, and the prospects for using these in devices. The review is heuristically organized by the predominant intermolecular interactions used and emphasizes how the organization affects properties and potential performance in devices.

Phthalocyanine Blends Improve Bulk Heterojunction Solar Cells

A core phthalocyanine platform allows engineering of the solubility properties the band gap, shifting the maximum absorption toward the red. A simple method for increasing the efficiency of heterojunction solar cells uses a self-organized blend of phthalocyanine chromophores fabricated by solution processing.

Commercially viable porphyrinoid dyes for solar cells

Multifunctional molecules bearing different dyes, such as donor–acceptor systems, synthesized by covalent chemistry have provided a wealth of information on the fundamental nature of electron and energy transfer in organic systems and there is a growing literature on the materials properties of dyes on surfaces. However, in the vast majority of cases the synthetic costs of producing these covalently bound systems prohibit them from deployment in commercially viable devices. Thus, to achieve both the needed multifunctionality and to bring the synthetic costs in line with potential commercialization, supramolecular approaches to the formation of photonic materials can be exploited. This perspective focuses on porphyrinoids as exemplary dyes, but the concepts and design principles extend to other chromophores.

Self-organized nanofibers and nanorods of porphyrins bearing hydrogen bonding motifs

Porphyrins bearing uracyl motifs at the four meso positions self-organize via homo-complementary hydrogen bonds and pi-stacking into nanofibers, nanorods and thin films on mica and glass surfaces depending on deposition conditions.

Ternary phthalocyanato Hf(IV) and Zr(IV) polyoxometalate complexes

Ternary phthalocyanine–metal–polyoxometalate (Pc–M–POM) complexes were synthesized and characterized. Group (IV) Hf or Zr ions reside outside the plane of the macrocycle and are coordinated to both the phthalocyanine and the lacunary polyoxometalate. The metal ions mediate the electronic communication between the Pc and the POM.

Hafnium (IV) and zirconium (IV) porphyrinoid diacetate complexes as new dyes for solar cells

New concepts in the design and function of organic dyes as sensitizers for solar energy harvesting are needed. Simple porphyrin dyes offer cost effective synthesis and long-term stability, but new modes of incorporation into devices are needed to increase the efficiency of charge separation that drives any photonic device designed to harvest light. We are developing a new strategy to couple dyes to oxide surfaces using hafnium and zirconium metalloporphyrins. The formation of ternary complexes of Hf(IV) and Zr(IV) porphyrins with a Keggin polyoxometalate (POM), PW11O397− suggested that one way to self-organize porphyrinoids onto oxide surfaces is to use oxophilic group IV metals Hf and Zr. The 3–4 open metal coordination sites of Hf(Por)2+ and Zr(Por)2+ are bound primarily to surface defect sites by displacement of the auxiliary acetate ligands.