EDITORIAL pubs.acs.org/JPCL
Self-Assembled Organic Aggregates he field of self-assembled organic aggregates brings together numerous expertise in synthetic organic chemistry, structural and mechanistic physical chemistry, electronic structure calculations, materials chemistry, and optical spectroscopy and photonics. Indeed, the formation of organic aggregates has already made an impact on the fields of nanoscience, biophysics, electronics, and membrane and interface science. The current Perspectives review three such important aspects and applications of organic aggregates. It appears that the field is still extremely fresh with new ideas and possible applications for real materials. The three Perspectives discuss electronic properties of phthalocyanine fullerene nanostructures, interfacial effects of organic aggregates in the process of solvation, and finally theoretical and experimental aspects of small organic molecular aggregates.1 3 In this issue, the three Perspectives illustrate nicely the increased activity in the area of self-assembled organic materials and application. The Perspective from Torres et al. describes the use of self-assembly of phthalocyanine fullerene and other nanomaterials to make singular structures.1 In particular, this Perspective describes how new architectures with these materials have probed the possibility of providing efficient mechanisms for photoinduced electron-transfer processes. The Perspective gives great detail as to some of the recent trends in both the design criteria of phthalocyanine carbon nanostructure materials and the correlation with the steady-state photophysics as well as the increase in electron-transfer efficiency.4,5 In general, it appears that the preparation and study of Pc fullerene systems that have the ability to self-assemble over large length scales often bring about significant changes in physical properties of these selfassembled systems with respect to their molecularly dispersed counterparts. Indeed, this is important as one is often looking for enhanced optical and electronic properties as a result of intramolecular interactions in creating new materials. Enhancing the optical properties as a result of aggregation is extremely important in regards to the experimental and theoretical optical properties in the solid state. The Perspective by Das gives great credence to this statement as the fundamental excitations both theoretically and experimentally are discussed.2 The new view offered by this Perspective is the care in describing recent developments and understanding of strong electronic coupling in organic aggregates in the solid state. Das and Varghese use the well-known DSB-type chromophore as a model system to discuss the many new developments in the understanding of packing and order in organic aggregates in the solid state and changes in their optical spectra.6 9 This is an area that had received some attention previously in the literature; however, with new synthetic materials created and with intensified emphasis of such materials to be used in photovoltaics and solar cells, it appears that there is still a great deal to be learned as to how we can optimize electronic properties by studying the selfassembly properties in the solid state as well as in solution. Finally, the study of organic self-assembly materials applied to surfactants and solvation is given a summary by Bhattacharya et al.3,10,11 What is basic to some of the new organic multihead
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group architectures is that the actual geometric order or size plays a role in the materials surfactant behavior. The Perspective discusses many of these important materials, which have recently come to great importance for future applications in biology and biophotonics. Both synthetic chemists and physical chemists have made great progress in understanding the structure function relationships between the morphology of the head groups in the self-assembly structure and properties such as the critical micellar concentration, aggregation number, counterion dissociation, and fractional charge. Indeed, organic dendrimers and hyperbranched structures have been very successful recently in providing new insights into the formation of particular interactions in water as well as novel bio/pharma applications as a result of these interactions. After reading these three Perspectives and looking at the amazing number of interesting materials and ideas of how to utilize such structures in optical and interfacial effects, I am extremely excited about the future of this field. Indeed, many of the important challenges still remain in these areas, but the relatively large amount of new information gives rise to new enthusiasm and welcomes further interactions with new faces. Theodore Goodson Senior Editor University of Michigan
’ REFERENCES (1) Bottari, G.; Trukhina, O.; Suanzes, J. A; Torres, T. Phthalocyanine Carbon Nanostructure Materials Assembled through Supramolecular Interactions. J. Phys. Chem. Lett. 2011, 2, 905–913. (2) Varghese, S.; Das, S. Role of Molecular Packing in Determining Solid-State Optical Properties of π-Conjugated Materials. J. Phys. Chem. Lett. 2011, 2, 863–873. (3) Samanta, S.; Bhattacharya, S. Surfactants Possessing Multiple Polar Heads. A Perspective on their Unique Aggregation Behavior and Applications. J. Phys. Chem. Lett. 2011, 2, 914–920. (4) de la Escosura, A.; Martinez-Diaz, M. V.; Thordarson, P.; Rowan, A. E.; Nolte, R. J. M.; Torres, T. Donor Acceptor Phthalocyanine Nanoaggregates. J. Am. Chem. Soc. 2003, 125, 12300–12308. (5) Bottari, G.; de la Torre, G.; Guldi, D. M.; Torres, T. Covalent and Noncovalent Phthalocyanine Carbon Nanostructure Systems: Synthesis, Photoinduced Electron Transfer, and Application to Molecular Photovoltaics. Chem. Rev. 2010, 110, 6768–6816. (6) Kumar, N. S. S.; Varghese, S.; Suresh, C. H.; Rath, N. P.; Das, S. Correlation between Solid-State Photophysical Properties and Molecular Packing in a Series of Indane-1,3-dione Containing Butadiene Derivatives. J. Phys. Chem. C 2009, 113, 11927–11935. (7) Kumar, N. S. S.; Varghese, S.; Rath, N. P.; Das, S. Solid State Optical Properties of 4-Alkoxypyridine Butadiene Derivatives: Reversible Thermal Switching of Luminescence. J. Phys.Chem. C 2008, 112, 8429. (8) Babu, S. S.; Kartha, K. K.; Ajayaghosh, A. Excited State Processes in Linear π-System-Based Organogels. J. Phys. Chem. Lett. 2010, 1, 3413–3424. Published: April 21, 2011 932
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(9) Venkataraman, D.; Yurt, S.; Venkatraman, B. H.; Gavvalapalli, N. Role of Molecular Architecture in Organic Photovoltaic Cells. J. Phys. Chem. Lett. 2010, 1, 947–958. (10) Samanta, S. K.; Bhattacharya, S.; Maiti, P. K. Coarse-Grained Molecular Dynamics Simulation of the Aggregation Properties of Multiheaded Cationic Surfactants in Water. J. Phys. Chem. B 2009, 113, 13545–13550. (11) Haldar, J.; Aswal, V. K.; Goyal, P. S.; Bhattacharya, S. Molecular Modulation of Surfactant Aggregation in Water: Effect of the Incorporation of Multiple Headgroups on Micellar Properties. Angew. Chem., Int. Ed. 2001, 40, 1228–1232.
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