Self-assembled organic optical materials

Article By:

Balakrishnan, Kaushik College of Optical Sciences, The University of Arizona, Tucson, Arizona.

Pau, Stanley College of Optical Sciences, The University of Arizona, Tucson, Arizona.

Last reviewed:2014

DOI:https://doi.org/10.1036/1097-8542.YB140261

Self-assembly refers to the spontaneous organization of a predesigned functional molecule (building block) under appropriate conditions by using the noncovalent forces of interactions between the molecules. The noncovalent interactions commonly used for the self-assembly of functional organic molecules rely on the use of π-stacking, hydrogen bonding, electrostatic, metal-coordination, hydrophobic, and van der Waals forces of interaction. Self-assembly, therefore, can be a very useful tool to generate structures much larger than the components (molecules) themselves (for example, large-scale crystals, nanostructures, and microstructures). The resulting structures are also referred to as supramolecular structures because of the large number of individual molecular building block units present in the final assembled structures. The vast array of π-conjugated molecules and polymers (some of the molecular structures are shown in Fig. 1) are particularly attractive for advancing both the materials and device applications because of the ability to tailor the molecular and self-assembled properties by predesigned synthesis. The π-conjugated molecules contain alternating single and double bonds. The double bonds are comprised of the sigma bonds (σ-) and three π-orbitals (p_x, p_y, and p_z). The p_z orbitals lie perpendicular to the coplanar carbon-to-carbon double bond (CC) and interact with neighboring orbitals, leading to additional bonding and delocalization of the electron density (both below and above the molecule). The interactions of the π-orbital lead to many stacking (π-stacking) possibilities and are evident in abundance in π-conjugated systems (such as dimers of benzene and stacking of DNA).

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