Structure-function relationships and novel approaches to electro-optic chromophores: Design, computational modeling, synthesis, and characterization

Delocalized organic materials are of significant fundamental and technological interest for electro-optic (EO) applications. Organic materials are demonstrated to have large non-resonant responses, ultrafast response times, low dielectric constants and dielectric losses, intrinsic tunability of the constituent molecular structure, and ease of thin-film processability. These are the major advantages of using organic materials for EO applications. Organic EO materials require that the individual chromophore components have large molecular hyperpolarizabilities (beta) and that they are arranged in a noncentrosymmetric architecture. This thesis aims to tackle these challenges via computationally aided rational design of novel chromophores, yielding both record-setting acentric PVD grown hydrogen-bond thin film responses and record-setting figures-of-merit (mubeta/Mw) for individual molecule response. Furthermore, the simulations and experiments address the impact of bulk changes in arene--arene junctions on tictoid response and aggregation in both solid-state and solution.;To address the requirements for noncentrosymmetric organization, a series of hydrogen-bonded fluorinated heteroaromatic organic chromophores are computationally designed, synthesized, and self-organized, from the vapor phase, into intrinsically acentric EO thin films. DFT-level electronic-structure calculations are employed to screen the substituent response effects and hydrogen-bonding motif directing capabilities. For vapor deposited films, this rational molecular engineering method yields a family of fluorinated chromophores capable of acentric growth and responses up to ∼ 302 pm/V. Additionally, insight is gained into the importance of an intrinsic chromophore response versus an intermolecular hydrogen-bonding-dependent response, which can cause variation in the bulk response properties.;In the later two chapters, a powerful and direct approach to chromophore design and response amplification is presented. Here, a series of zwitterionic tictoid chromophores are studied based on ortho-biaryl substitution patterns and the number of highly twisted benzene rings. The synthesis, structural and spectroscopic characterization, and non-linear optical response properties of these highly twisted zwitterionic chromophores are reported. X-ray diffraction data and DFT-minimized geometries confirm the structural features that are important to molecular response. The calculated Molecular hyperpolarizabilities (mubeta) approach 900,000 x 10-48 esu, while chromophore figures of merit approach 1,500 x 10-48 esu, which is nearly 1.5 times larger than previously reported values.