Exciton coupling model for the emergence of second harmonic generation from assemblies of centrosymmetric molecules.
A simple model is presented for interpreting the presence of substantial second harmonic generation (SHG) activity from assemblies of centrosymmetric molecular building blocks. Using butadiene as a computationally tractable centrosymmetric model system, time-dependent Hartree-Fock calculations of the nonlinear polarizability of butadiene dimer were well-described through exciton coupling arguments based on the electronic structure of the monomer and the relative orientation between the monomers within the dimer. Experimental studies of the centrosymmetric molecule 2,6-di-tert-butylanthraquinone suggest the formation of a combination of SHG-active and SHG-inactive crystal forms. The structure for the centrosymmetric form is known, serving as a negative control for the model, while the presence of an additional SHG-active metastable form is consistent with predictions of the model for alternative molecular packing configurations.
Department of Chemistry, Purdue University , West Lafayette Indiana 47907, United States.
Gregory R
GR
Snyder
Azhad U
AU
Chowdhury
Garth J
GJ
Simpson
D000880:Anthraquinones / Q000737:chemistry*; D002070:Butadienes / Q000737:chemistry*; D003198:Computer Simulation; D019281:Dimerization; D008956:Models, Chemical; D011789:Quantum Theory; D013816:Thermodynamics
D000880:Anthraquinones; D002070:Butadienes; C031763:1,3-butadiene