Relation Between Bond-Length Alternation and Second Electronic Hyperpolarizability of Conjugated Organic Molecules

• Published in: Science (American Association for the Advancement of Science) 1993-07, Vol.261 (5118), p.186-189
• Main Authors: Marder, Seth R., Perry, Joseph W., Bourhill, Grant, Gorman, Christopher B., Tiemann, Bruce G., Mansour, Kamjou
• Format: Article
• Language: English
• Subjects: Atomic and molecular physics; Charge separation; Chemistry And Materials (General); Dyes; Electric and magnetic moments (and derivatives), polarizability and magnetic susceptibility; Exact sciences and technology; Ground state; Jet propulsion; Materials; Molecular properties and interactions with photons; Molecular structure; Molecules; Nonlinear optics; Organic compounds; Physics; Polyenes; Properties of molecules and molecular ions; Solvents; Spectral bands
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.261.5118.186

The solvent dependence of the second hyperpolarizability, γ, of a variety of unsaturated organic compounds has been measured by third harmonic generation at 1907 nanometers. It is seen that the measured γ is a function of solvent polarity. These solvent-dependent hyperpolarizabilities are associated with changes in molecular geometry from a highly bond-length alternated, polyene-like structure for a formyl-substituted compound in non-polar solvents, to a cyanine-like structure, with little bond-length alternation, for a dicyanovinyl-substituted compound in polar solvents. By tuning bond-length alternation, γ can be optimized in either a positive or negative sense for polymethine dyes of a given conjugation length.