Molecular nonlinear optical materials, design

One of the advances in the field of PET is the design of molecular devices, in which D and A pairs are ingeniously linked by covalent bridges (B) to form D-B-A dyads. Electron transfers between D and A across B in a controlled manner may thus display useful functionalities, such as molecular rectifiers [25], switches [26], biosensors [27], photovoltaic cells [28], and nonlinear optical materials [29]. Spacers that have been utilized are versatile, including small molecules, such as cyclohexane [30], adamantane [31], bicyclo[2.2.2]octane [32], steroids [33], and oligomers of... 

Design and Characterization of Molecular and Polymeric Nonlinear Optical Materials ... 

The area of molecular nonlinear optics has been rejuvenated by efforts to investigate three-dimensional multipolar systems, functionalized polymers as optoelectronic materials, near infrared optical parametric oscillators and related aspects.71 There have been some advances in chromophore design for second-order nonlinear optical materials 72 these include onedimensional CT molecules, octopolar compounds and organometallics. Some of the polydiacetylenes and poly(/>-phenylenevinylene)s appear to possess the required properties for use as third-order nonlinear optical materials for photonic switching.73... 

Selective perturbation of metal-metal coupling by either inner-sphere or outer-sphere manipulations will continue. Aside from increasing our understanding of metal-metal superexchange coupling, these studies will probe the nature of solvent-solute interactions and perhaps be applicable to the design of molecular devices. The synthesis of novel nonlinear optical materials that incorporate mixed-valence metal systems will be the subject of much interest 100). 

Reorientation dynamics of molecular tracers in polymers is not only important for the understanding of slow relaxation phenomena in glassy polymers but plays also a critical role in practical problems such as molecular design of nonlinear optical materials with long-term stability based on dyes/polymers complexes. We show here the reorientation dynamics of molecular tracers in glassy polymers obtained by the armealing-after-irradiation method described below. These experimental results are compared to the local relaxation processes of glassy polymers obtained by the already established measurement techniques such as dielectric relaxation and solid state NMR. Finally, the molecular interpretation of the relaxation of free-volume distribution in polymers will be discussed. 

Champagne, B., Kirtman, B. Theoretical approach to the design of organic molecular and polymeric nonlinear optical materials. In Handbook of Advanced Electronic and Photonic Materials and Devices, vol. 9. Academic, San Diego (2001)... 

RECENT PROGRESS IN MOLECULAR DESIGN OF IONIC SECOND-ORDER NONLINEAR OPTICAL MATERIALS... 

The implementation of nonlinear optical applications depends strongly on the discovery and development of new nonlinear materials. Although in principle, all materials might show nonlinear optical effects, the response is generally too small to be of any use. Furthermore, in order to observe even-order nonlinear optical effects, the material has to be noncentrosymmetric at both the molecular and the bulk level. Therefore, the design of optoelectronic and photonic devices relies heavily in the development of new nonlinear optical materials. 

Organic-inorganic hybrid materials have attracted extensive fundamental and practical interest/ Molecular design of hybrid materials could produce materials with tunable properties for optoelectronic devices, including optical waveguides,electroluminescent devices,nonlinear optical materials, photorefractive materials, and semiconductors/ ... 

Meredith, G. R., Design and characterization of molecular and polymeric nonlinear optical materials successes and pitfalls, in Nonlinear Optical Properties of Organic and Polymeric Materials (ACS Symp. Sen, 233), Williams, D. J., Ed., American Chemical Society, Washington, D.C., 1983, 27. 

Dramatic advances in molecular synthetic chemistry have led to a high level of control over molecular interactions. However, we are only at the beginning of a more extended design of chemical interactions in two and three dimensions. If we learn how to control the structure, properties, and stability of desired supramolecular assemblies, many areas in materials science and technology, such as microelectronics, optics, sensors, and catalysis, will benefit substantially. Representative areas of research activity include selective monolayer assemblies on electrode surfaces functionalized pillared layered materials and assemblies of conductors, semiconductor clusters, or nonlinear optical materials in three-dimensionally ordered hosts such as zeolites. 

Inverse molecular design for nonlinear optical materials... 

The study of chiral materials with nonlinear optical properties might lead to new insights to design completely new materials for applications in the field of nonlinear optics and photonics. For example, we showed that chiral supramolecular organization can significantly enhance the second-order nonlinear optical response of materials and that magnetic contributions to the nonlinearity can further optimize the second-order nonlinearity. Again, a clear relationship between molecular structure, chirality, and nonlinearity is needed to fully exploit the properties of chiral materials in nonlinear optics. 

Two of the most important nonlinear optical (NLO) processess, electro-optic switching and second harmonic generation, are second order effects. As such, they occur in materials consisting of noncentrosymmetrically arranged molecular subunits whose polarizability contains a second order dependence on electric fields. Excluding the special cases of noncentrosymmetric but nonpolar crystals, which would be nearly impossible to design from first principles, the rational fabrication of an optimal material would result from the simultaneous maximization of the molecular second order coefficients (first hyperpolarizabilities, p) and the polar order parameters of the assembly of subunits. (1)... 

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