Nonlinear Optical Dyes

Conjugation of the alkyne units into the porphyrin or phthalocyanine backbone electronic structure leads to absorptivity enhancements and large red-shifts in their electronic spectra that have been sought for nonlinear optics, dyes, photonic materials, and photodynamic therapy types of applications. 

Laschewsky A, Wischerhoff E, Kauranen M, Persoons A. 1997. Polyelectrolyte multilayer assemblies containing nonlinear optical dyes. Macromolecules 30 8304 8309. 

Ultra-fast optical switches based on one dimensional-polymeric photonic crystals doped with nonlinear-optical dyes have been recently reported by Katouf et al. [150]. They presented optical switches operating at 1,064 nm wavelength, that can be controlled either by an applied electric-field voltage or by a pump light by use of two different optical-configurations. The response time of the electro-optic switch and the all-optical switch are limited by the applied voltage and the laser used. 

Liquid crystal polymers are also used in electrooptic displays. Side-chain polymers are quite suitable for this purpose, but usually involve much larger elastic and viscous constants, which slow the response of the device (33). The chiral smectic C phase is perhaps best suited for a polymer field effect device. The abiHty to attach dichroic or fluorescent dyes as a proportion of the side groups opens the door to appHcations not easily achieved with low molecular weight Hquid crystals. Polymers with smectic phases have also been used to create laser writable devices (30). The laser can address areas a few micrometers wide, changing a clear state to a strong scattering state or vice versa. Future uses of Hquid crystal polymers may include data storage devices. Polymers with nonlinear optical properties may also become important for device appHcations. 

Optical properties of cyanines can be usefiil for both chiral substituents/environments and also third-order nonlinear optical properties in polymer films. Methine-chain substituted die arbo cyanines have been prepared from a chiral dialdehyde (S)-(+)-2-j -butylmalonaldehyde [127473-57-8] (79), where the chiral properties are introduced via the chiral j -butyl group on the central methine carbon of the pentamethine (die arbo cyanine) chromophore. For a nonchiral oxadicarbocyanine, the dimeric aggregate form of the dye shows circular dichroism when trapped in y-cyclodextrin (80). Attempts to prepare polymers with carbocyanine repeat units (linked by flexible chains) gave oligomers with only two or three repeat units (81). However, these materials... 

Microscopy methods based on nonlinear optical phenomena that provide chemical information are a recent development. Infrared snm-frequency microscopy has been demonstrated for LB films of arachidic acid, allowing for surface-specific imaging of the lateral distribution of a selected vibrational mode, the asymmetric methyl stretch [60]. The method is sensitive to the snrface distribntion of the functional gronp as well as to lateral variations in the gronp environmental and conformation. Second-harmonic generation (SHG) microscopy has also been demonstrated for both spread monolayers and LB films of dye molecules [61,62]. The method images the molecular density and orientation field with optical resolution, and local qnantitative information can be extracted. 

The asymmetrical D-ji-A dyes, often referred to as push-pull polyenes, are an additional class of cyanine-like molecules of interest. Due to their dipolar nature, the linear and nonlinear optical properties of this series of dyes can be strongly influenced by solvent polarity [84]. The structures of a series of such dyes (G19,... 

These spectroscopic studies have advanced our knowledge of the structure-property relations, which are extremely important for understanding the nonlinear optical behavior of these dyes, and specifically for their 2PA properties discussed below. 

By the sol-gel-process, inorganic glassy and hybrid polymeric materials are accessible at comparatively low temperatures [1], Therefore, organic molecules or dyes can easily be incorporated into the oxide matrix. This combination is especially attractive for the development of the following devices optical filters, solid-state lasers, optical switches, nonlinear optical laser hosts, optical data storage media, and photoconductive devices and films [2]. 

The chapters cover the following areas (i) use of coordination complexes in all types of catalysis (Chapters 1-11) (ii) applications related to the optical properties of coordination complexes, which covers fields as diverse as solar cells, nonlinear optics, display devices, pigments and dyes, and optical data storage (Chapters 12-16) (iii) hydrometallurgical extraction (Chapter 17) (iv) medicinal and biomedical applications of coordination complexes, including both imaging and therapy (Chapters 18-22) and (v) use of coordination complexes as precursors to semiconductor films and nanoparticles (Chapter 23). As such, the material in this volume ranges from solid-state physics to biochemistry. 

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