Nonlinear optical organometallic polymers

Synthetic strategy has been developed that permits the efficient preparation of organometallic polymers which have structural characteristics necessary for nonlinear optical behavior. Complex t 5-C5H4CH20H - i 5-C5H4CH=C(CN)C02Et Fe (4) was prepared and homopolymerized through a thermally induced transesterification-polycondensation reaction. 

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... 

Besides other intriguing properties, such as inherent planar chirality, metallocenes are of interest due to their considerable Lewis basicity. Their direct or conjugative attachment to a polymer chain should enhance the electron density along the main chain and therefore lower the HOMO-LUMO band gap. In addition, organometallic compounds and metallocene-based monomers and polymers represent interesting potential nonlinear optical materials, useful for frequency doubling, modulation, and switching, for three reasons ... 

In the fields of organometallic polymer see Polymer) chemistry , in which complexes may have particularly interesting physical properties (liquid crystallinity, optical nonlinearity see Nonlinear Optical Materials), etc.), or of molecular electronics , metal alkynyl complexes play a significant role. These areas have been the subject of recent reviews, thus only a brief overview of methods to prepare iron alkynes will be given here. Liu has also recently reviewed the cyclization chemistry of alkynyl organometaUics, including those of iron. ... 

The expectation that organometallics containing ligands with conjugated and delocalized tt systems will provide useful applications for the synthesis of new polyunsaturated organic substrates or serve as precursors to organometallic polymers displaying electronic conductivity and nonlinear optical properties has stimulated intense research efforts into their synthesis and properties. 

For this reaction an organometallic photoinitiator was used that absorbs at 532 nm. Photocrosslinking of the oriented polymer can be used to produce a patterned material that exhibits a stable second-order nonlinear optics signal that lasts for several weeks at 100 °C. Addition of phenol is necessary to prevent thermal crosslinking. 

Nonlinear Optical (NLO) materials is a relatively new area of chemistry and has caught the attention of both the polymer and organometallic chemist. The use of ferrocene derivatives in NLO applications was first independently studied by two research groups. As anticipated, the metal center in ferrocene was found to serve as an excellent electron-donor. The crystalline compounds (see below) exhibited very high second harmonic generation (SHG) efficiencies relative to urea. ... 

Sidechain ferrocene-based polymers possessing nonlinear optical properties have been described by Wright and coworkers as shown in Scheme The copolymerization of 5 mol% of the ferrocenyl functionalized monomer 28 with methyl methacrylate 29 resulted in an organometallic polymer (30) displaying second-harmonic-generation activity. The Tg and T values of this organometallic polymer were 120 and 225°C, respectively, which are similar to those of poly(methyl methacrylate). 

Ferroelectric Polymers (1995), Nonlinear Optics of Organic Molecules and Polymers (1997) and Organic Electroluminescent Materials and Devices (1997), he has authored over 100 scientific publications in leading refereed journals and books, and has 18 patents either issued or applied for on electronic and photonic materials. He is the founder and Editor-in-Chief of the Journal of Porphyrins and Phthalocyanines and serves on the editorial board of Applied Organometallic Chemistry, Journal of Macromolecular Science-Physics and Photonics Science News. A member of the American Chemical Society and American Association for the Advancement of Science, he has also been awarded a number of prestigious fellowships in India and abroad National Merit Scholarship, Indian Space Research Organization (ISRO)... 

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