1. Novel Approach to Achieve Orientational Ordering of a Dipolar NLO Chromophore for Optical Communications G. Gonella, V. Krishnan, J. Strzalka, A. Tronin, H.-L. Dai, M. J. Therien & J. K. Blasie, NSEC DMR08-32802 Organic chromophores possessing highly polarizable, linearly extended-electron systemsoffer considerable potential for nonlinear optical (NLO) device applications. This potential arises from their large and ultrafast NLO response coupled with enormous design flexibility via molecular engineering. Dipolar “push-pull” chromophores effectively coupling metal-porphyrin electron donor & metal-polypyridyl acceptor components exhibit large hyperpolarizabilities in the longer wavelength regimes highly relevant to optical communications. Such dipolar chromophores thereby have the potential for a wide range of photonic device applications in this area, including frequency doublers, frequency converters and electro-optic modulators, based on the macroscopic 2nd-order nonlinear response of suitably organized ensembles. However, their dipolar nature make it inherently difficult to achieve such ensembles possessing the non-centrosymmetric ordering at high chromophore densities essential to maximizing the macroscopic NLO response. In this work, we describe a novel approach for achieving such orientational & positional ordering throughout a 2-D ensemble of the chromophores, utilizing a novel robust artificial protein based on a designed amphiphilic 4-helix bundle structure that also specifically vectorially incorporates such a chromophores possessing a metal-porphyrin. For one such prototypical dipolar chromophore, designated RuPZn, and the prototypical amphiphilc 4-helix bundle protein designated AP0, we have characterized both the structure of the ensemble via synchrotron x-ray scattering techniques (upper) and its macroscopic NLO response via the polarization dependence of optical 2nd harmonic generation (middle & lower). These recent results will appear in two back-to-back papers in J. Am. Chem. Soc.