Utilizing Coupled-Oscillator Photophysics to Elaborate Chromophores with Exceptional Molecular Hyperpolarizabilities
The syntheses and electrooptic properties of a family of nonlinear optical chromophores are described. Typically, these species feature an ethyne-elaborated, highly polarizable porphyrinic component, and metal polypyridyl complexes that serve as integral donor and acceptor elements. The frequency dependence of the dynamic hyperpolarizability of a wide-range of these chromophores, that vary widely with respect to their electronic structure, was determined from hyper-Rayleigh light scattering (HRS) measurements carried out at fundamental incident irradiation wavelengths (λinc) of 830, 1064, and 1300 nm. These data show that: (i) Coupled oscillator photophysics and metal-mediated cross-coupling can be exploited to elaborate high βλ supermolecules that exhibit significant excited-state electronic communication between their respective pigment building blocks; (ii) High-stability metal polypyridyl compounds constitute an attractive alternative to electron releasing dialkyl- and diarylamino groups, the most commonly used donor moieties in a wide-range of established NLO dyes, and long-recognized to be the moiety that often limits the thermal stability of such compounds; (iii) This design strategy clearly enables ready elaboration of extraordinarily large βλ chromophores at telecommunication-relevant wavelengths; and (iv) Multiple charge-transfer (CT) transitions within a single chromophore can be designed to have transition dipole moments of the same or opposite sign; because the sign of the resonance enhancement factor is frequency dependent, appropriate engineering of the relative contributions of these CT states at a given wavelength provides a new means to regulate the magnitude of dynamic hyperpolarizabilities.
Uyeda, HT; Miloradovic, I; Zhao, Y; Wostyn, K; Asselbergsh, I; Clays, K; Persoons, A; Therien, MJ
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