| Abstract
| - A series of novel nonlinear optical (NLO) chromophores 1−4 incorporating the ferrocenyl (Fc)group as an electron donor and 2-dicyanomethylene-3-cyano-4-methyl-2,5-dihydrofuran (TCF) derivativesas electron acceptors are presented. The use of a constant Fc donor and varied acceptors and bridgesmakes it possible to systematically determine the contribution of the conjugated bridge and the acceptorstrength to chromophore nonlinear optical activity. The X-ray crystal structures of all four chromophoresallow for the systematic investigation of the structure−property relationship for this class of molecules. Forexample, the crystal structures reveal that both cyclopentadienyl groups in the ferrocenyl donor contributeto the electron donating ability. The first-order hyperpolarizabilities β of these chromophores, measured byhyper-Rayleigh scattering (HRS) relative to p-nitroaniline are reported. These β values are compared tothose calculated by density functional theory (DFT). The excellent agreement between the theoretical andexperimental β values demonstrates that a linear relation exists between the hyperpolarizability and thebond length alternation. An electrooptic coefficient, r33, of ∼25 pm/V at 1300 nm, for compound 4,incorporated into a polymer matrix, is competitive with organic chromophores. Moreover, this r33 is morethan 30 times larger than the previously reported value for an organometallic chromophore in a poledpolymer matrix. This work not only underscores the potential for Fc donor moieties, which have beenunderutilized, but also demonstrates that experimental characterization and theoretical simulations are nowcongruent, viable methods for assessing potential performance of NLO materials.
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