(S)everal chiral molecules with C-2 symmetry derived from two geometries of the binaphthol (BN) system substituted with different accepters have been synthesized in order to study the possibility of producing noncentrosymmetric crystals formed from these chiral structures. All the molecules possess two equal donor-acceptor (D-A) systems linked together to give a bis(dipolar) V-shaped system. The dihedral angle a between the two connected D-A sys tems has been controlled by chemical methods; this leads to distinct changes in the optical spectra of the connected D-A chromophores, primarily changes caused by effective conjugation of the D-A system imposed by conformation constraints. The crystal structure of chiral (S)-2,2'-diethoxy-1,1'-binaphthyl-6,6'-dicarbaldehyde (4 a) has been elucidated and indicates that the dipoles in the naphthyl moiety within the overall noncentrosymmetric crystal can cancel out exactly despite the noncentrosymmetry. The crystal structure of racemic 9,14-dicyanodinaphtho[2,1-d:1',2'-f][1,3]-dioxepin (2b) was found to be centrosymmetric. The new compounds were investigated for second-harmonic generation (including BN derivatives reported earlier) by the Kurtz-Perry powder test to evaluate the second-order nonlinear optical (NLO) properties of polycrystalline samples. Although chirality ensures noncentrosymmetric crystals, only modest (approximate to 2-methyl-4-nitroaniline) or no nonlinearities were observed in the powder test, For a representative selection of the molecules, the first molecular hyperpolarizabilities beta(2) were shown to be very high (up to 888 x 10(-30) esu for 14a) by electric field induced second harmonic generation (EFISHG) measurements. Synthetic routes are reported for optically pure 6,6'-disubstituted-2,2'-diethoxy-1,1'-binaphthyls 2a, 3a, 6a, 10a, 11a, 14a, 15a [acceptor=CN, SO2CH3, (E)-CH=CHSO2CH3, (E)-CH-CH(p-PhCN), (E)-CH=CH(p-Ph-SO2CH3), (E)-CH=CH(p-PhCh=C-(CN)(2)), (E)-CH=CHCH=C(CN)(2)] and optically pure 9,14-disubstituted-dinaphtho[2,1-d:1',2'-f][1,3]dioxepins 2b, 3b, 10b, 11b, 13b, 14b, 15b [acceptor = CN (only racemic), SO2CH3, (E)-CH=CH-(p-PhCN), (E)-CH=CH(p-PhSO2CH3), (E)-CH=CH(p-PhNO2), (E)-CH=Ch-(p-PhCh=C(CN)(2)), (E)-CH=CH-CH=C(CN)(2)].
|Journal||Chemistry: A European Journal|
|Publication status||Published - 1998|
Deussen, H-J., Boutton, C., Thorup, N., Geisler, T., Hendrickx, E., Bechgaard, K., Persoons, A., & Bjørnholm, T. (1998). New Chiral Bis-Dipolar 6,6'-Disubstituted-Binaphthol Derivatives for Second-Order Nonlinear Optics. Chemistry: A European Journal, 4(2), 240-250. https://doi.org/10.1002/(SICI)1521-3765(19980210)4:2<240::AID-CHEM240>3.0.CO;2-H