Interchromophoric interactions in chiral X-type π-conjugated oligomers: a linear and nonlinear optical study.

A concept of chiral, X-type organized π-conjugated oligomers, linked by means of a binaphthalene pincer, is presented. NMR spectroscopy and cyclic and differential pulse voltammetry indicate that these oligomers are in close proximity and influence each other in a through-space manner in their neutral as well as in their oxidized states. The interaction between the oligomers was also confirmed by UV-vis, CD, and emission spectroscopy. The synthetic versatility of this design also enables the development of heterocoupled binaphthalene derivatives BN1-2 and BN1-3, consisting of an electron-neutral oligothiophene or electron-rich oligomer and an electron-poor oligothiazole. Hyper-Rayleigh scattering data show a significant enhancement of the second-order nonlinear hyperpolarizability β for BN1-3 and BN1-2, in contrast with the homocoupled binaphthalene derivatives (BN1-1, BN2-2, and BN3-3). This enhancement provides direct proof for the through-space charge-transfer interaction between the p-type and the n-type oligomers within BN1-3 and BN1-2.