Synthesis and structures of thieno[2,3-b]thiophene incorporated [3.3]dithiacyclophanes. Enhanced first hyperpolarizability in an unsymmetrically polarized cyclophane

The synthesis and structures of dithiacyclophanes incorporating thieno[2,3-b]thiophene are described. Donor-acceptor cyclophane 7 displayed significantly higher first hyperpolarizability β compared to the open model 10 presumably on account of an extra contribution to nonlinearity arising from through-space charge redistribution, a feature lacking in 10.