Compounds of the formula I ##STR1## in which R is a C.sub.1 - to C.sub.22 -alkyl radical, A.sup.1 and A.sup.2 are hydrogen or methyl or, A.sup.1 is hydrogen and A.sup.2 is the nitro group, and B is the cyano group, the nitro group or an electron-attracting organic group having a double bond which is in conjugation with the thieno\x9b3,2-b!thiophene ring system, have a high dipole moment and a high polarizability and are suitable for purposes of nonlinear optics. If R in the formula I is a C.sub.12 - to C.sub.22 -alkyl radical, monomolecular layers can be applied to a substrate by the Langmuir-Blodgett method. The resulting layer elements are suitable, inter alia, as waveguides.
式I的化合物##STR1##中,R为C.sub.1-C.sub.22烷基基团,A.sup.1和A.sup.2为氢或甲基,或者A.sup.1为氢,A.sup.2为硝基基团,B为
氰基,硝基基团或具有与
噻吩\x9b3,2-b!
噻吩环系共轭的电子吸引有机基团,具有高偶极矩和高极化度,适用于非线性光学目的。如果式I中的R为C.sub.12-C.sub.22烷基基团,则可以通过Langmuir-Blodgett法将单分子层应用于底物。由此产生的层元素适用于波导等用途。