EINKRISTALL-MOLEKÜLSTRUKTUREN 107^1.2: STRUKTURÄNDERUNGEN VON THIANTHREN, 2,3,6,7-TETRAMETHOXYTHIANTHREN UND 2,3,6,7-TETRAMETHOXYSELENANTHREN BEI KOMPLEXBILDUNG MIT ELEKTRONENAKZEPTOREN SOWIE BEI EINELEKTRONENOXIDATION ZU DEN RADIKALKATIONEN

Abstract

Information on structural changes due to partial and full one-electron transfer is obtained by comparing the single crystal structures of both donor/acceptor complexes of thianthrene and selenanthrene derivatives with those of their radical cation salts: The single crystal structures of {thianthrene pyromelliticdianhydride}, {2,3,6,7-tetramethoxythianthrene 1,2,4,5-tetracyanobenzene} and 2,3,6,7-tetramethoxyselenanthrene 1,2,4,5-tetracyanobenzene} do not exhibit any significant differences relative to that of their components. On the contrary, in the corresponding radical cation salts [2,3,6,7-tetramethoxythianthrene^⊕][Br₃ ^⊖] as well as [2,3,6,7-totramethoxyselenanthrene^⊕][I₃ ^⊖] severe structural changes are observed such as the flattening of the molecular skeletons or beginning cyanine distortions along the chains H₃CO[sbnd]C₃[sbnd]X[sbnd]C₃[sbnd]OCH₃. Accompanying UN/VIS measurements of solutions containing both donor and acceptor prove long-wavelengths charge transfer bands with drastically reduced excitation energies relative to that of the separated molecules. Therefore, in the ground state of the donor/acceptor complexes between electron-rich sulfur donors and suitable acceptors, only an almost negligible charge transfer occurs. The weak interactions in the van der Waals complexes can be rationalized by correlation of the respective orbital diagrams with the crystal lattice arrangements determined experimentally. Al-together, prospects for new materials are provided.

Key Words:

• 2,3,6,7-tetramethoxy-thianthrene and -selenanthrene structural changes
• (on partial electron transfer in) acceptor complexes (and on oxidation to) radical cations
• UV/VIS measurements
• MO calculations