NOVEL METALLOMESOGENS - FIRST SYNTHESIS AND INVESTIGATION OF LARGE MACROHETEROCYCLIC TETRAPLATINUM ORGANYLS

Two series (4 and 5, each with three members) of a new family of metal lomesogens have been synthesized starting from the bisimine ligands 1 and 2 and the dichloroplatinum compound 3. These one-pot reactions of 1 or 2 with 3 leading to 4a and 5a, respectively, give insights into p ossible self-assembly processes and constitute the first examples of f our-fold o-platinations in organic chemistry. The two pairs of halogen homologues 4b,c and 5b,c are then obtained by the usual exchange of t he four central chlorine bridges in their parent compounds 4a or 5a, r espectively, using the corresponding alkali-metal halides (potassium b romide, lithium iodide) in organic solvents at room temperature. Furth ermore, we report on the mesomorphism of these first tetraplatinum org anyls (applying a new system of mesophase notation for materials with sheet-like molecular structure) and describe some of their unusual lyo tropic (including charge-transfer-induced chiral nematic) properties i n apolar organic solvents in which, e.g., two nematic-columnar phases can be observed side by side.