Novel metallomesogens: first synthesis and investigation of large macroheterocyclic tetraplatinum organyls

Abstract

Two series (4 and 5, each with three members) of a new family of metallomesogens 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 possible self-assembly processes and constitute the first examples of four-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 the four central chlorine bridges in their parent compounds 4a or 5a, respectively, using the corresponding alkali-metal halides (potassium bromide, lithium iodide) in organic solvents at room temperature. Furthermore, we report on the mesomorphism of these first tetraplatinum organyls (applying a new system of mesophase notation for materials with sheet-like molecular structure) and describe some of their unusual lyotropic (including charge-transfer-induced chiral nematic) properties in apolar organic solvents in which, e.g., two nematic–columnar phases can be observed side by side.