From Mesomorphic Phosphine Oxide to Clustomesogens Containing Molybdenum and Tungsten Octahedral Cluster Cores

Angew Chem Int Ed Engl. 2015 Sep 7;54(37):10921-5. doi: 10.1002/anie.201503205. Epub 2015 Jul 21.

Abstract

New clustomesogens (i.e., metal atom clusters containing liquid crystalline (LC) materials) have been obtained by grafting neutral cyanobiphenyl (CB)- or cholesteryl-containing tailor-made dendritic mesomorphic triphenylphosphine oxide ligands on luminescent (M6 Cl(i) 8 )(4+) octahedral cluster cores (M=Mo, W). The LC properties were studied by a combination of polarizing optical microscopy (POM), differential scanning calorimetry (DSC), and X-ray powder diffraction analyses. While the organic ligands showed various mesophase types ranging from nematic, SmA columnar (SmACol ), SmA, and SmC phases, it turned out that the corresponding clustomesogens formed layered phases (SmA) over a wide range of temperatures that depend on the nature and density of mesogenic groups employed. Intrinsic luminescence properties of the cluster precursors are preserved over the entire range of LC phase existence.

Keywords: cluster compounds; liquid crystals; molybdenum; phosphine oxide; tungsten.