Brilliant Triboluminescence of a Lanthanide Coordination Polymer with Low-Vibrational-Frequency and Non-Centrosymmetric Structural Networks

Characteristic triboluminescence from a lanthanide coordination polymer with a non-centrosymmetric structure is reported. The lanthanide coordination polymer is composed of luminescent Eu-III ions and bidentate phosphane oxides, poly[3,3 '-bis(diphenylphosphoryl)-2,2 '-bipyridine][tris(hexafluoroacetylacetonate)]europium (poly-Eu-BIPYPO) crystals. The coordination geometry of poly-Eu-BIPYPO is categorized as an asymmetric eight-coordinate square antiprism (8-SAP). The space group of the crystal is also classified as the non-centrosymmetric Cc, which is suitable for piezoelectricity and triboluminescence. The photoluminescence quantum yield of poly-Eu-BIPYPO crystals excited at 380 nm is found to be 61%. Triboluminescence of the lanthanide coordination polymer is observed upon breaking, even at ambient temperature and in daylight. The remarkable triboluminescence phenomenon and geometrical structure of lanthanide coordination polymer are demonstrated.