Cyclometalated Pt(II)‐Terpyridine Metallomesogen: What Is Visible or Invisible That Is a Matter of Molecular Packing and Orientation

An anisotropic light emitting metallomesogen (PtM) consisting of a cyclometalated platinum(II)–terpyridine (Pt(II)–tpy) chromophore and a flexible dendron is newly synthesized as a thermal‐induced and polarization‐induced solid‐state luminescence switching material. The self‐assembled PtM is uniaxially aligned by mechanical shearing within the mesophase resulting in high optical anisotropy with chromophores. The shear‐induced metastable PtM crystal exhibits emission change depending on the polarization direction and thermally triggered reversible emission quenching‐recovery characteristic. In order to precisely control the optical feature of the PtM, the self‐assembled supramolecular structure and thermal‐sensitive photophysical properties are characterized. Based on the multiresponsive luminescence switching system of PtM, a multiplexed optical code is encrypted with a simple coating and its feasibility for optical anticounterfeiting applications is demonstrated.