Geometrically isomeric Pt(ii)/Fe(ii)-based heterometallo-supramolecular polymers with organometallic ligands for electrochromism and the electrochemical switching of Raman scattering (Geometrically isomeric Pt(II)/Fe(II)-based heterometallo-supramolecular polymers with organometallic ligands for electrochromism and the electrochemical switching of Raman scattering)