CONTROL OF THE CHARGE-DENSITY-WAVE STRENGTH IN MX SOLIDS USING A STRUCTURAL TEMPLATE EFFECT

A series of materials of stoichiometry [Pt(L-L)2Cl2][Pt(L-L)2]Y4, with L-L = amine and Y = counterion, were synthesized and characterized employing X-ray diffraction and resonance Raman spectroscopy. These solids contain one-dimensional chains of alternating metal and halogen atoms that have undergone a Peierls distortion and charge disproportionation, producing alternating valence states on the metals along the chain axis: X-Pt(IV)-Cl ... Pt(II) Cl. It was discovered that the electronic and optical properties of these one-dimensional materials could be widely controlled through employing different combinations of L-L and Y; templates composed of hydrogen bonded networks of L-L and Y were used to control Cl-Pt(II)-Cl ... Pt(IV) ... Cl chain geometry. Relationships between the charge-density-wave strength (measured as the ratio of the long Pt(II) ... Cl distance to the short Pt(IV)-Cl distance) and band gap energy, Pt-Pt separation, and Pt-Cl stretching frequency were developed. This work has provided a wealth of information for many-body theoretical calculations modeling electron-electron and electron-phonon interactions in one-dimensional materials.