[Pt(SCN)4]2–‐Based Coordination Polymers and Supramolecular Squares: Intermolecular Pt···H–C Interactions Probed by Luminescence Spectroscopy at Variable Pressure

The structures of four types of supramolecular systems containing [Pt(SCN)4]2– molecular units have been characterized. [Mn(bipy)2Pt(SCN)4]2·2MeOH (1) and [Zn(bipy)2Pt(SCN)4]2·2MeOH (2) show cis-thiocyanato ligands bridging the PtII and MnII or ZnII ions, leading to a molecular square motif. [Zn(bipy)2Pt(SCN)4]2 (3) presents chains where trans-thiocyanato ligands bridge the ZnII and PtII ions. For 1–3, free thiocyanato ligands are coordinated to the PtII centers to complete the square-planar coordination. [Pb(bipy)2Pt(SCN)4]2 (4) reveals a two-dimensional sheet structure where all SCN– ligands bridge the PbII and PtII ions. [Pb(terpy)Pt(SCN)4]2 (5) is similar to 3, with two bridging trans-SCN– ligands and two that are coordinated only to the PtII centers. For all compounds, d–d luminescence is observed with band maxima at approximately 14600 cm–1 (690 nm). Spectra show characteristic shifts with pressure, indicative of either intramolecular or intermolecular effects, depending on the sign of the shift. The pressure-dependent shifts for 1–5 show rich variations. A well-documented shift to higher energy due to metal–ligand bond compression is observed for 5 and can be used as a basis for a comparison. Compounds 1–4 show a shift of Emax to lower energy with pressures below 10 kbar. A change in sign for the shift of Emax occurs at 20, 12, and 10 kbar for 1, 2, and 3, respectively. For 4, only a shift to lower energy is observed. Competing intra- and intermolecular effects lead to these variations.