Non-covalent interactions between cations in the crystal structure of [Pt{4′-(p-tolyl)trpy}Cl]SbF6, where trpy is 2,2′:6′,2″-terpyridine, underpin the salt’s complex solid-state luminescence spectrum

• Published in: Inorganica Chimica Acta 2011-08, Vol.374 (1), p.197-204
• Main Authors: Field, John S., Wilson, Colin R., Munro, Orde Q.
• Format: Article
• Language: English
• Subjects: Luminescence; MMLCT; Platinum(II) complexes; Terpyridine; X-ray structure; π-Stack
• ISSN: 0020-1693; 1873-3255
• DOI: 10.1016/j.ica.2011.03.043

The emission spectrum (solid-state, 77K) of [Pt{4′-(p-tolyl)trpy}Cl]SbF6 exhibits decays from three photoexcited states: 3MLCT (MLCT=metal-to-ligand charge transfer) state; 3MMLCT (MMLCT=metal–metal-to-ligand charge transfer) state, and an excimeric 3π–π∗ state. These emitting states are rationalized by the chromophore packing in the X-ray structure at 100K. [Display omitted] ► Cations of [Pt{4′-(p-tolyl)trpy}Cl]SbF6 (trpy = 2,2′:6′,2″-terpyridine) stack in columns. ► Each cation is near-planar with the tolyl ring canted 9.3° out of the trpy ligand plane. ► The cations form inversion pairs (dimers) stabilized by short Pt···Pt interactions (3.434(1) Å). ► Unique π(trpy)–π(tolyl) interactions contribute to a complex solid emission spectrum at 77 K. ► Band maxima were assigned to 3MLCT (554 nm), 3MMLCT (604 nm), and excimeric 3π-π∗ (645 nm) states. The synthesis and characterization of [Pt{4′-(p-tolyl)trpy}Cl]SbF6 is described where trpy is 2,2′:6′,2″-terpyridine. A single crystal X-ray structure determination at 100K shows that the cations are stacked in columns that comprise cations arranged in a staircase motif. Successive cations within a column are linked by π(trpy)–π(phenyl) stabilizing interactions; and each cation in one column is linked to a cation in an adjacent column by a weakly stabilizing Pt···Pt interaction. The Pt···Pt distance is 3.434(1)Å. The metrics governing non-covalent interactions between [Pt{4′-(aryl)trpy}Cl]+ cations have been analyzed for the present structure and related structures in the CSD (Cambridge Structural Database). Cation dimers cluster into three distinct groups based on their lateral shifts and, to a lesser extent, the angular parameters governing their relative displacements; the dominant grouping exhibits Pt···Pt and π(trpy)–π(trpy) stabilizing interactions. An emission spectrum recorded at 77K on a solid sample of the compound is best interpreted as arising from the decay of three photoexcited states: a 3MLCT (MLCT=metal-to-ligand charge transfer) state; a 3MMLCT (MMLCT=metal–metal-to-ligand charge transfer) state, and an excimeric 3π–π∗ state.