Luminescent Benzoquinolate‐Isocyanide Platinum(II) Complexes: Effect of Pt⋅⋅⋅Pt and π⋅⋅⋅π Interactions on their Photophysical Properties

The neutral compounds [Pt(bzq)(CN)(CNR)] (R= t Bu ( 1 ), Xyl ( 2 ), 2‐Np ( 3 ); bzq= benzoquinolate, Xyl=2,6‐dimethylphenyl, 2‐Np=2‐napthyl) were isolated as the pure isomers with a trans ‐C bzq ,CNR configuration, as confirmed by 13 C{ 1 H} NMR spectroscopy in the isotopically marked [Pt(bzq)( 13 CN)(CNR)] (R= t Bu ( 1′ ), Xyl ( 2′ ), 2‐Np ( 3′ )) derivatives ( δ 13 C CN ≈110 ppm; 1 J( Pt, 13 C)≈1425 Hz]. By contrast, complex [Pt(bzq)(C≡CPh)(CNXyl)] ( 4 ) with a trans ‐N bzq ,CNR configuration, has been selectively isolated from [Pt(bzq)Cl(CNXyl)] ( trans ‐N bzq ,CNR) using Sonogashira conditions. X‐ray diffraction studies reveal that while 1 adopts a columnar‐stacked chain structure with Pt–Pt distances of 3.371(1) Å and significant π⋅⋅⋅π interactions (3.262 Å), complex 2 forms dimers supported only by short Pt⋅⋅⋅Pt (3.370(1) Å) interactions. In complex 4 the packing is directed by weak bzq⋅⋅⋅Xyl and bzq⋅⋅⋅C≡E (C, N) interactions. In solid state at room temperature, compounds 1 and 2 both show a bright red emission ( ϕ =42.1 % 1 , 57.6 % 2 ). Luminescence properties in the solid state at 77 K and concentration‐dependent emission studies in CH 2 Cl 2 at 298 K and at 77 K are also reported for 1 , 1·CHCl3 , 2 , 2' , 2·CHCl3 , 3 , 4 .