Luminescent benzoquinolate-isocyanide platinum(II) complexes: Effect of Pt⋯Pt and π⋯π interactions on their photophysical properties

Resumen

The neutral compounds [Pt(bzq)(CN)(CNR)] (R=tBu (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-Cbzq,CNR configuration, as confirmed by 13C{1H} NMR spectroscopy in the isotopically marked [Pt(bzq)(13CN)(CNR)] (R=tBu (1'), Xyl (2'), 2-Np (3')) derivatives (δ13CCN≈110 ppm; 1J(Pt, 13C)≈1425 Hz]. By contrast, complex [Pt(bzq)(C≡CPh)(CNXyl)] (4) with a trans-Nbzq,CNR configuration, has been selectively isolated from [Pt(bzq)Cl(CNXyl)] (trans-Nbzq,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 CH2Cl2 at 298 K and at 77 K are also reported for 1-4. Los compuestos neutros [Pt(bzq)(CN)(CNR)] [R=tBu 1, Xyl 2, 2-Np 3] fueron aislados como isõmeros puros con una configuraciõn trans-Cbzq,CNR, como se confirmõ por espectroscopía de RMN de 13C{1H} de los derivados marcados isotõpicamente [Pt(bzq)(13CN)(CNR)] [R=tBu 1', Xyl 2', 2-Np 3'] [δ13CCN≈110 ppm; 1J(Pt, 13C)≈1425 Hz]. Por el contrario, el complejo [Pt(bzq)(C≡CPh) (CNXyl)] (4) con una configuraciõn trans-Nbzq,CNR, ha sido aislado selectivamente a partir de [Pt(bzq)Cl(CNXyl)] (trans-N bzq,CNR) empleando la reacciõn de Sonogashira. Los estudios de difracciõn de rayos X revelan que mientras 1 adopta una estructura de apilamiento en columna con distancias Pt-Pt de 3.371(1) Å e importantes interacciones π⋯π (3.262 Å), el complejo 2 forma dímeros unidos solamente por interacciones Pt⋯Pt [3.370(1) Å]. En el complejo 4 el empaquetamiento está dirigido por débiles interacciones bzq⋯Xyl y bzq⋯C≡E (C, N). En estado sõlido a temperatura ambiente los compuestos 1 y 2 muestran una emisiõn roja muy intensa (φ=57.6 % 2, 42.1 % 1). Se describen también las propiedades luminiscentes en estado sõlido a 77 K y en CH2Cl2 en diversas concentraciones a 298 K y a 77 K de 1-4. Shining bright: New benzoquinolate isocyanide platinum(II) complexes, including the bright luminescent compounds (SP-4-3)-[Pt(bzq)(CN)(CNR)] (R=tBu (1), Xyl (2)), have been isolated as pure isomers. The title weak intermolecular interactions are responsible for their photophysical properties. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.