Platinum(II) Complexes with π‐Conjugated, Naphthyl‐Substituted, Cyclometalated Ligands (RC^N^N): Structures and Photo‐ and Electroluminescence

Abstract

The crystal structures and photophysical properties of mononuclear [(RC N N)PtX](ClO4)n ((RC N N)=3-(6'-(2''-naphthyl)-2'-pyridyl)isoquinolinyl and derivatives; X=Cl, n=0; X=PPh(3) or PCy(3), n=1), dinuclear [(RC N N)2Pt2(mu-dppm)](ClO4)2 (dppm=bis(diphenyphosphino)methyl) and trinuclear [(RC N N)3Pt3(mu-dpmp)](ClO4)3 (dpmp=bis(diphenylphosphinomethyl)phenylphosphine) complexes are presented. The crystal structures show extensive intra- and/or intermolecular pipi interactions; the two (RC N N) planes of [(RC N N)2Pt2(mu-dppm)](ClO4)2 (R=Ph, 3,5-tBu2Ph or 3,5-(CF3)2Ph) are in a nearly eclipsed configuration with torsion angles close to 0 degrees. [(RC N N)PtCl], [(RC N N)2Pt2(mu-dppm)](ClO4)2, and [(RC N N)3Pt3(mu-dpmp)](ClO4)3 are strongly emissive with quantum yields of up to 0.68 in CH2Cl2 or MeCN solution at room temperature. The [(RC N N)PtCl] complexes have a high thermal stability (T(d)=470-549 degrees C). High-performance light-emitting devices containing [(RC N N)PtCl] (R=H or 3,5-tBu2Ph) as a light-emitting material have been fabricated; they have a maximum luminance of 63,000 cd m(-2) and CIE 1931 coordinates at x=0.36, y=0.54.

Emissive or Nonemissive? A Theoretical Analysis of the Phosphorescence Efficiencies of Cyclometalated Platinum(II) Complexes

“…The results are collected in Tables S2-S6, together with their simulated absorption spectra ( Figure S1), in the Supporting Information. The calculated absorption energies are generally in satisfactory agreement with the experimental values, [16,17,19,22] except for 1, for which the TDDFT method overestimates the absorption energies by as much as 2500 cm…”

“…The corresponding X-ray data of 4 were reported to be 1.997 (8) and 2.088(5) , respectively. [22] However, the Pt À N lat distance is much longer (2.12(2) ) when the 4'-position of the central pyridyl ring of 4 is substituted with a phenyl ring. [22] The transition energies of 1-5 in CH 2 Cl 2 solution at their respective S 0 optimized geometries were also evaluated by the TDDFT approach.…”

“…[22] However, the Pt À N lat distance is much longer (2.12(2) ) when the 4'-position of the central pyridyl ring of 4 is substituted with a phenyl ring. [22] The transition energies of 1-5 in CH 2 Cl 2 solution at their respective S 0 optimized geometries were also evaluated by the TDDFT approach. The results are collected in Tables S2-S6, together with their simulated absorption spectra ( Figure S1), in the Supporting Information.…”

“…deviations 0.06 and 68), [15,16,19,22,26,35] except for 4, for which the PtÀN lat and PtÀ C lat distances were calculated to be 2.170 and 1.998 , respectively (N lat and C lat are respectively the nitrogen atom of the lateral isoquinolinyl ring and the carbon atom of the lateral naphthyl ring directly coordinated to the Pt II ion). The corresponding X-ray data of 4 were reported to be 1.997 (8) and 2.088(5) , respectively.…”

“…Recently, Yersin and coworkers proposed that closer proximity of the occupied d orbitals in quasi-octahedral transition metal complexes than in quasi-square-planar transition metal complexes is likely the reason why the former are usually better emitters than the latter. [20,21] In this work, we attempt to provide a theoretical basis to account for the luminescence properties of a family of square-planar platinum(II) complexes 1-5 with tridentate cyclometalated ligands, which have received widespread interest in recent years because 1) they are strongly emissive when the platinum(II) ion is coordinated to appropriate auxiliary ligands; [15,16,22] 2) their emission intensities are sensitive to their local environments; [17,[23][24][25] 3) their open square-planar geometries allow intermolecular interactions, which in turn significantly change the emission intensities and energies; [19,26] and 4) they have demonstrated usefulness in optoelectronic device applications such as high performance white-light and near-infrared organic lightemitting diodes, as well as luminescent probes for signaling studies. [19,[27][28][29][30][31] …”