Synthesis, Light-Emitting, and Two-Photon Absorption Properties of Platinum-Containing Poly(arylene-ethynylene)s Linked by 1,3,4-Oxadiazole Units

A series of soluble and thermally stable group 10 platinum(II) polyyne polymers of the type [-C equivalent to C- P1(PBu3)(2)-C equivalent to C-Ar-Ox-Ar-](n) (where Ox = 1,3,4-oxadiazole, Ar = p-C6H4 or 2,7-dihexy]-9.9-fluorene) and [-C equivalent to C-Pt(PBu3)(2)-C equivalent to C-Ar-Ox-Ar-Ox-Ar](n) (where Ar = 2,7-dihexy]-9.9-fluorene) along with their corresponding dinuclear model compounds [Ph-P1(PEt3)(2)-C equivalent to C-Ar-l(2)-Ox-(where Ar = p-C6H4 or 2,7-dihexy1-9,9-fluorene) and [Ph-Pt(PEt3)(2)-C equivalent to C-Ar-Ox-](2)-Ar- (where Ar = 2,7-dihexyl-9,9-fluorene) were prepared and characterized. The regiochemical structure of the polymers has been ascertained by single-crystal X-ray analysis on the model compound [Ph-Pt(PEt3)(2)-C equivalent to C-p-C6H4-l(2)-Ox- The photophysical properties (absorption, excitation, emission, and nanosecond transient absorption spectra) of these metalated compounds in 2MeTHF at 298 and 77 K are reported. These findings are correlated by density functional theory (DFT) calculations. Geometry optimizations predict totally planar molecules for these metalated complexes and polymers, allowing better pi-conjugation across the main chain. The ligands are strongly fluorescent but become also phosphorescent when the Pt atom is introduced in the backbone of the conjugated organometa Hie complexes and polymers. These emissions arc assigned to pi pi* transitions in all cases involving the Ptd(xy) orbitals. These Pt compounds exhibit two-photon absorption (2PA), and their 2PA cross sections (sigma 2) have been determined. The potential of exploiting such metallopolymers for the design of electrophosphorescent polymer light-emitting devices (PLEDs) and their use as single-dopant for white PLEDs have also been discussed.