Electroluminescent and photophysical properties of near-infrared luminescent lanthanide (III) monoporphyrinate complexes and pendant polymers.

摘要

The photoluminescent and electroluminescent properties of substituted lanthanide monoporphyrinate complexes were investigated. The lanthanide complexes consisted of a lanthanide (Yb3+) coordinated to a substituted porphyrin, 5,10,15,20-tetraphenylporphyrin (TPP), 5,10,15,20-tetrakis(3,4, 5-trimethoxyphenyl)porphyrin(TMPP), 5,10,15,20-tetra(4-pyridyl)porphyrin (TPyP), or 5,10,15,20-tetra(4(2'-ethylhexyloxy)porphyrin (TPP_OEH) and a capping ligand, L. The capping ligand was either an tris-pyrazoylborate (TP), (cyclopentadienyl)tris(diethoxyphosphito-P)cobaltate (L(OEt)3) or quinolinato (Q) anion. The complexes were synthesized to influence the electronic properties of the complex. The optical absorption and emission of these complexes resembled previously studied lanthanide porphyrin complexes, with photoluminescent yields ranging from 0.01 to 0.04. Electroluminescence was observed for the porphyrin complexes blended into polystyrene. External quantum efficiencies were typically 10-4, suggesting that changes to the porphyrin structure have little effect on the electronic nature of the complex. Blending the electron transporting AlQ3 into the device improved the external quantum efficiencies by an order of magnitude, suggesting that carrier transport is the culprit for poor device performance.; Conjugated polyacetylenes containing a Zinc porphyrin pendant were synthesized by an insertion type polymerization using [Rh(NBD)Cl]2. The homopolymer (poly(ZnETPP) and copolymers of ethynyl benzene (poly(ZnETPP)-co-(PE)), an oxadiazole containing group (poly(ZnETPP)-co-(PEOXAD), or 1-ethynyl-3,5-trifluoromethylbenzene (poly(ZnETPP)-co-(3,5CF3PE) were synthesized. The optical properties were studied and it was found that the homopolymer exhibited excitonic coupling due to the overlap of the porphyrin pendants. Substitution of other co-monomers reduced this coupling allowing the return of typical ZnTPP optical properties. Neither absorption nor emission from the polyacetylene backbone was identified. A thermally induced cis to trans isomerization was observed for the homopolymer, poly(ZnETPP), with the emergence of polyacetylene backbone emission. Electroluminescent devices were fabricated using the polymers neat or in a blend with polystyrene. The electroluminescent performance of the homopolymer was poor with a maximum external quantum efficiency of 10-6. Addition of polystyrene increased the efficiency 10-fold. The copolymers with PE also showed similar characteristics. The copolymers with either PEOXAD or 3,5CF3PE further increased the external efficiency by an order of magnitude. This suggest that adding hole blocking/electron transporting pendants to the polymer further enhances carrier transport, allowing for more efficient devices.