Filamentous cyanobacteria of the genus Lyngbya are important contributors to coral reef ecosystems, occasionally forming dominant cover and impacting the health of many other co-occurring organisms. Moreover, they are extraordinarily rich sources of bioactive secondary metabolites, with 35% of all reported cyanobacterial natural products deriving from this single pantropical genus. However, the true natural product potential and life strategies of Lyngbya strains are poorly understood because of phylogenetic ambiguity, lack of genomic information, and their close associations with heterotrophic bacteria and other cyanobacteria. To gauge the natural product potential of Lyngbya and gain insights into potential microbial interactions, we sequenced the genome of Lyngbya majuscula 3L, a Caribbean strain that produces the tubulin polymerization inhibitor curacin A and the molluscicide barbamide, using a combination of Sanger and 454 sequencing approaches. Whereas ∼293,000 nucleotides of the draft genome are putatively dedicated to secondary metabolism, this is far too few to encode a large suite of Lyngbya metabolites, suggesting Lyngbya metabolites are strain specific and may be useful in species delineation. Our analysis revealed a complex gene regulatory network, including a large number of sigma factors and other regulatory proteins, indicating an enhanced ability for environmental adaptation or microbial associations. Although Lyngbya species are reported to fix nitrogen, nitrogenase genes were not found in the genome or by PCR of genomic DNA. Subsequent growth experiments confirmed that L. majuscula 3L is unable to fix atmospheric nitrogen. These unanticipated life history characteristics challenge current views of the genus Lyngbya. diazotrophy | polyketide synthase/nonribosomal peptide synthetase | mass spectrometry | harmful algal bloom | marine biology

A series of new donor-substituted 1,3,5-triazines (TRZ 1−7) has been prepared by nucleophilic substitution of cyanuric chloride with carbazole, 3-methylcarbazole, phenol, and 3,5-dimethylphenol. These s-triazines have been investigated as host material for blue phosphorescent light-emitting diodes (OLEDs). All triazine based hosts were characterized regarding their optical and thermal properties. Different substitution patterns resulted in high glass-transition temperatures (T g) of up to 170 °C and triplet energies (ΔE(T1−S0)) of up to 2.96 eV. The application as host material for the blue phosphor bis(4,6-difluorophenylpyridinato-N,C2)picolinato-iridium(III) (FIrpic) yielded maximum current efficiencies up to 21 cd/A.

Carbazole-based materials such as 4,4'-bis(N-carbazolyl)-2,2'-biphenyl (CBP) and its derivatives are frequently used as matrix materials for phosphorescent emitters in organic light emitting diodes (OLED)s. An essential requirement for such matrix materials is a high energy of their first triplet excited state. Here we present a detailed spectroscopic investigation supported by density functional theory (DFT) calculations on two series of CBP derivatives, where CH(3) and CF(3) substituents on the 2- and 2'-position of the biphenyl introduce strong torsion into the molecular structure. We find that the resulting poor coupling between the two halves of the molecules leads to an electronic structure similar to that of N-phenyl-3,6-dimethylcarbazole, with a high triplet-state energy of 2.95 eV. However, we also observe a triplet excimer emission centered at about 2.5-2.6 eV in all compounds. We associate this triplet excimer with a sandwich geometry of neighboring carbazole moieties. For compounds with the more polar CF(3) substituents, the lifetime of the intermolecular triplet excited state extends into the millisecond range for neat films at room temperature. We attribute this to an increased charge-transfer character of the intermolecular excited state for the more polar substituents.

Here, a study of the electric field induced quenching on the phosphorescence intensity of a deep‐blue triplet emitter dispersed in different host materials is presented. The hosts are characterized by a higher triplet excitonic level with respect to the emitter, ensuring efficient energy transfer and exciton confinement, whereas they differ in the highest occupied molecular orbital (HOMO) alignment, forming type I and type II host/guest heterostructures. While the type I structure shows negligible electric field induced quenching, a quenching up to 25% for the type II at a field of 2 MV/cm is reported. A similar quenching behaviour is also reported for thin films of the pure emitter, revealing an important luminescence loss mechanism for aggregated emitter molecules. These results are interpreted by considering Coulomb stabilized excitons in the type II heterostructure and in the pure emitter, that become very sensitive to dissociation upon application of the field. These results clarify the role of external electric field quenching on the phosphorescence of triplet emitters and provide useful insights for the design of deep‐blue electrophosphorescent devices with a reduced efficiency roll‐off.

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