Designing molecules to bypass the singlet-triplet bottleneck in the electroluminescence of organic light-emitting-diode materials

Electroluminescence in organic light emitting diode (OLED) materials occurs via the recombination of excitonic electrons-hole pairs Only the singlet excitons of commonly used OLED materials, e.g., Aluminum trihydroxyquinoline (AlQ$_3$), decay radiatively, limiting the external quantum efficiency to a maximum 25%. Thus 75% of the energy is lost due to the triplet bottleneck for radiative recombination. We consider molecules derived from AlQ$_3$ which bypass the triplet bottleneck by designing structures which contain strong spin-orbit coupling. As a first stage of this work, groundstate energies and vertical excitation energies of Al-arsenoquinolines and Al-boroarsenoquinolines are calculated. It is found that the substitution of N by As leads to very favourable results, while the boron substitution leads to no advantage.Comment: 4 pages, 4 figue

A Molecular Bis(isocyanide)silver(I) Nitrate Complex

Bis(p-tolylsulfonylmethylisocyanide)silver nitrate is obtained from the reaction of the isocyanide ligand with silver nitrate in chloroform regardless of the applied ratio of the reactands (1:1 or 2:1). The crystal structure of the product has been determined. In the complex molecule with C 2 symmetry, the nitrate anion is attached to the silver center as an η 2 -chelating ligand. Owing to this approach of the NO 3 ligand, the RNC-Ag-CNR axis (R = 4-Me-C 6 H 4 -SO 2 -CH 2 ) is bent [from 180 to 162.1(2) • ], but the geometry of the nitrate is not significantly distorted, suggesting only weak coordinative bonding. The structure is thus intermediate between that of a molecular complex with a tetrahedral coordination and that of an ionic compound with linear coordination of the silver center

The experimental gas-phase structures of 1,3,5-trisilylbenzene and hexasilylbenzene and the theoretical structures of all benzenes with three or more silyl substituents

The structures of 1,3,5-trisilylbenzene and hexasilylbenzene in the gas phase have been determined by electron diffraction, and that of 1,3,5-trisilylbenzene by X-ray crystallography. The structures of three trisilylbenzene isomers, three tetrasilylbenzenes, pentasilylbenzene and hexasilylbenzene have been computed, ab initio and using Density Functional Theory, at levels up to MP2/6-31G*. The primary effect of silyl substituents is to narrow the ring angle at the substituted carbon atoms. Steric interactions between silyl groups on neighbouring carbon atoms lead first to displacement of these groups away from one another, and then to displacement out of the ring plane, with alternate groups moving to opposite sides of the ring. In the extreme example, hexasilylbenzene, the SiCCSi dihedral angle is 17.8(8)°

On the selection and design of proteins and peptide derivatives for the production of photoluminescent, red-emitting gold quantum clusters

Novel pathways of the synthesis of photoluminescent gold quantum clusters (AuQCs) using biomolecules as reactants provide biocompatible products for biological imaging techniques. In order to rationalize the rules for the preparation of red-emitting AuQCs in aqueous phase using proteins or peptides, the role of different organic structural units was investigated. Three systems were studied: proteins, peptides, and amino acid mixtures, respectively. We have found that cysteine and tyrosine are indispensable residues. The SH/S-S ratio in a single molecule is not a critical factor in the synthesis, but on the other hand, the stoichiometry of cysteine residues and the gold precursor is crucial. These observations indicate the importance of proper chemical behavior of all species in a wide size range extending from the atomic distances (in the AuI-S semi ring) to nanometer distances covering the larger sizes of proteins assuring the hierarchical structure of the whole self-assembled system

Reactivity of Gold Hydrides: O2 Insertion into the Au–H Bond

Dioxygen reacts with the gold(I) hydride (IPr)AuH under insertion to give the hydroperoxide, (IPr)AuOOH, a long-postulated reaction in gold catalysis and the first demonstration of O2 activation by Au-H in a well-defined system. Subsequent condensation gave the peroxide (IPr)Au-OO-Au(IPr) (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazole-2-ylidene). The reaction kinetics are reported, as well as the reactivity of Au(I) hydrides with radical scavengers

Symbiotic organs shaped by distinct modes of genome evolution in cephalopods.

Microbes have been critical drivers of evolutionary innovation in animals. To understand the processes that influence the origin of specialized symbiotic organs, we report the sequencing and analysis of the genome of Euprymna scolopes, a model cephalopod with richly characterized host-microbe interactions. We identified large-scale genomic reorganization shared between E. scolopes and Octopus bimaculoides and posit that this reorganization has contributed to the evolution of cephalopod complexity. To reveal genomic signatures of host-symbiont interactions, we focused on two specialized organs of E. scolopes: the light organ, which harbors a monoculture of Vibrio fischeri, and the accessory nidamental gland (ANG), a reproductive organ containing a bacterial consortium. Our findings suggest that the two symbiotic organs within E. scolopes originated by different evolutionary mechanisms. Transcripts expressed in these microbe-associated tissues displayed their own unique signatures in both coding sequences and the surrounding regulatory regions. Compared with other tissues, the light organ showed an abundance of genes associated with immunity and mediating light, whereas the ANG was enriched in orphan genes known only from E. scolopes Together, these analyses provide evidence for different patterns of genomic evolution of symbiotic organs within a single host

Light-Activated Metal-Coordinated Supramolecular Complexes with Charge-Directed Self-Assembly

This document is the Accepted Manuscript version of a Published Work that appeared in final form in The Journal of Physical Chemistry C, copyright © American Chemical Society after peer review and technical editing by publisher. To access the final edited and published work see http://dx.doi.org/10.1021/jp3121403Metal-coordinated materials are attractive for many applications including catalysis, sensing, and controlled release. Adenine and its derivatives have been widely used to generate many coordination complexes, polymers, and nanoparticles. However, few of these materials display fluorescence. Herein, we report fluorescent gold complexes and nanoclusters formed with adenosine, deoxyadenosine, AMP, and ATP, where the former two produced micrometer-sized particles and the latter two produced molecular clusters. Only weak fluorescence was produced with adenine, while no emission was observed with uridine, cytidine, or guanosine. We found that adding citrate and light exposure are two key factors to generate fluorescence, and their mechanistic roles have been explored. In all the products, the ratio between gold and adenine was determined to be 1:1 using UV–vis spectroscopy. Mass spectrometry showed clusters containing 2, 4, and 6 gold atoms in the gas phase. The fluorescence peak is around 470 nm for the AMP and ATP complex and 480 nm for the (deoxy)adenosine complexes. This work has provided a systematic approach to obtain fluorescent metal coordinated polymers and materials with tunable sizes, which will find applications in analytical chemistry, drug delivery, and imaging. The fundamental physical chemistry of these materials has been systematically explored.University of Waterloo || Canadian Foundation for Innovation || Ontario Ministry of Research & Innovation || Natural Sciences and Engineering Research Council |