Rigid biimidazole ancillary ligands as an avenue to bright deep blue cationic iridium(III) complexes

EZ-C acknowledges the University of St Andrews for financial support. Date of Acceptance: 03/06/2014Herein we report the synthesis and optoelectronic characterisation of three deep blue-emitting cationic iridium complexes, of the form [Ir(dFppy)2(N^N)]PF6, bearing biimidazole-type N^N ancillary ligands (dFppyH = 2-(2,4-difluorophenyl)pyridine). Complex 1 contains the parent biimidazole, biim, while 2 contains a dimethylated analog, dMebiim, and 3 contains an ortho-xylyl-tethered biimidzole, o-xylbiim. We explore a strategy of tethering the biimidazole in order to rigidify the complex and increase the photoluminescent quantum yield, culminating in deep blue (λmax: 457 nm in MeOH at 298 K) ligand-centered emission with a very high photoluminescent quantum yield of 68% and microsecond emission lifetime. Density functional theory calculations elucidate the origin of such disparate excited state kinetics across this series, especially in light of virtually identical optoelectronic properties observed for these compounds.PostprintPeer reviewe

Synthesizing bird song

Journal ArticleIn this work we present an electronic syrinx: an analogical integrator of the equations describing a model for sound production by oscine birds. The model depends on time varying parameters with clear biological interpretation: the air sac pressure and the tension of ventral syringeal muscles. We test the hypothesis that these physiological parameters can be reconstructed from the song. In order to do so, we built two transducers. The input for these transducers is an acoustic signal. The first transducer generates an electric signal that we use to reconstruct the bronchial pressure. The second transducer allows us to reconstruct the syringeal tension (in both cases, for the time intervals where phonation takes place). By driving the electronic syrinx with the output of the transducers we generate synthetic song. Important qualitative features of the acoustic input signal are reproduced by the synthetic song. These devices are especially useful to carry out altered feedback experiences, and applications as biomimetic resources are discussed

Supramolecular assemblies showing thermally activated delayed fluorescence

We thank the East of Scotland Industrial Catalysis Centre for Doctoral Training (EaSI-CAT) for financial support [Ph.D. studentship to “T.A.C”].Supramolecular assemblies based on luminescent components can offer significant advantages over their discrete counterparts, including improved quantum yields, stability, and tunability. Following interest as advanced optoelectronic materials, thermally activated delayed fluorescence (TADF) emitters have been incorporated into a range of supramolecular structures. Here we present a summary of the known examples of emissive supramolecular systems that operate via a TADF mechanism with comparisons, where possible, to their discrete counterparts. While the types of supramolecular structures are diverse, there are limited examples shown for each class. With the increase in photophysical performance and/or emergence of new photochemical properties upon going from molecular to supramolecular, the potential that these systems hold becomes apparent.Publisher PDFPeer reviewe

O contato com a natureza: efeitos de viagens ao campo sobre os conhecimentos intenções e atitudes pró-ambientais

The effects of direct contact with nature on pro-environmental attitudes, values and knowledge were assessed by taking college students on field trips at Parque Estadual Turístico do Alto Ribeira (PETAR), and applying a system of directed activities developed throughout 16 years. The changes in knowledge, values and attitudes were evaluated in these students (experimental groups) and other students who were not exposed to the field trips (control groups) through questionnaires which were applied before (pre-tests) and after the trip (post-tests). Meaningful differences were verified between the control and the experimental groups, as well as discrepancies between the pre- and post-tests applied to the experimental groups - a clear indication that the direct contact with nature affected the positioning of the students towards environmental matters. These outcomes reinforce the idea of the importance of contact with nature as a way of implementing pro-environmental behaviors.Os efeitos do contato direto com a natureza nos conhecimentos, nas intenções e atitudes pró-ambientais foram avaliados durante viagens com estudantes universitários ao Parque Estadual Turístico do Alto Ribeira (PETAR), onde foram realizadas atividades dirigidas desenvolvidas ao longo de 16 anos. As mudanças nos conhecimentos, valores e atitudes foram avaliadas nesses alunos (grupos experimentais) e em outros, que não participaram das viagens (grupos- controle), por meio de questionários que foram aplicados antes (pré-testes) e depois da viagem (pós-testes). Diferenças significativas foram verificadas entre os grupos-controle e experimentais, bem como discrepâncias entre os pré e pós-testes aplicados aos grupos experimentais - uma clara indicação de que o contato direto com a natureza afetou o posicionamento dos alunos em relação às questões ambientais. Estes resultados reforçam a ideia da importância do contato com a natureza como forma de implementar comportamentos pró-ambientais.Universidade Federal de São Paulo (UNIFESP)UNIFESP, ICAQFSciEL

Mechanophotocatalysis : a generalizable approach to solvent-minimized photocatalytic reactions for organic synthesis

The authors thank the Leverhulme Trust (RPG-2023-110), the Engineering and Physical Sciences Research Council for funding (EP/W007517, EP/W015137/1) and the European Commission (PhotoReAct ITN: 956324). F. M. thanks the EaSI-CAT CDT at the University of St Andrews for support in the form of a studentship.This proof-of-concept study cements the viability and generality of mechanophotocatalysis, merging mechanochemistry and photocatalysis to enable solvent-minimized photocatalytic reactions. We demonstrate the transmutation of four archetypal solution-state photocatalysis reactions to a solvent-minimized environment driven by the combined actions of milling, light, and photocatalysts. The chlorosulfonylation of alkenes and the pinacol coupling of aldehydes and ketones were conducted under solvent-free conditions with competitive or superior efficiencies to their solution-state analogues. Furthermore, decarboxylative alkylations are shown to function efficiently under solvent-minimized conditions, while the photoinduced energy transfer promoted [2+2] cycloaddition of chalcone experiences a significant initial rate enhancement over its solution-state variant. This work serves as a platform for future discoveries in an underexplored field: validating that solvent-minimized photocatalysis is not only generalizable and competitive with solution-state photocatalysis, but can also offer valuable advantages.Peer reviewe

Luminescent iridium complexes used in Light Emitting Electrochemical Cells (LEECs)

EZ-C acknowledges the University of St Andrews for financial support. The authors would like to thank the Engineering and Physical Sciences Research Council for financial support for Adam Henwood: EPSRC DTG Grants: EP/J500549/1; EP/K503162/1; EP/L505097/1.Cationic iridium(III) complexes represent the single largest class of emitters used in light emitting electrochemical cells (LEECs). In this chapter, we highlight the state-of-the-art emitters in terms of efficiency and stability in LEEC devices, highlighting blue, green, yellow/orange, red and white devices, and provide an outlook to the future of LEECs.Publisher PDFPeer reviewe

Materials for electrochemiluminescence : TADF, hydrogen-bonding, and aggregation- and crystallization-induced emission luminophores

Authors thank the Natural Sciences and Engineering Research Council Canada (NSERC, DG RGPIN-2018- 06556, DG RGPIN-2023-05337 and SPG STPGP-2016-493924), New Frontiers in Research Fund (NFRFR-2021-00272), Canada Foundation of Innovation/Ontario Innovation Trust (CFI/OIT, 9040) and The University of Western Ontario for the support to this research. KC is an Ontario Graduate Scholar.Electrochemiluminescence (ECL) is a rapidly growing discipline with many analytical applications from immunoassays to single-molecule detection. At the forefront of ECL research is materials chemistry, which looks at engineering new materials and compounds exhibiting enhanced ECL efficiencies compared to conventional fluorescent materials. In this review, we summarize recent molecular design strategies that lead to high efficiency ECL. In particular, we feature recent advances in the use of thermally activated delayed fluorescence (TADF) emitters to produce enhanced electrochemiluminescence. We also document how hydrogen bonding, aggregation, and crystallization can each be recruited in the design of materials showing enhanced electrochemiluminescence.Publisher PDFPeer reviewe

Compositional variation in hybrid organic-inorganic lead halide perovskites : kinetically- versus thermodynamically-controlled synthesis

Authors thank the Chinese Scholarship Council and the University of St Andrews for Ph.D. Studentship support (to JT, CSC No. 201603780020).The formation and study of partial solid solutions in Az1-xFAxPbBr3, using reportedly similar sized cations azetidinium (Az+) and formamidinium (FA+), was explored via mechanosynthesis and precipitation synthesis. The composition and lattice parameters of samples from both syntheses were analyzed by 1H NMR and Rietveld refinement of powder X-ray diffraction. A clear mismatch in the composition of the perovskite was found between the precipitated samples and the corresponding solutions. Such a mismatch was not observed for samples obtained via mechanosynthesis. The discrepancy suggests products are kinetically-controlled during precipitation, compared to thermodynamically controlled mechanosynthesis. Furthermore, the cell volume as a function of composition in both hexagonal, 6H (Az-rich) and cubic, 3C (FA-rich) perovskite solid solutions suggests that FA+ is actually smaller than Az+, contradicting the literature. In the 3C (Az-poor) solid solutions, the extent of Az1-xFAxPbBr3 is unexpectedly smaller than in the corresponding methylammonium (MA+) system, Az1-xMAxPbBr3, which suggests that the extent of solid solution formation in these halide perovskites is predominantly dependent on the average A-cation size while the size mismatch plays a lesser role in comparison to oxides.PostprintPeer reviewe