Near-Infrared Emissive B-N Lewis Pair-Functionalized Anthracenes via Selective LUMO Delocalization in Extended Conjugated Dimer and Polymer.

Acenes are attractive as building blocks for low gap organic materials with applications, for example, in organic light emitting diodes, solar cells, bioimaging and diagnostics. Previously, we have shown that modification of dipyridylanthracene via B-N Lewis pair fusion (BDPA) strongly redshifts the emission, while facilitating self-sensitized reactivity toward O2 to reversibly generate the corresponding endoperoxides. Herein, we report on the further expansion of the p-system of BDPA to a vinyl-substituted monomer, vinylene-bridged dimer, and a polymer with an average of 20 chromophores. The extension of π-conjugation results in largely reduced band gaps of 1.8 eV for the dimer and 1.7 eV for the polymer, the latter giving rise to NIR emission with a maximum at 731 nm and an appreciable quantum yield of 7%. Electrochemical and computational studies reveal efficient delocalization of the lowest unoccupied molecular orbital (LUMO) along the pyridyl-anthracene-pyridyl axis, which results in effective electronic communication between BDPA units, selectively lowers the LUMO, and ultimately narrows the band gap. Time-resolved emission and transient absorption (TA) measurements offer insights into the pertinent photophysical processes. Extension of π-conjugation also slows down the self-sensitized formation of endoperoxides, while significantly accelerating the thermal release of singlet oxygen to regenerate the parent acenes.

Tuning the electronic properties of the γ-Al2O3 surface by phosphorus doping.

Tuning the electronic properties of oxide surfaces is of pivotal importance, because they find applicability in a variety of industrial processes, including catalysis. Currently, the industrial protocols for synthesizing oxide surfaces are limited to only partial control of the oxide's properties. This is because the ceramic processes result in complex morphologies and a priori unpredictable behavior of the products. While the bulk doping of alumina surfaces has been demonstrated to enhance their catalytic applications (i.e. hydrodesulphurization (HDS)), the fundamental understanding of this phenomenon and its effect at an atomic level remain unexplored. In our joint experimental and computational study, simulations based on Density Functional Theory (DFT), synthesis, and a variety of surface characterization techniques are exploited for the specific goal of understanding the structure-function relationship of phosphorus-doped γ-Al2O3 surfaces. Our theoretical calculations and experimental results agree in finding that P doping of γ-Al2O3 leads to a significant decrease in its work function. Our computational models show that this decrease is due to the formation of a new surface dipole, providing a clear picture of the effect of P doping at the surface of γ-Al2O3. In this study, we uncover a general paradigm for tuning support-catalyst interactions that involves electrostatic properties of doped γ-Al2O3 surface, specifically the surface dipole. Our findings open a new pathway for engineering the electronic properties of metal oxides' surfaces.

Poly(cyclopentadienylene ethynylene)s: Breaking Conventional Polyenyne Motifs.

Conjugated polyenynes comprising dienyne constituents have been synthesized for the first time, expanding the architectural scope of this unique polymer class. The poly(cyclopentadienylene ethynylene)s (PCE)s are soluble in common organic solvents, a rare feature among polyenynes, and possess physicochemical properties that are influenced by the structure of their solubilizing groups. A comparative analysis between the PCEs and other soluble polyenynes, poly(arylene ethynylene)s, and a hybrid of both polymer classes show among other characteristics that the inclusion of cyclopentadienes into the conjugated backbone significantly reduces electronic transition energies while completely suppressing photoluminescence.