Towards non-blinking and photostable perovskite quantum dots.

Surface defect-induced photoluminescence blinking and photodarkening are ubiquitous in lead halide perovskite quantum dots. Despite efforts to stabilize the surface by chemically engineering ligand binding moieties, blinking accompanied by photodegradation still poses barriers to implementing perovskite quantum dots in quantum emitters. To date, ligand tail engineering in the solid state has rarely been explored for perovskite quantum dots.

Structure-property relationships in dicyanopyrazinoquinoxalines and their hydrogen-bonding-capable dihydropyrazinoquinoxalinedione derivatives.

Presented here is the design, synthesis, and study of a variety of novel hydrogen-bonding-capable π-conjugated -heteroacenes, 1,4-dihydropyrazino[2,3-]quinoxaline-2,3-diones (DPQDs). The DPQDs were accessed from the corresponding weakly hydrogen-bonding dicyanopyrazinoquinoxaline (DCPQ) suspensions with excess potassium hydroxide, resulting in moderate to good yields. Both families of compounds were analyzed by UV-vis and NMR spectroscopy, where the consequences of hydrogen bonding capability could be assessed through the structure-property studies.

Organometallic Intermediates in the Synthesis of Photoluminescent Zirconium and Hafnium Complexes with Pyridine Dipyrrolide Ligands.

The two commercially available zirconium complexes tetrakis(dimethylamido)zirconium, Zr(NMe), and tetrabenzylzirconium, ZrBn, were investigated for their utility as starting materials in the synthesis of bis(pyridine dipyrrolide)zirconium photosensitizers, Zr(PDP). Reaction with one equivalent of the ligand precursor 2,6-bis(5-methyl-3-phenyl-1-pyrrol-2-yl)pyridine, HPDP, resulted in the isolation and structural characterization of the complexes (PDP)Zr(NMe)thf and (PDP)ZrBn, which could be converted to the desired photosensitizer Zr(PDP) upon addition of a second equivalent of HPDP. Using the more sterically encumbered ligand precursor 2,6-bis(5-(2,4,6-trimethylphenyl)-3-phenyl-1-pyrrol-2-yl)pyridine, HPDP, only ZrBn yielded the desired bis-ligand complex Zr(PDP).

Long-lived photoluminescence from an eight-coordinate zirconium(IV) complex with four 2-(2'-pyridyl)pyrrolide ligands.

The photoluminescent eight-coordinate zirconium complex Zr(PMP) supported by four monoanionic 2-(2'-pyridine)pyrrolide ligands was synthesized. This molecule shows dual emission fluorescence and phosphorescence with an overall quantum efficiency of 4% at room temperature in solution. The phosphorescence lifetime is dependent on concentration, indicating excimer formation at higher concentrations, and reaches almost 800 μs at high dilution.

Synthesis of the tricyclic indole alkaloids, dilemmaones A and B.

Dilemmaones A-C are naturally occurring tricyclic indole alkaloids possessing a unique hydroxymethylene or methoxymethylene substituent at the C2 position of the indole core and a C6-C7 fused cyclopentanone. Dilemmaone B has been prepared in 5 steps from 5-methylindan-1-one, and dilemmaone A has been prepared in 3 steps from a common precursor, 6-bromo-5-methyl-7-nitroindan-1-one. In both syntheses, key steps include a Kosugi-Migita-Stille cross coupling and a reductive cyclization using hydrogen gas and a transition metal catalyst.