Structure-Activity Relationship Study of N-Hydroxyphtalimide Derivatives for the Detection of Amines during Fmoc-Solid-Phase Peptide Synthesis.

Previously, we developed a method for the detection of unprotected amino groups based on their reversible reaction with N-hydroxyphthalimide (NHPI) to form intensely colored products, which can be useful when conducting solid-phase peptide synthesis. Here, we describe a structure-activity relationship study of NHPI derivatives to identify the derivative best suited for this method using a spectrophotometer toward the estimation of chemical yields. We found that the products resulting from the reaction of the derivative with an unprotected amino group were only intensely colored if the structure of the derivative incorporated an NHPI framework. We also prepared five peptides, including those containing N-methyl and D-amino acid, and Pro residues, using our reversible detection method to detect unprotected amino groups. The mechanism of the detection reaction was also studied by the structural analysis of the NHPI (1) and diisopropylamine complex and concluded to entail salt formation between the N-hydroxy group and amine.

Novel Series of Mononuclear Aluminum Complexes for High-Performance Solution-Processed Organic Light-Emitting Devices.

Light metal complexes, such as lithium (Li), sodium (Na), magnesium (Mg), and aluminum (Al) complexes, are attractive candidates for the fabrication of thermally activated delayed fluorescent (TADF) materials. Nevertheless, mononuclear Al complexes with delayed fluorescence have not been developed so far. In this study, we successfully developed a novel series of highly luminescent Al complexes with two phenylacridine-modified asymmetric acetylacetonate-type ligands. These complexes exhibit high photoluminescence quantum yields (PLQYs) of up to 79 % in the solid state with a short delayed fluorescence lifetime of approximately 4 µs. Solution-processed organic light-emitting devices (OLEDs) using these Al complexes exhibit excellent performance with an external quantum efficiency of 17.5 % at 100 cd m-2 . This is the best performance in light metal-based TADF OLEDs reported so far. The results are expected to guide the advancement of the next-generation solid-state lighting technology.

Control of Molecular Orientation in Organic Semiconductors Using Weak Iodine-Iodine Interactions.

Controlling the molecular orientation of materials is a key issue for improving the performance of organic semiconductor devices. Herein, we demonstrate the structure-property relationships of iodinated and noniodinated molecules based on an asymmetric thienoacene framework. The noniodinated molecule formed an antiparallel slip-stack structure with small orbital overlap between molecules. In contrast, the iodinated molecule formed a head-to-head layered-herringbone structure, and as a result, the transfer integrals became larger and the hole mobility increased significantly compared with the noniodinated material. The iodinated molecule was made into a stable and solution-processable p-type organic semiconductor with a mobility of 2.2 cm2 V-1 s-1, which was 2 orders of magnitude higher than that of the noniodinated molecule. This study reveals that controlling molecular orientations using iodine-iodine interactions is a promising strategy for accelerating the development of organic semiconductor materials.