The unique features of the metal-organic frameworks (MOFs), including ultrahigh porosities and surface areas, tunable pores, endow the MOFs with special utilizations as host matrices. In this work, various neutral and ionic guest dye molecules, such as fluorescent brighteners, coumarin derivatives, 4-(dicyanomethylene)-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran (DCM), and 4-(p-dimethylaminostyryl)-1-methylpyridinium (DSM), are encapsulated in a neutral MOF, yielding novel blue-, green-, and red-phosphors, respectively. Furthermore, this study introduces the red-, green-, and blue-emitting dyes into a MOF together for the first time, producing white-light materials with nearly ideal Commission International ed'Eclairage (CIE) coordinates, high color-rendering index values (up to 92%) and quantum yields (up to 26%), and moderate correlated color temperature values. The white light is tunable by changing the content or type of the three dye guests, or the excitation wavelength. Significantly, the introduction of blue-emitting guests in the methodology makes the available MOF host more extensive, and the final white-light output more tunable and high-quality. Such strategy can be widely adopted to design and prepare white-light-emitting materials.
Rare red‐fluorescent fluorene derivatives have been designed and synthesized. The long‐wavelength red fluorescence is achieved by incorporating a di(4‐tolyl)amino or diphenylamino electron donor and a dicyanovinyl electron acceptor. The single‐crystal X‐ray structures of the di(4‐tolyl)amino (pTSPDCV) and diphenylamino (PhSPDCV) compounds indicate only weak non‐π van der Waals contacts in addition to long‐distance dipole–dipole interactions of the red‐emitting fluorene molecules in the solid state. The aggregation of the dipolar fluorene is largely suppressed by introducing bulky 9,9‐substituents (spiro‐fused bifluorene) as well as a non‐planar di(4‐tolyl)amino or diphenylamino group. In the solid state, these fluorene derivatives all show red fluorescence that is much brighter than with the red dopants Nile Red and DCM (4‐(dicyanomethylene)‐2‐methyl‐6‐[4‐(dimethylaminostyryl)‐4H‐pyran]). The unique photophysical properties of red‐emitting fluorene derivatives differ from other known red dopants and facilitate the fabrication of non‐doped red organic light‐emitting diodes (OLEDs). Authentic red (CIE, x = 0.65, y = 0.35) electroluminescence with a brightness of more than 12 000 cd m–2 (greater than 600 cd m–2 at 20 mA cm–2) and a remarkable external quantum efficiency as high as 3.6 % have been observed for the red‐emitting OLEDs with pTSPDCV or PhSPDCV as the sole emitting host.
An efficient preparation of rare 2-O-benzoyl-3-O-benzyl-1,6-anhydro-beta-l-idopyranose from commercially available diacetone alpha-d-glucose in five straightforward steps is described here. With this key building block in hand, the total syntheses of heparin oligosaccharides with three, five, seven, and nine sugar units are successfully carried out.
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