Synthesis, Photophysical, and Electroluminescent Device Properties of Zn(II)‐Chelated Complexes Based on Functionalized Benzothiazole Derivatives

Abstract

New Zn(II)‐chelated complexes based on benzothiazole derivatives, including substituted functional groups such as methyl (MeZn), methoxy (MeOZn), or fluorenyl unit (FuZn), are investigated to produce white‐light emission. 2‐(2‐Hydroxyphenyl)benzothiazole derivatives in toluene and DMSO exhibit excited‐state intramolecular proton transfer (ESIPT), leading to a large Stokes shift of the fluorescence emission. However, in methanol they exhibit no ESIPT due to the intermolecular hydrogen bonding between the 2‐(2‐hydroxyphenyl)benzothiazole derivative and methanol. Their Zn(II)‐chelated complexes exhibit the absorption band red‐shifted at 500 nm in nonpolar solvent and the absorption band blue‐shifted at about 420 nm in protic solvent. In multilayer electroluminescent devices, methyl‐substituted Zn(II)‐chelated complex (MeZn) exhibits excellent power efficiency and fluorene‐substituted Zn(II)‐chelated complex (FuZn) has a high luminance efficiency (1 cd m−2 at 3.5 V, 10 400 cd m−2 at 14 V). The EL spectra of Zn(II)‐chelated complexes based on benzothiazole derivatives exhibit broad emission bands. In addition, their electron‐transport property for red–green–blue (RGB) organic light‐emitting diodes (OLEDs) is systematically studied, in comparison with that of Alq3. The results demonstrate the promising potential of MeZn as an electron‐transporting layer (ETL) material in preference to Alq3, which is widely used as an ETL material.

Luminescence Enhancement by p‐Substituent Variation

“…The fluorinated complex might be more soluble because of the enhanced intermolecular repulsion, while the luminescence characteristics are also affected, for instance, by the substitution of high‐frequency C–H vibrations with low‐frequency C–F vibrations, which results in reduced quenching , . Likewise, Roh and co‐workers observed that the near‐IR emission of erbium pentafluorobenzoate increased 1.5‐fold relative to that of erbium benzoate. Ye and co‐workers proved that the fluorination of the organic ligand leads to the increase of the luminescence efficiency, as reflected in the values of Judd–Ofelt parameters.…”

Dinuclear ZnII Complexes Exhibiting Thermally Activated Delayed Fluorescence and Luminescence Polymorphism

“…For decades, fluorescent zinc(II) complexes have been widely studied for chemical sensing, bio‐imaging, and optoelectronic device applications . The archetypal luminescent Zn II complexes are usually supported by 2‐hydroxylphenylbenzothiazole (BTZ), bis‐dipyrrinato, and Schiff base ligands . In comparison with the low‐to‐moderate yields in syntheses of organometallic emitters, which usually require harsh reaction conditions, syntheses of these Zn II complexes can be performed under very mild conditions in high yields because of the facile coordination of phenolate and imine ligands to the Zn II ion.…”

Applications of Nanomaterials Based on Magnetite and Mesoporous Silica on the Selective Detection of Zinc Ion in Live Cell Imaging

“…We have chosen fluorescent benzothiazole derivatives as they are good candidates for the functionalization of nanoparticles because of their biocompatibility. For example, the photophysical, photochemical, and biological properties of 2-(2-hydroxyphenyl)benzothiazole ( hpbtz ) have been studied as antitumor, anti-inflammatory, and as positron-emission tomography (PET) imaging in the diagnosis of Alzheimer’s disease [ 21 , 22 , 23 ], and there are a good number of reports on reactive probes based on the hpbtz moiety for the selective detection of different analytes, such as Zn 2+ ion [ 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 ]. However, several probes are prepared under harsh conditions or by using multi-step procedures [ 31 , 32 , 34 ].…”