Synthesis and Dual-Emission Feature of Salen-Al/Triarylborane Dyads

Abstract

Novel salen-Al/triarylborane dyad complexes were prepared and characterized with their corresponding mononuclear compounds. The UV-vis and photoluminescence experiments for dyads exhibited photoinduced energy transfer from borane to the salen-Al moiety in an intramolecular manner. Theoretical calculation and fluoride titration results further supported these intramolecular energy-transfer features.

Quinolinol‐based Al/Triarylborane Dyad Assembly: Alteration of Electronic Transition States Mediated by Fluoride Anion Binding

“…Additionally, the decay lifetimes (τ obs ) of D1 – D3 were in the range of 13–23 ns, thereby indicating slightly long fluorescent features (Table and Figure S12). Moreover, the fluorescence quantum efficiencies (Φ em ) of these complexes were ranging from 0.05 to 0.08 (Table ), which are reasonable values compared to those of Al‐based luminophores …”

“…The absorption and emission properties of q 2 Al/triarylborane dyads D1 – D3 were investigated with UV/Vis absorption and PL measurements (Figures and Table ) at ambient temperature. All absorption spectra of the dyads in THF (3.0 × 10 −5 M) exhibited major absorption bands in the range of 300–350 nm, which can be assigned to the π(Mes)–p π (B) charge‐transfer (CT) transition in the tri‐coordinated borane moiety (Figure (a)–(c), black line) . The spectra also showed a low‐energy shoulder absorption band in the region above 350 nm, which corresponded to the CT transition from the phenoxy bridge moiety to the q 2 Al parts (for details, refer to the Section “Theoretical Calculations”).…”

“…Commercial reagents 2‐methylquinolin‐8‐ol (q), trimethylaluminum (2.0 M in toluene), dimesitylboron fluoride (Mes 2 BF), 1‐bromo‐4‐methoxybenzene, 2‐bromo‐6‐methoxynaphthalene, 4‐hydroxyphenylboronic acid, boron trifluoride diethyl etherate (BF 3 ·Et 2 O), boron tribromide, Pd(PPh 3 ) 4 , K 2 CO 3 , and tetrabutylammonium fluoride (TBAF), were employed without any further purification after purchasing from Sigma‐Aldrich. Reagents (4‐bromophenyl)dimesitylborane, B1 , and A1 (Scheme ) were prepared according to the reported procedures. Deuterated CDCl 3 solvent was obtained from Cambridge Isotope Laboratories (Tewksbury, MA, USA) and was used after drying over activated molecular sieves (5 Å).…”

“…Such a photophysical change in the dyad complexes, which links triarylborane and luminophore together, is generally evoked by the alteration of their intramolecular charge‐transfer (ICT) transition. In this respect, the five‐coordinated aluminum complexes have received a great attention as promising and attractive luminophore‐scaffolds for inducing photophysical changes in triarylborane‐based dyad complexes due to their high quantum efficiency and good chemical stability . In particular, Alq 3 (tis‐(8‐hydroxyquinoline)aluminum) derivatives are well‐known for their use in optoelectronic materials of organic light‐emitting diodes (OLEDs), based on their intriguing luminescent properties and reasonable thermal and electrochemical stabilities.…”

Nido‐Carboranes: Donors for Thermally Activated Delayed Fluorescence

“…Along with the strong emission, weak high‐energy bands are concomitantly observed for nido ‐ m2 – m4 and nido ‐ p3 in the region of 360–440 nm. The absence of the high‐energy band in the rigid state, such as a PMMA film (Supporting Information, Figure S12), indicates that the bands can be ascribed to local emission from the PhBMes 2 moiety . PL quantum yields (PLQY, Φ PL ) of nido ‐ m1 – m4 measured in oxygen‐free THF solutions show that nido ‐ m1 and ‐ m4 are moderately emissive whereas nido ‐ m2 and ‐ m3 are poorly emissive ( Φ PL =3–4 % in THF).…”