Bis[1]benzothieno[1,4]thiaborins as a Platform for BODIPY Singlet Oxygen Photosensitizers

Abstract

A synthetic approach to two regioisomeric πelectron extended [1,4]thiaborins annulated with two benzothiophene units has been developed. The central thiaborin rings of the boracycles obtained exhibit different electronic properties; this is reflected in their different aromatic characters, boron Lewis acidity and UV-vis spectroscopic behavior. Thiaborins were converted to boron dipyrromethene (BODIPY) complexes. Their emission spectra exhibit two distinct bands resulting from 1 LE and 1 CT transitions. Strong near-infrared phosphorescence in Zeonex thin films at 77 K indicates efficient intersystem crossing and the formation of triplet states. Separation of HOMO and LUMO orbitals between boracyclic and BODIPY moieties facilitates electron transfer to a 1 CT state followed by a transition to the 3 LE triplet state located on the ligand. These unique properties of spiro thiaborin-BODIPY complexes were explored for their application as singlet-oxygen photosensitizers. They show excellent photocatalytic performance with singlet oxygen quantum yields reaching 77 % and full conversion of the model organic substrate achieved after 1.5 h with only 0.05 % mol catalyst load.

Highly electron-deficient 3,6-diaza-9-borafluorene scaffolds for the construction of luminescent chelate complexes

“…5 ), mainly through mutual interactions between ligands (3c and 3d) or alternating ligand-borafluorene moiety stacking (3f). Notably, J-aggregate motifs, commonly encountered in spiro-organoboron compounds, 13 are solely observed for 3e (Fig. S2.4, ESI † ).…”

Conjugated Building Blocks Based on Electron-Deficient Thiaborin S-Oxides

“…Thiophene-fused thiaborin (DTSB) compounds, which are hybrid building blocks of boron and sulfur, have also been reported . We have shown that polymers based on the F DTSB unit exhibit strong intermolecular interactions in the solid state, which are relatively rare for p-π* conjugated systems because triarylboranes require large steric groups on boron to prevent hydrolysis and oxidation .…”

Performance of new cyclotriphosphazene derivatives in photocatalytic reactions

“…5,22–24 Thiophene groups were included in the structure due to their advantages such as absorption ability in the visible region, moderate band gap, and promotion of intersystem crossing. 25,26 In this context, three new cyclotriphosphazene derivatives were synthesized, and their molecular structures were characterized (Fig. 1).…”