Process for the synthesis of symmetric and unsymmetric oxygen bridged dimers of boron subphthalocyanines (μ-oxo-(BsubPc)₂s)

Abstract

A process for the gram scale synthesis of the oxygen bridged dimer of boron subphthalocyanine, μ-oxo-(BsubPc)2, has been developed. During the development it was found that a wide range of reaction pathways under diverse conditions lead to μ-oxo-(BsubPc)2 formation. However, obtaining μ-oxo-(BsubPc)2 as the main reaction product in appreciable yields and its subsequent isolation were extremely challenging. The best balance of purity, yield and conversion was achieved with a time controlled reaction of an equimolar reaction of HO-BsubPc with Br-BsubPc in the presence of K3PO4. The purification involved sequentially Soxhlet extraction, Kauffman column chromatography and train sublimation. We have repeated the process and yields ranged from 27 to 30% of pure, doubly-sublimed μ-oxo-(BsubPc)2. This process also enabled the synthesis of unsymmetric μ-oxo-(BsubPc)2s by reaction of HO-BsubPc with Br-F12BsubPc, Cl-Cl6BsubPc and Cl-Cl12BsubPc. After synthesis the solution-state properties of the unsymmetric μ-oxo-(BsubPc)2s were investigated, and compared to the symmetric μ-oxo-(BsubPc)2 and more broadly to other BsubPcs. The electronic properties of μ-oxo-(BsubPc)2 were found to differ from its unsymmetric counterparts, but were found to be similar to halo-BsubPcs. Furthermore, the photophysical properties of μ-oxo-(BsubPc)2, both symmetric and unsymmetric, differed greatly from all other known BsubPcs.

A Comprehensive Scope of Peripheral and Axial Substituent Effect on the Spectroelectrochemistry of Boron Subphthalocyanines

“…A more time-efficient synthetic procedure for the BsubPc acceptor used in this study (PhO-Cl 6 BsubPc) was adapted from Ebenhoch et al, based on our synthetic methodology. ,, Rather than refluxing phenol with Cl–Cl 6 BsubPc in toluene for 7 days, we have previously found that bromine in the axial position of BsubPc is more labile than chlorine and, thus, undergoes a faster reaction . Therefore, bromo-hexachloro-boron-subphthalocyanine (Br-Cl 6 BsubPc) was first synthesized.…”

Ability To Fine-Tune the Electronic Properties and Open-Circuit Voltage of Phenoxy-Boron Subphthalocyanines through Meta-Fluorination of the Axial Substituent

“…BsubPcs contain a boron center surrounded by three nitrogen-linked isoindoline groups, which form a unique bowl shape. We have proven experimentally that the physical properties of BsubPcs, such as maximum absorption wavelength, sublimation temperature, solubility, , melting point, crystal structure, extinction coefficient, and electronic characteristics, can be altered through the functionalization of the axial position or substitution of the hydrogens in the periphery. − This array of modifications is highly desirable compared with the inability to alter the electronic and optical properties of typical fullerene electron acceptors, which are limited to an open-circuit voltage ( V OC ) of <1 V in OPVs …”

Axial/Peripheral Chloride/Fluoride-Substituted Boron Subphthalocyanines as Electron Acceptors

“…We have now decided to systematically investigate the detailed electrochemical properties of Cl-F 6 BsubPc, Cl-F 12 BsubPc, F-F 12 BsubPc, and F-F 6 BsubPc, together with the established Cl-BsubPc, F-BsubPc, Cl-Cl 6 BsubPc, and Cl-Cl 12 BsubPc as additional points of comparison. This became feasible after having described the improved synthesis of F-F 12 BsubPc and F-F 6 BsubPc and how to obtain all herein-studied compounds in high analytical purity .…”