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

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.

The first report of the crystal structure of non-solvated µ-oxo boron subphthalocyanine and the crystal structures of two solvated forms.

The first instance of the solvent-free X-ray determined single-crystal structure of the oxygen-bridged boron subphthalocyanine dimer [µ-oxo-(BsubPc)(2), C(48)H(24)B(2)N(12)O] is reported. Single crystals obtained by train sublimation were found to have µ-oxo-(BsubPc)(2) organized into a C2/c space group. The crystal structure obtained by sublimation is of particular interest as it is highly symmetric and also of notably high density when compared with other BsubPc crystals. The acquisition of this crystal structure came about from the direct chemical synthesis of µ-oxo-(BsubPc)(2) followed by a work-up which culminated in obtaining the single crystals by sublimation. Several methods for the direct chemical synthesis of µ-oxo-(BsubPc)(2) were also investigated each using dichlorobenzene as the solvent. On standing, these reaction mixtures produced a crystal of the dichlorobenzene (DCB) solvate of µ-oxo-(BsubPc)(2) [µ-oxo-(BsubPc)(2)·2DCB]. It is also reported that the conversion of bromo-boron subphthalocyanine (Br-BsubPc) to µ-oxo-(BsubPc)(2) happens on train sublimation which resulted in the acquisition of a partially hydrated crystal [µ-oxo-(BsubPc)(2)·0.25H(2)O].