Reaction Calorimetry and Scale-Up Considerations of Bromo- and Chloro-Boron Subphthalocyanine

Abstract

The formation mechanism of boron subphthalocyanines (BsubPcs) has thus far evaded researchers, making it nearly impossible to accurately estimate the overall reaction enthalpy�a critical metric for determining chemical process safety for scale-up. To address this gap, reaction calorimetry was used to collect thermokinetic data for a baseline Br-BsubPc reaction at three temperatures and two BBr 3 reagent ratios and a proposed semibatch process for Cl-BsubPc. For the Br-BsubPc process, the magnitude of the enthalpy of reaction (ΔH r ) increased with increasing reaction temperature, from −244.6 kJ/mol-BBr 3 at 25 °C to −332.7 kJ/mol-BBr 3 at 50 °C to −391.3 kJ/mol-BBr 3 at 75 °C. However, this increase in the magnitude of ΔH r did not result in a noticeable increase in Br-BsubPc yield, achieving 50%, 49%, and 52% yields at 25 °C, 50 °C, and 75 °C, respectively. When the molar equivalence of BBr 3 was increased by 1.5× at 25 °C, the magnitude of ΔH r increased slightly (−252.2 kJ/mol-BBr 3 ), but the yield did not improve (47%). Therefore, further attempts were made to try and improve the yield of Br-BsubPc by increasing the molar equivalence of BBr 3 . It was found that BBr 3 equivalencies greater than 0.48 resulted in significant reductions in Br-BsubPc yield. The ΔH r of the semibatch Cl-BsubPc process was −266.5 kJ/mol-BCl 3 with a yield of 33%. These processes were assessed based on criticality criteria and were both found to be "Criticality Class 1", which is relatively safe for scale-up. Based on the calorimetry measurements, preliminary estimates for process conditions and reactor design for scale-up are provided.

Boron subphthalocyanine axial groups: a comprehensive set for studying the tuning of photophysical and electrochemical properties

“…16,17,21,46 The lower reactivity of the B–Cl bond also tends to lead to long reaction times at very high temperatures, which could also result in degradation of the macrocycle. 16,22,25,46 Based on the higher reactivity of Br-BsubPc, as well as the recent report from our group that Br-BsubPc has a higher potential for scale-up than Cl-BsubPc, 51 Br-BsubPc was chosen as the template for all axial exchange reactions in this study.…”

Embodied Energy Investigation of the Chloro-Boron Subphthalocyanine Formation Process to Improve Its Sustainability

“…The results of this study are directly applicable to future LCAs and scale-up considerations assessing the various impacts of Cl-BsubPc and toward an alternative set of BsubPcs and their applications. 28 More broadly, the framework used for Cl-BsubPc can help improve the overall sustainability of the dye and pigment field, as embodied energy has been an underutilized impact factor within the phthalocyanine space.…”