Avoiding the random bay-position halogenation of boron subnapthalocyanines and to balance of Lewis's acidity and basicity to enable the formation.

A diverse range of computational methods have been used to calibrate against available data and to compare against the correlation for the prediction of frontier orbital energies and optical gaps of novel boron subphthalocyanine (BsubPc) derivatives and related compounds. These properties are of fundamental importance to organic electronic material applications and development, making BsubPcs ideal candidates in pursuit of identifying promising materials for targeted applications. This work employs a database of highly accurate experimental data from materials produced and characterized in-house. The models presented herein calibrate these properties with R2 values > 0.95. We find that computationally inexpensive semiempirical methods such as PM6 and PM7 outperform most density functional theory methods for calibration. We are excited to share these results with the field as it empowers the community to determine key physical properties of BsubPcs with confidence using free software and a standard laptop prior to the arduous synthesis and purification thereof. This study is a follow up to our previous work calibrating PM3, RM1, and B3LYP-6-31G(d), which used a smaller set of BsubPc derivatives at a past point when less data were available.

Halides and pseudohalides of boron subphthalocyanine (BsubPc) are promising candidates for efficient yet stable organic photovoltaics. Here, the electronic structure of such molecules, obtained using density functional theory, is considered. Based on the calculations, it is found that the tetrameric boron bond is stabilized by an inductive effect at the axial substituent and by conjugative effects across the ring system. It is further found that stability is dictated mostly by the axial moiety, such that Br‐BsubPc is the most fitting precursor structure for further synthesis steps, whereas F‐BsubPc is the most suitable candidate for long‐term device performance. H‐BsubPc is examined as a new BsubPc derivative, and found to be too volatile for long term device performance. Finally, it is shown that peripheral substitution dictates the position of frontier orbitals, thereby allowing for essentially separate optimization of material properties and material stability.

For some time, our group has been focused on the molecular design, synthesis and application of boron subphthalocyanines (BsubPcs) and subnaphthalocyanines (BsubNcs), which are macrocycles with a chelated central boron atom via nitrogen and a p-conjugated ligand. Our focal point balances between the basic and applied chemistry of the BsubPcs and BsubNcs, their physical properties (electrochemistry included) and their application as light emitting, light absorbing and electronic conducting materials for application in organic light emitting diodes (OLEDs) and organic photovoltaics (OPVs)/organic solar cells (OSCs), the basic electrochemical and photophysical properties being critical to these applications. For this presentation, I will focus on our progress on the development of BsubNcs. In the past we have shown that BsubNcs end up being a mixed alloyed composition based on bay-position halogenation that was formed randomly during the reaction of BCl3 with 2,3-dicyanonaphthalene at temperature to form the BsubNcs. The random bay-position halogenation has been shown to be impactful in a positive way within OPV devices, negative within OLED devices and also has electrochemical variations. However given it is random halogenation, it is desirable to truly understand its impact systematically. We have recently been able to develop a separation method and therefore separate the mixed alloyed BsubNc compositions and acquire data to show the impact of the percentage/number of bay-position halogens, chlorine and bromine included, on the electrochemical potentials and the photoluminescence. I will also present a new synthetic methodology to avoid the random bay-position halogenation of the associated BsubNcs. We have also applied a computational model to look at the relative impact of the random bay-position halogenation on the electronics. We have found that the frequency of halogenation has a larger impact on the predicted HOMO/LUMO energy levels than does the random halogen positioning around the bay-positions of the BsubNcs. As this was in parallel with the separations method that was developed, this computational data is therefore comparable to the acquired electrochemical data. We have also developed BsubNc + BsubPc hybrid materials. For the hybrids, there is a way to avoid bay-position halogenation and once this was avoided, we have the first example of electrochemical and photoluminescence data for the associated BsubNc + BsubPc hybrids. I will also outline our approach to accelerated development of BsubNcs, BsubPcs and the hybrids whereby their molecular design and synthesis was first been justified through a re-adopted computational model. Figure 1

For some time, our group has been focused on the molecular design, synthesis and application of derivatives of boron subphthalocyanines (BsubPcs) and subnaphthalocyanines (BsubNcs), which are compounds with a chelated central boron atom and an extensive p-conjugated macrocyclic ligand. Our focal point continues to be balanced between the basic and applied chemistry of the BsubPcs and BsubNcs, their physical properties (electrochemistry included) and their application as light emitting, light absorbing and electronic conducting materials in organic light emitting diodes (OLEDs) and organic photovoltaics (OPVs)/organic solar cells (OSCs) respectively; the basic electrochemical and photophysical properties being critical to these applications. For this presentation, I will focus on our progress on the development of BsubNcs. In the past we have shown that BsubNcs end up being a mixed allowed composition based on bay-position halogenation that was formed randomly during the reaction of BCl3 with 2,3-dicyanonaphthalene at temperature on forming the BsubNcs. The random bay-position halogenation has been shown to be impactful in a positive way within OPV devices, negative within OLED devices and also has electrochemical variations. However given it is random halogenation, it is desirable to truly understand its impact systematically. I will outline how the use of BBr3 for the formation of the BsubNcs impacts the outcome, also enables random bay-position halogenation and does enable the first example of the bay-position halogenated BsubNcs to be separable. From a basic chemistry perspective, I will then highlight that we have progressed on blocking the random bay-position halogenation by developing a method to entirely avoid the bay-position halogenation. I will outline the approach and show the first basic characterization of non-bay-position halogenated BsubNc and the relative characteristics of the associated BsubNcs. Electrochemical comparison of the BsubNcs will also be outlined and also spectroelectrochemistry characterization. We have also applied computational modelling to look at the relative impact of the random bay-position halogenation. We have found that the frequency of halogenation has a larger impact on the predicted HOMO/LUMO energy levels than does the random halogen positioning and will be discussed. I will also outline our approach to accelerated development of BsubNcs whereby their molecular design and synthesis is first justified through a re-adopted computational model. I will show how we calibrate several levels of computational modelling relative to and against a firm set of experimental data. I will then move onto several examples of how we have developed BsubNcs for their application in organic electronic devices utilizing this method. Figure 1

The relative impact of position and type of halogens on the boron subphthalocyanine periphery has been established as well as their ability to form mixed alloys and the impact on organic electronic properties utilizing organic solar cell base data.

The synthesis of axially brominated boron subnaphthalocyanine (BsubNc) was investigated using BBr3 as the Lewis acid source. Random bay position bromination was found to occur as previously described by our group during the synthesis of chloro-(chloro)(n)-boron subnaphthalocyanines (Cl-Cl(n)BsubNcs) using BCl3. The direct substitution of BBr3 for BCl3 in the synthesis of BsubNc was found to increase bay position halogenation. We found in this study that it is possible to avoid bay position bromination by employing low temperature synthetic methods. However, these methods were found to yield only analytical amounts of the BsubNc macrocycles, preventing any isolation and physical characterization. We identify herein an appropriate method for scaling of the synthesis of bromo-(bromo)(n)-boron subnaphthalocyanines (Br-Br(n)BsubNcs). On the appropriate scaling of the synthesis of bromo-(bromo)(n)-boron subnaphthalocyanines (Br-Br(n)BsubNcs), we then conducted axial phenoxylation (ArO-Br(n)BsubNcs) reactions to enable the separation of the mixture of bay position brominated species by column chromatography. Partial separation was accomplished. Separation and/or purification of Br-Br(n)BsubNcs is problematic given the known weakness of the B-Br bond which is widely open for hydrolysis. After partial separation, we describe herein analytical methods for the characterization of bay position halogenated BsubNcs with improved resolution and accuracy. These analytical techniques enable the accurate determination of the degrees of bay position halogenation that are present within a mixture of BsubNcs. Quantification of the average bay position halogenation and a description of the halogenated benz(f)isoindoline units within a mixture of bay position BsubNcs is also presented. The photophysical and electrochemical properties of the partially separated ArO-Br(n)BsubNcs were investigated. Bay position bromination was found to significantly influence these properties. A diminishing influence of bromination as the degree of bromination increased was observed in all cases. Fluorescence quantum yields of ArO-Br(n)BsubNcs were found to be close to an order of magnitude lower than those of their bay position chlorinated counterparts, presumably due to the heavy atom effect. Solution stability was also investigated, and a degradation product was identified by single-crystal X-ray diffraction analysis.

Organic electronics are particularly susceptible to minor impurities within a materials sample because any amount of impurity can alter device performance. Here we outline and explore a specific example of how the sudden decrease in our organic photovoltaic (OPV) performance was attributed to purchased material with a minor impurity not acknowledged by an external supplier. Had there been no standard procedure in place to evaluate a new batch of materials, the issue could have gone unchecked and inadvertently affected other results in the future. In this specific example, we confirmed the presence of impurities in an alpha-sexithiophene sample purchased from a supplier that drastically affected baseline device data. Our goal is to bring awareness to the issue, and emphasise the importance of verifying the purity of any materials purchased for organic electronics by establishing a baseline which would flag any major fabrication changes or the presence of impurities. We hope these analogous issues and methodologies are reported more in pursuit of advancing the pace of research and development.

For some time, our group has been focused on the molecular design, synthesis and application of derivatives of boron subphthalocyanines (BsubPcs) and subnaphthalocyanines (BsubNcs), which are macrocyclic molecules with a chelated central boron atom. Our focal point has been and continues to be equally balanced between the basic and applied chemistry of BsubPcs/BsubNcs and their application as light absorbing and electronic conducting materials in organic photovoltaics (OPVs)/organic solar cells. Electrochemical properties being critical to this application. For OPVs, we selected a preferred approach to the development of BsubPcs/BsubNcs whereby their molecular design and their synthesis is justified through a development cycle which includes data accumulation of their basic physical chemistry properties, their immediate integration into OPVs and their stability evaluation when applied into OPVs/organic solar cells. Based on data acquisition, we then cycle back to consider alternative molecular designs of BsubPcs/BsubNcs. Recently we have re-Integrated into this cycle our computational modeling methodology which is used to screen potential BsubPcs/BsubNcs for their application in OPVs/organic solar cells and other organic electronic devices. For this presentation I will begin by outlining how we have re-adopted our past computational model to help develop these materials. I will start by showing how we calibrate several levels of computational modeling relative to firm experimental data. I will highlight how a low level and high level computational model can be calibrated and the difference between them. I will then move onto several examples of how we have developed BsubPcs/BsubNcs for application in OPVs and other organic electronic devices utilizing this method. An example I will show is that we have recently identified a pathway to BsubPcs whereby all carbons are bio-sourced. In order to justify their synthesis with the desired OPV application, I will highlight how the computational model justified the time and resource commitment to their synthesis and development. I will also show how the computational calibration model did accurately predict their relevant properties, the prediction being a level of justification for their development. I will outline several other BsubPc/BsubNc macrocycle structures that where either justified by the computational model to be developed or where not justified. I will also highlight to the community progress in avoiding bay-position halogenation of the BsubNc macrocycles during their formation. Additional co-authors/investigators will be identified during this presentation. Figure 1