Additive-Assisted Perylene Polymorphism Controlled via Secondary Bonding Interactions

Abstract

The influence of molecular additives or impurities on crystal growth, morphology, and polymorphism has broad importance in various fields of material science and pharmaceutical engineering. There are numerous examples demonstrating the effect of impurities on the crystallization of pharmaceutical substances; however, systematic studies on the additives' effect on crystallization and properties of organic semiconductors have not yet been reported. Here, we studied additive-assisted crystallization of a model aromatic hydrocarbon compound−perylene−to elaborate the crystal engineering tool for organic optoelectronics and to reveal the underlying mechanism. Anthracene, tetracene, 9,10diphenylanthracene, and rubrene were used as representative additives. We found the optimal additive and conditions for perylene crystallization allowing us to control its polymorphic outcome. The addition of 9,10-diphenylanthracene was demonstrated to lead to a preferable crystallization of metastable β-form of perylene, whereas in the neat conditions, α-form was typically obtained as a stable one. The crystallization of perylene with 9,10diphenylanthracene in high concentrations resulted in their stoichiometric co-crystallization. The perylene:9,10-diphenylanthracene co-crystal structure and optoelectronic properties were evaluated. The co-crystal demonstrated a photoluminescence quantum yield of 45% and hole mobility of 0.025 cm 2 /V s. The co-crystal structure analysis pointed on the stabilization of herringbone packing of perylene by interlayer C−H•••π interactions, allowing the 9,10diphenylanthracene layers to serve as the template for perylene β-polymorph nucleation. The results obtained could serve as the basis for crystallization control and engineering of high-performance materials in organic optoelectronics.

Additive-Assisted Crystallization of 9,10-Diphenylanthracene

“…However, PYR-DPA co-crystal demonstrated a blue-shifted emission with two PL maxima at 431 nm and 453 nm with a high PL QY of 51%, which could be assigned to the less dense crystal structure and non-typical herringbone packing of PYR molecules within the co-crystal (vide supra). The PL QY of PYR-DPA cocrystal is also consistent with its isostructural analogue PRN-DPA co-crystal demonstrating a PLQY of 45% [24].…”

“…The co-crystal demonstrated bright photoluminescence with a photoluminescence quantum yield of 51%. Finally, considering the TET molecular length, DPA polymorphs' structures and the PYR-DPA and PRN-DPA [24] co-crystals' structures, we have proposed the mechanism of additive-assisted DPA polymorphism based on the promotion of the segregated layered crystallization corresponding to metastable DPA polymorphs. Our work highlights the additive-assisted crystallization method for tuning of molecular packing and functional properties of materials for organic optoelectronics.…”

“…For qualitative phase analyses, the published CIFs of DPA polymorphs have been chosen at ambient temperature and better R f (<5%) values according to the following refs: α-DPA (CSD-DPANTR01) [56], β-DPA (CSD-DPANTR08) [57], γ-DPA (CSD-DPANTR11) [57]. Crystal structure of tetracene (CSD-TETCEN01) [58] and perylene-9,10-diphenylanthacene (PRN-DPA) co-crystal (CSD-QIFKAV) [24] were used for crystal packing comparison with polymorphic forms of DPA.…”

“…Among the variety of conjugated small molecules, symmetric aromatic hydrocarbon derivatives represent a convenient model for the fundamental study of "structure-property" relationships due to their condensed π-systems, known molecular packing extracted from X-ray data, low concentration of defects, and hence, outstanding charge carrier mobility and luminescent properties [5][6][7]. To tune a crystalline structure of organic semiconductors, several approaches were suggested and extensively exploited: variation of a conjugated framework [8][9][10][11], introduction of substituents [12][13][14][15][16][17], polymorphism [18][19][20][21][22][23], cocrystallization [24][25][26][27][28], template-induced [4,[29][30][31] and specific crystallizations [22,[32][33][34][35][36] allowing the control of crystal orientation on a substrate, and morphology. Polymorphism is considered to be one of the most powerful approaches in material science and pharmaceutical engineering for the study of "structure-activity" relationships and control of the properties of a given compound without changing its chemical structure [37][38][39].…”

“…The additive-assisted crystallization of conjugated small molecules is rarely studied in material science and only a few examples were previously reported and analyzed [48]. We have previously reported additive-assisted crystallization of perylene (PRN), and the underlying mechanism was proposed based on the assumption that the 9,10-diphenylanthracene (DPA) layer serves as a template for perylene β-polymorph nucleation [24]. However, DPA itself also has three polymorphs differing by molecular packing, crystal morphologies and intermolecular interactions.…”