Theory-Driven Insight into the Crystal Packing of Trialkylsilylethynyl Pentacenes

Abstract

The functionalization of oligoacenes and similar π-conjugated chromophores with trialkylsilylethynyl groups has proven to be a versatile means to enhance solubility and solution processability and engineer solid-state packing arrangements to produce organic semiconductors that demonstrate outstanding charge-carrier transport characteristics. While a general, empirical-based geometric model has been developed and implemented to direct the solid-state packing arrangements of these molecular materials, there exist numerous examples where the model falters. Here, we employ electronic structure methods to probe the noncovalent, intermolecular interactions of two closely related systems that result in two very different crystal packing configurations: triisopropylsilylethynyl (TIPS) pentacene and its triethylsilylethynyl (TES) analog. The quantum-chemical evaluation details how the slightly larger electron density contained within the volume of the TIPS moiety with respect to TES is in part responsible for the solid-state packing variations. We also make use of periodic density functional theory (DFT) methods to develop in silico polymorphs of these systems and explore the electronic characteristics of varied packing arrangements. The results suggest that TES pentacene, if processed correctly, could be developed into a material with improved charge-carrier transport characteristics when compared to its native form. Overall, the theory-driven insight developed in this work lays an important foundation to build a more robust crystal engineering paradigm for these technologically relevant organic semiconductors.

Striking the right balance of intermolecular coupling for high-efficiency singlet fission

“…, nanoparticles and films) lack the conformational flexibility in other disordered media, such as solution-phase covalently-tethered molecular pairs, yet retain the propensity to adopt multiple packing configurations. Although various strategies have been implemented to vary molecular packing in amorphous systems, such as by embedding molecules in an inert host matrix to increase the intermolecular spacing between chromophores, 91 we (and others 61 ) posited that side chains—which are known to play a profound role in the packing 92 – 95 —could be used as an incisive handle to influence local molecular packing, couplings relevant to singlet fission, and ultimately singlet fission dynamics.…”

On the possibility of singlet fission in crystalline quaterrylene

“…Oligoacenes [23][24][25][26][27][28][29][30][31][32][33][34] and their derivatives 35,36 stand out among organic chromophores and have been pivotal in fundamental research of SF. Both tetracene [37][38][39][40][41] and pentacene [42][43][44] are top performers, exhibiting fast SF and near 200% triplet yield.…”

γ‐Herringbone Polymorph of 6,13‐Bis(trimethylsilylethynyl)pentacene: A Potential Material for Enhanced Hole Mobility

“…Chem.E ur.J. 2018,24,[8679][8680][8681][8682][8683][8684][8685] www.chemeurj.org contribution from induction for D 2 in 2 could be attributed to polarization of the pentacene core, as discussed earlier.…”

“…[20][21][22][23] Trialkylsilylethynyl pentacene derivatives display diverse packing arrangements in the crystalline state, with varying p-orbital overlap. [24] The most commonly observed amongt hese arrangements is the slip-stacked packing, which is exemplifiedb yt he reported structure (1)o f6,13-bis(trimethylsilylethynyl)pentacene (TMS-pentacene). [13] Herein, we reportanewp olymorph (2)o fTMS-pentacene, which crystallizes in a g-herringbonem otif due to the presence of edge-toface interactions that are absent in 1.With our continued interest in polymorphism [25,26] and structure-packing-property correlations, [27][28][29] we also presenth erein ac omputational analysis to compare the crystal packing, stability,a nd charge-transport characteristics of 2 with those of 1.…”

“…Therefore, it is essential to obtain a clear idea of the structure adopted by the molecules in each polymorph and the conditions under which each polymorph is formed . Trialkylsilylethynyl pentacene derivatives display diverse packing arrangements in the crystalline state, with varying π‐orbital overlap . The most commonly observed among these arrangements is the slip‐stacked packing, which is exemplified by the reported structure ( 1 ) of 6,13‐bis(trimethylsilylethynyl)pentacene (TMS‐pentacene) .…”