BN-Substitution in Dithienylpyrenes Prevents Excimer Formation in Solution and in the Solid State

Abstract

Boron–nitrogen substitutions in polycyclic aromatic hydrocarbons (PAHs) have a strong impact on the optical properties of the molecules due to a significantly more heterogeneous electron distribution. However, besides these single-molecule properties, the observed optical properties of PAHs critically depend on the degree of intermolecular interactions such as π–π-stacking, dipolar interactions, or the formation of dimers in the excited state. Pyrene is the most prominent example showing the latter as it exhibits a broadened and strongly bathochromically shifted emission band at high concentrations in solution compared to the respective monomers. In the solid state, the impact of intermolecular interactions is even higher as it determines the crystal packing crucially. In this work, a thiophene-flanked BN-pyrene ( BNP ) was synthesized and compared with its all-carbon analogue ( CCP ) in solution and in the solid state by means of crystallography, NMR spectroscopy, UV–vis spectroscopy, and photoluminescence (PL) spectroscopy. In solution, PL spectroscopy revealed the solvent-dependent presence of excimers of CCP at high concentrations. In contrast, no excimers were found in BNP . Clear differences were also observed in the single-crystal packing motifs. While CCP revealed overlapped pyrene planes with centroid distances in the range of classical π-stacking interactions, the BNP scaffolds were displaced and significantly more spatially separated.

Synthesis and Properties of Thieno[2′,3′,4′:4,5]naphtho[1,8-cd]pyridines

“…Such a short natural lifetime and radiative decay rate, as shown by TNP-3a, is a rather common feature of pyrenes substituted at the 1-, 3-, 6-, and 8positions, where electronic coupling is most effective and the energetic order of the S 0 → S 1 ( 1 L b (α)) and S 0 → S 2 ( 1 L a (p)) transition of pyrene is strongly affected. 17,21,89,113−116 On the other hand, the natural lifetime of 2AP-Ph is comparable to those of K-region-substituted 4-azapyrenes 110 (τ 0 = 25−30 ns) and in the lower lifetime range when compared to K-regionsubstituted pyrenes 19,21,24,50,80,109 (τ 0 = 8−650 ns), 2-and 7substituted pyrenes 17,80 (τ 0 = 31−1200 ns), and pyrenes functionalized at both the K-region and 2,7-positions 24,111,112 (τ 0 = 13−226 ns). This also demonstrates the stronger perturbation of the excited states by doping with heteroatoms than it is generally induced by peripheral functionalization at these positions.…”

“…13 (51), 207 (15), 163 (22), 150 (15), 135 (15), 126 (29), 77 (77), 76 (14), 74 (16), 73 (74), 63 (20), 51 (27), 45 (36), 39 (23). (46), 387 (11), 375 (15), 374 (50), 373 (42), 372 (12), 359 (13), 187 (10), 186 (9), 179 (8), 170 (8). HRMS (EI) m/z: [M + ] calcd for C 27 H 19 NS, 389.1233; found, 389.1223.…”

Supramolecular Phthalimide Networks Via Tandem Diels–Alder Reaction–Aromatization Using Biomass‐Derived Furanic Dienes

“…It is known that photoluminescence (PL) measurements may prove the existence of 𝜋-𝜋 stackings by excimer formation. [36,37] Unfortunately, our materials were PL inactive, so we could not proceed with the measurement. However, when we measured the Fourier transform infrared (FT-IR) spectra of Pht-bNC gels, we were able to observe that the C=O stretching peak shifted from 1722 to 1716 cm −1 .…”

Electronic Structures and Charge Mobilities of Several Regioisomeric B2N2-Substituted Perylenediimides

“…In general, imide-N functionalization strongly modulates the crystal packing, resulting in the alteration of carrier transport, whereas the core functionalization of PDI (at ortho and bay positions) substantially affects the optoelectronic properties. , Though there exist several charge-transport studies conducted on imide-N and core-functionalized PDIs, only a few reports are available on substitutional doping in the PDI skeleton itself. To this end, BN substitutional doping in polycyclic aromatic hydrocarbon (PAH) has been shown to not only alter the electronic structure but also affect morphology and the monomer aggregation fashion that are expected to strongly modulate PAH charge mobilities. , In fact, tunable and enhanced electron mobility was predicted for substitutionally doped coronene using boron and nitrogen atoms depending upon their concentration and positions …”

“…To this end, BN substitutional doping in polycyclic aromatic hydrocarbon (PAH) has been shown to not only alter the electronic structure but also affect morphology and the monomer aggregation fashion that are expected to strongly modulate PAH charge mobilities. 21,22 In fact, tunable and enhanced electron mobility was predicted for substitutionally doped coronene using boron and nitrogen atoms depending upon their concentration and positions. 23 Very recently, Zhao et al have synthesized a novel class of B 2 N 2 -substituted PDI (B 2 N 2 -PDI hereafter) with a regiospecific BN-substitution exhibiting rich electronic, optical, and charge carrier mobilities that are further tunable with varied functional groups at the imide-N position.…”