Rylene and Rylene Diimides: Comparison of Theoretical and

Article pubs.acs.org/JPCA

Rylene and Rylene Diimides: Comparison of Theoretical and Experimental Results and Prediction for High-Rylene Derivatives Xiaohong Zhao,* Yushuai Xiong, Jie Ma, and Zhongyi Yuan* College of Chemistry, Nanchang University, Nanchang 330031, P. R. China S Supporting Information *

ABSTRACT: Low rylene (R) and rylene diimides (RD) are important organic semiconductors and dyes. High R and RD with larger conjugated cores show different properties compared with their low counterparts. Herein, absorption spectra, frontier molecular orbitals, band gaps, innersphere reorganization energy (λi), ionization potential, electron affinity, and atomic charge population of 20 rylene compounds were calculated by the density functional theory method. The theoretical results agree well with experimental ones. We predict some unusual properties of some high rylene derivatives that are unknown compounds due to synthetic difficulties. The lowest unoccupied molecular orbital energy levels of RD compounds change slightly, from −3.61 to −3.79 eV, which makes them strong electron acceptors. The band gaps narrow with the size increase of conjugated cores, which makes high rylene derivatives near-infrared dyes. The rising highest occupied molecular orbital energy levels of high rylene derivatives makes them unstable in the air. The λi falls with the size increase of the conjugated core, and the size of RD-4 or R-4 is big enough for the small λi to favor charge transport. The charge population analysis indicates R and RD have different charge distribution under the effect of electron-withdrawing imide groups, which contributes to distinct properties.

1. INTRODUCTION Rylene (R) are polycyclic hydrocarbons that are formed by connecting the peri positions of naphthalene (R-1). Rylene diimides (RD) have two diimide groups at the end positions of rylene. Their conjugated cores are shown in Figure 1. They are widely used as organic semiconductors and dyes in various applications because of their large absorption coefficient, strong fluorescence, and high chemical and thermal stabilities.1,2 For example, perylene diimides (RD-2) with high molar extinction coefficient maximum 88 700 M−1 cm−1 show strong emission, and the fluorescence quantum yield is close to 1.3 RD-2 and naphthalene diimides (RD-1) are two types of important n-type semiconductors. Organic bulk heterojunction solar cells with power conversion efficiency over 8% has been obtained recently, in which RD-2 derivatives are excellent acceptors.4 As air-stable n-type semiconductors, perfluoroalkyl- or chloro-substituted RD-1 derivatives demonstrate electron mobility over 1 cm2 V−1 s−1.5,6 RD-1 and RD-2 are excellent n-type semiconductors (electron acceptors), although only a little research has been conducted for higher rylene derivatives, because the synthesis is complicated for these long conjugated compounds.7,8 At present, the longest reported rylene compound is octarylene diimide (ODI; the core is the same as RD-8), which is synthesized by one author in this study.9 The intrinsic absorption peak in the solution is unavailable for ODI, and only a broad absorption profile could be found due to the serious aggregation. The absorption spectra, energy levels, stability, and molecular interaction of rylene derivatives vary significantly with the size © 2016 American Chemical Society

increase of the conjugated cores, which is concluded from known low rylene compounds.3,10−12 For high rylene derivatives, intrinsic properties could not be obtained through experiments, owing to the severe aggregation or nonexistence of these long conjugated molecules, so the theoretical calculation is the only effective option to get their information. Rylene diimides with two electron-withdrawing imide groups have much broader applications than their rylene counterparts in the field of organic optoelectronics, because of the lower lowest unoccupied molecular orbital (LUMO) energy levels, stronger electron accepting ability, and higher stability of former compounds.13 The theoretical investigation on the difference between rylene diimides and their rylene counterparts will help us recognize the essential effect of the imide group, which also offers a basic principle for the rational design of functional rylene compounds.14 At present, low rylene derivatives like RD-1, RD-2, R-1, and R2 with different functional groups have been investigated thoroughly by theoretical study.15−22 Only a few works reported the theoretical results of some known high rylene compounds.23−27 No work has explored rylene diimides and rylene derivatives systematically. One author in this study has been designing and synthesizing rylene compounds as semiconductors for many years.3,9,28−31 Another author has been working on the theoretical study of the Received: July 29, 2016 Revised: September 2, 2016 Published: September 8, 2016 7554

DOI: 10.1021/acs.jpca.6b07552 J. Phys. Chem. A 2016, 120, 7554−7560

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The Journal of Physical Chemistry A

Figure 1. Structures of rylene and rylene diimides.

small molecules.32,33 Herein, frontier molecular orbitals, steady spectra, electron affinity (EA), ionization potential (IP), innersphere reorganization energy (λi), and atomic charge population of 20 rylene compounds were calculated. Some theoretical properties were compared with experimental results. Properties for unknown high rylene derivatives were predicted. Stability of these compounds was analyzed by highest occupied molecular orbital (HOMO) energy levels. Charge transport properties are predicated by λi. The effect of imide groups was discussed by the atomic charge population.

3. RESULTS AND DISCUSSION Optimization of Density Functional Models. N,N′-Bis(2ethylhexyl)perylene diimides (PDI-C8, the conjugated core is the same as RD-2), which have been widely used in experiments, are used to screen a reliable method. As shown in Table 1, Table 1. Experimental and Theoretical λmax, LUMO, HOMO, and Band Gaps of N,N′-(2-Ethylhexyl)perylene Diimides CAM-B3LYP PBEPBE B3LYP experimentala

2. EXPERIMENTAL AND COMPUTATIONAL DETAILS N,N′-Bis(1-pentylhexyl)perylene diimide was synthesized according to the literature method.34 R-1 and R-2 were obtained by the commercial source. Absorption data were recorded with a UV−visible spectrometer. LUMO and HOMO levels were measured by the cyclic voltammetry method combined with optical band gaps.3 The ground-state geometries of all molecules were optimized using density functional theory (DFT) method with Becke’s three-parameter hybrid exchange function with Lee−Yang−Parr gradient-corrected correlation functional (B3LYP hybrid functional).35 The 6311g (d, p) was chosen as a basis set. For comparison, the cam-B3LYP functional,36 PBEPBE functional,37 and solvent effect were also considered. IP, EA, and λi were calculated under adiabatic condition. Cation, neutral, and anion species were optimized under fully relaxed conditions. IP and EA were computed as the vertical energy difference between the neutral molecule and its cationic and anionic forms, respectively, with the following equations.38

a

λmax, nm

LUMO, eV

HOMO, eV

gap, eV

445 581 516 524

−2.65 −4.18 −3.45 −3.71

−7.34 −5.66 −5.98 −6.01

4.69 1.48 2.53 2.30

In CH2Cl2.3

theoretical and experimental absorption maximum (λmax), LUMO levels, HOMO levels, and band gaps of PDI-C8 match well with B3LYP functional, while there is the big difference with the functional of CAM-B3LYP and PBEPBE. B3LYP functional was also found to be a precise method to calculate the reorganization energy of large conjugated molecules. It is much more precise than the BH, LLYP, and MP2 methods.41 Solvent Models. All the parameters were calculated in the gas phase. Table 1 shows that the calculated results with B3LYP functional are close to the experimental results. The λmax and optical band gaps of PDI-C11 (the core is the same as RD-2) and R-2 in different solvents are listed in Table 2, which shows that different solvents make little influence on the λmax and optical band gaps. So the effect of solvents is neglected. Table 2. Λmax and Optical Band Gaps of PDI-C11 and R-2 in Different Solvents

IP = Ecation − Eneutral

PDI-C11

EA = Eneutral − Eanion

The λi was obtained by the following equation

cyclohexane CH2Cl2 toluene THF 1,4-dioxane

λ i = λ1 + λ 2

λ1 = E±(Q N) − E±(Q ±)

R-2

λmax, nm

gap, eV

λmax, nm

gap, eV

516 525 527 521 522

2.34 2.30 2.28 2.30 2.30

436 438 439 437 437

2.80 2.76 2.76 2.78 2.78

PDI-C11: N,N′-bis(1-pentylhexyl)perylene diimides, R-2: perylene, in 1 × 10−5 M solution. The structures of all the compounds in this study are listed in the Figure 1. The alkyl groups attached to the nitrogen atoms in the RD derivatives are simplified to the methyl group, because they influence the electronic properties of conjugated cores slightly. Geometries, Frontier Molecular Orbitals, Band Gaps, Absorption Maximum. The geometries have a major impact on the molecule packing, which is important in the field of

λ 2 = E N(Q ±) − E N(Q N)

E±(QN) is the charged state energy with neutral state structure, E±(Q±) is the charged state energy with charged state structure, EN(QN) is the neutral state energy with neutral state structure, and EN(Q±) is the neutral state energy with charged state structure.39 All the electronic structure calculations were performed with Gaussian 09 program.40 7555


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conjugated core is the same as RD-8) with theoretical HOMO energy level of −4.75 eV is very stable in the solution or solid, which is confirmed by the author’s previous stability test.9 The stability of ODI is even higher than that of HDI. The high stability may be attributed to the serious aggregation of ODI. Although six bulky alkyl groups are attached at the conjugated core, single dispersed ODI could not be obtained, even when the concentration is as low as 1 × 10−6 M. So RD compounds with naphthalene units more than eight and high theoretical HOMO level are possible to be stable in the air, because strong intermolecular force leads to only aggregated forms. In the field of organic field-effect transistors (OFET), the LUMO energy level of electron transporting material should be close to −4.0 eV, and the HOMO energy level of hole transporting materials is usually in the range of −5.1 ± 0.3 eV.44 The low-lying LUMO energy level of RD compounds (−3.61 to −3.79 eV) makes them candidates for electron transporting materials (n-type semiconductors, electron acceptors) that could accept electron injection from metal electrode. For RD-1 and RD-2, their HOMO (−6.78, −6.01) is too low to be hole transporting materials. However, RD-3 and RD-4 with HOMO levels of −5.52 and −5.22 eV are suitable for the hole injection from metal electrodes. Judging from HOMO energy levels, RD-3 to RD-8 are right candidates for hole transporting compounds. For R derivatives, the LUMO energy levels fall and HOMO energy levels rise with the increasing size of conjugated cores, and the trend is the same as experimental results for R-1 to R-4, as shown in Table 3. For R-1 to R-4, the theoretical results match well with experimental ones.With increasing size of the conjugated core, the band gap decreases obviously, and the λmax redshifts remarkably. For example, λmax of R-4 (660 nm) red shift for 224 nm compared with that of R-2, and band gap of R-4 (2.77 eV) is 1.12 eV broader than that of R-2. For higher R compounds, the band gaps change slightly; for example, from R-8 to R-10, it decreases by only 0.19 eV. For R derivatives, the LUMO energy levels in the range from −1.25 to −3.28 eV is too high for stable electron transporting materials, so no applications of these compounds as stable n-type semiconductors are reported in the experiments. Judging from the HOMO energy levels, only R-2 and R-3 with HOMO energies of −5.21 and −4.84 eV are suitable candidates for hole transporting materials. Narrow bandgaps and large conjugated systems of high rylene derivatives make them have strong absorption in infrared range, and they are near-infrared (NIR) dyes. Reorganization Energy, Ionization Potential, and Electron Affinity. According to Marcus theory for charge transfer, reorganization energy plays a decisive role in the process of electron transfer.45 The charge mobility is decided by both inner-sphere reorganization energy (λi) and outer-sphere reorganization energy (λo). The λi depends on the molecule structure, while the λo depends on the molecular packing, which relates to the crystal structure. To develop high-performance semiconductors, evaluating the λi is a simple and practical process, and it is the first step before minimizing more complicated λo.39 As shown in Table 4, from RD-1 to RD-4, both electron and hole mobility reorganization energy (λie and λih) decreases by 0.143 and 0.099 eV, respectively, which declines fast. From RD-4 to RD-7, the λie and λih decline slowly. From RD-7 to RD-10, the λie and λih is almost unchanged. However, in experiments, the smaller size of conjugated core, the higher electron mobility. For

electronic materials. The energy levels of HOMO and LUMO (Figure 2), band gaps, and absorption are critical parameters for the applications of semiconductors.

Figure 2. Theoretical HOMO and LUMO energy levels of R and RD derivatives.

All the compounds in this study show planar conjugated cores. All the optimized geometries and frontier molecular orbitals are listed in the Supporting Information. The planar cores lead to the complete conjugation, which makes π electrons move in the conjugated systems freely. Planar and large conjugated cores cause strong π−π stacking, which results in their poor solubility, so the bulky alkyl groups must be introduced to the conjugated cores in the experiments to make them soluble.28 For RD compounds, the LUMO energy levels change slightly with the increasing size of the conjugated cores, from −3.61 to −3.79 eV, which agree well with experimental results (−3.63 to −3.82 eV). The reason is that the first electron-accepting position is at the oxygen atom in the carbonyl group due to its strong electron-withdrawing property, and there is little energy difference on the carbonyl groups among these RD molecules, as shown in Figure 3. The same rule was explored in detail for RD-2, RD-3, and RD-4 in the literature.42 The similar low-lying LUMO energy levels guarantee these compounds excellent electron acceptors.

Figure 3. Proposed reduction reaction for RD compounds.

For RD compounds, band gaps decrease from 3.64 to 0.80 eV with the conjugated size from RD-1 to RD-10. The calculated band gaps agree well with experimental data, as shown in Table 3. Narrower band gaps lead to longer absorption wavelengths corresponding to lower energy levels. So the λmax redshifts remarkably with the increasing size of conjugated cores. For example, RD-1 with λmax 367 nm has much smaller λmax than that of RD-6 (959 nm). The experimental results (382 and 908 nm for RD-1 and RD-6, respectively) have only small difference with theoretical ones. With the decrease of band gaps, the HOMO energy levels of RD compounds rise from −7.25 to −4.59 eV. Generally, to guarantee the air stability of organic semiconductors (resistant to oxidation), their HOMO energy level should be lower than −4.9 eV (assuming that the energy level of standard calomel electrode is 4.4 eV below the vacuum level).43 However, ODI (Figure 4, 7556


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The Journal of Physical Chemistry A Table 3. LUMO and HOMO Energy Levels, Band Gaps, and λmax of R and RD Derivatives experimentala

calculated RD-1 RD-2 RD-3 RD-4 RD-5 RD-6 RD-7 RD-8 RD-9 RD-10 R-1 R-2 R3̅ R-4 R-5 R-6 R-7 R-8 R-9 R-10

LUMO, eV

HOMO, eV

gap, eV

λmax, nm

LUMO, eV

HOMO, eV

gap, eV

−3.61 −3.69 −3.73 −3.74 −3.76 −3.77 −3.77 −3.78 −3.79 −3.79 −1.25 −2.17 −2.58 −2.81 −2.96 −3.07 −3.16 −3.22 −3.28 −3.32

−7.25 −6.22 −5.7 −5.37 −5.15 −4.98 −4.85 −4.75 −4.66 −4.59 −6.05 −5.21 −4.84 −4.64 −4.5 −4.4 −4.33 −4.27 −4.22 −4.18

3.64 2.53 1.97 1.63 1.39 1.22 1.08 0.97 0.88 0.8 4.8 3.03 2.26 1.83 1.54 1.33 1.17 1.05 0.95 0.86

367 512 637 745 856 959 1060 1160 1260 1361 201 435 565 680 787 889 989 1087 1185 1284

−3.63 −3.71 −3.77 −3.82

−6.78 −6.01 −5.52 −5.22

3.15 2.30 1.75 1.40

382, CH2Cl2, ref 3 516, cyclohexane 651, CHCl3, ref 10 762, CHCl3, ref 10

−3.67

−4.88

1.21

908, THF, ref 9

−3.66

−1.24 −2.41 −2.83 −2.98

λmax, nm, solvent

No intrinsic λmax, ref 9

−5.47 −5.18 −4.83 −4.63

4.23 2.77 2.00 1.65

220, cyclohexane 436, cyclohexane 560, dioxane, ref 23 660, dioxane, ref 23

a

The conjugated cores of experimental compounds are the same as their theoretical counterparts. All the energy levels in the literature are revised by the assuming that the energy level of Fc/Fc+ is 4.80 eV relative to vacuum.

Figure 4. Structures of HDI and ODI.

cm2 V−1 s−1.47 It is attributed to the easy crystallization of naphthalene diimides, which decreases the λo. So, λi falls with the size increase of the conjugated core, and the size of RD-4 is big enough for the small λi to favor charge transport. Varied HOMO and LUMO energy levels of rylene compounds are also reflected on the IP and EA. From RD-1 to RD-10, the IP decreases from 8.72 to 5.10 eV, and EA increases from 2.27 to 3.31 eV. With the increasing size of the conjugated core, IP value decreases monotonically, which indicates the electron-deficient property of the low RD compounds, while the IP value varies in the small range from 2.27 to 3.31 eV, which is consistent with almost constant LUMO energy levels of RD compounds. All the IP values of RD compounds are higher than their rylene counterparts, which indicates RD compounds are more difficult to oxidize than their R counterparts. Atomic Charge Population. The charge population plays an important role in the quantum chemical calculation of organic molecules, because it affects dipole moment, molecular polarizability, electronic structure, and many other properties of molecular systems.48 The charge distribution over atoms indicates the formation of donor and acceptor pairs that are involved in the intermolecular charge transfer.49 The charge population was obtained at ground state with a natural bond orbital analysis method based on the energyminimized structure, and the representative results of RD-1, RD10, R-1, and R-10 were organized in Table 5. The atoms are

Table 4. Λie, λih, Electron Affinity, and Ionization Potential RD-1 RD-2 RD-3 RD-4 RD-5 RD-6 RD-7 RD-8 RD-9 RD-10 R-1 R-2 R3̅ R-4 R-5 R-6 R-7 R-8 R-9 R-10

λie, eV

λih, eV

IP, eV

EA, eV

0.349 0.271 0.230 0.206 0.192 0.182 0.177 0.173 0.172 0.171 0.266 0.178 0.147 0.133 0.126 0.123 0.121 0.121 0.120 0.124

0.210 0.161 0.135 0.121 0.113 0.109 0.106 0.105 0.105 0.106 0.190 0.148 0.134 0.127 0.124 0.122 0.123 0.124 0.124 0.128

8.72 7.42 6.72 6.27 5.95 5.70 5.51 5.35 5.21 5.10 7.82 6.58 5.98 5.62 5.36 5.18 5.03 4.90 4.80 4.71

2.27 2.57 2.76 2.89 3.00 3.08 3.15 3.21 3.26 3.31 −0.42 0.84 1.46 1.84 2.11 2.31 2.46 2.59 2.70 2.79

example, the electron mobility of N,N′-bis(cyclohexyl)naphthalene diimides in OFET approaches 6 cm2 V−1 s−1,46 while the electron mobility of quaterrylene diimides is only 0.088 7557


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The Journal of Physical Chemistry A Table 5. Charge Population of RD-1, RD-10, R-1, and R-10 RD-1 C1/−0.358 C2/0.691 C3/−0.100 C4/−0.131 C5/−0.131 C6/−0.100 C7/−0.020 C8/−0.020 H1/0.197 H2/0.234 H3/0.234 N1/−0.479 O1/−0.581

CH3N(CO)2/−0.027 a

RD-10 atom/charge C1/−0.359 C2/0.688 C3/−0.134 C4/−0.123 C5/−0.187 C6/0.000 C7/−0.021 C8/−0.003 C9/−0.034 C10/−0.154 C11/−0.172 C12/−0.015 C13/−0.010 C14/−0.005 C15/−0.028 CH3N(CO)2/−0.080 3rd naph/0.028

C16/−0.161 C17/−0.169 C18/−0.019 C19/−0.008 C20/−0.007 C21/−0.026 C22/−0.163 C23/−0.167 C24/−0.021 C25/−0.008 C26/−0.007 C27/−0.024 C28/−0.165 C29−0.166 C30/−0.023 1st napha/−0.057 4th naph/0.025

R-1 C31/−0.007 C32/−0.007 H1/0.199 H2/0.228 H3/0.200 H4/0.201 H5/0.199 H6/0.199 H7/0.199 H8/0.199 H9/0.199 H10/0.199 H11/0.199 N1/−0.477 O1/−0.609 2nd naph/0.035 5th naph/0.024

C1/−0.176 C2/−0.197 C3/−0.197 C4/−0.176 C5/−0.055 C6/−0.055 H1/0.200 H2/0.201 H3/0.201

R-10 atom/charge C1/−0.173 C2/−0.190 C3/−0.176 C4/−0.028 C5/−0.017 C6/−0.047 C7/−0.023 C8/−0.169 C9/−0.168 C10/−0.026 C11/−0.007 C12/−0.010 C13/−0.024 C14/−0.169

C15/−0.168 C16/−0.026 C17/−0.007 C18/−0.008 C19/−0.025 C20/−0.169 C21/−0.168 C22/−0.026 C23/−0.007 C24/−0.008 C25/−0.025 C26/−0.169 C27/−0.169 C28/−0.026

C29/−0.007 C30/−0.007 H1/0.201 H2/0.203 H3/0.196 H4/0.198 H5/0.197 H6/0.197 H7/0.197 H8/0.197 H9/0.197 H10/0.197 H11/0.197

1st naph/0.002 3rd naph/−0.001

2nd naph/0.001 4th naph/−0.001

5th naph/−0.001

naph, abbreviation of naphthalene unit.

Figure 5. Atomic labels and optimized geometries of RD-1, RD-10, R-1, and R-10.

charge, and the middle one has −0.001 negative charge. There is only weak push−pull structure. Effect of Carboxylic Imide Group. RD compounds with carboxylic imide groups possess various applications in the field of optoelectronics. R compounds without electron-withdrawing imide group show few applications as semiconductors. What role does carboxylic imide group play? First, the special structure of electron-withdrawing carboxylic imide group lowers the LUMO energy level of RD compounds and keeps that value in the small range from −3.61 to −3.79 eV, which makes them suitable candidates of electron transporting materials.50 In contrast, R compounds have higher LUMO energy level from −1.25 to −3.32 eV, which makes it impossible for them to be n-type semiconductors. In experiments, RD-1, RD-2, RD-3, and RD-4 have proved to be excellent electrontransporting materials. Higher RD compounds have not been investigated in the organic electronics owing to their synthetic difficulties. Second, electron-withdrawing imide group lower the HOMO energy levels of RD compounds and makes their IP value lower than those of their R counterparts. For example, the IP value of

labled in Figure 5. The results for the rest of the compounds are listed in the Supporting Information. As shown in Table 5, RD and R compounds show different charge distribution patterns that originate from their different structures. For RD compounds the negative charge is located at the imide group and the first naphthalene unit, which neighbors the carbonyl group. There is a “pull−push” composition in the conjugated core of RD compounds, while the charge spreads almost equably in R compounds. The pull−push structure makes RD compounds narrower band gaps and red-shifted absorption compared to their R counterparts. The imide group of RD-10 with charge −0.08 has more negative charge than that of RD-1 (with charge of −0.027), which leads to stronger “push−pull” structure in RD-10. Strong push−pull structure contributes to the low band gap and strong absorption in the infrared range. For RD-10, the negative charge distributes at the imide groups and the first naphthalene unit, and the positive charge is at the remaining eight naphthalene units. It is a different case for R compounds, compared with RD derivatives. The charge scatters almost equally in the conjugated core of R-10. The first naphthalene unit holds 0.002 positive 7558


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electron acceptors in high-performance bulk heterojunction solar cells. Nat. Commun. 2015, 6, 8242. (5) He, T.; Stolte, M.; Würthner, F. Air-Stable n-Channel Organic Single Crystal Field-Effect Transistors Based on Microribbons of CoreChlorinated Naphthalene Diimide. Adv. Mater. 2013, 25 (48), 6951− 6955. (6) Oh, J. H.; Suraru, S. L.; Lee, W. Y.; Könemann, M.; Höffken, H. W.; Röger, C.; Schmidt, R.; Chung, Y.; Chen, W. C.; Würthner, F.; et al. High-Performance Air-Stable n-Type Organic Transistors Based on Core-Chlorinated Naphthalene Tetracarboxylic Diimides. Adv. Funct. Mater. 2010, 20 (13), 2148−2156. (7) Liu, C.; Liu, Z.; Lemke, H. T.; Tsao, H. N.; Naber, R. C.; Li, Y.; Banger, K.; Müllen, K.; Nielsen, M. M.; Sirringhaus, H. Highperformance solution-deposited ambipolar organic transistors based on terrylene diimides. Chem. Mater. 2010, 22 (6), 2120−2124. (8) Tsao, H. N.; Pisula, W.; Liu, Z.; Osikowicz, W.; Salaneck, W. R.; Müllen, K. From Ambi-to Unipolar Behavior in Discotic Dye FieldEffect Transistors. Adv. Mater. 2008, 20 (14), 2715−2719. (9) Yuan, Z.; Lee, S. L.; Chen, L.; Li, C.; Mali, K. S.; De Feyter, S.; Müllen, K. Processable Rylene Diimide Dyes up to 4 nm in Length: Synthesis and STM Visualization. Chem. - Eur. J. 2013, 19 (36), 11842− 11846. (10) Nolde, F.; Pisula, W.; Müller, S.; Kohl, C.; Müllen, K. Synthesis and self-organization of core-extended perylene tetracarboxdiimides with branched alkyl substituents. Chem. Mater. 2006, 18 (16), 3715− 3725. (11) Quante, H.; Müllen, K. Quaterrylenebis (dicarboximides). Angew. Chem., Int. Ed. Engl. 1995, 34 (12), 1323−1325. (12) Pschirer, N. G.; Kohl, C.; Nolde, F.; Qu, J.; Müllen, K. Pentarylene-and Hexarylenebis (dicarboximide) s: Near-InfraredAbsorbing Polyaromatic Dyes. Angew. Chem., Int. Ed. 2006, 45 (9), 1401−1404. (13) Zhan, X.; Facchetti, A.; Barlow, S.; Marks, T. J.; Ratner, M. A.; Wasielewski, M. R.; Marder, S. R. Rylene and related diimides for organic electronics. Adv. Mater. 2011, 23 (2), 268−284. (14) Houari, Y. n.; Laurent, A. l. D.; Jacquemin, D. Spectral signatures of perylene diimide derivatives: insights from theory. J. Phys. Chem. C 2013, 117 (42), 21682−21691. (15) Settels, V.; Liu, W.; Pflaum, J.; Fink, R. F.; Engels, B. Comparison of the electronic structure of different perylene-based dye-aggregates. J. Comput. Chem. 2012, 33 (18), 1544−1553. (16) Casanova, D. Theoretical investigations of the perylene electronic structure: Monomer, dimers, and excimers. Int. J. Quantum Chem. 2015, 115 (7), 442−452. (17) Liang, B.; Zhang, Y.; Wang, Y.; Xu, W.; Li, X. Structures and properties of 1, 7-disubstituted perylene tetracarboxylic diimides: The substitutional effect study based on density functional theory calculations. J. Mol. Struct. 2009, 917 (2), 133−141. (18) Clark, A. E.; Qin, C.; Li, A. D. Beyond exciton theory: A timedependent dft and franck-condon study of perylene diimide and its chromophoric dimer. J. Am. Chem. Soc. 2007, 129 (24), 7586−7595. (19) Al-Galiby, Q.; Grace, I.; Sadeghi, H.; Lambert, C. J. Exploiting the extended π-system of perylene bisimide for label-free single-molecule sensing. J. Mater. Chem. C 2015, 3 (9), 2101−2106. (20) Diehl, F. P.; Roos, C.; Jankowiak, H.-C.; Berger, R.; Köhn, A.; Diezemann, G.; Basché, T. Combined Experimental and theoretical study of the vibronic spectra of perylenecarboximides. J. Phys. Chem. B 2010, 114 (4), 1638−1647. (21) Engel, E.; Schmidt, K.; Beljonne, D.; Brédas, J.-L.; Assa, J.; Fröb, H.; Leo, K.; Hoffmann, M. Transient absorption spectroscopy and quantum-chemical studies of matrix-isolated perylene derivatives. Phys. Rev. B: Condens. Matter Mater. Phys. 2006, 73 (24), 245216. (22) Oltean, M.; Calborean, A.; Mile, G.; Vidrighin, M.; Iosin, M.; Leopold, L.; Maniu, D.; Leopold, N.; Chiş, V. Absorption spectra of PTCDI: a combined UV−vis and TD-DFT study. Spectrochim. Acta, Part A 2012, 97, 703−710. (23) Bohnen, A.; Koch, K. H.; Lüttke, W.; Müllen, K. Oligorylene as a Model for “Poly (perinaphthalene). Angew. Chem., Int. Ed. Engl. 1990, 29 (5), 525−527.

RD-1 to RD-4 is 0.90−0.65 eV lower than those of R-1 to R-4, respectively. Higher IP and lower HOMO energy levels make RD compounds more resistant to oxygen than R series. High rylene compounds with high HOMO energy level and low IP value should be unstable to the oxygen in the air. Third, the introduction of alkyl groups at N atoms is convenient for RD compounds. Alkyl groups play a key role in the chemistry of rylene derivatives. They depress the intermolecular π−π stacking and increase the solubility of the compounds, which makes the synthesis facile. The special alkyl groups are also helpful for ordered packing of the molecule, which favors the high mobility of charge transfer.51

4. CONCLUSION In summary, we successfully simulated 20 rylene derivatives with and without carboxylic imide groups by the DFT method. The theoretical and experimental results agree well. Unusual properties for unknown high rylene derivatives were predicted. R and RD compounds show different λmax, HOMO, LUMO, EA, IP, and λi, which originate from distinct charge distribution due to the strong electron-withdrawing imide groups. RD derivatives show almost constant low-lying LUMO level, which makes them strong electron acceptors. The narrow band gaps of high rylene series make them suitable NIR dyes. The conjugated core of RD4 and R-4 is big enough for the small λi to favor charge transport. The study is hoped to be a guidance for the future research of rylene derivatives.

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.jpca.6b07552. Optimized structures and molecular orbitals of 20 rylene compounds, natural bond analysis of compounds RD-2 to RD-9 and R-2 to R-9. (PDF)

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AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected]. Phone: +86-791-8396-8830. (X.Z.) *E-mail: [email protected]. (Z.Y.) Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS The authors thank National Natural Science Foundation of China (No. 21562031) and Natural Science Foundation of Jiangxi Province in China (Nos. 20161BAB213063 and No. 20161BAB213064) for financial support.

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REFERENCES

(1) Chen, L.; Li, C.; Müllen, K. Beyond perylene diimides: synthesis, assembly and function of higher rylene chromophores. J. Mater. Chem. C 2014, 2 (11), 1938−1956. (2) Weil, T.; Vosch, T.; Hofkens, J.; Peneva, K.; Müllen, K. The rylene colorant familytailored nanoemitters for photonics research and applications. Angew. Chem., Int. Ed. 2010, 49 (48), 9068−9093. (3) Yuan, Z.; Li, J.; Xiao, Y.; Li, Z.; Qian, X. Core-perfluoroalkylated perylene diimides and naphthalene diimides: Versatile synthesis, solubility, electrochemistry, and optical properties. J. Org. Chem. 2010, 75 (9), 3007−3016. (4) Zhong, Y.; Trinh, M. T.; Chen, R.; Purdum, G. E.; Khlyabich, P. P.; Sezen, M.; Oh, S.; Zhu, H.; Fowler, B.; Zhang, B. Molecular helices as 7559


Article

The Journal of Physical Chemistry A (24) Malloci, G.; Cappellini, G.; Mulas, G.; Mattoni, A. Electronic and optical properties of families of polycyclic aromatic hydrocarbons: A systematic (time-dependent) density functional theory study. Chem. Phys. 2011, 384 (1), 19−27. (25) Navarro, P.; Bocquet, F.; Deperasinska, I.; Pirug, G.; Tautz, F.; Orrit, M. Electron Energy Loss of Terrylene Deposited on Au (111): Vibrational and Electronic Spectroscopy. J. Phys. Chem. C 2015, 119 (1), 277−283. (26) Baumgarten, M.; Karabunarliev, S.; Koch, K.-H.; Müllen, K.; Tyutyulkov, N. Band structure of quasi-one-dimensional polycondensed aromatic hydrocarbons I. Poly (periacene) s. Synth. Met. 1992, 47 (1), 21−36. (27) Karabunarliev, S.; Gherghel, L.; Koch, K.-H.; Baumgarten, M. Structure and optical absorption of oligorylenes upon doping. Chem. Phys. 1994, 189 (1), 53−65. (28) Yuan, Z.; Xiao, Y.; Qian, X. A design concept of planar conjugated ladder oligomers of perylene bisimides and efficient synthetic strategy via regioselective photocyclization. Chem. Commun. 2010, 46 (16), 2772−2774. (29) Lee, S.-L.; Yuan, Z.; Chen, L.; Mali, K. S.; Müllen, K.; De Feyter, S. Flow-Assisted 2D Polymorph Selection: Stabilizing Metastable Monolayers at the Liquid−Solid Interface. J. Am. Chem. Soc. 2014, 136 (21), 7595−7598. (30) Yuan, Z.; Ma, Y.; Geßner, T.; Li, M.; Chen, L.; Eustachi, M.; Weitz, R. T.; Li, C.; Müllen, K. Core-Fluorinated Naphthalene Diimides: Synthesis, Characterization, and Application in n-Type Organic FieldEffect Transistors. Org. Lett. 2016, 18 (3), 456−459. (31) Yuan, Z.; Xiao, Y.; Yang, Y.; Xiong, T. Soluble ladder conjugated polymer composed of perylenediimides and thieno [3, 2-b] thiophene (LCPT): a highly efficient synthesis via photocyclization with the sunlight. Macromolecules 2011, 44 (7), 1788−1791. (32) Zhao, X.; Chen, M. A TDDFT study on the singlet and triplet excited-state hydrogen bonding and proton transfer of 10-hydroxybenzo [h] quinoline (HBQ) and 7, 9-diiodo-10-hydroxybenzo [h] quinoline (DIHBQ). Chem. Phys. Lett. 2011, 512 (1), 35−39. (33) Zhao, X.; Chen, M. Excited state charge transfer coupled double proton transfer reaction of 7-azaindole derivatives in methanol: a theoretical study. J. Phys. Chem. A 2010, 114 (29), 7786−7790. (34) Boobalan, G.; Imran, P. M.; Nagarajan, S. Self-assembly, optical and electrical properties of fork-tailed perylene bisimides. Superlattices Microstruct. 2012, 51 (6), 921−932. (35) Becke, A. D. Density-functional exchange-energy approximation with correct asymptotic behavior. Phys. Rev. A: At., Mol., Opt. Phys. 1988, 38 (6), 3098. (36) Yanai, T.; Tew, D. P.; Handy, N. C. A new hybrid exchange− correlation functional using the Coulomb-attenuating method (CAMB3LYP). Chem. Phys. Lett. 2004, 393 (1), 51−57. (37) Perdew, J. P.; Burke, K.; Ernzerhof, M. Generalized gradient approximation made simple. Phys. Rev. Lett. 1996, 77 (18), 3865. (38) Zhan, C.-G.; Nichols, J. A.; Dixon, D. A. Ionization potential, electron affinity, electronegativity, hardness, and electron excitation energy: molecular properties from density functional theory orbital energies. J. Phys. Chem. A 2003, 107 (20), 4184−4195. (39) Sun, H.; Putta, A.; Billion, M. Arene trifluoromethylation: An effective strategy to obtain air-stable n-type organic semiconductors with tunable optoelectronic and electron transfer properties. J. Phys. Chem. A 2012, 116 (30), 8015−8022. (40) Frisch, M. J.; Trucks, G.; Schlegel, H.; Scuseria, G.; Robb, M.; Cheeseman, J.; Scalmani, G.; Barone, V.; Mennucci, B.; Petersson, G. Gaussian 09, revision A. 1; Gaussian Inc: Wallingford, CT, 2009. (41) Gruhn, N. E.; da Silva Filho, D. A.; Bill, T. G.; Malagoli, M.; Coropceanu, V.; Kahn, A.; Brédas, J.-L. The vibrational reorganization energy in pentacene: molecular influences on charge transport. J. Am. Chem. Soc. 2002, 124 (27), 7918−7919. (42) Lee, S. K.; Zu, Y.; Herrmann, A.; Geerts, Y.; Müllen, K.; Bard, A. J. Electrochemistry, spectroscopy and electrogenerated chemiluminescence of perylene, terrylene, and quaterrylene diimides in aprotic solution. J. Am. Chem. Soc. 1999, 121 (14), 3513−3520.

(43) Cui, Y.; Zhang, X.; Jenekhe, S. A. Thiophene-linked polyphenylquinoxaline: a new electron transport conjugated polymer for electroluminescent devices. Macromolecules 1999, 32 (11), 3824− 3826. (44) Zhang, W.; Liu, Y.; Yu, G. Heteroatom Substituted Organic/ Polymeric Semiconductors and their Applications in Field-Effect Transistors. Adv. Mater. 2014, 26 (40), 6898−6904. (45) Marcus, R. A. Electron transfer reactions in chemistry. Theory and experiment. Rev. Mod. Phys. 1993, 65 (3), 599. (46) Shukla, D.; Nelson, S. F.; Freeman, D. C.; Rajeswaran, M.; Ahearn, W. G.; Meyer, D. M.; Carey, J. T. Thin-film morphology control in naphthalene-diimide-based semiconductors: high mobility n-type semiconductor for organic thin-film transistors. Chem. Mater. 2008, 20 (24), 7486−7491. (47) Oh, J. H.; Lee, W.-Y.; Noe, T.; Chen, W.-C.; Könemann, M.; Bao, Z. Solution-shear-processed quaterrylene diimide thin-film transistors prepared by pressure-assisted thermal cleavage of swallow tails. J. Am. Chem. Soc. 2011, 133 (12), 4204−4207. (48) Gangadharan, R. P.; Sampath Krishnan, S. Natural bond orbital (NBO) population analysis of 1-azanapthalene-8-ol. Acta Phys. Pol., A 2014, 125 (1), 18−22. (49) Jacquemin, D.; Le Bahers, T.; Adamo, C.; Ciofini, I. What is the “best” atomic charge model to describe through-space charge-transfer excitations? Phys. Chem. Chem. Phys. 2012, 14 (16), 5383−5388. (50) Black, H. T.; Dadvand, A.; Liu, S.; Ashby, V. S.; Perepichka, D. F. Perfluoroalkyl-substitution versus electron-deficient building blocks in design of oligothiophene semiconductors. J. Mater. Chem. C 2013, 1 (2), 260−267. (51) Zhang, F.; Hu, Y.; Schuettfort, T.; Di, C.-a.; Gao, X.; McNeill, C. R.; Thomsen, L.; Mannsfeld, S. C.; Yuan, W.; Sirringhaus, H.; et al. Critical role of alkyl chain branching of organic semiconductors in enabling solution-processed n-channel organic thin-film transistors with mobility of up to 3.50 cm2 V−1 s−1. J. Am. Chem. Soc. 2013, 135 (6), 2338−2349.

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Rylene and Rylene Diimides: Comparison of Theoretical and

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