DFT study of electron donor-acceptor (EDA) complexes of 1H-indole and benzyl bromide derivatives: mechanism exploration and theoretical prediction

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DFT study of electron donor-acceptor (EDA) complexes of 1H-indole and benzyl bromide derivatives: mechanism exploration and theoretical prediction

https://doi.org/10.21203/rs.3.rs-4224084/v1

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Organic synthesis methods initiated by visible light have received increasing attention from synthetic chemists. Reactions initiated by EDA complexes do not require the use of toxic or expensive photoredox catalysts compared to traditional photoreaction processes. However, this kind of reaction requires the structure of the substrate, so it is important to study the detailed and systematic reaction mechanism for its design. The EDA complexes of substituted 1 H-indole and substituted benzyl bromide derivatives were studied by density functional theory (DFT). The difference between EDA complexes with substituents of different kinds and locations were compared by theoretical study and new EDA complex was predicted.

1H-indole

EDA complex

DFT

TD-DFT

Theoretical prediction

In recent years, visible light photocatalysis has become a useful tool in the hands of organic synthesis chemists because of its mild, clean, easy to operate and environmentally friendly characteristics.^[1–6] Under normal circumstances, most organic compounds do not absorb visible light well.^[7] Thus, this method relies on the ability of metal complexes or organic dyes to undergo single electron transfer (SET) processes with organic substrates under excitation of photon. For metal complex type photosensitizers, although there are various metals used, but the most classic are polypyridyl complexes of ruthenium (Ru) and iridium (Ir). These complexes are widely used due to their advantages of absorbing light in the visible region of the electromagnetic spectrum, resulting in stable and long-life photoexcited states.^{[3, 8–10]} However, the high price limits the application scope and scale of iridium or ruthenium complexes as photoredox catalysts. In addition, the widespread use of such complexes also puts pressure on the environment due to high toxicity. Although organic photoredox catalysts have low cost and toxicity, poor photostability and catalyst recovery difficulties still impose great limitations on the amplification synthesis.^[11–13] Therefore, it is still very important to develop new systems of photoless redox catalysts. Whether from a practical point of view or from the perspective of large-scale industrial applications, the development of new photosensitizer-free reaction systems is undoubtedly crucial and attractive.

The phenomenon of intense color when two colorless or nearly colorless organic compounds are combined inspired Robert Mulliken to propose charge transfer theory.^[14–16] An electron-rich substrate and an electron-poor substrate can form a complex called electron donor-acceptor complex.^{[17, 18]} The UV-Vis absorption of the EDA complex is redshifted relative to the substrate that forms it, which makes the substrate more able to absorb visible light. This is because the substrate appears a weak absorption band, namely charge transfer band, related to the transfer of electrons from donor to acceptor during the formation of EDA complex, and this absorption band is often in the range of visible light. This enables EDA complex to complete the single electron transfer process under the excitation of visible light similar to that of photoredox catalyst.^{[19, 20]} Compared with traditional photocatalytic processes, EDA-type reactions do not require external photosensitizers to generate electron transfer, so it has received great attention from synthesis workers. The application of EDA complexes in synthesis has been widely studied in recent years.^[21–37]

In 2015, Paolo Melchiorre’s group found an electron donor–acceptor complex that drives the photochemical alkylation of indoles. They believed that the combination of 1H-indoles 1 as electron donor and alkyl halide 2 as electron acceptor can effectively form EDA complex (I), and the formed EDA complex can form radical pair (II) under light irradiation, and then the free radical coupling can generate corresponding products (shown in Scheme 1). Unfortunately, despite the practical importance of such transformations and the very interesting mechanistic nature, the mechanisms are still not completely perceived.

Our group has long been committed to the development of new visible-light-induced organic synthesis methods^[38–40]; The study of molecular properties and reaction mechanisms through computational chemistry.^[41–46] Hence, we can raise a number of interesting questions: 1) How does changing the substituents of the donor and acceptor affect the strength of the interaction? 2) The electron donor-acceptor interaction may be the Π-Π interaction, but we still don't know the exact distribution between them. 3) Can we use theoretical calculations to guide the discovery of EDA complexes so as to avoid tedious experimental screening?

In this paper, density functional theory calculations are used to investigate the EDA complex formed by substituted 1 H-indole with substituted benzyl bromide derivatives. We obtained a large number of different EDA complex cases by changing the type and position of the substituents on the two substrates. The zero-point energy (ZPE) was used to obtain the binding energy of each EDA complex. Through theoretical calculation, analysis and comparison of EDA complexes with substituents of different kinds and locations was compared, we try to explore the factors that are crucial to the formation of EDA complexes that can trigger the initiation reaction, so as to make theoretical pre-design of new similar EDA-reactions.

EDA complexes formed by 3-methyl-1H-indole derivatives and substituted benzyl bromide.

To determine the effect of different positions and types of substituents on the benzyl bromide derivatives and indole derivatives comprising the EDA complexes on the magnitude of the binding energies of their constituent EDA complexes. We considered and calculated the EDA complexes of benzyl bromide derivatives substituted at different positions of the electron-withdrawing group (e.g., nitro, nitroso, cyano, or aldehyde) with 3-methyl-1H-indole derivatives; EDA complexes of benzyl bromide derivatives substituted at different positions of the electron-donor group (e.g., methyl or methoxy) with 3-methyl-1H-indole derivatives; Finally, the EDA complexes of nitro-substituted 3-methyl-1H-indole derivatives at different positions and in different amounts with methoxy-substituted, unsubstituted and methoxy-substituted benzyl bromide. In the process of obtaining the bonding energies of the complexes mentioned above, we chose the zero-point energy and compared the bonding energies of the mentioned EDA complexes (for details, see ESI, † Fig. S1-S5).

All electron-withdrawing group substituted benzyl bromide derivatives have lower binding energies than unsubstituted benzyl bromide for the formation of EDA complexes with 3-methyl-1H-indole derivatives (-9.98 to -16.59 kcal/mol, see Fig. S1-S2). For the electron-donating group, the binding energies of the EDA complexes formed with the 3-methyl-1H-indole derivatives were also all lower than unsubstituted benzyl bromide derivatives, but not numerically as large as those of the electron-withdrawing ones (-8.44 to -9.92 kcal/mol, see Fig. S1 and S3). For the bonding energies of EDA complexes formed by nitro-substituted 3-methyl-1H-indole derivatives with benzyl bromide derivatives, we found an interesting pattern. That is, in general, for the values of binding energies methoxy-substituted is greater than methyl-substituted is greater than unsubstituted (-7.75 to -16.98 kcal/mol, see Fig. S4 and S5). In summary, we found that the binding energy of EDA complexes may be related to the difference between rich and poor electrons of aromatic rings forming it, so in the next study we chose six representative EDA complexes (Scheme 2) to carry out detailed calculations and property analysis.

The structures, bonding energy and thermodynamic properties of representative EDA complexes.

The structure of the optimized EDA complex is shown in Fig. 1. Based on the analysis of the structures of the six selected EDA complexes, we found that all benzyl bromide derivatives are "face-to-face" with 3-methyl-1H-indole derivatives. Moreover, all the benzyl bromide derivatives are tilted to a certain extent during binding, and their structures are not spatially parallel to those of the 3-methyl-1H-indole derivatives. For the reasons mentioned above, we may not be able to obtain the exact distance between the two molecules. Therefore, we added a dummy atom in the plane where the indole is located in the optimized structure, and then measured the distance between the dummy atom and the specified atom on the benzyl bromide derivative and used it to estimate the distance between the planes where the two molecules are located (for details, see ESI†, Fig. S6). The results indicate that the distance between the two molecules in complex 13a-1c is the greatest

at 3.48 Å. The distance between the two molecules in complex 3b-1c is 3.16 Å, which closely aligns with single crystal data of EDA complex obtained by Melchiorre et al. Furthermore, there is only a minor difference of 0.32 Å between the maximum and minimum values, which is not significant. Therefore, we proceeded to analyze the binding energy, free energy, enthalpy and entropy values of the EDA complexes.

Table 1

The binding energies (ZPE), ΔG, ΔH and ΔS of EDA complexes ¹.
EDA complexes	ZPE	ΔG	ΔH	ΔS
3b-1c	-14.70	-0.77	-14.43	-0.05
13a-1c	-6.92	4.58	-6.39	-0.01
6a-1c	-9.90	2.28	-9.36	-0.02
3b-10c	-15.73	-0.69	-15.47	-0.05
13a-10c	-10.57	1.25	-9.97	-0.03
6a-10c	-15.22	-1.26	-14.88	-0.05

¹ Energies in kcal/mol.

The binding energy can measure the difficulty and stability of the formation of EDA complexes. According to the data in Table 1, in general, the binding energy of 3-methyl-1H-indole with nitro (10c) and the selected benzyl bromide derivatives is greater than that of 3-methyl-1H-indole without nitro (1c). In addition, for the three 1c-complexes, the electron-withdrawing 2, 4-dinitrobenzyl bromide (3b) has the lowest bonding energy. The bonding energy of benzyl bromide without any substituents (13a) is the highest. For the 10c-complexes, we got similar result. Through the above results, we found that the bonding energy of EDA complexes formed by different substituents (electron withdrawing or electron donating) is significant. For example, the complexes formed by electron-poor benzyl bromide 3b with 3-methyl-1H-indole 1c and 3-methyl-4,6-dinitro-1H-indole 10c have energies of about − 15 kcal/mol; The complex energy of electron-rich benzyl bromide 6a and electron-poor 3-methyl-4,6-dinitro-1H-indole 10c is -15.22 kcal/mol; The binding energy of the unsubstituted benzyl bromide with 10c is lower than that with 1c. The formation of 3b-1c, 3b-10c, and 6a-10c complexes is spontaneous (ΔG values are all negative). All complexes formation processes have exothermic properties (ΔH values are negative). The ΔS values of all complexes were less than zero, which indicated that the process was an entropy decreasing and reversible process, it was also confirmed that the formation of complexes was spontaneous. These results indicate that different substituents have important effects on the stability of EDA complexes, and the electron differences between aromatic rings of EDA complexes may be one of the main reasons for their stability.

The interaction region indicator (IRI) analysis of representative EDA complexes.

Interactions between atoms are ubiquitous in chemical systems. Graphical representations of interactions are certainly useful in examining chemical problems, allowing the chemist to quickly visualize what interactions are occurring where in the system. We show the IRI analysis results of selected complexes in Fig. 2. Overall, the Π-Π interaction between the benzyl bromide derivatives and the indole derivatives is almost distributed between the two aromatic rings, and the intensity is close to the vdW interaction. The interaction area between unsubstituted benzyl bromide and indole derivatives is the smallest, and both nitro-substitution and methoxy-substitution can increase the interaction area. In addition, the interaction area of nitro-substituted indole is larger than that of unsubstituted indole.

The FMO analyses of representative EDA complexes.

As an effective method to analyze the characteristics of electron donors and acceptors, FMOs theory has been widely used. Generally accepted by researchers, the mechanism of EDA complex triggering reaction is that under the excitation of visible light, the electrons in the complex HOMO (distributed in the electron donor molecule) are excited to transfer to the LUMO orbital (distributed in the electron acceptor molecule), thus a single electron transfer (SET) process occurs. Therefore, a reasonable distribution of HOMO and LUMO as well as an energy gap in the appropriate range are necessary conditions for the creation of a functional EDA complex. Hence, it is necessary to study the distribution of HOMO and LUMO and the energy gap in EDA complexes. For the complexes formed by benzyl bromides with 1c, the distribution of their FMOs is quite similar, and HOMO always distributed on 1c and LUMO always distributed on the benzyl bromide derivatives. However, in complexes 6a-1c, a slight amount of HOMO was distributed on the 2,4-dimethoxybenzyl bromide (6a). This may be due to the fact that compound 6a carries two electron-donating substituents on the benzene ring. When we look at another set of EDA complexes, that is, the three complexes formed by the benzyl bromide derivatives with 10c, we observe that there is a large difference in the distributions of the FMOs of these complexes with respect to the complexes associated with 1c. First, in 3b-10, HOMO is distributed on 10c while LUMO is distributed on 3b. But when the two nitro groups are removed, a small amount of HOMO in 13a-10c has been distributed on 13a. Finally, when the benzyl bromide was replaced by the electron-rich 6a, the situation was reversed, with HOMO distributed mainly on 6a and to a lesser extent on 10c, while LUMO was distributed entirely on 10c. The probable reason for these phenomena is that 10c is an electron-poor aromatic ring, and thus the formation of a complex with the electron-rich benzyl bromide 6a leads to a completely opposite distribution of FMOs. Therefore, we suspect that the extent of difference between the rich and poor electrons of the two aryl rings cannot be regulated only by considering them in the pre-design of the EDA complexes. Although the Π-Π interaction between 6a-10c's is close to that of 3b-1c (which can react smoothly), the distribution of FMOs tells us that its use as a functioning EDA complex is almost impossible.

In Table 2, we list the HOMO and LUMO energies of EDA complexes and the energy gap. Among them, 3b-1c has a minimum energy gap of 4.87 eV, but 3b-10c has a large energy gap of 6.74 eV, second only to 13a-1c with a value of 6.87 eV. The energy gap of 13a-10c is 5.48 eV, which is smaller than 13a-1c. The energy gap of 6a-1c is 5.74 eV, which is 0.27 eV lower compared to that of 6a-10c. Summarizing the above data, we find that the energy gap of EDA complexes is relatively low when EDA complexes have electron deficient-rich or electron rich-deficient components.

Table 2

The E_HOMO, E_LUMO and E_g of EDA complexes.
EDA Complexes	E_HOMO/eV	E_LUMO/eV	E_g/eV
3b-1c	-6.69	-2.09	4.87
13a-1c	-6.78	0.09	6.87
6a-1c	-7.56	-1.82	5.74
3b-10c	-6.83	-0.10	6.74
13a-10c	-7.65	-2.18	5.48
6a-10c	-7.32	-1.84	5.47

Then, we calculated the energy gap of the EDA complex in the unbound state and compared the energy gap of the EDA complex in Table 3. It was found that only 3b-1c, 13a-1c and 3b-10c showed a decrease, and the energy gap of the remaining complexes increased compared with that before the unbound state (details are shown in Table 3).

Table 3

The amount of difference in Eg before and after combining.
EDA Complexes	E_g (unbinding)/eV	E_g (EDA)/eV	ΔE_g/eV
3b-1c	-4.79	4.87	-0.08
13a-1c	-6.73	6.87	-0.13
6a-1c	-6.93	5.74	1.19
3b-10c	-5.52	6.74	-1.22
13a-10c	-7.46	5.48	1.98
6a-10c	-7.65	5.47	2.18

The theoretical UV-Vis spectrum of representative EDA complexes.

The redshift of the mixed solution after mixing the reactants relative to the substrate in the UV-Vis spectrum is one of the important means to detect or verify the formation of effective EDA complexes. As shown in Fig. 4a, among the three possible EDA complexes formed by benzyl bromide derivatives and 1c, only 3b-1c showed obvious redshift and has clear absorption in visible light region, while in the report of Paolo et al., 3b-1c was smoothly transformed and corresponding products were obtained. As shown in Fig. 4b, none of the three possible EDA complexes formed by the remaining benzyl bromide derivatives and 10c showed obvious redshift. Although the complexes had obvious absorption in the visible light range, we believed that this was probably due to the absorption of the 10c compound itself in the visible light region, the absorption in the visible light region of the spectrum is likely to come from 10c rather than EDA complexes. Therefore, only 3b-1c of the six EDA complexes we consider is an effective EDA complex from the theoretical UV-Vis spectrum point of view.

Spin density analysis of EDA complexes (excited triplet state).

In the reaction process that can be stimulated by light and triggered by charge transfer between EDA complexes, the electron donor molecule transfers a single electron to the electron acceptor molecule under the excitation of light, thus forming two molecular fragments with single electrons. In the above process, the main possible photophysical mechanism is that the EDA complex in the

ground state (S0) is excited to generate its corresponding excited singlet state (S1), and then through the intersystem crossing (ISC) to the excited triplet state (T1). Therefore, for EDA complexes, it is very important to study the energy of excited triplet state and the distribution of single electrons on the molecular fragment. We show energy of the T1 state (relative to the S0 state) and the spin analysis results in Fig. 5. The lowest energy of complex 3b-1c-T1 (can react smoothly) is 40.9 kcal/mol, and the energy of other complexes is 7.0 to 11.4 kcal/mol higher than it. In the distribution diagram of spin density, the spin density of EDA complexes in T1 state formed by different benzyl bromide derivatives and 1c is distributed above both benzyl bromide derivatives and 1c, but in 13a-1c-T1 and 6a-1c-T1, the bond length of C-Br bond has shown a very large extension and is close to dissociation (see Fig. S8). These observations suggest that the stability of 13a-1c-T1 and 6a-1c-T1 may be insufficient, despite the reasonable electron distribution of the excited triplet state of the complexes associated with 1c. However, for the excited triple states of the three EDA complexes associated with 10c, except 3b-10c-T1, the spin density of the remaining complexes is mainly distributed on the 10c molecule, and we can think that the excitation of electrons in 13a-10c-T1 and 6a-10c-T1 may be mainly within the 10c molecule. Therefore, we speculate that the electron-deficient donor may not be able to form effective EDA complexes.

Study on EDA complexes formed by 3-methylpyrrole and 2, 4-dinitrobenzyl bromide.

As one of the most important five-membered heterocyclic compounds, pyrrole is commonly found in many biologically active natural products and synthetic drugs.^[47–53] Therefore, the development of green and mild direct modification of pyrrole method is very important and meaningful. On the basis of the above studies, we designed the EDA complex formed by 3-methylpyrrole and 2, 4-dinitrobenzyl bromide and predicted the related properties of the complex and showed them in Fig. 6. In Fig. 6a, the energy difference between the S0 and T1 of the complex 3b-methylpyrrole complex is 39.0 kcal/mol, which is smaller than that of the 3b-1c complex that can react smoothly, indicating that it is possible to excite to the T1 state under visible light. The FMO distribution and energy gap of 3b-methylpyrrole are shown in Fig. 6b. HOMO is mainly distributed on pyrrole and LUMO is mainly distributed on 3b. However, its energy gap is 0.24 eV larger than 3b-1c. We also obtain similar results to 3b-1c in IRI analysis, theoretical UV-Vis spectroscopy and spin density analysis of the T1 state of the complex 3b-methylpyrrole, (Fig. 6c-e). Hence, we speculate that this complex may be an effective EDA complex.

In summary, we investigated the properties of selected representative EDA complexes in detail by calculating binding energy, FMO distribution, energy gap, IRI and theoretical UV-Vis spectra based on density functional theory (DFT), and answered the questions raised above. 1) Strong interactions generally occur between electron-rich and electron-poor aromatic rings. 2) This interaction is mainly distributed between two aromatic rings. 3) By comparing the property differences of EDA complexes 3b-1c that can react smoothly with other complexes, the factors to be considered in designing similar effective EDA complexes through theoretical calculation are listed as follows: a) The electron difference between the two aromatic rings must be large enough to form an interaction of sufficient strength to form a sufficiently stable complex, which can be measured by the bonding energy; b) In general, the electron donor needs to be an electron-rich aromatic ring with a heteroatom with unbonded electrons (in this case, the nitrogen atom of indole), and the electron acceptor needs to be an electron-poor aromatic ring to ensure that the HOMO is mainly distributed on the donor molecule and the LUMO is mainly distributed on the acceptor molecule. c) The energy gap of the EDA complex formed should not be too large, which will make it difficult for visible light to excite it; d) In the theoretical UV-Vis spectrum, the absorption of the EDA complex obtained has a redshift phenomenon relative to the substrate and an obvious absorption near the visible region. This work provides valuable experience and cases for the mechanism research and theoretical design of EDA type reactions. The experimental verification of EDA complex activity of 3b-methylpyrrole and the development of related synthesis methods of polysubstituted-pyrrole are also carried out in our laboratory.

Conflicts of interest

There are no conflicts to declare.

Author Contribution

S.-T. Wang conceived the scientific research project. Z. Liu, Z.-Q. Liu and Shutao Wang completed the main content of this study. Y.-T. Ding performed the drawing of pictures in this paper. Y.-S. Hu was responsible for data processing. R.-Z. Liu finished the data proofreading. Z.-Z. Zhang is responsible for the maintenance and management of the computing cluster. S.-T. Wang, Z. Liu and J.-Q. Lei wrote the original manuscript. J.-Q. Lei completed review and proofreading of the manuscript. The final version of the manuscript has received unanimous approval from all authors.

Acknowledgement

We gratefully acknowledge the National Natural Science Foundation of China (No. 81960323). We also thank associate professor Hong Gao (Lanzhou University) and professor Yuan Zhang (Lanzhou University) for helpful discussion.

J. M. Narayanam and C. R. Stephenson, Chem. Soc. Rev., 2011, 40, 102–113.
J. Xuan and W. J. Xiao, Angew. Chem. Int. Ed., 2012, 51, 6828–6838.
C. K. Prier, D. A. Rankic and D. W. MacMillan, Chem. Rev., 2013, 113, 5322–5363.
N. Corrigan, S. Shanmugam, J. Xu and C. Boyer, Chem. Soc. Rev., 2016, 45, 6165–6212.
M. D. Karkas, J. A. Porco, Jr. and C. R. Stephenson, Chem. Rev., 2016, 116, 9683–9747.
D. Ravelli, S. Protti and M. Fagnoni, Chem. Rev., 2016, 116, 9850–9913.
J. M. R. Narayanam and C. R. J. Stephenson, Chem. Soc. Rev., 2011, 40, 102–113.
K. Kalyanasundaram, Coordin. Chem. Rev., 1982, 46, 159–244.
A. Juris, V. Balzani, F. Barigelletti, S. Campagna, P. Belser and A. von Zelewsky, Coordin. Chem. Rev., 1988, 84, 85–277.
A. Juris, V. Balzani, P. Belser and A. von Zelewsky, Helv. Chim. Acta., 1981, 64, 2175–2182.
N. A. Romero and D. A. Nicewicz, Chem. Rev., 2016, 116, 10075–10166.
D. A. Nicewicz and T. M. Nguyen, ACS Catal., 2013, 4, 355–360.
T. Bortolato, S. Cuadros, G. Simionato and L. Dell'Amico, Chem. Commun., 2022, 58, 1263–1283.
R. S. Mulliken, J. Phys. Chem., 2002, 56, 801–822.
R. M. Keefer and L. J. Andrews, J. Am. Chem. Soc., 2002, 72, 4677–4681.
R. S. Mulliken, J. Am. Chem. Soc., 2002, 72, 600–608.
R. Foster, J. Phys. Chem., 2002, 84, 2135–2141.
S. V. Rosokha and J. K. Kochi, Acc. Chem. Res., 2008, 41, 641–653.
E. F. Hilinski, J. M. Masnovi, C. Amatore, J. K. Kochi and P. M. Rentzepis, J. Am. Chem. Soc., 2002, 105, 6167–6168.
S. M. Hubig, T. M. Bockman and J. K. Kochi, J. Am. Chem. Soc., 1996, 118, 3842–3851.
E. Arceo, I. D. Jurberg, A. Alvarez-Fernandez and P. Melchiorre, Nat. Chem., 2013, 5, 750–756.
M. Nappi, G. Bergonzini and P. Melchiorre, Angew. Chem. Int. Ed., 2014, 53, 4921–4925.
G. P. da Silva, A. Ali, R. C. da Silva, H. Jiang and M. W. Paixao, Chem. Commun., 2015, 51, 15110–15113.
S. R. Kandukuri, A. Bahamonde, I. Chatterjee, I. D. Jurberg, E. C. Escudero-Adan and P. Melchiorre, Angew. Chem. Int. Ed., 2015, 54, 1485–1489.
V. Quint, F. Morlet-Savary, J. F. Lohier, J. Lalevee, A. C. Gaumont and S. Lakhdar, J. Am. Chem. Soc., 2016, 138, 7436–7441.
M. L. Spell, K. Deveaux, C. G. Bresnahan, B. L. Bernard, W. Sheffield, R. Kumar and J. R. Ragains, Angew. Chem. Int. Ed., 2016, 55, 6515–6519.
B. Liu, C. H. Lim and G. M. Miyake, J. Am. Chem. Soc., 2017, 139, 13616–13619.
Y. Li, T. Miao, P. Li and L. Wang, Org. Lett., 2018, 20, 1735–1739.
F. Sandfort, F. Strieth-Kalthoff, F. J. R. Klauck, M. J. James and F. Glorius, Chem., 2018, 24, 17210–17214.
M. J. James, F. Strieth-Kalthoff, F. Sandfort, F. J. R. Klauck, F. Wagener and F. Glorius, Chem., 2019, 25, 8240–8244.
Y. Li, F. Ma, P. Li, T. Miao and L. Wang, Adv. Synth. & Catal., 2019, 361, 1606–1616.
J.-L. Liu, Z.-F. Zhu and F. Liu, Org. Chem. Front., 2019, 6, 241–244.
J. Wu, R. M. Bar, L. Guo, A. Noble and V. K. Aggarwal, Angew. Chem. Int. Ed., 2019, 58, 18830–18834.
M. Yang, T. Cao, T. Xu and S. Liao, Org. Lett., 2019, 21, 8673–8678.
C. Wang, R. Qi, H. Xue, Y. Shen, M. Chang, Y. Chen, R. Wang and Z. Xu, Angew. Chem. Int. Ed., 2020, 59, 7461–7466.
Y. Lu, C. Z. Fang, Q. Liu, B. L. Li, Z. X. Wang and X. Y. Chen, Org. Lett., 2021, 23, 5425–5429.
X. Yang, Y. Zhu, Z. Xie, Y. Li and Y. Zhang, Org. Lett., 2020, 22, 1638–1643.
S. Wang, Y. Ye, H. Shen, J. Liu, Z. Liu, Z. Jiang, J. Lei and Y. Zhang, Org. Biomol. Chem., 2023, 21, 8364–8371.
S. Wang, Y. Gao, Y. Hu, J. Zhou, Z. Chen, Z. Liu and Y. Zhang, Chem. Commun., 2023, 59, 12783–12786.
S. Wang, Y. Ye, Y. Hu, X. Meng, Z. Liu, J. Liu, K. Chen, Z. Zhang and Y. Zhang, Chem. Commun., 2023, 59, 2628–2631.
Z. Liu, X. Meng, Z. Zhang, R. Liu, S. Wang and J.-Q. Lei, J. Fluoresc., 2023, DOI: 10.1007/s10895-023-03525-4.
Z. Liu, S.-T. Wang, Y.-S. Hu, J.-R. You, Y.-S. Xv and J.-Q. Lei, J. Chem., 2022, 2022, 1–8.
S. Wang, Z. Liu, Y. Ye, X. Meng, P. Yang, Z. Zhang, Y. Qiu and J. Lei, New J. Chem., 2023, 47, 421–427.
Y. F. Qiu, S. P. Chen, J. H. Cao, S. Wang, J. H. Li, M. Li, Z. J. Quan, X. C. Wang and Y. M. Liang, Org. Lett., 2022, 24, 8609–8614.
Y. F. Qiu, J. H. Cao, S. Wang, Q. Wang, M. Li, J. J. Wang, Z. J. Quan and X. C. Wang, Org. Biomol. Chem., 2023, 21, 8744–8748.
S. Li, R. Li, Y. K. Zhang, S. Wang, B. Ma, B. Zhang and P. An, Chem. Sci., 2023, 14, 3286–3292.
D. P. O'Malley, K. Li, M. Maue, A. L. Zografos and P. S. Baran, J. Am. Chem. Soc., 2007, 129, 4762–4775.
C. C. Hughes, A. Prieto-Davo, P. R. Jensen and W. Fenical, Org. Lett., 2008, 10, 629–631.
D. L. Boger, C. W. Boyce, M. A. Labroli, C. A. Sehon and Q. Jin, J. Am. Chem. Soc., 1998, 121, 54–62.
M. Biava, G. C. Porretta, D. Deidda, R. Pompei, A. Tafi and F. Manetti, Bioorg. Med. Chem., 2004, 12, 1453–1458.
C. Teixeira, F. Barbault, J. Rebehmed, K. Liu, L. Xie, H. Lu, S. Jiang, B. Fan and F. Maurel, Bioorg. Med. Chem., 2008, 16, 3039–3048.
W. Tian, B. Li, D. Tian and W. Tang, Chinese Chem. Lett., 2022, 33, 197–200.
M. Protopopova, E. Bogatcheva, B. Nikonenko, S. Hundert, L. Einck and C. A. Nacy, Med. Chem., 2007, 3, 301–316.

Scheme 1 and 2 are available in the Supplementary Files section.

No competing interests reported.

SupplementaryInformation.docx
1.png
Scheme 1. Electron donor-acceptor complex that drives the photochemical alkylation of indoles.
2.png
Scheme 2. Selected substrates that form representative EDA complexes.

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DFT study of electron donor-acceptor (EDA) complexes of 1H-indole and benzyl bromide derivatives: mechanism exploration and theoretical prediction

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Abstract

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Introduction

Results and discussion

Conclusions

Declarations

Conflicts of interest

Author Contribution

Acknowledgement

References

Scheme

Additional Declarations

Supplementary Files

Status:

Version 1