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CC BY 4.0 · Synlett 2024; 35(09): 1033-1041
DOI: 10.1055/a-2236-8949
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Chemical Synthesis and Catalysis in Germany

Design of Imidazo[1,2-a]pyridine-Based Donor–Acceptor Chromophores through a Multicomponent Approach

Mareen Stahlberger
a   Institute of Organic Chemistry (IOC), Karlsruhe Institute of Technology (KIT), Kaiserstrasse 12, 76131 Karlsruhe, Germany
,
Milada Mergel
a   Institute of Organic Chemistry (IOC), Karlsruhe Institute of Technology (KIT), Kaiserstrasse 12, 76131 Karlsruhe, Germany
,
John Marques dos Santos
b   Organic Semiconductor Centre, EaStCHEM School of Chemistry, University of St Andrews, St Andrews, Fife, KY16 9ST, UK
,
Tomas Matulaitis
b   Organic Semiconductor Centre, EaStCHEM School of Chemistry, University of St Andrews, St Andrews, Fife, KY16 9ST, UK
,
Martin Nieger
c   Department of Chemistry University of Helsinki, P. O. Box 55, 00014 University of Helsinki, Finland
,
Eli Zysman-Colman∗
b   Organic Semiconductor Centre, EaStCHEM School of Chemistry, University of St Andrews, St Andrews, Fife, KY16 9ST, UK
,
Stefan Bräse  ∗
a   Institute of Organic Chemistry (IOC), Karlsruhe Institute of Technology (KIT), Kaiserstrasse 12, 76131 Karlsruhe, Germany
d   Institute of Biological and Chemical Systems Functional Molecular Systems (IBCS-FMS), Karlsruhe Institute of Technology (KIT), Kaiserstrasse 12, 76131 Karlsruhe, Germany
› Author AffiliationsThe authors acknowledge Deutsche Forschungsgemeinschaft (DFG) support under Germany’s Excellence Strategy – 3DMM2O – EXC-2082/1-390761711, the KIT Campus Transfer GmbH for the financial support to M.S. for her Ph.D. studies. The St Andrews team thanks the Engineering and Physical Sciences Research Council (EP/R035164/1, EP/W007517/1).
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Abstract

A series of donor-acceptor chromophores was synthesized bearing a 3-aminoimidazo[1,2-a]pyridine donor motive. Through DFT calculations, different combinations of the ImPy donor motive and different electron acceptors were assessed. In combination with an anthraquinone acceptor, the calculated ΔE ST values were in range to suggest that these compounds would emit via thermally activated delayed fluorescence. Based on these findings, a series of ImPy-Aq emitters with different geometries and substitution patterns was synthesized through GBB-3CR and Suzuki coupling reactions. According to preliminary experimental data, the compounds were only slightly emissive at ambient temperatures due to a combination of low radiative rates and competing non-radiative deactivation pathways.

Key words

multicomponent reaction - imidazo[1,2-a]pyridine - Suzuki coupling - thermally activated delayed fluorescence - donor-acceptor chromophores

Supporting Information

    Supporting information for this article is available online at https://doi.org/10.1055/a-2236-8949.
  • Supporting Information

Primary Data

    The primary data and additional information on the chemical syntheses in this report are available via Chemotion repository: https://dx.doi.org/10.14272/collection/MSB_2023-07-12. The research data supporting this publication can be accessed at https://doi.org/10.17630/85cd88f6-5e2f-4916-a8fd-b121ac024d61.
  • Primary Data


Publication History

Received: 28 September 2023

Accepted after revision: 02 January 2024

Accepted Manuscript online:
02 January 2024

Article published online:
01 February 2024

© 2024. The Author(s). This is an open access article published by Thieme under the terms of the Creative Commons Attribution License, permitting copying and reproduction so long as the original work is given appropriate credit. Contents may not be used for commercial purposes or adapted, remixed, transformed or built upon. (https://creativecommons.org/licenses/by/4.0/)

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  • 12 Synthesis of p-ImPyAq (7): Compound 4a (111 mg, 298 μmol, 1.00 equiv), 6 (100 mg, 298 μmol, 1.00 equiv), Pd(OAc)2 (3.36 mg, 14 μmol, 5 mol%), RuPhos (14 mg, 29 μmol, 1.00 equiv), and Cs2CO3 (293 mg, 89 μmol, 3.00 equiv) were dissolved in a mixture of toluene and water (4:1, 4 mL). The mixture was stirred argon atmosphere for 16 h at 110 °C. The solvent was removed under reduced pressure and the residue was purified via flash chromatography (SiO2, CH/EtOAc 7:1 to 1:1). Compound 7 (91 mg, 182 μmol, 61%) was obtained as an orange solid. Analytical data of 7: Rf = 0.43 (SiO2, cyclohexane/EtOAc 1:1). 1H NMR (500 MHz, CDCl3): δ = 8.39 (d, J = 7.9 Hz, 1 H, CHAr), 8.35–8.31 (m, 2 H, CHAr), 8.23 (dt, J = 6.9, 1.2 Hz, 1 H, CHAr), 8.17 (d, J = 1.7 Hz, 1 H, CHAr), 7.82–7.78 (m, 2 H, CHAr), 7.76 (s, 2 H, CHAr), 7.65 (dd, J = 7.9, 1.7 Hz, 1 H, CHAr), 7.55 (dt, J = 9.0, 1.2 Hz, 1 H, CHAr), 7.13 (ddd, J = 9.0, 6.6, 1.3 Hz, 1 H, CHAr), 6.77 (td, J = 6.8, 1.2 Hz, 1 H, CHAr), 3.12 (br, 1 H, NH), 2.10 (s, 6 H, CH3), 1.11 (s, 9 H, CH3). 13C NMR (126 MHz, CDCl3): δ = 183.5 (Cq, CO), 183.2 (Cq, CO), 148.0 (Cq), 142.2 (Cq), 139.1 (Cq), 139.0 (Cq), 135.5 (Cq), 135.4 (CHAr), 134.9 (Cq), 134.3 (Cq), 134.2 (CHAr), 134.2 (CHAr), 133.7 (2C, Cq), 132.2 (Cq), 128.3 (CHAr), 127.7 (CHAr), 127.4 (CHAr), 127.4 (CHAr), 127.3 (CHAr), 127.3 (2C, CHAr), 124.1 (CHAr), 123.7 (Cq), 123.6 (CHAr), 117.5 (CHAr), 111.4 (CHAr), 56.3 (Cq), 30.4 (3C, CH3), 20.8 (2C, CH3). IR (ATR): 2965 (w), 2921 (w), 1666 (vs), 1588 (s), 1445 (w), 1363 (w), 1343 (m), 1323 (s), 1299 (s), 1286 (s), 1268 (s), 1241 (s), 1214 (m), 1183 (m), 1159 (m), 1037 (w), 1031 (w), 1004 (w), 959 (w), 929 (s), 895 (w), 882 (m), 858 (m), 841 (w), 817 (w), 789 (w), 762 (vs), 741 (w), 731 (m), 710 (vs), 674 (m), 636 (w), 625 (w), 606 (w), 588 (m), 561 (w), 524 (w), 436 (m), 407 (m), 382 (m) cm–1. FAB-MS: m/z (%) = 500 (53), 155 (33), 154 (100), 138 (43), 137 (69), 136 (80), 107 (34), 95 (28), 91 (42). HRMS-FAB: m/z [M + H]+ calcd for C33H30O2N3: 500.2333; found: 500.2330.
    • 13a Synthesis of m-BisImPyAq (8): Compound 4b (557 mg, 1.05 mmol, 1.00 equiv), 6 (350 mg, 1.05 mmol, 1.00 equiv), RuPhos (48.9 mg, 105 μmol, 0.10 equiv), Cs2CO3 (1.02 g, 3.14 mmol, 3.00 equiv) and Pd(OAc)2 (11.8 mg, 52.4 μmol, 0.05 equiv) were dissolved under argon atmosphere in a mixture of toluene and water (4:1, 25 mL) and stirred for 16 h at 110 °C. The solvent was removed under reduced pressure, and the residue was purified via flash chromatography (SiO2, CH/EE 7:1 to 1:10). Compound 8 (656 mg, 995 μmol, 95%) was isolated as a red solid. Analytical data of 8: Rf = 0.16 (SiO2, cyclohexane/EtOAc 1:6). 1H NMR (500 MHz, CDCl3): δ = 8.71 (d, J = 1.9 Hz, 1 H, CHAr), 8.64 (t, J = 1.6 Hz, 1 H, CHAr), 8.41 (d, J = 8.1 Hz, 1 H, CHAr), 8.39–8.31 (m, 4 H, CHAr), 8.27 (dt, J = 6.9, 1.2 Hz, 2 H, CHAr), 8.23 (dd, J = 8.1, 2.0 Hz, 1 H, CHAr), 7.87–7.77 (m, 2 H, CHAr), 7.57 (dt, J = 9.0, 1.1 Hz, 2 H, CHAr), 7.17 (ddd, J = 9.0, 6.6, 1.4 Hz, 2 H, CHAr), 6.81 (td, J = 6.8, 1.2 Hz, 2 H, CHAr), 3.34 (s, 2 H, NH), 1.11 (s, 18 H, CH3). 13C NMR (126 MHz, CDCl3): δ = 183.4 (2C, Cq, CO), 183.2 (2C, Cq, CO), 147.2 (Cq), 142.3 (2C, Cq), 139.2 (2C, Cq), 139.1 (Cq,), 136.4 (2C, Cq), 134.3 (CHAr), 134.2 (CHAr), 134.0 (Cq), 133.9 (Cq), 132.8 (CHAr), 132.3 (Cq), 128.5 (CHAr), 128.2 (CHAr), 127.4 (CHAr), 126.3 (2C, CHAr), 125.8 (CHAr), 124.3 (2C, CHAr), 124.1 (2C, Cq), 123.7 (2C, CHAr), 117.5 (2C, CHAr), 111.6 (2C, CHAr), 56.8 (2C, Cq), 30.6 (6C, CH3). IR (ATR): 2965 (m), 2929 (w), 2904 (w), 2868 (w), 1732 (w), 1672 (vs), 1632 (w), 1591 (vs), 1504 (w), 1473 (w), 1460 (w), 1441 (w), 1390 (w), 1361 (vs), 1323 (vs), 1296 (vs), 1239 (s), 1215 (vs), 1201 (vs), 1162 (m), 1112 (m), 1044 (m), 975 (m), 931 (s), 887 (m), 853 (m), 795 (w), 754 (vs), 732 (vs), 711 (vs), 670 (s), 639 (s), 633 (s), 605 (s), 483 (s), 448 (s), 404 (s), 392 (s), 381 (s) cm–1. FAB-MS: m/z (%) = 661 (19), 660 (55), 659 (100) [M + H]+, 658 (30), 602 (30), 601 (39), 546 (26), 545 (27), 484 (25), 483 (73), 441 (26). HRMS-FAB: m/z [M + H]+ calcd for C42H39O2N6: 659.3129; found: 659.3130.
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  • 14 Synthesis of o-BisImPyAq (9): 2-Aminopyridine (41.5 mg, 440 µmol, 2.00 equiv), 10 (75 mg, 220 μmol, 1.00 equiv), tert-butyl isonitrile (36.6 mg, 50 μL, 440 μmol, 2.00 equiv) and a solution of perchloric acid in methanol (1 M, 4.42 mg, 44 μL, 44.0 μmol, 0.20 equiv) were dissolved in chloroform and stirred at 60 °C for 1 d. The solvent was removed under reduced pressure, and the residue was purified via flash chromatography (SiO2, CH/EtOAc 5:1 to 1:10). Compound 9 (134 mg, 203 μmol, 92%) was isolated as an orange solid. Analytical data of 9: Rf = 0.06 (SiO2, CH/EtOAc 1:6). 1H NMR (500 MHz, CDCl3): δ = 8.71 (d, J = 1.9 Hz, 1 H, CHAr), 8.64 (t, J = 1.6 Hz, 1 H, CHAr), 8.39–8.31 (m, 4 H, CHAr), 8.30–8.17 (m, 4 H, CHAr), 7.87–7.78 (m, 2 H, CHAr), 7.57 (dt, J = 8.9, 1.1 Hz, 2 H, CHAr), 7.25–7.13 (m, 2 H, CHAr), 6.80 (td, J = 6.8, 1.2 Hz, 2 H, CHAr), 3.35 (s, 2 H, NH), 1.10 (s, 18 H, CH3). 13C NMR (126 MHz, CDCl3): δ = 182.9 (Cq, CO), 181.9 (Cq, CO), 147.0 (Cq), 142.6 (2C, Cq), 139.3 (Cq), 137.7 (Cq), 136.2 (CHAr), 135.2 (2C, Cq), 134.2 (2C, Cq), 134.2 (2C, CHAr), 133.7 (CHAr), 133.5 (Cq), 133.4 (Cq), 133.1 (Cq), 132.5 (2C, Cq), 131.7 (CHAr), 129.1 (CHAr), 128.9 (CHAr), 127.5 (CHAr), 127.3 (CHAr), 127.0 (CHAr), 124.6 (Cq), 124.4 (2C, CHAr), 123.5 (2C, CHAr), 117.4 (2C, CHAr), 111.4 (2C, CHAr), 56.7 (2C, Cq), 30.6 (6C, CH3). IR: 3369 (w), 2958 (w), 2924 (w), 2854 (w), 1672 (vs), 1630 (w), 1591 (m), 1554 (w), 1550 (w), 1500 (w), 1473 (w), 1455 (w), 1441 (w), 1388 (w), 1364 (m), 1339 (m), 1322 (s), 1299 (vs), 1266 (m), 1242 (m), 1221 (s), 1211 (s), 1198 (s), 1173 (m), 1146 (w), 1135 (w), 1081 (w), 972 (w), 962 (w), 952 (w), 931 (m), 907 (w), 857 (m), 817 (m), 756 (vs), 737 (vs), 710 (vs), 673 (m), 646 (w), 633 (w), 612 (w), 572 (w), 458 (w), 428 (w), 401 (w), 382 (s) cm–1. FAB-MS: m/z (%) = 665 (43), 664 (100), 662 (42), 661 (31), 660 (46), 659 (85), 658 (30), 648 (31), 647 (67), 530 (73), 219 (83), 191 (33), 163 (31), 161 (32), 159 (30), 154 (41), 149 (32), 147 (61), 136 (41), 131 (38), 119 (34), 107 (37), 105 (43), 97 (38), 95 (53), 91 (71). HRMS-FAB: m/z [M + H]+ calcd for C42H39O2N6: 659.3129; found: 659.3127.
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