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Institut Utinam UMR CNRS 6213, UFR Sciences et Techniques, Université de Bourgogne-Franche-Comté, 16 route de Gray, 25030 Besançon, France
Author to whom correspondence should be addressed.
Academic Editors: Dimitrios Matiadis and Eleftherios Halevas
Molbank 2021, 2021(1), M1183;
Received: 8 December 2020 / Revised: 18 January 2021 / Accepted: 20 January 2021 / Published: 21 January 2021


A new thiophene-substituted terpyridine derivative has been prepared through the reaction between 5-n-propylthiophene-2-carboxaldehyde and 2-acetylpyridine. This terpyridine derivative bears an alkyl chain linked via a thiophene heterocycle.
Keywords: chalcogenophene; heterocycles; ligands; pyridine derivatives; thiophene derivatives chalcogenophene; heterocycles; ligands; pyridine derivatives; thiophene derivatives

1. Introduction

2,2′:6′,2″-Terpyridine (terpy) ligands and their metal complexes have been widely studied [1] owing to the broad range of applications for such molecules. Varying the nature of the substituents on the ligands and/or the metallic centre offers the possibility to prepare an enormous number of different substances. In particular, terpyridines that contain the five membered heterocycle thiophene [2] have attracted widespread of attention. In fact, they can be used in the preparation of materials for solar cells [3,4,5], for the functionalization of nanoparticles [6], as fluorescent probes [7,8], as antimicrobial agents [9], as electrochromic materials [10] or as chromophores [11], just to name a few. The substituents that are present on the thiophene ring have an important impact, especially on properties of thiophene-substituted terpyridine-based materials [12]. Therefore, the preparation of new thiophene-substituted terpyridines is still of interest. This paper presents the synthesis of the novel 4′-(5-N-propylthiophen-2-yl)-2,2′:6′,2″-terpyridine ligand (1) (Figure 1).

2. Results and Discussion

Many synthetic methods are available for the preparation of terpyridine derivatives [13,14,15]. In order to prepare 4′-(5-N-propylthiophen-2-yl)-2,2′:6′,2″-terpyridine, the method described by Wang and Hanan in 2005 [16] was selected. This procedure allowed the facile preparation of 1 from 2-acetylpyridine and 5-N-propylthiophene-2-carboxaldehyde.
As in many cases with this synthetic protocol, the crude product was sufficiently pure (>98% by quantitative NMR [17,18] and by combustion analysis) to be used (e.g., for the preparation of metal complexes) without purification.
Ligand 1 was characterized by 1H and 13C-NMR as well as by HR-MS. Firstly, the 1H-NMR spectrum agrees with the chemical structure. NMR spectra of 4′-functionalized terpyridines exhibit a typical singlet for proton 3′ and 5′. In the present molecule, this singlet is seen at δ = 8.63 ppm. Furthermore, as expected, hydrogens that belong to the thiophene heterocycle (a and b) appear as doublets centered at 7.60 and 6.84 ppm, respectively, with a coupling constant of 3.6 Hz. Finally, signals for the propyl chain can be observed as two triplets (at 2.84 and 1.02 ppm) and a multiplet at 1.76 ppm (Figure 2).
Additionally, the structure of 1 was further confirmed by 13C-NMR as well as by HR-MS (Supplementary Materials). For instance, the 13C-NMR spectrum features 15 signals due to the symmetry of the molecule, while mass spectra exhibit the molecular ion peak at 358.13703 (calc. for [C22H19N3S + H]+: 358.13724). The UV-Vis spectrum of compound 1 recorded in acetonitrile exhibits bands at 231, 252, 286 and 314 nm (Figure 3).
The strong absorption band can be assigned to ππ* transitions of the terpyridine part, and the shape of the spectrum is similar to previously reported ones for such five-membered heterocycle-substituted terpyridines [11,19].
As expected, introduction of an aliphatic chain onto the thiophene ring subsequently lowered the melting point of the product (98–99 °C) when compared to other non-functionalized chalcogenophene-substituted terpyridine molecule [20,21,22,23]. This phenomenon is also observed in an hexylthiophene-functionalized 2,2′:2′,2″-terpyridine [11] (Table 1).

3. Materials and Methods

All reagents were purchased from commercial suppliers (ACROS Organics, Geel, Belgium and TCI Chemicals, Zwijndrecht, Belgium) and used as received. Starting material 5-N-propylthiophene-2-carboxaldehyde [24] was prepared from thiophene via 2-N-propylthiophene [25] and 1-(thiophen-2-yl)-propan-1-one [26] according to literature procedures. 1H and 13C-NMR spectra were recorded on a Brucker AC 400 (Bruker, Wissembourg, France) at 400 and 100 MHz, respectively, using CDCl3 as a solvent. Melting point was recorded with a Stuart SMP 10 melting point apparatus (Bibby Sterilin, Stone, UK) and was uncorrected. The UV-Vis spectrum was recorded on a Cary 300 (Agilent Technologies, Santa Clara, CA, USA) using acetonitrile (C = 1.21 × 104 M) as solvent. HR-MS was recorded at Sayence SATT, Dijon, France. Elemental analysis was performed at Service d’Analyse Élémentaire, Vandoeuvre-les-Nancy, France.
4′-(5-N-Propylthiophen-2-yl)-2,2′:6′,2″-terpyridine (1): to a solution of 2-acetylpyridine (7.43 g; 61 mmol) in ethanol (154 mL), 5-N-propylthiophene-2-carboxaldehyde (4.73 g; 31 mmol), 85% potassium hydroxide pellets (4.73 g; 72 mmol) and 25% aqueous ammonia (89 mL) were added. The reaction mixture was stirred at room temperature for 24 h. The solid was then filtered on a glass sintered funnel and washed with ice-cold 50% ethanol until washings were colorless. The product was dried under vacuum over phosphorus pentoxide. Compound 1 was obtained as a light-yellow solid (4.25 g; 39%). Mp= 98–99 °C. 1H-NMR (CDCl3, 400 MHz), δ (ppm): 8.73 (d, 2H H6, 6″, J = 4.2 Hz), 8.63 (d, 2H, H3, 3″, J = 7.6 Hz), 8.63 (s, 2H, H3′, 5′), 7.85 (m, 2H, H4, 4″), 7.60 (d, 1H, Ha, J = 3.6 Hz), 7.34 (dd, 2H, H5, 5″, J = 6.5 Hz, J = 4.9 Hz), 6.84 (d, 1H, Hb, J = 3.6 Hz),2.84 (t, 2H, Hc, J = 7.5 Hz), 1.76 (m, 2H, Hd), 1.02 (t, 3H, He, J = 7.3 Hz). 13C-NMR (CDCl3, 100 MHz), δ (ppm): 156.2, 155.9, 149.1, 148.1, 143.8, 139.1, 136.8, 125.7, 125.6, 123.8, 121.3, 116.7, 32.4, 24.8, 13.7. HR-MS: calc. for [C22H19N3S + H]+ 358.13724, found 358.13703. Elemental analysis for C22H19N3S: C, 73.92; H, 5.36; N, 11.75; S, 8.97, found C, 73.27; H, 5.39; N, 11.90; S, 8.96. UV-Vis (nm): λabs = 231, 252, 286, 314.

4. Conclusions

A new thiophene-containing terpyridine was prepared and characterized. This ligand features an alkyl chain on the thiophene ring. This resulted in a lowering of the melting point of this type of molecule, a feature that can be interesting in view of future applications (e.g., for the preparation of low melting complexes).
Experiments are currently in progress to incorporate this ligand into organometallic materials. Results will be reported in due course.

Supplementary Materials

The following are available online, 1H and 13C-NMR, HR-MS, UV-Vis and IR spectra of terpyridine 1.

Author Contributions

J.H. conceived and carried out the experiments, analyzed data and prepared the manuscript. L.G. analyzed data and contributed to manuscript preparation. All authors have read and agreed to the published version of the manuscript.


This research did not receive specific funding.

Data Availability Statement

The data from this study are available in this paper and in its Supplementary Materials.

Conflicts of Interest

The authors declare no conflict of interest.


  1. Schubert, U.S.; Hofmeier, H.; Newkome, G.R. Modern Terpyridine Chemistry; Wiley-VCH: Weinheim, Germany, 2006. [Google Scholar]
  2. Husson, J.; Knorr, M. 2,2′:6′,2″-Terpyridines Functionalized with Thienyl Substituents: Synthesis and Applications. J. Heterocycl. Chem. 2012, 49, 453–478. [Google Scholar] [CrossRef]
  3. Vincent Joseph, K.L.; Anthonysamy, A.; Easwaramoorthi, R.; Shinde, D.V.; Ganapathy, V.; Karthikeyan, S.; Lee, J.; Park, T.; Rhee, S.-W.; Kim, K.S.; et al. Cyanoacetic acid tethered thiophene for well-matched LUMO level in Ru(II)-terpyridine dye sensitized solar cells. Dyes Pigment. 2016, 126, 270–278. [Google Scholar] [CrossRef]
  4. Dehaudt, J.; Husson, J.; Guyard, L.; Oswald, F.; Martineau, D. A simple access to “Black-Dye” analogs with good efficiencies in dye-sensitized solar cells. Renew. Energy 2014, 66, 588–595. [Google Scholar] [CrossRef]
  5. Caramori, S.; Husson, J.; Beley, M.; Bignozzi, C.A.; Argazzi, R.; Gros, P.C. Combination of Cobalt and Iron Polypyridine Complexes for Improving the Charge Separation and Collection in Ru(terpyridine)2-Sensitised Solar Cells. Chem. Eur. J. 2010, 16, 2611–2618. [Google Scholar] [CrossRef] [PubMed]
  6. Pruskova, M.; Sutrova, V.; Slouf, M.; Vlckova, B.; Vohlidal, J.; Sloufova, I. Arrays of Ag and Au Nanoparticles with Terpyridine- and Thiophene-Based Ligands: Morphology and Optical Responses. Langmuir 2017, 33, 4146–4156. [Google Scholar] [CrossRef]
  7. Shen, Y.; Shao, T.; Fang, B.; Du, W.; Zhang, M.; Liu, J.; Liu, T.; Tian, X.; Zhang, Q.; Wang, A.; et al. Visualization of mitochondrial DNA in living cells with super-resolution microscopy using thiophene-based terpyridine Zn(II) complexes. Chem. Commun. 2018, 54, 11288–11291. [Google Scholar] [CrossRef]
  8. Feng, Z.; Li, D.; Zhang, M.; Shao, T.; Shen, T.; Tian, X.; Zhang, Q.; Li, S.; Wu, J.; Tian, Y. Enhanced three-photon activity triggered by the AIE behavior of a novel terpyridine-based Zn(II) complex bearing a thiophene bridge. Chem. Sci. 2019, 10, 7228–7232. [Google Scholar] [CrossRef]
  9. Njogu, E.M.; Martincigh, B.S.; Omondi, B.; Nyamori, V.O. Synthesis, characterization, antimicrobial screening and DNA binding of novel silver(I)-thienylterpyridine and silver(I)-furylterpyridine. Appl. Organomet. Chem. 2018, 32, e4554. [Google Scholar] [CrossRef]
  10. Liang, Y.W.; Strohecker, D.; Lynch, V.; Holliday, B.J.; Jones, R.A. A Thiophene-Containing Conductive Metallopolymer Using an Fe(II) Bis(terpyridine) Core for Electrochromic Materials. ACS Appl. Mater. Interfaces 2016, 8, 34568–34580. [Google Scholar] [CrossRef]
  11. Fernandes, S.S.M.; Besley, M.; Ciarrocchi, C.; Licchelli, M.; Raposo, M.M.M. Terpyridine derivatives functionalized with (hetero)aromatic groups and the corresponding Ru complexes: Synthesis and characterization as SHG chromophores. Dyes Pigment. 2018, 150, 49–58. [Google Scholar] [CrossRef]
  12. Mukherjee, S.; Torres, D.E.; Jakubikova, E. HOMO inversion as a strategy for improving the light-absorption properties of Fe(II) chromophores. Chem. Sci. 2017, 8, 8115–8126. [Google Scholar] [CrossRef] [PubMed]
  13. Heller, M.; Schubert, U.S. Syntheses of functionalized 2,2′:6′,2″-terpyridines. Eur. J. Org. Chem. 2003, 6, 947–961. [Google Scholar] [CrossRef]
  14. Fallahpour, R.A. Synthesis of 4′-substituted-2,2′:6′,2″-terpyridines. Synthesis 2003, 2, 155–184. [Google Scholar] [CrossRef]
  15. Thompson, A.M.W.C. The synthesis of 2,2′:6′,2″-terpyridine ligands- versatile building blocks for supramolecular chemistry. Coord. Chem. Rev. 1997, 160, 1–52. [Google Scholar] [CrossRef]
  16. Wang, J.; Hanan, G.S. A Facile Route to Sterically Hindered and Non-Hindered 4′-Aryl-2,2′:6′,2″-Terpyridines. Synlett 2005, 8, 1251–1254. [Google Scholar] [CrossRef]
  17. Organic Syntheses. Available online: (accessed on 9 October 2020).
  18. Pinciroli, V.; Biancardi, V.; Visentin, G.; Rizzo, V. The Well-Characterized Synthetic Molecule: A Role for Quantitative 1H NMR. Org. Process. Res. Dev. 2004, 8, 381–384. [Google Scholar] [CrossRef]
  19. Husson, J.; Guyard, L. 4′-(5-Methylfuran-2-yl)-2,2′:6′,2″-terpyridine: A New Ligand Obtained from a Biomass-Derived Aldehyde with Potential Application in Metal-Catalyzed Reactions. Molbank 2018, 2018, M1032. [Google Scholar] [CrossRef]
  20. Beley, M.; Delabouglise, D.; Houppy, G.; Husson, J.; Petit, J.-P. Preparation and properties of ruthenium (II) complexes of 2,2′:6′,2″-terpyridines substituted at the 4′-position with heterocyclic groups. Inorg. Chim. Acta 2005, 358, 3075–3083. [Google Scholar] [CrossRef]
  21. Husson, J.; Dehaudt, J.; Guyard, L. Preparation of carboxylate derivatives of terpyridine via the furan pathway. Nat. Protoc. 2014, 9, 21–26. [Google Scholar] [CrossRef]
  22. Et Taouil, A.; Husson, J.; Guyard, L. Synthesis and characterization of electrochromic [Ru(terpy)2 selenophene]-based polymer film. J. Electroanal. Chem. 2014, 728, 81–85. [Google Scholar] [CrossRef]
  23. Husson, J.; Abdeslam, E.T.; Guyard, L. A missing member in the family of chalcogenophene-substituted 2,2′:6′,2″-terpyridine: 4′-(tellurophen-2-yl)-2,2′:6′,2″-terpyridine, its Ru(II) complex and its electropolymerization as a thin film. J. Electroanal. Chem. 2019, 855, 113594. [Google Scholar] [CrossRef]
  24. Zheng, C.; Pu, S.; Xu, J.; Luo, M.; Huang, D.; Shen, L. Synthesis and the effect of alkyl chain length onoptoelectronic properties of diarylethene derivatives. Tetrahedron Lett. 2007, 63, 5437–5449. [Google Scholar] [CrossRef]
  25. Howbert, J.J.; Mohamadi, F.; Spees, M.M. Antitumor Compositions and methods of Treatment. U.S. Patent 5,302,724, 12 April 1994. [Google Scholar]
  26. Zhang, S.; Huang, S.; Feng, C.; Cai, J.; Chen, J.; Ji, M. Novel Preparation of Tiaprofenic Acid. J. Chem. Res. 2013, 37, 406–408. [Google Scholar] [CrossRef]
Figure 1. Chemical structure 4′-(5-N-propylthiophen-2-yl)-2,2′:6′,2″-terpyridine (1).
Figure 1. Chemical structure 4′-(5-N-propylthiophen-2-yl)-2,2′:6′,2″-terpyridine (1).
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Figure 2. 1H-NMR spectra of compound 1 (inset: structure and atom numbering of 1).
Figure 2. 1H-NMR spectra of compound 1 (inset: structure and atom numbering of 1).
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Figure 3. UV-Vis. spectrum of terpyridine 1 (1.21 × 10−4 M in acetonitrile).
Figure 3. UV-Vis. spectrum of terpyridine 1 (1.21 × 10−4 M in acetonitrile).
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Table 1. Comparison of melting points for some chalcogenophene-substituted terpyridines. a Values from literature.
Table 1. Comparison of melting points for some chalcogenophene-substituted terpyridines. a Values from literature.
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Mp (°C)70–72 a98–99197–199 a219 a215–218 a196–200 a
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