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CC BY-NC-ND 4.0 · Organic Materials 2020; 02(03): 235-239
DOI: 10.1055/s-0040-1714295
Focus Issue: Curved Organic π-Systems
Short Communication

Calix[n]phenothiazines: Optoelectronic and Structural Properties and Host–Guest Chemistry

Maximilian Schmidt
a   Institute for Organic Chemistry, University of Freiburg, Albertstr. 21, 79104 Freiburg, Germany
,
Mathias Hermann
a   Institute for Organic Chemistry, University of Freiburg, Albertstr. 21, 79104 Freiburg, Germany
,
Fabian Otteny
a   Institute for Organic Chemistry, University of Freiburg, Albertstr. 21, 79104 Freiburg, Germany
,
Birgit Esser
a   Institute for Organic Chemistry, University of Freiburg, Albertstr. 21, 79104 Freiburg, Germany
b   Freiburg Materials Research Center, University of Freiburg, Stefan-Meier-Str. 21, 79104 Freiburg, Germany
c   Cluster of Excellence livMatS @ FIT – Freiburg Center for Interactive Materials and Bioinspired Technologies, University of Freiburg, Georges-Köhler-Allee 105, 79110 Freiburg, Germany
› Author Affiliations Funding Information This study was funded by the German Research Foundation (ES 361/2-1, INST 40/467-1 FUGG).
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Abstract

Calixarenes are of interest as receptors for ions and small molecules and as organic materials. Exchanging the arene units through heteroaromatics allows changing their optoelectronic and host–guest properties. We herein present calix[n]phenothiazines (n = 3, 4) as novel macrocycles, accessible in two-step syntheses. The phenothiazine units show reversible redox events and emissive properties, and N-hexyl-substituted calix[3]phenothiazine binds to both ammonium ions and a bisimidazole as neutral guests.

Key words

Calixarenes - macrocycles - phenothiazine - host–guest chemistry - conformational flexibility

Supporting Information

Supporting information for this article is available online at http://doi.org/10.1055/s-0040-1714295.


References and Notes

Experimental procedures and characterization data: Details on materials and methods as well as synthetic procedures for compounds not mentioned in the following can be found in the SI.


Syntheses of [3]CPT-Hex and [4]CPT-Hex: 10-Hexyl-10H-phenothiazine (2, 100 mg, 353 µmol) and paraformaldehyde (10.8 mg, 353 µmol, 1 eq.) were dissolved in degassed 1,2–dichloroethane (350 mL). Trifluoroacetic acid (17.5 mL) was added, and the mixture was stirred at 80 °C for 5 d until no more starting material was observed by analytical gel permeation chromatography. After cooling to rt, the organic layer was washed with aq. sat. NaHCO3 (2 × 100 mL), dried over Na2SO4, and the solvent was removed under reduced pressure. Linear oligomers were removed by column chromatography (SiO2, cyclohexane/EtOAc: 20/1) to obtain the crude mixture containing different ring sizes and residues of linear oligomers (49 mg, 52 µmol, 44%). The different ring sizes were separated by semipreparative gel permeation chromatography to obtain [3]CPT-Hex (16 mg, 18 µmol, 15%) and [4]CPT-Hex (4 mg, 1 µmol, 4%) as light yellow solids. Analytical data for [3]CPT-Hex: R f 0.49–0.60 (cyclohexane/EtOAc: 20/1); 1H NMR (500 MHz, CD2Cl2): δ 7.03 (dd, J = 8.3, 2.0 Hz, 6 H), 6.75 (d, J = 8.2 Hz, 6 H), 6.68 (d, J = 2.0 Hz, 6 H), 3.78 (t, J = 7.1 Hz, 6 H), 3.66 (s, 6 H), 1.77–1.71 (m, 6 H), 1.43–1.37 (m, 6 H), 1.31–1.26 (m, 12 H), 0.88–0.84 (m, 9 H); 13C NMR (126 MHz, CD2Cl2): δ 144.2, 136.1, 128.0, 127.7, 125.4, 115.4, 47.7, 40.4, 32.1, 27.4, 27.2, 23.2, 14.3; HRMS (ESI+): m/z calcd. for C57H63N3S3 885.4179 [M]+, found 885.4179. Analytical data for [4]CPT-Hex: R f 0.49–0.60 (cyclohexane/EtOAc: 20/1); 1H NMR (500 MHz, CD2Cl2): δ 6.96 (dd, J = 8.3, 2.0 Hz, 8 H), 6.74 (d, J = 8.3 Hz, 8 H), 6.74 (d, J = 2.1 Hz, 8 H), 3.76 (t, J = 7.3 Hz, 8 H), 3.71 (s, 8 H), 1.78–1.72 (m, 8 H), 1.44–1.37 (m, 8 H), 1.32–1.27 (m, 16 H), 0.88–0.85 (m, 12 H); 13C NMR (126 MHz, CDCl3): δ 143.8, 135.7, 128.0, 127.7, 124.9, 115.2, 47.7, 40.0, 31.9, 27.1, 27.0, 23.0, 14.1; HRMS (ESI+): m/z calcd. for C76H84N4S4 1181.5672 [M + H]+, found 1181.5673.


Synthesis of [3]CPT-Tol: N-(para-tolyl)phenothiazine (3, 300 mg, 1.04 mmol) and paraformaldehyde (32.6 mg, 1.04 mmol, 1 eq.) were dissolved in degassed 1,2–dichloroethane (200 mL). Trifluoroacetic acid (10 mL) was added, and the mixture was stirred at 80 °C for 5 d until no more starting material was observed by analytical gel permeation chromatography. After cooling to rt, the organic layer was washed with aq. sat. NaHCO3 (3 × 100 mL), dried over Na2SO4, and the solvent was removed under reduced pressure. The residue was purified by column chromatography (SiO2, cyclohexane/EtOAc: 50/1 to 10/1) and semipreparative gel permeation chromatography to obtain [3]CPT-Tol (95 mg, 105 µmol, 30%) as a colorless solid. R f 0.29–0.43 (cyclohexane/EtOAc: 20/1); 1H NMR (500 MHz, CD2Cl2): δ 7.42–7.39 (m, 6 H), 7.25–7.22 (m, 6 H), 6.74 (dd, J = 8.4, 2.1 Hz, 6 H), 6.64 (d, J = 2.1 Hz, 6 H), 6.16 (d, J = 8.2 Hz, 6 H), 3.55 (s, 6 H), 2.45 (s, 9H); 13C NMR (126 MHz, CD2Cl2): δ 143.9, 138.8, 138.5, 136.6, 131.5, 130.8, 127.4, 127.2, 121.1, 116.0, 40.1, 21.3; HRMS (ESI+): m/z calcd. for C60H45N3S3 903.2770 [M]+, found 903.2769.


Supporting Information

Primary Data



Publication History

Received: 20 May 2020

Accepted: 08 June 2020

Article published online:
28 September 2020

© 2020. The Author(s). This is an open access article published by Thieme under the terms of the Creative Commons Attribution-NonDerivative-NonCommercial-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-nc-nd/4.0/).

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