Design and Synthesis of a New Kind of Cavitand: Tetrapyrazolylcalix[4]arenes and Their Supramolecular Assemblies

Abstract

Two novel calix[4]arene-based tetrapyrazolyl cavitands with different cavity size were synthesized by multistep reactions. In the solid state, one of the cavitands forms an infinite chain by ­intermolecular hydrogen bonding. The other cavitand undergoes coordination self-assembly with dimetal corners to form a supramolecular cage.

Key words

cavitands - calixarenes - hydrogen bonding - self-assembly - macrocycles

• References

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• 9 5,11,17,23-Tetrakis(3,5-dimethyl-1H-pyrazol-4-yl)-25,26,27,28-tetrapropoxycalix[4]arene (1) White powder; yield: 546 mg (85%); mp 285–289 °C; ¹H NMR (400 MHz, DMSO-d ₆, 20 °C): δ = 11.86 (s, 4 H, HN-pyrazole), 6.64 (s, 8 H, H-Ar), 4.44 and 3.24 (d, Ј = 12.1 Hz, 8 H, Ar-CH ₂-Ar), 3.82 (t, Ј = 8.6 Hz, 8 H, ArOCH₂ CH₂CH₃), 2.03 and 1.62 (s, 24 H, pyrazole-CH ₃ ), 1.96 (ψ-sextet, 8 H, ArOCH₂ CH₂ CH₃), 0.98 (t, J = 8.4 Hz, 12 H, ArOCH₂CH₂ CH₃ ); ¹³C NMR (100 MHz, DMSO-d ₆, 25 °C): δ = 135.6, 134.3, 128.9, 118.41, 79.26, 56.59, 23.31, 18.63, 10.52; MS (MALDI–TOF, MeOH): m/z: calcd for [M + Na]⁺ 991.56; found 991.6. 5,11,17,23-Tetrakis[4-(3,5-dimethyl-1H-pyrazol-4-yl)phenyl]-25,26,27,28-tetrapropoxycalix[4]arene (2) White power; yield: 55 mg (75%); mp 233–240 °C; ¹H NMR (400 MHz, DMSO-d ₆, 25 °C): δ = 12.19 (s, 4 H, HN-pyrazole), 7.34 (s, J = 8.8 Hz, 8 H, phenyl-H), 7.01–7.08 (d, J = 8.4 Hz, 8 H, phenyl-H), 6.98 (s, 8 H, calixarene-Ar-H), 4.51 and 3.43 (d, J = 7.8 Hz, 8 H, ArCH₂ Ar), 3.98 (d, J = 12.8 Hz, 8 H, ArOCH₂ CH₂CH₃), 2.17 (s, 24 H, pyrazole-CH₃ ), 1.97–2.01 (4-sextet, J = 8.0 Hz, 8 H, ArOCH₂ CH₂ CH₃), 1.00 (t, J = 7.4 Hz, 12 H, ArOCH₂CH₂ CH₃ ). ¹³C NMR (100 MHz, CDCl₃, 25 °C): δ = 157.32, 146.72, 135.55, 134.46, 133.56, 129.92, 127.26, 126.74, 31.33, 23.34, 10.38. MS (MALDI–TOF, MeOH–DMSO): m/z: calcd for [M + H₂O + H⁺]: 1291.7; found: 1290.1. Anal Calcd for C₈₄H₈₈N₈O₄·2H₂O: C, 77.03; H, 7.08; N, 8.56. Found: C, 77.11, H, 7.06; N, 8.52.
• 10 Crystallographic data for compound 1 have been deposited with the accession number CCDC 928591, and can be obtained free of charge from the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; Fax: [phone]; E-mail: [e-mail]; Web site: www.ccdc.cam.ac.uk/conts/retrieving.html.