Preparation of an Ester-Substituted Triscatechol Ligand and Characterization of the Corresponding M₄L₄ Titanium(IV) Complex

Abstract

The ester-substituted triscatechol ligand L-H₆ can be easily prepared in a triple imine condensation reaction. The required trisamine is prepared starting from diphenylamine and 2-bromobenzoic acid methylester. Upon coordination of titanium(IV) ions the tetrahedral M₄L₄ coordination compound is obtained, which due to the symmetry breaking substituent exists as a mixture of isomers. However, the complex can be unambiguously characterized by ESI-MS.

ligand - self assembly - coordination compound - imine - container molecule

References and Notes

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Related work by others:

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Characterization of L-H₆: mp 179 ˚C; ^¹H NMR (300 MHz, DMSO-d ₆): δ = 13.36, 12.89, 9.18 (three broad signals, 6 H total, OH), 9.02 (s, 1 H, HC=N), 8.93 (s, 2 H, HC=N), 7.78-7.65 (m, 2 H, CH_ar), 7.40-7.32 (m, 5 H, CH_ar), 7.17-6.96 (m, 9 H, CH_ar), 6.85-6.74 (m, 4 H, CH_ar), 3.48 (s, 3 H, OCH₃). MS (EI, 70 eV): m/z = 709 [M + H] ⁺. Anal. Calcd for C₄₁H₃₂N₄O₈ (708.71): C, 69.48; H, 4.55; N, 7.91. Found: C, 69.39; H, 4.08; N, 8.00.

For ESI-MS as characterization tool in supramolecular chemistry, see:

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<A NAME="RG28610ST-7B">7b</A> Schalley CA. Mass Spectrom. Rev.  2001,  20:  253