A digold(I) – Tetraalkynyl macrocycle with host-guest properties

Abstract

In this contribution we wish to describe the synthesis and characterization of an anthraquinone-based dialkynyl ligand AQ-(OCH2CCH)2 (1, AQ = anthraquinone) and its coordination to Au(I) centers, to form a negatively charged tetraalkynyldigold macrocycle ([AQ-(OCH2CC)2Au]2(NPr4)2 (2)), capable to act as a host for positively charged species. X-Ray diffraction studies revealed that compound 1 crystalizes in the monoclinic crystal system, space group C2/c, with the unit cell dimensions a = 33.4705(19) Å, b = 6.8582(4) Å, c = 12.8850(7) Å, and β = 90.7990(10)°, with Z = 8. The supramolecular structure of 1 consists of ribbons running along the b axis of the unit cell, and it is supported by CC-H ··· O hydrogen bonds and π – π stacking interactions. Complex 2 crystalizes in the monoclinic crystal system, space group P21/c, with the unit cell dimensions a = 21.5515(9) Å, b = 15.3851(6) Å, c = 25.2615(10) Å, and β = 99.6730(10)°, with Z = 4. X-Ray diffraction investigations showed that the structure of 2 consists of two anthraquinone groups connected by two CC–Au–CC spacers, with an overall basket-like shape of the macrocycle. One tetrapropylammonium cation is positioned inside the macrocycle with two n-Pr groups being threaded through the cavity of the macrocycle, and the other two situated between the two anthraquinone moieties of the complex. This species is best described as an inclusion compound, formulated as {N[n-Pr]4+⊂22–}{N[n-Pr]4+}.