Intermolecular Interactions in Polymorphs of Trinuclear Gold(I) Complexes: Insight into the Solvoluminescence of AuI3(MeNCOMe)3

Abstract

The trinuclear complex, Au^I₃(MeNCOMe)₃, which displays a number of remarkable properties including solvoluminescence, has been found to crystallize as three polymorphs. The new triclinic and monoclinic polymorphs crystallized as colorless blocks, whereas the original hexagonal polymorph formed colorless needles. These polymorphs differ in the manner in which the nearly planar molecules pack and in the nature of the aurophilic interactions between them. Each of the three polymorphs of Au^I₃(MeNCOMe)₃shows a distinctive emission spectrum, but only the original hexagonal polymorph shows the low-energy emission that is responsible for its solvoluminescence. Colorless Au^I₃(n-PentNCOMe)₃crystallized from diethyl ether as needles of an orthorhombic polymorph and blocks of a triclinic polymorph. These polymorphs differ in the orientation of the n-Pent substituents, in the orientation of the trimers with respect to one another, and in the nature of the aurophilic interactions between the molecules. Only the triclinic polymorph of Au^I₃(n-PentNCOMe)₃ shows luminescence at room temperature, but it is not solvoluminescent. Colorless Au^I₃(i-PrNCOMe)₃has also been prepared and crystallographically characterized. The isopropyl groups protrude out of the plane of the nine-membered ring and prevent self-association. The closest Au···Au contact between molecules is 6.417 Å. Crystalline Au^I₃(i-PrNCOMe)₃ is not luminescent at room temperature.