Pseudo-polymorphism in the Tri(o-tolyl)phosphinegold(I) 2-Mercaptobenzoates: Crystallographic, Thermal Decomposition, and Luminescence Studies

Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) analysis of four crystallographically characterized pseudo-polymorphs of tri( o -tolyl) 3 PAu(2-mercaptobenzoate)·solvent, ( o -tol) 3 PAu(2-mbaH)·solvent, featuring linear P−Au−S entities and different modes of supramolecular association depending on the nature of the included solvent molecule, have been performed. Whereas the thermal decomposition mechanisms of the four pseudo-polymorphs do not differ significantly from each other, the enthalpies of phase change do vary somewhat, indicating influence of solvent upon coherence of the crystal lattice. Crystals of ( o -tol) 3 PAu(2-mbaH)·solvent are very luminescent. UV excitation produced three emission bands for ( o -tol) 3 PAu-(2-mbaH)·solvent. Contrary to the free ligands, ( o -tol) 3 P and 2-HmbaH, the emission shapes of the Au compounds are very dependent on the excitation energy. The single excitation configuration interaction (CIS) post-Hartree−Fock (HF) calculations were performed to model the electronic structures of the free ligands and ( o -tol) 3 PAu(2-mbaH). The configurational interaction supports the notion that the observed electronic transitions of the complex are strongly associated with the charge transfer from S to Au. The assignment of the emission bands is presented in terms of the relaxed excited states responsible for the charge-transfer transitions, in which the crystal field and the vibronic interactions are taken into account as additional perturbations.