Gold(i) chloride complexes with the diarsenic ligands cis-1,4-dihydro-1,4-diarsinines (cis-DHDAs) were synthesized. X-ray diffraction revealed that they formed one-dimensional polymeric structures through aurophilic interactions. Their higher-ordered structures are controlled by the ligand structure; methyl- and t-butyl substituted ligands offered transoid-transoid and transoid-cisoid conformations, respectively. Density functional theory (DFT) calculations indicated that the electronic structure of the aurophilic network was highly dependent on the conformations. This is the first study on the relationship between the chain conformation and 5d-orbital structures of gold complexes.
Stimuli-responsive gold(I) chloride complexes were developed based on a diarsenic ligand, cis-1,4-dihydro-1,4-dimethyl-2,3,5,6-tetrakis(alchoxycarbonyl)-1,4-diarsinine (cis-DHDA). The crystals of the complexes showed intense luminescence due to the aurophilic interactions. Interestingly, methyl- and t-butyl substituted cis-DHDAs offered different stimuli-responsive behaviors accompanied with emission color changes. The crystal samples of the complexes with both ligands changed their emission colors by mechanical stimulus such as grinding in a mortar, but the effect of CH2Cl2-treatment for the recovery of the original emission was dependent on the substituent structures. Furthermore, only the crystals of the complex with t-butyl substituted cis-DHDAs showed vapochromic luminescence. These differences arise from steric hindrance of substituents at the ester groups. Relationship between chemical structure and emission behaviors was studied based on a simple ligand backbone.
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