Crystallographic and Computational Studies of Luminescent, Binuclear Gold(I) Complexes, AuI2(Ph2P(CH2)nPPh2)2I2 (n = 3–6)

Four crystalline dimers of the type, AuI2(μ-PnP)2I2, where PnP is PPh2(CH2)nPPh2 with n = 3, 4, 5, and 6 have been prepared and characterized by single-crystal X-ray diffraction and by 31P NMR and infrared spectroscopy. AuI2(μ-P3P)2I2 and AuI2(μ-P6P)2I2 are centrosymmetric dimers with the planar AuIP2I units oriented in antiparallel fashion. Remarkably, noncentrosymmetric AuI2(μ-P5P)2I2 has its planar AuIP2I units oriented in parallel manner. AuI2(μ-P4P)2(μ-I)2 is unique, since it contains four-coordinate gold centers that are bridged by both iodide and diphosphine ligands. All four compounds are luminescent as solids at room temperature. B3LYP, B2PLYP, and spectroscopically oriented configuration interaction (SORCI) calculations have been conducted to give insight into the electronic and geometric structures of the ground and first excited triplet states of the three trigonal-planar complexes. The emission energies for the trigonal planar complexes are more strongly correlated with changes in the Au–I bond length rather than changes in the P–Au–P angle.