A new series of luminescent phosphine stabilised platinum ethynyl complexes

A series of cis-platinum ethynyl complexes with the general formula cis-Pt(dppe)(Ctriple bond]CR)2](dppe = 1,2-bis(diphenylphosphino)ethane; R = C6H4-p-NO2 1, C6H4-p-CH3 2, C6H4-p-Ctriple bond]CH 3 and C6H4-p-C6H4-p-Ctriple bond]CH 4) have been prepared by the coupling reaction of cis-Pt(dppe)Cl2] with two equivalents of the appropriate alkyne. The new complexes have been fully characterized by spectroscopic techniques, and the cis square planar arrangement at the platinum centre has been confirmed by single-crystal X-ray diffraction studies of complexes 1, 2 and 4. The absorption spectra of the complexes 1-4 are dominated by a pi-->pi* band that contains some platinum (n + 1) p orbital character. The position of the band is dependent on the electron donating or withdrawing properties of the ethynyl substituents, R. Complex 1 displays a triplet emission in the green, at room temperature, while complexes 2-4, display singlet emissions in the blue. Again, the difference can be attributed to the nature of the R substituents.