There are two key features in the calculated AH emission spectra (Figure ) that determine the broadness of the emission. Firstly, there is the relative height of the main vibrational band (at ca. 600 nm), which for Irpic, is 95% of the 0-0 transition band, while for N4 and N5, it is only 85% of the intensity of the 0-0 transition band. Secondly, there is the size of the low energy shoulder, which is smallest for N4 and N5 and increase moving to Irpic and then the remaining complexes. Comparison of the calculated vibronic transitions for the trimethylsilyl-substituted complexes shows that there are fewer coupled vibrational modes contributing to the emission spectra compared to IrPic (Table ). In addition, visualisation of the vibrational modes of the new complexes shows a damping of the ring breathing modes that contributed strongly to the vibrational modes of Irpic. The vibrational modes for the complexes are tabulated in Table , while selected vibrational modes are shown in Figure .