Vibrational calculations were performed using the Gaussian16 (Rev. C.01) suite of software. Vibrational emission spectra were calculated using either the Adiabatic Hessian (AH) or Vertical Hessian (VH) implementation of the Franck-Condon principle. The calculations were performed using the B3LYP functional and the 6-31G(d,p) basis set for non-metal atoms and the SBKJC VDZ ECP basis set for Ir atoms, this level of theory has shown to provide a good match between calculated and experimental emission spectra. The excited state (T1) vibrational frequencies were calculated at the TD-DFT optimised structure, while vibrational frequencies were calculated in the ground state (S0) at the same structure (VH method) or the optimised ground state geometry (AH). Where imaginary (negative) frequencies were found for the T1 or S0 structures, the low frequency components of the vibrational spectra were removed. FC calculations were performed with a unitary transition dipole, considering 10 classes, with a maximum of 10 10 integrals considered and a gaussian HWHM of 500 cm -1 used to simulate the emission spectra.