This question is regarding an Ir(ppy)2(bpy) complex. After analysing the UV-Vis spectrum (attached below) of the complex I could assign[1], λabs for (spin allowed)LC π -π * = 254 nm and λabs for (spin allowed) MLCT = 302 nm. However, in previous publications they have used the wavelength of λ MLCT (302 nm) to excite the complex to obtain the emission spectra.
Iridium is reported to show phosphorescence from both 3LC and 3MLCT triplet states.[2]
My question is, why is λ MLCT used to excite the complex? What will happen if I use λ LC = 254 nm to excite the complex to get the emission spectra ?
I have attached the general molecular orbital diagram of Ir heteroleptic complexes and the UV spectra observed below.
Would be a great help if someone could help me to clarify this :)
References:
1 K. Hasan, A. K. Bansal, I. D. W. Samuel, C. Roldán-Carmona, H. J. Bolink and E. Zysman-Colman, Sci. Rep., 2015, 5, 12325.
2 J.-H. Kim, S.-Y. Kim, Y.-J. Cho, H.-J. Son, D. W. Cho and S. O. Kang, J. Phys. Chem. C, 2018, 122, 4029–4036.
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