TD-DFT Benchmark on Inorganic Pt(II) and Ir(III) Complexes

Abstract

We report in the present paper a comprehensive investigation of representative Pt(II) and Ir(III) complexes with special reference to their one-photon absorption spectra employing methods rooted in density functional theory and its time dependent extension. We have compared nine different functionals ranging from generalized gradient approximation (GGA) to global or range-separated hybrids, and two different basis sets, including pseudopotentials for 4 iridium and 7 platinum complexes. It turns out that hybrid functionals with the same exchange part give comparable results irrespective of the specific correlation functional (i.e., B3LYP is very close to B3PW91 and PBE0 is very close to MPW1PW91). More recent functionals, such as CAM-B3LYP and M06-2X, overestimate excitation energies, whereas local functionals (BP86 -GGA-, M06-L -Meta GGA-) strongly underestimate transition energies with respect to experimental results. As expected, basis set effects are weak, and the use of a triple-ζ polarized (def2-TZVP) basis set does not significantly improve the computed excitation energies with respect to a classical double-ζ basis set (LANL2DZ) augmented by polarization functions, but it significantly raises the computational effort.

Vibronic coupling to simulate the phosphorescence spectra of Ir(III)-based OLED systems: TD-DFT results meet experimental data

“…As recently stated by some authors, the computational protocol that we used to perform excited state investigations on Ir(III) complexes seems to be efficient, e. g. B3PW91/LANL2DZ+pol. [9,10] Complexes 2 and 3 have shown a strong phosphorescence signature, which have been nicely reproduced and rationalized in our simulations. Indeed, the simulated phosphorescence spectra using the VMS approach allowed a direct vis-à-vis between experiment and simulations.…”

“…[59] On the basis of several previous studies, [9,10,22] we have chosen the B3PW91 functional to perform the computations. [60-62] The associated basis set is the socalled LANL2DZ one, including a pseudopotential for Time-Dependent Density Functional Theory (TD-DFT) computations have been performed, using the optimized ground state geometries, to obtain excitations energies and spectra.…”

“…For instance, the reliability of the VMS on phosphorescence spectra, especially on transition metal complexes, has seldom been investigated. [9,10,22] First, we compute the excited state (ES) geometry. As one can see in Figure 3, the GS and ES geometries of complex 2 are almost identical.…”

“…[4][5][6][7][8][9][10] Furthermore, iridium, ruthenium or platinum complexes are among the most investigated compounds and numerous studies from both the experimental and computational sides have been reported due to their strong ability to be embedded in devices. [4,5,[8][9][10][11][12][13][14][15][16][17] From an experimental point view, it remains challenging and difficult to fully characterize the electronic processes at work within the targeted compounds. As a matter of fact, chemists performing quantum chemical computations are now able to give crucial information on these electronic processes, namely those relevant to excitation and emission phenomena and the nature of the reached excited states, especially thanks to the very recent developments in this area.…”

“…[18][19][20][21][22][23] Moreover, Density Functional Theory (DFT) and its time dependent extension (TD-DFT) are now routinely used to get both electronic and vibrational information from small organic to large-size organometallic and transition metal complexes systems. [10,[24][25][26][27][28][29][30] Indeed, DFT calculations are now accurate enough to predict or confirm the stability or existence of compounds, and they can also explain the luminescent and/or spectroscopic properties of complex systems. [31][32][33][34][35][36][37][38][39][40] In the field of spectroscopy calculations, Vlcek Jr. and Zális among other authors, have shown how DFT and TD-DFT are useful tools to study d 6 metal complexes.…”