Crystal Structure offac−Ir(ppy)₃and Emission Properties under Ambient Conditions and at High Pressure

Abstract

Solution and refinement of the crystal structure of fac-Ir(ppy) 3 is severely hampered by systematic twinning and pseudo-symmetry. fac-Ir(ppy) 3 crystallizes in the centrosymmetric space group P3 h as has been deduced from single-crystal structure refinement and investigations of the second harmonic generation (SHG) of fac-Ir(ppy) 3 powder as compared to two standard materials. The topology of the molecular packing of fac-Ir(ppy) 3 is identical to the packing observed for [Ru(bpy) 3 ] 0 , however, the site symmetry of all Ir(ppy) 3 molecules is necessarily lowered from D 3 to C 3 . Packing motifs with intermolecular "π-π interactions" of T-shaped and "shifted π stack" geometry are realized. The systematic twinning leads to the occurrence of crystalline domains with rigorously alternating chirality within the bulk of the domains but with homochiral fac-Ir(ppy) 3 contacts at the domain interfaces. These differences in packing motifs are displayed in the emission spectra and in the high-pressure-induced shifts of the emission. The emission maximum of the bulk material at 18 350 cm -1 (545 nm) and of the domain interfaces at 19 700 cm -1 (507 nm) experience for p < 25 kbar and T ) 295 K red shifts of ∆ν j/∆p ) -( 12( 2) cm -1 /kbar, and -(22 ( 4) cm -1 /kbar, respectively.

Blue Phosphorescent Iridium(III) Complex. Aromaticity of the Triplet Potential Energy Surface

“…On the triplet PES, the precise assignation of the MLCT character is complicated by the presence of a strong metal-ligand mixing in the orbitals, nonetheless, the calculations confirm that the lowest excited state corresponds to a triplet MLCT. The results obtained for Ir(N-phenyl-pim) 3 , are similar. On the triplet PES associated with Ir(N-methyl-pim) 3 , the isomer of type AA, has an energy E AA of +69.2 kcal/mol.…”

“…The results obtained for Ir(N-phenyl-pim) 3 , are similar. On the triplet PES associated with Ir(N-methyl-pim) 3 , the isomer of type AA, has an energy E AA of +69.2 kcal/mol. and the isomer of type A has an energy E A of + 64.6 kcal/mol.…”

“…3 shows the frontier orbitals of the ground state of Ir(N-methyl-pim) 3 facial isomer. Performing an excitation from the HOMO to the LUMO would correspond to a MLCT transition.…”

“…The calculations predict therefore that the departure of the methyl group stabilizes the complex. On the triplet PES associated with Ir(N-phenyl-pim) 3 , the isomer of type AA, has an energy E AA of +59.3 kcal/mol. and the isomer of type A has an energy E A of + 72.3 kcal/mol.…”

“…Unrestricted DFT was used to investigate several cyclometalated complexes and the validity of the results obtained by the calculations were confirmed experimentally [2,3]. The unrestricted DFT permits the analysis of the triplet state properties and the calculation of energy variation as a function of the geometric changes, i.e., the potential energy surface (PES) [4].…”