Abstract: A series of iridium(Ⅲ) complexes [(C^N)2IrL]+[C^N=ppy, L=pzpy(1); C^N=dfppy, L=pzpy(2); C^N=ppy, L=pybi(3); C^N=tpy, L=acac(4); ppy=2-phenyl-pyridine, dfppy=2-(2,4-difluorophenyl)pyridine, pzpy=2-(1H-pyrazol-1-yl)pyridine, pybi=1-phenyl-2-(pyridin-2-yl)-1H-benzoimidazole, tpy=2-(4-tolyl)-pyridine, acac=acetoylacetonate] was investigated theoretically to explore their electronic structures and spectroscopic properties. Their structures in the ground and excited states were optimized at the B3LYP/LanL2DZ and CIS/LanL2DZ levels, respectively. The results indicate that the calculated bond lengths of Ir—N, Ir—C, and Ir—O in the ground state agree well with the corresponding experimental results. Upon excitation, the bond lengths of Ir—N and Ir—C lengthen by 0.0003—0.003 nm and that of Ir—O shortens by ca. 0.0012 nm compared with those of ground states. At the time-dependent density functional theory(TD-DFT) level with the polarized continuum model(PCM), complexes 1—4give rise to lowestying absorptions at 398 nm(1), 370 nm(2), 419 nm(3), and 437 nm(4) and phosphorescent emissions at 511 nm(1), 457 nm(2), 602 nm(3), and 479 nm(4), respectively. The transitions of complexes 1, 2 and 4 are attributed to d(Ir)+π(C^N)→π*(C^N) charge transfer, whereas those of complex 3 are related to d(Ir)+π(C^N)]→π*(pybi). It is shown that the emissions are significantly dominated by the metal participating in the frontier molecular orbitals and affected by the L ligands.

Key words: Cationic iridium(Ⅲ) complex, Electronic structure, Excited state, Time-dependent density functional theory, Spectroscopic property