Shedding light on unusual photophysical properties of bis-cyclometalated iridium(III) complexes containing 2,5-diaryl-1,3,4-oxadiazole-based and acetylacetonate ligands.

Title Shedding light on unusual photophysical properties of bis-cyclometalated iridium(III) complexes containing 2,5-diaryl-1,3,4-oxadiazole-based and acetylacetonate ligands.
Authors G. Godefroid; J. Su; X. Qu; Y. Liu; Y. Si; X. Shang; Z. Wu
Journal Dalton Trans
DOI 10.1039/c2dt30792h
Abstract

A DFT/TDDFT investigation was conducted on a series of cyclometalated iridium(iii) complexes with 2,5-diaryl-1,3,4-oxadiazole (oxd(n)) derivatives to shed light on the effects of the stereoisomeric and steric factors on the photophysical properties. On the basis of the results reported herein, we attempt to explain the experimental observations according to which complexes N,N-trans [Ir(oxd(0))(2)(acac)] (1a) and N,N-trans [Ir(oxd(1))(2)(acac)] (2a) [with oxd(0) = 2,5-diphenyl-1,3,4-oxadiazole, oxd(1) = 2,5-bis(4-fluorophenyl)-1,3,4-oxadiazole and acac = acetylacetonate] show high quantum phosphorescence efficiencies (?(PL)) of 35 and 44%, while an extremely low ?(PL) (<1%) was observed for a number of oxd(n) based complexes including N,N-cis [Ir(oxd(3))(2)(acac)] (4b) [with oxd(3) = 2-(4-fluorophenyl)-5-(2,4,6-triisopropylphenyl)-1,3,4-oxadiazole]. While new insights were gained on structural and electronic properties, the unusual photophysical properties recently reported for 4b were found to be not inherent to spin-orbit coupling (SOC) effects, but determined by both the S(1)-T(1) splitting energy (?E(S1-T1)) and the transition dipole moment (?(S1)) upon the S(0)? S(1) transition. Drastically large ?E(S1-T1) and small ?(S1) for 4b (0.70 eV and 0.23 D, respectively) comparative to those for 2a (0.38 eV and 2.76 D, respectively) and 1a (0.58 eV and 2.44 D, respectively) were found to be tightly linked to the twisting degree of the oxd(n) ligand and to the trans-cis structural isomerism. On the basis of these parameters, the unusual physical properties of 4b were interpreted with respect to 1a and 2a, and the higher ?(PL) of 2a with respect to that for 1a was explained.

Citation G. Godefroid; J. Su; X. Qu; Y. Liu; Y. Si; X. Shang; Z. Wu.Shedding light on unusual photophysical properties of bis-cyclometalated iridium(III) complexes containing 2,5-diaryl-1,3,4-oxadiazole-based and acetylacetonate ligands.. Dalton Trans. 2012;41(34):1022837. doi:10.1039/c2dt30792h

Related Elements

Iridium

See more Iridium products. Iridium (atomic symbol: Ir, atomic number: 77) is a Block D, Group 9, Period 6 element with an atomic weight of 192.217. The number of electrons in each of iridium's shells is [2, 8, 18, 32, 15, 2] and its electron configuration is [Xe] 4f14 5d7 6s2. Iridium Bohr ModelThe iridium atom has a radius of 136 pm and a Van der Waals radius of 202 pm. Iridium was discovered and first isolated by Smithson Tennant in 1803. In its elemental form, Iridium has a silvery white appearance. Iridium is a member of the platinum group of metals.Elemental Iridium It is the most corrosion resistant metal known and is the second-densest element (after osmium). It will not react with any acid and can only be attacked by certain molten salts, such as molten sodium chloride. Iridium is found as an uncombined element and in iridium-osmium alloys. Iridium's name is derived from the Greek goddess Iris, personification of the rainbow, on account of the striking and diverse colors of its salts.

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