Theoretical Design Study on the Electronic Structures and Phosphorescent Properties of Four Iridium(III) Complexes

<div><p>The geometry structures, electronic structures, absorption, and phosphorescent properties of four Ir(III) complexes have been investigated using the density functional method. Calculations of ionization potential (IP) and electron affinity (EA) were used to evaluate the injection abilities of holes and electrons into these complexes. The result also indicates that the –CF₃ substituent group on the ligand not only change the character of transition but affect the rate and balance of charge transfer. The lowest energy absorption wavelengths are located at 428 nm for <b>1a</b>, 446 nm for <b>1b</b>, 385 nm for <b>2a</b>, and 399 nm for <b>2b</b>, respectively, in good agreement with the energy gap (Δ<i>E</i>_L-H) trend because the HOMO–LUMO transition configurations are predominantly responsible for the <i>S</i>₀→<i>S</i>₁ transition. <b>2b</b> has the 433 nm blue emission, which might be a potential candidate for blue emitters in phosphorescent dopant emitters in organic light emitting diodes (OLEDs). The study could provide constructive information for designing novel OLEDs materials in the future.</p><p><i>[Supplemental materials are available for this article. Go to the publisher's online edition of Molecular Crystals and Liquid Crystals to view the free supplemental file.]</i></p></div

Theoretical study on the electronic structures and spectral properties of two series of osmium(II) complexes with different substituent groups

<p>Two series of osmium(II) complexes with different substituent groups (-CF₃, -N(CH₃)₂) have been studied by using the density functional theory (DFT) and time-dependent density functional theory (TDDFT) methods, to investigate their electronic structures, absorption, and emission properties. The influence of different substituted groups on their photophysical properties has also been explored. The lowest energy absorption and emission wavelengths calculated are in good agreement with the available experimental values. Besides, ionization potential (IP), electron affinities (EA), and reorganization energy (λ) were calculated to evaluate the charge transfer and balance properties between hole and electron. It is expected that the theoretical studies could provide valuable information for the phosphorescent osmium(II) material for use in the organic light-emitting diodes.</p

Theoretical insight into a series of cyclometalated platinum(II) complexes with the substituted 2-phenylimidazole ligand

<p>The photophysical properties of a series of platinum(II) complexes have been theoretically investigated. The effect of the electron-withdrawing and electron-donating substituents on charge injection, transport, absorption and phosphorescent properties has been studied. For complexes <b>1</b>–<b>5</b>, the phosphorescence at 474, 453, 451, 524 and 461 nm are assigned to ³MLCT(triplet metal-to-ligand charge transfer)/³ILCT(triplet intraligand charge transfer). In addition, ionization potential (IP), electron affinities (EA) and reorganization energy have also been analyzed to evaluate the charge transfer and balance properties between hole and electron. The calculated results show the complex <b>2</b> possibly possesses the largest radiative decay rate value among these studied complexes.</p

DFT/TDDFT investigation on the photophysical properties of a series of phosphorescent cyclometalated complexes based on the benchmark complex FIrpic

<p>The photophysical properties of four Ir(III) complexes have been investigated by means of the density functional theory/time-dependent density functional theory (DFT/TDDFT). The effect of the electron-withdrawing and electron-donating substituents on charge injection, transport, absorption and phosphorescent properties has been studied. The theoretical calculation shows that the lowest-lying singlet absorptions for complexes <b>1</b>–<b>4</b> are located at 387, 385, 418 and 386 nm, respectively. For <b>1</b>–<b>4</b>, the phosphorescence at 465, 485, 494 and 478 nm is mainly attributed to the LUMO → HOMO and LUMO → HOMO-1 transition configurations characteristics. In addition, ionisation potential (IP), electron affinities (EAs) and reorganisation energy have been investigated to evaluate the charge transfer and balance properties between hole and electron. The balance of the reorganisation energies for complex <b>3</b> is better than others. The difference between hole transport and electron transport for complex <b>3</b> is the smallest among these complexes, which is beneficial to achieve the hole and electron transfer balance in emitting layer.</p

DFT and TD-DFT Study on the Electronic Structures and Phosphorescent Properties of a Series of Heteroleptic Iridium(III) Complexes

The electronic structures and phosphorescent properties of a series of heteroleptic iridium­(III) complexes (mpmi)₂Ir­(dmpypz) (<b>1</b>; mpmi = 1-(4-tolyl)-3-methylimidazolium, dmpypz = 3,5-dimethyl-2-(pyrazol-3-yl)­pyridine), (bpmi)₂Ir­(dmpypz) (<b>2</b>; bpmi = 1-biphenyl-4-yl-3-methylimidazole), (dfmi)₂Ir­(dmpypz) (<b>3</b>; dfmi = 1-(2,6-difluorobiphenyl)-3-methylimidazole), (mtmi)₂Ir­(dmpypz) (<b>4</b>; mtmi = 1-methyl-3-(4′-(trifluoromethyl)­biphenyl-4-yl)­imidazole), (fmmi)₂Ir­(dmpypz) (<b>5</b>; fmmi = 1-(fluoren-2-yl)-3-methylimidazole), and (mhmi)₂Ir­(dmpypz) (<b>6</b>; mhmi = 1-methyl-3-phenanthren-2-ylimidazole) have been investigated by using density functional theory (DFT) and time-dependent density functional theory (TDDFT) methods. The influence of different substituent groups and π-conjugation degrees on the optical and electronic properties of Ir­(III) complexes was also explored by introducing phenyl, fluorophenyl, (trifluoromethyl)­phenyl, and rigid construction on the phenylimidazole moiety of a cyclometalated ligand (C^∧C) in complex <b>1</b>. The calculated results show that the lowest energy absorption wavelengths of complexes <b>1</b>–<b>6</b> are 387, 380, 378, 375, 391, and 384 nm, respectively. The introduction of different substituent groups leads to different degrees of red shift for complexes <b>2</b>–<b>6</b> in emission spectra in comparison with that of complex <b>1</b>. It is believed that the highest triplet metal to ligand charge transfer ³MLCT (%) contribution, smallest Δ<i>E</i>_S₁–T₁ and higher μ_S₁ values, and larger ³MC–³MLCT energy gap for <b>3</b> ensure its higher quantum yield in comparison with that of other complexes

Theoretical study on the electronic structures and phosphorescent properties of a series of iridium(III) complexes with N^C^N-coordinating terdentate ligands

<p>The geometry structures, electronic structures, absorption, and phosphorescent properties of a series of iridium(III) complexes with the structure Ir(N^C^N)(N^C)Cl, (N^C^N represents a terdentate coordination with different substituent groups C₂H₅ (<b>1</b>), NH₂ (<b>2</b>), CH₃ (<b>3</b>), H (<b>4</b>), CN (<b>5</b>), NO₂ (<b>6</b>), and CF₃ (<b>7</b>), N^C is 2-phenylpyridine) have been investigated using the density functional theory and time-dependent density functional theory. Calculations of ionisation potential and electron affinity were used to evaluate the injection abilities of holes and electrons into these complexes. The lowest energy absorption wavelength calculated is in good agreement with the experimental value. The lowest energy emissions of complexes <b>1</b>−<b>7</b> are localised at 552, 559, 549, 517, 627, 788, and 574 nm, respectively, at CAM-B3LYP level. For complexes <b>1</b> and <b>3</b>, the calculated results showed a lower and larger ³MLCT contributions and higher values, which could result in the larger <i>k</i>_r value than those of other complexes. It is anticipated that the theoretical studies can provide useful information for designing and synthesising the candidated phosphorescent material for use in the organic light-emitting diodes.</p

Photochemical Reduction of Particle Bound Mercury in Atmospheric Aerosol Water

Particle bound mercury (PBM) deposition on the Earth’s surface threatens biota and humans. The photoreduction of PBM competes with deposition and thereby modifies global mercury cycling; yet, its pathway and mechanism remain poorly understood. Herein, we reveal the photoreduction process of PBM by comprehensively using field observation, mercury stable isotope analysis, and controlled experiment. We found the Δ199Hg values in wet haze episodes (0.34‰ ± 0.30‰) were significantly higher than those in clean periods (0.14‰ ± 0.19‰), majorly attributed to the elevated aerosol water content (AWC), which shifts the aerosol phase from the solid state to the liquid state, promoting soluble HgCl2 and HgBr2 photoreduction reactions. The carboxyl functional groups of water-soluble organic carbon (WSOC) were further identified as the crucial compounds that induce PBM photoreduction, whose reaction rates were ∼2 times higher than those of phenol and ketone ligands and 3–6 times higher than those observed in other atmospheric aqueous phases. Considering the ubiquitously distributed carboxyl ligands and significant positive Δ199Hg signals in the atmospheric aqueous phases, the PBM photoreduction mediated by carboxyl ligands is highlighted to significantly influence global mercury transformations, regional depositions, and isotopic compositions of atmospheric mercury pools