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The accurate prediction for the emission energies of the phosphorescent Ir (III) complexes is very useful for the realizing of full-color displays and large-area solid-state lighting in OLED fields. Quantum chemistry calculations based on TDDFT methods are most widely used to directly compute the triplet vertical excitation energies, yet sometimes the universality of these calculations can be limited because of the lack of experimental data for the relative family of structural analogues. In this letter, 16 literature emission energies at low temperature are linearly correlated with their theoretical values computed by TDDFT using exchange-correlation functionals containing various HF exchange percentage with the relation of E = 1.2 Ē. The relation is proven to be robust across a wide range of structures for Ir (III) complexes. These theoretical studies should be expected to provide some guides for the design and synthesis of efficient emitting materials. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

• Two-coordinate N-heterocyclic carbene Cu(I) complexes are synthesized and characterized. • The photophysical properties of the resulting complexes is investigated. • Ligand-centered blue to green to yellow emission observed with π-π* character. • DFT and TDDFT calculations are employed to explain the photophysical properties. Here, we report a series of two-coordinate N-heterocyclic carbene (NHC) copper(I) complexes having monodenate NHC 1,3-bis(2,6- diisopropylphenyl)imidazol-2-ylidene) (IPr) as a σ donor and quinoline and its derivatives as π-chromophore ligands, [Cu(IPr)(Quinoline)]BF 4 (P1), [Cu(IPr)(Chloroquinoline)]BF 4 (P2), [Cu(IPr)(Phenylquinoline)]BF 4 (P3), and [Cu(IPr)(Aminoquinoline)]BF 4 (P4), (Chloroquinoline = 2,4-dichloroquinoline, Phenylquinoline = 2-phenylquinoline, Aminoquinoline = 2,4-diaminequinoline). The X-ray diffraction studies of P1 and P3 revealed the linear coordination around the copper atom. P1 and P2 exhibit the typical metal-to-ligand charge transfer (1MLCT) absorption bands in the lowest-lying energy region, while P3 and P4 show the mixed characters of ligand-to-ligand charge transfer (1LLCT) and π→π* transition. The emission wavelengths of all NHC Cu(I) complexes can be fine-tuned to cover the spectral range of 419–543 nm with the main 3(π-π) emission origin in the solid state. The differences for photophysical properties of NHC Cu(I) complexes were rationalized using density functional theory (DFT) and time dependent density functional theory (TDDFT) calculations. [Display omitted] [ABSTRACT FROM AUTHOR]

• Four-coordinate N -heterocyclic carbene (NHC) Cu(I) complexes having the pyridyl-imidazolylidene ligand are synthesized and characterized. • The photophysical properties of the resulting complexes is investigated. • Complexes show yellow-green emission in 543–555 nm region with the higher photoluminescence efficiency. • DFT and TDDFT calculations are taken to support the differences of the photophysical properties. The synthesis, characterization and photophysical properties of a series of the four-coordinate N -heterocyclic carbene (NHC) copper(I) complexes are reported. These NHC-Cu(I) complexes contain two bidentate ligands, the R -substituted pyridyl-imidazolylidene-type ligand and diphosphine ligand bis [(2-diphenylphosphino)phenyl] ether (POP). The photophysical properties of these complexes can be adjusted depending on the nature of substituents at 4-position of the phenyl ring in the NHC ligand. The metal-to-ligand charge transfer (MLCT) absorption band can be observed for all complexes at 348–362 nm, and the emission wavelengths can be fine-tuned to cover the spectral range of 543–555 nm with the higher photoluminescence efficiency of up to 66.2% in the solid state. Density functional theory (DFT) and time dependent density functional theory (TDDFT) calculations were employed to support potophysical properties of the NHC-Cu(I) complexes. [Display omitted] [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Copper (I) complexes containing pyridine-imidazole ligands were synthesized. • Different substituents such as bromide, methyl, and phenyl groups were functionalized onto the pyridine ring. • Efficient green-yellow emission was achieved with emission wavelength of 547–569 nm and quantum yields of 24.8–53.0%. • DFT and TDDFT methods were employed to explain the experimental results. Abstract A series of the pyridine-imidazole (PyIm) Cu(I) complexes with different substituents (bromide (P1), methyl (P2), and phenyl (P3)) attached on the pyridine ring are synthesized and characterized. All the complexes show the typical metal-to-ligand charge transfer (MLCT) absorption in the visible region. Complex P1 with an electron-withdrawing substituent on the pyridine ring, e.g., a bromine group, shows a red shift of the emission wavelength. Conversely, an electron-donating substituent on the pyridine ring in complex P2 , e.g., a methyl group, shifts the emission to longer wavelength. Similarly, complex P3 containing the extended π-conjugation system of the ligand also exhibits a red shift of the emission wavelength. All of the complexes exhibit efficient green-yellow emission in PMMA films at room temperature with emission wavelength of 547–569 nm and quantum yields of 24.8–53.0%. Meanwhile, DFT and TDDFT methods were employed to explain the photophysical properties. [ABSTRACT FROM AUTHOR]

• Four-coordinate N-heterocyclic carbene (NHC) Cu(I) complexes bearing different diphosphine ligands are synthesized and characterized. • The photophysical properties of the resulting complexes is investigated. • Complexes show yellow-green emission in 525–555 nm region with the phosphorescent origin. • The differences of the photophysical properties were rationalized by DFT and TDDFT calculations. Here, we report a series of the four-coordinate N-heterocyclic carbene (NHC) copper(I) complexes having the same bidenate NHC ligand and different bisphosphine (P^P) ligands, [Cu(CNbenPy-benzIm)(Naphphos)]PF 6 (P1), [Cu(CNbenPy-benzIm)(cyc-xantphos)]PF 6 (P2), and [Cu(CNbenPy-benzIm)(xantphos)]PF 6 (P3), (CNbenPy-benzIm = 3-(3-cyanobenzyl)-1-(5-phenylpyridin-2-yl)-1 H -imidazolylidene; BINAP = 2,2′-bis(diphenylphosphino)-1,1′-binaphthalene; cyc-xantphos = (9,9-dimethyl-9 H -xanthene-4,5-diyl)bis(dicyclohexylphosphine), xantphos = 9,9-dimethyl-9 H -xanthene-4,5-diyl)bis(diphenylphosphine)). P1 exhibits the metal-to-ligand charge transfer (MLCT) absorption band at 366 nm with high molar extinction coefficient of 2.44 × 104 M−1 cm−1, while P2 and P3 show a blue-shift of the MLCT absorption band at 336–341 nm with the molar extinction coefficients of 0.82–1.16 × 104 M−1 cm−1, which are just a little lower than that of P1. The emission wavelengths of all NHC-Cu(I) complexes can be fine-tuned to cover the spectral range of 525–555 nm with the phosphorescent origin in PMMA films. P1 has the lowest photoluminescence efficiency of 5.50% with the red-shifted emission wavelength at 555 nm and the emission lifetime of 237 μs, whereas P3 show the highest photoluminescence efficiency of 39.5% with the blue-shifted emission wavelength at 525 nm and the emission lifetime of 64.4 μs. The differences for photophysical properties of NHC-Cu(I) complexes were rationalized using density functional theory (DFT) and time dependent density functional theory (TDDFT) calculations. [Display omitted] [ABSTRACT FROM AUTHOR]

Three four-coordinated N-heterocyclic carbene (NHC) copper(I) complexes, [Cu(NaphIm-Py)(POP)]PF 6 ( 1 ), [Cu(AnthrIm-Py)(POP)]PF 6 ( 2 ), and [Cu(PhBenIm- c -Py)(POP)]PF 6 ( 3 ) (NaphIm-Py = 3-(naphthalen-2-ylmethyl-1-(pyridin-2-yl)-1 H -imidazolylidene, AnthrIm-Py = 3-(anthracen-9-ylmethyl)-1-(pyridin-2-yl)-1 H -imidazolylidene, PhBenIm- c -Py = 3-benzyl-1-(pyridin-2-ylmethyl)-1 H -benzo[ d ]imidazolylidene, POP = bis[2-diphenylphosphino]-phenyl)ether) have been synthesized and characterized. The effect of varying carbene ligands with different substituents on the structural aspects and photophysical properties of the complexes is systematically investigated. The lowest absorption bands of 1 at about 350 nm are assigned as metal-to-ligand charge transfer (MLCT) character with some contribution from ligand-to-ligand charge transfer (LLCT) character, while the π-π* transition of the anthryl group are responsible for the lowest absorption band of 2 . For 3 , no MLCT absorption band are observed in lower energy region. The emission wavelengths of all NHC-Cu(I) complexes are in the range of 520–550 nm with the phosphorescent origin in the solid state. 1 and 2 with naphthyl and anthryl groups show the lower photoluminescence efficiency due to the strong π-π stacking interactions, whereas 3 exhibit good photoluminescence properties companying with the higher quantum yields and long excited-state lifetimes. Density functional theory (DFT) and time dependent density functional theory (TDDFT) calculations were employed to rationalize the photophysical properties of the NHC-Cu(I) complexes. [ABSTRACT FROM AUTHOR]

Two phenanthroline derivatives, 1H-imidazo[4,5-f][1,10]phenanthroline ( imPhen ) and 2-(9H-fluoren-2-yl)-1H-imidazo[4,5-f][1,10]phenanthroline ( Flu-imPhen ), have been synthesized and characterized and the corresponding absorption and emission spectroscopic properties have been studied in CH 2 Cl 2 solution. The imPhen exhibits the main two absorption bands at 282 nm and 229 nm and these bands are assigned as the typical π → π* (Phen) state. In addition, the weak absorption bands at 313 nm associated with a shoulder near 302 nm were assigned to the π → π* (Phen) state with partial charge transfer (CT) character. A similar absorption spectra are observed in the case of the Flu-imPhen in the region of 200–300 nm, while the region of 300–400 nm of the spectra are dominated by the characteristic π → π* transition of the fluorene moiety. imPhen shows the typical ligand-centered 1 π → π* emission, while Flu-imPhen emits from the mixed 1 π → π*/CT states. Density functional theory (DFT) and time-dependent density functional theory (TDDFT) were employed to rationalize the photophysical properties of these ligands studied. The theoretical data confirm the assignment of the experimental absorption spectra and the nature of the emitting states. [ABSTRACT FROM AUTHOR]

Three N,N-bidentate ligands, 2-phenyl-1H-imidazo[4,5-f][1,10]phenanthroline ( 1 ), 2-(2-naphyl)-1H-imidazo[4,5-f]phenanthroline ( 2 ), and 2-(2-anthryl)-1H-imidazo[4,5-f]phenanthroline ( 3 ) have been synthesized and characterized. Effects of aryl subsistiuents (phenyl, naphthyl, and anthryl) on the photophysical properties of these ligands in solution have been studied. Ligand 1 exhibit the main absorption band at 283 nm with the shoulder bands at 300–350 nm and these bands are assigned as the typical π→π* (imPhen) state (imPhen = 1H-imidazo[4,5-f][1,10]phenanthroline). A similar absorption spectrum was also observed in the case of 2, in which the charge transfer (CT) state should be considered. 3 shows the slightly different absorption properties compared to that of 1 and 2 . The highest-lying absorption band at 257 nm is assigned as a mixed π→π* (imPhen) /π→π* (Anth) (Anth = anthracene) state. Additionally, the characteristic absorption band of anthryl group with three vibronic bands at 352, 367, and 386 nm also observed in the visible region range from 340 to 400 nm. 1 shows the typical ligand-centered 1 π→π* emission, while 2 and 3 emit from the mixed 1 π→π*/CT states. Density functional theory (DFT) and time-dependent density functional theory (TDDFT) were employed to rationalize the photophysical properties of these ligands studied. The theoretical data confirm the assignment of the experimental absorption spectra and the nature of the emitting states. [ABSTRACT FROM AUTHOR]

The three novel copper (I) complexes bearing Schiff base ligands are reported. The different groups such as methoxyphenyl, adamantyl and diisopropylphenyl were functionalized onto the azomethine moiety of the Schiff base ligands to tune the photophysical behaviors of the resulting Schiff base Cu(I) complexes. All the complexes exhibit the higher molar extinction coefficients on the order of 104 M−1 cm−1. The photophysical properties are investigated theoretically using density functional theory (DFT) and time dependent DFT. [Display omitted] Herein, the three novel copper (I) complexes bearing Schiff base ligands of the types [Cu(Methoxyphenyl-NaphthylPyridyl-Meth-Aniline)(POP)]PF 6 (P1), [Cu(NaphthylPy-Methylene-Adam-Amine)(POP)]PF 6 (P2), and [Cu(Dipp-NaphthylPyridyl-Meth-Aniline)(POP)]PF 6 (P3) (Methoxyphenyl-NaphthylPyridyl-Meth-Aniline = 4-methoxyphenyl-N-((5-(naphthalen-1-yl)pyridin-2-yl)methylene)aniline, NaphylPy-Methylene-Adam-Amine = N-((5-(naphthalen-1-yl)pyridin-2-yl)methylene)adamantan-1-amine, Dipp-NaphylPyridyl-Meth-Aniline = 2,6-diisopropylphenyl-N-((5-(naphthalen-1-yl)pyridin-2-yl)methylene)aniline, POP = bis[2-diphenylphosphino]-phenyl)ether) have been prepared and investigated. The different groups such as methoxyphenyl, adamantyl and diisopropylphenyl were functionalized onto the azomethine unit of the Schiff base ligands to tune the photophysical behaviors of the resulting Schiff base Cu(I) complexes. All the complexes exhibit the lowest energy metal-to-ligand charge transfer (MLCT) characters in the visible region with higher molar extinction coefficients on the order of 104 M−1 cm−1, making them much attractive as photosensitizers in optoelectronic and light-harvesting applications. Blue-green emissions in the region of 479–513 nm with photoluminescence quantum yields (PLQY) of 0.8–1.2 % can be observed in CH 2 Cl 2 solution. Additionally, the photophysical properties are also investigated theoretically using density functional theory (DFT) and time dependent DFT. [ABSTRACT FROM AUTHOR]

• Three-coordinate copper(I) complexes bearing POP and monodentate substituted-quinoline ligands were synthesized and characterized. • The electron-donating/withdrawing groups including methoxyphenyl and trifluoromethylphenyl groups were inserted into the complexes. • Cu(I) complexes exhibited yellow-green emissions at 542-558 nm with longer excited-state lifetimes of 179–487 µs. • The photophysical properties were explained by DFT and TDDFT calculations. The three-coordinate Cu(I) complexes [Cu(POP)(X)]PF 6 , X = quinoline (P1), 2-(4-methoxyphenyl)quinoline (P2), 2-(4-(trifluoromethyl)phenyl)quinoline (P3), POP = bis[(2-diphenylphosphino)phenyl] ether were synthesized and characterized. The photophysical properties of these Cu(I) complexes were tuned by the addition of organic groups including methoxyphenyl and trifluoromethylphenyl groups into the quinoline ligand. The resulting complexes exhibit the metal-to-ligand charge transfer (MLCT) band in the lower energy. The emissions for all the complexes in solid state are in the range of 542–558 nm with higher quantum yields of 11.4–14.2% and long-lived excited lifetimes of 179–481 µs at room temperature. The photophysical properties were further explained by DFT and TDDFT methods. [Display omitted] [ABSTRACT FROM AUTHOR]

A series of copper(I) complexes bearing benzothiazole-imidazolylidene-type N -heterocyclic carbene (NHC) ligands are reported. All the complexes emit bright yellow-green light (λ em = 543–551 nm) with higher emission quantum yields of 24.9–44.1% and excited state lifetimes on the microsecond scale (t = 13.7–32.7 μs) in PMMA films. [Display omitted] The synthesis and photophysical investigation of a series of copper(I) complexes bearing benzothiazole-imidazolylidene-type N -heterocyclic carbene (NHC) ligands are reported. Their photophysical properties are tuned by adjusting the different substituens at 6-position of the benzothiazole ring. C1 and C2 exhibit the lowest-lying metal-to-ligand charge transfer (MLCT) absorption bands at 325–400 nm, while the MLCT band of C3 is almost unresolved owing to the blue shift of this band. Upon excitation with UV light all the complexes emit bright yellow-green light (λ em = 543–551 nm) with higher emission quantum yields of 24.9–44.1% and excited state lifetimes on the microsecond scale (τ = 13.7–32.7 μs) in PMMA films. Additionally, the electronic properties, absorption and emission profiles of these complexes were further explored using DFT/TDDFT methods. [ABSTRACT FROM AUTHOR]

• Schiff base copper (I) complexes bearing the bulky adamantyl moiety were synthesized and characterized. • The electron-donating/withdrawing groups including –OCH 3 and –CF 3 were inserted into the complexes. • Cu(I) omplexes exhibited organe-red emissions at 611–619 nm with shorter excited-state lifetimes of 5.55–7.53 μs. • The origin of the emission is attributed the 3MLCT/3LLCT/3π-π* state supported by the TDDFT calculations. Herein, the three novel copper (I) complexes bearing Schiff base ligands of the types [Cu(Phen-PyMethylene-Adam-Amine)(POP)]PF6 (P1), [Cu(Methoxyl-Phen-PyMethylene-Adam-Amine)(POP)]PF6 (P2), and [Cu(TriflMethyl-Phen-PyMethylene-Adam-Amine)(POP)]PF6 (P3) (Phen-PyMethylene-Adam-Amine = ((5-phenylpyridin-2-yl)methylene)adamantan-1-amie, Methoxyl-Phen-PyMethylene-Adam-Amine = ((5-(4-methoxyphenyl)pyridin-2-yl)methylene)adamantan-1-amine, TriflMethyl-Phen-PyMethylene-Adam-Amine = ((5-(4-(trifluoromethyl)phenyl)pyridin-2-yl)methylene)adamantan-1-amine, POP=bis[2- diphenylphosphino ]-phenyl)ether) have been prepared and investigated. Incorporation of the bulky adamantyl group into the complexes can enhance the stability of the complexes. The different electron-donating/withdrawing groups such as –H, –OCH 3 , and –CF 3 substituents were functionalized onto the pyridine ring part of Schiff base ligands to tune the emission behavior of the resulting Schiff base Cu(I) complexes. All complexes exhibit the lowest energy metal-to-ligand charge transfer (MLCT) characters in 400–450 nm region showing a slight blue-shift of the absorption wavelengths in the order P3 > P1 > P2. Organe-red emissions in the region of 611-619 nm with photoluminescence quantum yields (PLQY) of 1.0–1.3% can be observed in the solid state. Additionally, the photophysical properties are also investigated theoretically using density functional theory (DFT) and time dependent DFT. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Four-coordinate N-heterocyclic carbene (NHC) Cu(I) complexes with various substituents are synthesized and characterized. • The photophysical properties of the corresponding complexes is studied. • Complexes exbihit bright photoluminescence with orange-red color. • DFT and TDDFT calculations were employed to rationalize the photophysical properties. Herein, three four-coordinate N-hetercycle carbene (NHC) copper (I) complexes of the types [Cu(BenDimBenIm-CHOPy)(POP)]PF 6 (P1), [Cu(BenDimBenIm-CNPy)(POP)]PF 6 (P2), and [Cu(DimbenDimBenIm-CNPy)(POP)]PF 6 (P3) (BenDimBenIm-CHOPy = 3-benzyl-1-(5-formyl -pyridin-2-yl)-1 H -5,6-dimethylbenzimidazolylidene, BenDimBenIm-CNPy = 3-benzyl-1-(5-cyano -pyridin-2-yl)-1 H -5,6-dimethylbenzimidazolylidene, DimbenDimBenIm-CNPy = 3-(3,5-dimethylbenzyl-1-(5-cyano-pyridin-2-yl)-1 H -5,6-dimethylbenzimidazolylidene, POP = bis[2-diphenylphosphino]-phenyl)ether) have been prepared and investigated. All complexes exhibit the lowest energy metal-to-ligand charge transfer (MLCT) characters in 320–360 nm region showing a slight blue-shift of the absorption maxima in the order P1 > P2 > P3. The emissive wavelength can be fine-tuned to cover the orange-red spectral range of 615−638 nm with higher photoluminescence quantum yields (PLQY) of 17.6–40.3 %. Additionally, the photophysical properties are also investigated theoretically using density functional theory (DFT) and time dependent DFT. [ABSTRACT FROM AUTHOR]

• Different adsorption height of Li atoms will affect the final structure on graphene. • Li atoms can form nanoclusters on graphene if the adsorption height is over 4 Å. • Cl atoms can affect the structure of Li nanoclusters adsorbed on graphene. Lithium (Li) atoms tend to form nanoclusters when they are adsorbed on a graphene surface, hampering the potential use of Li to modify graphene. The adsorption of chlorine (Cl) atoms can improve the charge-collecting ability of graphene. In this work, the effects of Cl adatoms on small Li nanoclusters adsorbed on opposing sides of a graphene surface are studied by first principles calculations of the adsorption energy, charge transfer, adsorption distance, charge density difference, total density of states (TDOS), and partial density of states (PDOS). The results show that the geometry and electronic structure of Li nanoclusters changed in the presence of Cl and that the interaction between Li adatoms and graphene is significantly enhanced. [ABSTRACT FROM AUTHOR]