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• 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]

• 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]

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]

[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]