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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]

[Display omitted] • Dinuclear N-heterocyclic carbene (NHC) Cu(I) complexes bearing the mixed bis-NHC and POP ligands are synthesized and characterized. • Complexes show intense yellow-green emission in 531–571 nm region originated from the delayed fluorescence. • The photophysical properties were rationalized by DFT and TDDFT calculations. • Green and yellow light-emitting diodes and anti-counterfeiting applications were fabricated successfully. Here, a series of dinuclear N-heterocyclic carbene (NHC) copper(I) complexes having 3,3′-(1,4-phenylenebis(methylene))bis(1-(pyridin-2-yl)-1H-imidazolylidene as bis-NHC ligand and bis[(2-diphenylphosphino)phenyl]ether (POP) as auxiliary ligand have been successfully prepared, and their photophysical properites were investigaged experimentally and theocitcally. The resulting complexes all exhibited intense green to yellow emission that originated from the thermally activated delayed fluorescence (TADF) with a high photoluminescence quantum yield of up to 0.67 and longer excited-state lifetimes on the microsecond time scale in the solid state. Green and yellow light-emitting diode (LED) devices based on Cu(I) complexes have successfully achieved good color rendering indices. Moreover, the anti-counterfeiting patterns and QR codes made of Cu(I) complexes have been applied to clothing, banknotes, books and glass plates with excellent anti-counterfeiting effects. [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]

Abstract Three novel dopant-free hole-transporting materials (HTMs) based on phthalocyanine core containing (4-methyl formate) phenoxy or (4-butyl formate) phenoxy as the peripheral groups with cupper or zinc as the core metals (CuPcNO 2 -OMFPh, CuPcNO 2 -OBFPh, ZnPcNO 2 -OBFPh) were designed and synthesized. All of the phthalocyanine complexes show excellent thermal stabilities, appropriate energy levels and suitable hole mobilities. The potential of three HTMs were tested in perovskite solar cells (PSCs) and ZnPcNO 2 -OBFPh based PSC obtained power conversion efficiency (PCE) of 15.74% under 100 mA cm−2 standard AM 1.5G solar illumination. Most important of all, PSC based on ZnPcNO 2 -OBFPh shows better stability than that of the other two phthalocyanines and Spiro-OMeTAD under continuous light irradiation at 60 °C and maximum power point tracking in ambient air without encapsulation after 500 h. The results show that the introduction of appropriate peripheral groups and core metals can improve the performance and stability of PSCs dramatically, which provides an alternative way to develop HTMs for efficient and stable PSCs. Graphical abstract Image 1 Highlights • Novel asymmetric metallophthalocyanines (CuPcNO 2 -OMFPh, CuPcNO 2 -OBFPh and ZnPcNO 2 -OBFPh) were synthesized. • They were applied in perovskite solar cells as hole transporting material. • The cell devices based on ZnPcNO 2 -OBFPh show excellent stability under continuous light irradiation. • The power conversion efficiency of the device based on dopant-free ZnPcNO 2 -OBFPh is up to 15.74%. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Copper (I) complexes functionalized by organic chromophores are synthesized and characterized. • Both the enhanced light absorption abilities and the long-lived excited state lifetimes are achieved. • The nature of the emitting state can be tuned by altering the energy levels of the ligands. • DFT and TDDFT methods were employed to explain the experimental results. Abstract A series of Cu(I) pyridyl-imidazole (PyIm) complexes with different aryl groups (Ar = naphthalene (P2), phenanthrene (P3), and anthracene (P4)) attached on the pyridyl ring are synthesized and characterized. The influence of these organic chromophore groups on the photophysical properties of the resulting complexes is investigated. Complexes P2 – P4 show stronger light harvesting efficiencies in the visible region compared with the parent complex P1. The emitting state of complex P1 originates from the 3MLCT state with some 3LLCT character, while complexes P2 and P3 predominantly exhibit the 3LLCT character. For complex P4 , the triplet emitting state is dominated by the 3(π → π) state localized on the anthryl moiety, together with a lesser contribution form the 3LLCT state. These changes in the photophysical properties were rationalized by DFT and TDDFT methods. [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]

Two CuI complexes, [Cu(imPhen)(POP)]PF6 ( 1, imPhen = 1 H-imidazo[4,5- f][1,10]phenanthroline, POP = bis[2-diphenylphosphino]phenyl ether) and [Cu(Flu-imPhen)(POP)]PF6 { 2, Flu-imPhen = 2-(9 H-fluoren-2-yl)-1 H-imidazo[4,5- f][1,10]phenanthroline} were synthesized and characterized. a weak metal-to-ligand charge-transfer (MLCT) absorption band at λ = 401 nm with a relatively low molar extinction coefficient ( ε = 3170 m-1 cm-1) was observed for 1. In contrast, 2 displayed a higher MLCT absorption band at λ = 405 nm ( ε = 5400 m-1 cm-1) owing to the incorporation of a fluorene group to imPhen ring. Complexes 1 and 2 exhibited similar emission wavelengths and quantum yields ( λem = 564 nm, ϕ = 11.2 % for 1 and λem = 568 nm, ϕ = 9.0 % for 2); however, the excited-state lifetime of 2 ( τ = 51.2 µs) was almost four times longer than that of 1 ( τ = 13.8 µs). The prolonged luminescence lifetime of 2 was rationalized by the reversible energy transfer between the 3MLCT state of the Cu atom and the 3π→π* state of fluorene moiety. To the best of our knowledge, this is the first use of a fluorene group as a triplet energy reservoir to extend the excited-state lifetime of an emissive 3MLCT state of a CuI complex. [ABSTRACT FROM AUTHOR]

• Four-coordinate N-heterocyclic carbene (NHC) Cu(I) complexes with thiazole/benzoxazole moiety are synthesized and characterized. • The photophysical properties of the resulting complexes is investigated. • Complexes show blue-green emission in 517–551 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 with imidazolylidene and POP ligands, [Cu(BenzThiazolyl-Im)(POP)]PF 6 (P1), [Cu(BenzThiazolyl-BenIm)(POP)]PF 6 (P2), [Cu(BenzBenzoxazolyl-Im)(POP)]PF 6 (P3), and [Cu(BenzBenzoxazolyl-BenIm)(POP)]PF 6 (P4), (BenzThiazolyl-Im=3-benzyl-1-(thiazol-2-yl)-1 H -imidazolylidene, BenzThiazolyl-BenIm=3-benzyl-1-(thiazol-2-yl)-1 H -Benzoimidazolylidene BenzBenzoxazolyl-Im=3-benzyl-1-(benzoxazol-2-yl)-1 H -imidazolylidene, BenzBenzoxazolyl-BenIm=3-benzyl-1-(benzocazol-2-yl)-1 H -imidazolylidene, POP=bis[2-diphenylphosphino]-phenyl)ether). Thiazole/benzoxazole moiety were functionalized onto imidazolylidene ligand to tune the photophysical properties of the corresponding complexes. P1 and P2 exhibit the metal-to-ligand charge transfer (MLCT) absorption band with the onset at 406–412 nm, while P3 and P4 have similar MLCT band with the onset at 380–389 nm. The emission wavelengths of all NHC Cu(I) complexes can be fine-tuned to cover the spectral range of 517–551 nm with the phosphorescent origin in PMMA films. P2 show the highest photoluminescence efficiency of 40.9% with the red-shifted emission wavelength at 551 nm, whereas P4 has the lowest photoluminescence efficiency of 1.80% with the blue-shifted emission wavelength at 517 nm. Density functional theory (DFT) and time dependent density functional theory (TDDFT) calculations were employed to rationalize the differences for photophysical properties of the NHC Cu(I) complexes. [Display omitted] [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-type copper(I) complexes were synthesized and characterized. • Triphenylamine group was employed to construct copper(I) complexes with high light absorption abilities. • The photophysical properties of complexes including phenyl, naphthyl and adamantanyl groups were investigated.. • DFT/TDDFT methods were employed to rationalize the photophysical properties. The three Schiff base-type Cu(I) complexes [Cu(POP)(N^N)]PF 6 , N^ N = N ,N-diphenyl-4-(6-((phenylimino)methyl)pyridin-3-yl)aniline (P1), N-((5-(4-(diphenylamino)phenyl)pyridin-2-yl)methylene)naphthalen-2-amine (P2), N-((5-(4-(diphenylamino)phenyl)pyridin-2-yl)methylene)adamantan-1-amine (P3), were prepared and characterized. The photophysical properties of these Cu(I) complexes is tuned by the addition of different substituents such as phenyl, naphthyl and adamantanyl groups into the backbone of Schiff base ligand. The resulting complexes exhibit high absorption ability in the visible region with molar extinction coefficients of up to 3 7400 M−1 cm−1. The emissions in CH 2 Cl 2 solution are in the range of 551–552 nm with lower quantum yields of 1.1–2.0% and short-lived excited lifetimes of 2.78–3.09 ns for all the complexes at room temperature. The photophysical properties were further explained by DFT and TDDFT methods. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Cu(I) complexes with polyaromatic substituents are synthesized and characterized. • The photophysical properties of the corresponding complexes is studied. • Extended π system has important influence on the light absorption abilities. • DFT/TDDFT methods were employed to understand the photophysical properties. The three Cu(I) complexes [Cu(POP)(N^N)]PF 6 , N^N = 2-(1 H -imidazol-2-yl)-5-(naphthalen-2-ylethynyl)pyridine (P1), 2-(1 H -imidazol-2-yl)-5-(phenanthren-9-ylethynyl)pyridine (P2), 2-(5-(naphthalen-2-ylethynyl)pyridin-2-yl)-1 H -phenanthro[9,10- d ]imidazole (P3), were prepared and characterized. The photophysical properties of these Cu(I) complexes is tuned by extending π- system of the N^N ligand through the addition of polyaromatic groups such as naphthalene and phenanthrene into the pyridine ring part of the diimine ligands via an acetylide linker or phenanthrene-fused imidazole ring. The resulting complexes exhibit higher absorption ability in the visible region. The emissions are in the range of 582–601 nm with quantum yields of 2.30–7.70% and the excited lifetimes of 77.4–115.8 μs for all complexes at room temperature. The photophysical properties were further explained by DFT and TDDFT methods. [ABSTRACT FROM AUTHOR]

A series of six N -heterocyclic carbene (NHC) copper(I) complexes bearing benzimidazolylidene-type carbene ligands with different substituents are reported. All complexes emit bright yellow-green light (λ em = 540–573 nm) with higher photoluminescence quantum yields (PLQY) of 21.1–55.6 % and excited state lifetimes on the microsecond scale (τ = 30.6–62.1 μs) in PMMA films. [Display omitted] The synthesis and photophysical investigation of a series of six copper(I) complexes bearing benzimidazolylidene–type N–heterocyclic carbene (NHC) ligands with different groups are reported. Their photophysical properties can be tuned by adjusting the groups at the R 1 /R 2 positions of the pyridine ring. The lowest-lying metal–to–ligand (MLCT) absorption bands at 325–437 nm can be observed for all the complexes. Upon excitation with UV light all the complexes emit bright yellow-green light (λ em = 540–573 nm) with higher emission quantum yields of 21.1–55.6% and excited state lifetimes on the microsecond scale (τ = 30.6–62.1 μs) in PMMA films. The substituents (R 2 = COCH 3 , F, Br, CH 3 , or OCH 3) on R 2 –position of the pyridine ring were shown to have effects on the emission wavelengths of these complexes, while the introduction of R 1 substituents (R 1 = CH 3) shows negligible effects on the emission wavelength but allow the enhancement of photoluminescence quantum yield (Φ) of the complexes. Additionally, the electronic properties, absorption and emission profiles of these complexes were further explored using DFT/TDDFT methods. [ABSTRACT FROM AUTHOR]

• Copper (I) complexes were functionalized with various electron-donating groups. • The enhanced light absorption abilities were achieved vis an acetylide linker. • Complexes have the emission wavelengths of 579–590 nm and quantum yields of 8.40–15.1%. • The nature of the emitting state was discussed using the theoretical calculations. The three Cu(I) complexes [Cu(POP)(N^N)]PF 6 , N^N = 2-(1 H -imidazol-2-yl)-5-(p -tolylethynyl)pyridine (P1), 2-(1 H -imidazol-2-yl)-5-((4-methoxyphenyl)ethynyl)pyridine (P2), 4-((6-(1 H -imidazol-2-yl)pyridin-3-yl)ethynyl)- N , N -diphenylaniline (P3), were prepared and characterized. The different electron-donating groups such as methylphenyl, methoxyphenyl, and diphenylamine substituents were functionalized onto the pyridine ring part of the diimine ligands through an acetylide linker to enhance the light-absorption abilities, giving the larger light-absorption ability and red-shifted absorption bands for the investigated Cu(I) complexes. Yellow emissions in the range of 579–590 nm with quantum yields of 8.40–15.1% can be observed for all complexes at room temperature. The photophysical properties were further explained by DFT and TDDFT methods. [ABSTRACT FROM AUTHOR]