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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] • Four-coordinate N-heterocyclic carbene (NHC) Cu(I) complexes with nonconjugated NHC ligand are synthesized and characterized. • The photophysical properties of the corresponding complexes is studied. • Complexes show deep blue emission in 452–466 nm region. • DFT and TDDFT calculations were employed to rationalize the photophysical properties. In the present study, a series of the four-coordinate N-hetercycle carbene (NHC) copper (I) complexes [Cu(MethyIm-Meth-benzTriazole)(POP)]PF 6 (P1), [Cu(BenzyIm-Meth-benzTriazole)(POP)]PF 6 (P2), and [Cu(BenzyBenzoIm-Meth-benzTriazole)(Xantphos)]PF 6 (P3), MethyIm-Meth-benzTriazole = 1-((1-benzyl-1 H -1,2,3-triazol-4-yl)methyl)-3-methyl-1 H -imidazolylidene, BenzyIm-Meth-benzTriazole = 1-((1-benzyl-1 H- 1,2,3-triazol-4-yl)methyl)-3-phenyl-1 H -imidazolylidene, BenzyBenIm-Meth-benzTriazole = 3-benzyl-1-((1-benzyl-1 H -1,2,3-triazol-4-yl)methyl)-1 H -benzo[d]imidazolylidene, POP = bis[(2-diphenylphosphino)phenyl]ether, have been synthesized and characterized. The molecular structure of P2 has been established by single-crystal X-ray diffraction study. The addition of the methylene spacer into the NHC ligand effectively breaks the π-conjugation of the ligand, resulting in a larger HOMO-LUMO energy gap. In the solid state, P1 – P3 exhibit deep blue emission in the range of 452–466 nm with the excited-state lifetimes (τ) of 14.9–16.2 μs and the emission quantum yields (Φ) of 8.50–11.9 % at room temperature. Additionally, the photophysical properties are explained by using density functional theory (DFT) and time dependent DFT. [ABSTRACT FROM AUTHOR]

In the present study, a series of the four-coordinate N-hetercycle carbene (NHC) copper (I) complexes [Cu(Ph-Im-cyPy)(Xantphos)]PF 6 (P1), [Cu(DimBenPh-Im-cyPy)(Xantphos)]PF 6 (P2), and [Cu(BenDimBenIm-CNPy)(Xantphos)]PF 6 (P3), Ph-Im-cyPy=3-benzyl-1-(4-cyano-pyridin-2-yl)-1 H -imidazolylidene, DimBenPh-Im-cyPy=3-(3,5-dimethylbenzyl-1-(4-cyano-pyridin-2-yl)-1 H -imidazolylidene, BenDimBenIm-CNPy=3-benzyl-1-(4-cyano-pyridin-2-yl)-1 H -5,6-dimethylbenzimidazolylidene, Xantphos=9,9-dimethyl-4,5-bis(diphenylphosphino)-9 H -xanthene, have been synthesized and characterized. The molecular structures of P1 – P3 have been established by single-crystal X-ray diffraction study. In the solid state, P1 – P3 exhibit orange-red emission in the range of 621–643 nm with shorter excited-state lifetimes (τ) of 5.73–6.42 μs and the emission quantum yields (Φ) of 1.0–3.9 % at room temperature. Additionally, the photophysical properties are explained by using density functional theory (DFT) and time dependent DFT. [Display omitted] [ABSTRACT FROM AUTHOR]