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[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]

[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]

[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]