DFT studies for three Cu(II) coordination polymers: Geometrical and electronic structures, g factors and UV–visible spectra.

This work presents a systematic density functional theory (DFT) study for geometrical and electronic structures, g factors and UV–vis spectra of three Cu(II) coordination polymers (CPs) [Cu(XL)(NO 3 ) 2 ] n (1), {[Cu(XL)(4,4′-bpy)(NO 3 ) 2 ]∙CH 3 CN} n (2) and {[Cu(XL) 3 ](NO 3 ) 2 ·3.5H 2 O} n (3) based on the ligand N,N′-bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxdiimide bi(1,2,4-triazole) (XL) with the linker triazole coordinated with copper to construct the CPs. For three CPs with distinct ligands, the optimized molecular structures with PBE0 hybrid functional and the 6-311g basis set agree well with the corresponding XRD data. Meanwhile, the electronic properties are also analyzed for all the systems. The calculated g factors are found sensitive to the (Hartree-Fock) HF character due to the significant hybridization between copper and ligand orbitals. The calculated UV–visible spectra reveal that the main electronic transitions for CP 1 contain d-d and CT transitions, while those for CPs 2 and 3 largely belong to CT ones. The present CPs seem difficult to adsorb small molecules, e.g., CP 1 with H 2 O and NO 2 exhibit unfavorable adsorption and deformation structures near the Cu 2+ site. [ABSTRACT FROM AUTHOR]