The UV‐Vis absorption spectra of self‐assembly Cu (II) complexes for bis(pyrrol‐2‐ylmethyleneamine) linked by alkyl(CH2)n(n = 2,3,4,6) spacers were recorded. The ground‐state geometries and electronic structures were investigated by density functional theory employing generalized‐gradient approximation Perdew‐Burke‐Ernzerhof (PBE) and hybrid B3LYP (20% Ex,HF)and PBE0 (25% Ex,HF) functional, in conjugation with four basis set combinations.[BS1:6‐31G(d); BS2:Lanl2dz for Cu and 6‐31G(d) for C,H,N; BS3:6‐31+G(d); BS4:6‐311+G(d,p) for C,H,N and Lanl2dz for Cu]. Compared the optimized geometries with XRD structures, it was found that the choice of methods appeared to have a more pronounced effect on structure than that of the basis set. PBE0/BS4 optimized geometries provide the best agreement with XRD experimental results and the mean absolute errors for bond length is 0.018 Å and for bond angle is 2.1°. Transition excited states of complexes 1–4 in the gas phase and in CH2ClCH2Cl solution have been studied by the time‐dependent density functional theory in conjugated with the Polarizable Continuum Model. Pure PBE and hybrid B3LYP, PBE0 functionals, as well as BS1, BS2, and BS5 [6‐311++G (d,p)] were selected. Calculations indicate that PBE functional provides more accurate descriptions on main UV‐vis absorptions than B3LYP and PBE0 functionals. The strongest absorption bands located at 338–356 nm are due to intraligand charge transfer (ILCT) transitions, a mixed‐character ILCT + metal‐ligand charge transfer (MLCT) absorptions are calculated at 280–291 nm, the shoulder bands located at 250–257 nm mainly arise from MLCT or ligand‐metal charge transfer transitions. Alkyl spacer does not play a crucial role on the main electron transitions. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011