A DFT study on the structures and absorption spectra of the M-1-nitroso-2-naphthol complexes (M = Ni, Cu, Cr, Cd, Pb)

Electronic structures and absorption spectra of the M-1-nitroso-2-naphthol complexes (M = Ni(II), Cu(II), Cr(II), Cd(II), Pb(II)) have been studied by using density functional theory (DFT) calculations at the B3LYP/Lanl2dz level of theory. The absorption spectra of these complexes are obtained by using TD-DFT method associated with the PCM model. Computed binding energies have shown that the binding strength is maximum for copper and minimum for chromium cations. The sequence of binding strengths of cations has been found as Cu > Ni > Cd > Pb > Cr. The NBO analyses have shown that Ni, Cu, Cr accept electrons to their 4s and 3d orbitals, while Cd gains electrons to its s and p orbitals and Pb gains electrons to its p orbital. According to the absorption spectra, the strongest absorptions of [M-NN-1]⁺ and [M-NN-2]⁺ complexes (M = Ni, Cu, Cr, Cd and Pb) are found at 443, 461, 524, 389, 464 nm and at 447, 444, 466, 393, 452 nm in water and at 459, 479, 523, 418, 493 nm and 464, 460, 493, 416, 469 nm in chloroform, respectively.