https://doi.org/10.1140/epjd/e2013-40531-5
Regular Article
Theoretical studies of ground and excited states in a series of Zn(II) complexes, derived from thiourea and thiosemicarbazide*
1
Institute of Environmental and Analytical Sciences, College of
Chemistry and Chemical Engineering, Henan University, Kaifeng,
Henan
475004, P.R.
China
2
Wuhan Center for Magnetic Resonance, State Key Laboratory of
Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and
Mathematics, Chinese Academy of Sciences, Wuhan
430071, P.R.
China
b
e-mail: chemwangl@henu.edu.cn
Received: 27 August 2013
Published online: 4 February 2014
Theoretical studies for a series of mono- and binuclear zinc (II) complexes Zn(CH3COO)2(H2L)2 [H2L = N-2-propenyl-N′-2-pyridinylthiourea] (A), Zn2(CH3COO)2(H3L-a)2 [H3L-a = 2-[(2-hydroxy phenyl)methylene]hydrazine-N-phenylcarbothioamide] (B), and Zn(H3L-b)2 [H3L-b = 2-[(2-hydroxy phenyl)methylene]hydrazine-N-(2-propenyl)carbothioamide] (C) have been performed on their structures and excited-state absorption spectra. The singlet ground-state geometries are fully optimised at three DFT levels, i.e., B3LYP, B3PW91, and M06. Different geometries, i.e., strongly distorted tetrahedral coordination environment in complex A, distorted square-pyramidal environment in complex B, and irregular octahedral mode in complex C are identified. Consequently, the spectroscopic properties are calculated by means of time-dependent density functional theory (TDDFT) with the Polarisable Continuum Model (PCM) based on the optimised gas-phase geometries. Three absorption peaks are identified for every complex, which are in good agreement with the experimental ones. For complex A, all three absorption peaks centered at 280.33 nm, 268.09 nm, and 250.87 nm, respectively, are ascribed to the (p,π) → π* transition with a mixed intraligand charge-transfer (ILCT)/ligand-ligand charge-transfer (LLCT) character. The composition of frontier orbitals involved in major absorption bands for the three complexes shows similarities, which results in the almost homologous transition attributions and characteristics. A remarkable bathochromic shift in the lowest-lying absorption band is observed for complexes B and C as compared with complex A, which is attributed to the decreased H (HOMO)-L (LUMO) energy gap (ΔE |HOMO-LUMO|) by the formation of conjugate metallocycles in complexes B and C.
Key words: Molecular Physics and Chemical Physics
Supplementary material in the form of one pdf file available from the Journal web page at http://dx.doi.org/10.1140/epjd/e2013-40531-5
© EDP Sciences, Società Italiana di Fisica and Springer-Verlag 2014
