Electronic Factors Affecting Second-Order NLO Properties: Case Study of Four Different Push-Pull Bis-Dithiolene Nickel Complexes
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- 作者：Simona Curreli ; Paola Deplano ; Christophe Faulmann ; Andrea Ienco ; Carlo Mealli ; Maria Laura Mercuri ; Luca Pilia ; Gloria Pintus ; Angela Serpe ; and Emanuele F. Trogu
- 刊名：Inorganic Chemistry
- 出版年：2004
- 出版时间：August 9, 2004
- 年：2004
- 卷：43
- 期：16
- 页码：5069 - 5079
- 全文大小：316K
- 年卷期：v.43,no.16(August 9, 2004)
- ISSN：1520-510X
文摘
The paper presents a detailed experimental and theoretical study of the four mixed nickel-bisdithiolene complexes[Ni(Pri2pipdt)(dmit)] (1b, Pri2pipdt = 1,4-diisopropyl-piperazine-3,2-dithione; dmit = 1,3-dithiolo-2-tione-4,5-dithiolato),[Ni(R2pipdt)(mnt)] (2b' ', R = 2-ethylhexyl; mnt = maleonitriledithiolato), [Ni(Pri2timdt)(dmit)] (3b, Pri2timdt = 1,3-diisopropyl-imidazoline-2,4,5-trithione), and [Ni(Pri2timdt)(mnt)] (4b), and their models. All the complexes, with common(C2S2)Ni(C2S2) core and two different terminal groups, are uncharged and square-planar coordinated. Previousmeasurements of the first molecular hyperpolarizability indicated that some of the species are potential NLOchromophores due to the 
-delocalized character of two frontier levels (HOMO and LUMO) which is asymmetricallyperturbed by the combination of one push (R2pipdt, R2timdt) with one pull ligand (dmit and mnt). The X-ray structureof complex 1b is presented and its geometry is compared with those available in the literature for the four typesof complexes under study. The results of electrochemical and spectroscopic measurements (oxidation and reductionpotentials, IR, dipole moment, molecular absorptivities, etc.) indicate rather different responses between the pairsof complexes 1-2 and 3-4. Hence, DFT calculations on the model compounds 1a-4a, where hydrogen atomsreplace the alkyl groups of R2pipdt and R2timdt, have been carried out to correlate geometries and electronicstructures. Moreover, the first molecular hyperpolarizabilities have been calculated and their components havebeen analyzed with the simplest two-level approximation. The derived picture highlights the different roles of thetwo push and pull ligands, but also the peculiar perturbation of the -electron density induced by the terminal CS3grouping of the ligand dmit.
-delocalized character of two frontier levels (HOMO and LUMO) which is asymmetricallyperturbed by the combination of one push (R2pipdt, R2timdt) with one pull ligand (dmit and mnt). The X-ray structureof complex 1b is presented and its geometry is compared with those available in the literature for the four typesof complexes under study. The results of electrochemical and spectroscopic measurements (oxidation and reductionpotentials, IR, dipole moment, molecular absorptivities, etc.) indicate rather different responses between the pairsof complexes 1-2 and 3-4. Hence, DFT calculations on the model compounds 1a-4a, where hydrogen atomsreplace the alkyl groups of R2pipdt and R2timdt, have been carried out to correlate geometries and electronicstructures. Moreover, the first molecular hyperpolarizabilities have been calculated and their components havebeen analyzed with the simplest two-level approximation. The derived picture highlights the different roles of thetwo push and pull ligands, but also the peculiar perturbation of the -electron density induced by the terminal CS3grouping of the ligand dmit.