Abstract
Push–pull terpyridine derivatives 3 were synthesized and characterized in order to study the variations produced in their optical and electronic properties by linking different (hetero)aromatic electron donor moieties at 4′-position of the electron deficient terpyridine moiety. The final donor-acceptor systems 3a-g were synthesized in fair to good yields by Kröhnke condensation of the precursor aldehydes 1, with 2-acetylpyridine 2. Hyper-Rayleigh scattering in dioxane solutions using a fundamental wavelength of 1064 nm was employed to evaluate their second-order nonlinear optical properties. Terpyridine derivative 3g functionalized with the 9-ethyl-9H-carbazolyl group exhibited the largest first hyperpolarizability (β = 610 × 10−30 esu, using the T convention) thus indicating its potential application as a second harmonic generation (SHG) chromophore. Terpyridine derivatives 3 were also used as ligands for the synthesis of novel [RuII(tpy)(NCS)3]– complexes, prepared in good yields by a two-step procedure involving the preparation of [RuIII(tpy)(Cl3)] as intermediates. RutheniumII complexes display a broad absorption in the visible range, accounting for their very dark color. Their redox behaviour is mainly characterized by the RuII-RuIII oxidation and by the ligand-centered reduction, whose potentials can be finely tuned by the electronic properties of the aromatic substituents on the terpyridine ligand. Hyper-Rayleigh scattering in methanol solutions using a fundamental wavelength of 1064 nm was also employed to evaluate their second order nonlinear optical properties.
Highlights
Push–pull terpyridine derivatives 3 were synthesized and characterized in order to study the variations produced in their optical and electronic properties by linking differentaromatic electron donor moieties at 4′position of the electron deficient terpyridine moiety
Terpyridine derivative 3g functionalized with the 9-ethyl-9Hcarbazolyl group exhibited the largest first hyperpolarizability (β = 610 × 10−30 esu, using the T convention) indicating its potential application as a second harmonic generation (SHG) chromophore
Terpyridine derivatives 3 were used as ligands for the synthesis of novel [RuII(tpy)(NCS)3]– complexes, prepared in good yields by a two-step procedure involving the preparation of [RuIII(tpy)(Cl3)] as intermediates
Summary
Push–pull terpyridine derivatives 3 were synthesized and characterized in order to study the variations produced in their optical and electronic properties by linking different (hetero)aromatic electron donor moieties at 4′position of the electron deficient terpyridine moiety. Another interesting matter is the possibility of differently functionalized terpyridine ligands being coordinated to the same metal ion [2] Due to their distinct photophysical, electrochemical, catalytic and magnetic properties, terpyridines and their complexes have been studied regarding a wide range of potential applications such as photovoltaics [3], light emitting electrochemical cells (LECs) [4], and nonlinear optics. Pharmaceutical applications are currently fast-growing fields of research, ranging from colorimetric metal determination to DNA binding agents and anti-tumour research [7] Terpyridines and their transition metal complexes has been employed for catalytic applications such as in asymmetric catalysis [8] in oxidation of alcohols [9], carbonylation of aromatic compounds [10], hydroformylation reactions [11] and as oxygen-binding molecules [12]. One of the most promising fields for new terpyridine compounds is their application in supramolecular chemistry [13]
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