Synthesis, structural studies, theoretical calculations, and linear and nonlinear optical properties of terpyridyl lanthanide complexes: new evidence for the contribution of f electrons to the NLO activity.
ABSTRACT The synthesis and structural, photophysical, and second-order nonlinear optical (NLO) properties of a novel lanthanide terpyridyl-like complex family LLn(NO(3))(3) (Ln = La, Gd, Dy, Yb, and Y) are reported. The isostructural character of this series in solution and in the solid state has been established on the basis of X-ray diffraction analysis in the cases of yttrium and gadolinium complexes, theoretical optimization of geometry (DFT), and NMR spectroscopy. The absorption, emission, and solvatochromic properties of the free terpyridyl-like ligand L were thoroughly investigated, and the twist intramolecular charge transfer (TICT) character of the lowest energy transition was confirmed by theoretical calculation (TDDFT and CIS). The similar ionochromic effect of the different lanthanide ions was evidenced by the similar UV-visible spectra of the complete family of complexes. On the other hand, the quadratic hyperpolarizability coefficient beta, measured by the harmonic light scattering (HLS) technique, is clearly dependent on the nature of the metal, and a careful examination of the particular case of yttrium unambiguously confirms the contribution of metal f electrons to the NLO activity.
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ABSTRACT: A series of fifteen dipolar polymeric lanthanide complexes of trans-cinnamic acid, [Ln(C9H7O2)3]n, which crystallize in the non-centrosymmetric space groupsR3c and P21, have been synthesized and the crystal structures of 14 of these have been determined. From the crystallographic data, two different coordination scenarios for these complexes have been found: Type I, CN = 9, Ln = La, Ce, Nd, Sm, Eu, Gd and Tb, and Type II, CN = 7, Ln = Y, Dy, Ho, Er, Tm, Yb and Lu. The linear and nonlinear photophysical properties of these complexes have been studied using various laser excitation wavelengths. The low temperature photoluminescence spectrum shows a distortion from the C3 site symmetry of the Eu3+ complex. Strong second harmonic generation (SHG) has been observed for both Types I and II in the solid state. The normalized SHG intensities of the members of the entire series of lanthanide complexes have been compared and the solution state hyperpolarizabilities have also been measured for the study of the effects of 4f-electrons on nonlinear photophysical properties. These SHG parameters show maximum values near the center of the lanthanide series, as opposed to previously reported fairly linear or independent variations.Journal of Materials Chemistry 01/2010; 20(20). · 5.97 Impact Factor
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ABSTRACT: Aza[n]helicene phosphole derivatives have been prepared from aza[n]helicene diynes by the Fagan-Nugent route. Their photophysical properties (UV/Vis absorption and emission behavior) have been evaluated. Their behavior as P,N chelates towards coordination to Pd(II) and Cu(I) has been investigated: metal-bis(aza[n]helicene phosphole) assemblies are formed by a highly stereoselective coordination process, as demonstrated by X-ray crystallography. An azahelicene phosphole bearing an enantiopure helicene part has been obtained, which allows the preparation of enantiopure Pd(II) and Cu(I) complexes with original topologies and high molar rotation (MR) and circular dichroism (CD). The structure-property relationship established from the experimental data has been studied in detail by theoretical studies (TDDFT calculations of UV/Vis, CD, and MR). Aza[n]helicene phosphole derivatives show pi conjugation extended over the entire molecule, and its influence on the MR of azahelicene phosphole 5 c has been demonstrated. Finally, it has been shown that the nature of the metal (coordination geometry and electronic interaction) can have a great impact on the amplitude of the chiroptical properties in metal-bis(aza[n]helicene phosphole) assemblies.Chemistry 05/2010; 16(20):5976-6005. · 5.93 Impact Factor
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ABSTRACT: Herein, we provide some structural evidence of the complexation color-change of murexide solutions in presence of lanthanide, which has been used for decades in complexometric studies. For Ln=Sm to Lu and Y, the compounds crystallize as monomeric [Ln(Murex)3 ]⋅11 H2 O with an N3O6 tricapped square-antiprism environment, which are stable up to 250 °C. Single-ion magnet (SIM) behavior is then observed on the Yb(III) derivative in an original nine-coordinated environment. In-field slow relaxation (Δ=(15.6±1) K; τ0 =2.73×10(-6) s) is observed with a very narrow distribution of the relaxation time (αmax =0.09). Magnetic and photophysical properties can be correlated. On one hand the analysis of NIR emission spectrum permits to have access to crystal field parameters and to compare them with those extracted from dc measurements. On the other hand, magnetic measurements permit to identify the nature of the MJ states involved in the (2) F5/2 →(2) F7/2 luminescence spectrum. The gap between the low-lying states is in agreement with the energy barrier obtained from magnetic slow-relaxation measurement.Chemistry 01/2014; · 5.93 Impact Factor