2020 Fiscal Year Annual Research Report
非線形光学特性および多色発光を示す多機能単分子磁石の構築
| Project/Area Number |
20J20245
|
|---|
| Research Institution | The University of Tokyo |
|---|
Principal Investigator |
KUMAR Kunal 東京大学, 理学系研究科, 特別研究員(DC1)
|
|---|
| Project Period (FY) |
2020-04-24 – 2023-03-31
|
| Keywords | Lanthanide / octacyanide / SecondHarmonicGeneration / MOLCAS / ExchangeParameter |
|---|
| Outline of Annual Research Achievements |
I prepared nine isostructural zigzag Ln(III)-W(V) (1-9, where Ln(III) = = Gd (1), Tb(2), Dy(3), Ho(4), Er(5), Tm(6), Yb(7), Lu(8) and Y(9)) chains . All these complexes crystallize in the non-centrosymmetric P21 space group. All materials show a second harmonic generation (SHG) non-linear phenomenon. Furthermore, the SH signals increase starting from Gd(III) to Dy(III) based assemblies, followed by the decrease for the complexes with later lanthanides. This studies on non-linear optical (NLO) activity for series of lanthanide molecular complexes have shown the changes in NLO behaviour due to variation in the number of f-electrons. In this work, we observe complex relations between observed SHG intensity and structural parameters of lanthanide ions for the polycrystalline samples. Additionally, compounds with unpaired electrons in valence f-orbitals exhibit relatively strong superexchange interaction between lanthanides(III) and tungsten(V). Fits of temperature dependencies of magnetic susceptibilities, supported by the crystal-field parameters for Ln(III) ions determined by the ab initio CASSCF calculations, resulted in obtaining magnetic coupling constants of -1 to -5 cm-1. Calculated exchange coupling constants are the largest for Gd(III), Dy(III), Tb(III) and Er(III) containing complexes among 1 - 7, as they are likely dominated by dipolar interactions. Moreover, magnetic susceptibilities are strongly temperature-dependent below 50 K, and weak interchain magnetic coupling has been also observed at very low temperatures.
|
| Current Status of Research Progress |
Current Status of Research Progress
1: Research has progressed more than it was originally planned.
Reason
I prepared nine isostructural zigzag Ln(III)-W(V) (1-9, where Ln(III) = = Gd (1), Tb(2), Dy(3), Ho(4), Er(5), Tm(6), Yb(7), Lu(8) and Y(9)) chains. All of these complexes crystallize in the non-centrosymmetric P21 space group and exhibit second harmonic generation (SHG) phenomenon. They also exhibit strong super-exchange coupling between Ln(III) and W(V) ions for paramagnetic lanthanide-containing complexes. Additionally, I have performed various synthesis to prepare precursors containing thiocyanide or selenocyanide (such as - K2[Au(SCN)2], K2[Pt(SCN)4], K4[Pt(SCN)6], K2[Pd(SCN)4], K4[Pd(SCN)6], K2[Au(SeCN)2], K2[Pt(SeCN)4], TBA3[Ln(NCS)7] etc.) by changing the synthetic conditions. I successfully prepared K2[Au(SCN)2] and K3[Ag(SCN)4], and used it for post synthetic modification with lanthanides (Ln(III)). I noticed with other precursors especially with [Ln(NCS)7]3- is that bleaching of thiocyanide ligands happen in the presence of other d-transition metal ions, suggesting that the coordination environment around metal center with SCN- is not stable. In this process, Yb(SCN)3(TPPO)3 (YbS) and Yb(SeCN)3(TPPO)3 (YbSe) have been crystallized showing diverse set of properties like non-linear activity, luminescence and magnetic behaviour. Moreover, Gaussian and OpenMOLCAS were utilized to calculate the molecular orbitals and energy levels to explain the UV-VIS and emission properties.
|
| Strategy for Future Research Activity |
I have already explored the right combination of solvents, organic ligands and metal salts to prepare the objective coordination polymers. Mainly, I will be using K2[Au(SCN)2] and K3[Ag(SCN)4] metal salt to mix with various lanthanide salts in ethanol or acetonitrile solvent. Meanwhile, I will be also looking for possibilities to use other metal thiocyanide salts with lanthanide ions. In this year of research, I will be trying to obtain chiral magneto luminescent complexes with bulkier or chiral organic ligands. The chiral analogues of the achiral precursors which were successfully used in the first year of research, or, use camphor based ligands to modify the coordination geometry.The physical properties of these compounds will be optimized by changing the ligands and central metal ions. Additionally, effect of external stimuli - such as temperature, excitation light, humidity etc. will be explored.
|
