Phenothiazine metal-organic framework materials with excellent third-order nonlinear properties

The third-order nonlinear optical material with excellent performance is a molecule with a large π-conjugated structure for absorption structure and a high degree of delocalization. Nitrogen-sulfur derivatives have lone pairs of electrons in their N and S atoms, which makes them have a strong intramolecular charge transfer ability, which is conducive to the formation of donor-acceptor molecules. In this paper, phenothiazine is used as the matrix structure of the third-order nonlinear optical material, modified, and then metal coordination is performed to obtain [Zn(Py)₂Cl₂]_n and [Cd(Py)₂Cl₂]_n. Its structure is characterized by infrared spectroscopy, single crystal X-ray diffraction and powder X-ray diffraction. The morphology of the material was characterized by scanning electron microscopy. The photophysical properties, thermal properties and third-order nonlinear properties were tested, and the theoretical verification was carried out with the DFT calculation method, and the relationship between the structure and the third-order nonlinear properties was summarized. The experimental results show that phenothiazine has good electron donating ability, the two-photon absorption coefficient β is between 1.334–38.400 × 10⁻¹⁰ m/W, and the third-order nonlinear polarizability χ⁽³⁾ is between 2.752–79.247 × 10⁻¹¹ esu, The second-order hyperpolarizability γ of the ligand molecule is 5.213 × 10⁻³⁴ esu. The χ⁽³⁾ values of [Zn(Py)₂Cl₂]_n and [Cd(Py)₂Cl₂]_n are 4 orders of magnitude higher than ordinary α-quartz (χ⁽³⁾ = 2.6 × 10⁻¹⁴ esu).