Tunable Nonlinear Optical Property and Photocatalytic Activity on Luminescent Chiral Lanthanide Chains

Five chiral (P2(1)) isostructural lanthanide coordination complexes Ln(pic)(3) [pic=picolinic acid, Ln=La (1), Gd (2), Nd (3), Sm (4) and Eu (5)] have been hydrothermally generated, featuring one dimensional right-handed 2(1) helical chains constructed from LnN(3)O(6) of square antiprism geometry and N,O-chelated pic-groups, in which 3, 4 and 5 have been reported, but we explore undiscovered properties of their own systematically. In special, 1 undergoes an abnormal transformation of symmetry as the temperature cooling to 100 K. TG-DSC studies demonstrated that all isologues have good thermal stability with the decomposition temperature up to 400 degrees C. Then, UV-Vis-NIR transmission spectroscopy measurements indicated that they possess a short-wavelength absorption edge onset at 377 nm, corresponding to the optical band gap of 3.29 eV. Meanwhile, powder second harmonic generation (SHG) measurements revealed that the SHG intensity of 1, 2, 4 and 5 may be about 1.2, 2.0, 0.9 and 0.75 times that of KH2PO4, respectively. Interestingly, 1 and 3 exhibit efficient photocatalytic degradation for MB (Methylene Blue) upon UV-light irradiation. Moreover, both 1 and 2 show strong blue luminescence.