Four orotate-based lanthanide coordination polymers with rhomboid [Ln4(μ3-OH)2]-based 1D chainlike structure exhibiting luminescence and large magnetocaloric effect.

Four co-edge rhomboid [Ln 4 (μ 3 -OH) 2 ]-based 1D chainlike LnCPs were synthesized based on orotic acid. The Gd-containing complex displays a large MCE of −Δ S m max = 37.11 J kg−1 K−1, and the Eu- and Tb-based polymers exhibit characteristic Ln(III) luminescence. [Display omitted] • Four isostructural 1D LnCPs with rhomboid [Ln 4 (μ 3 -OH) 2 ]-based chainlike structure were obtained hydrothermally. • The Gd(III)-containing polymer displays a large MCE with − Δ S m max value of 37.11 J kg−1 K−1. • The Eu- and Tb-based polymers exhibit characteristic Eu(III)/Tb(III) luminescence. Four isostructural lanthanide coordination polymers with orotic acid (H 3 OA) as building ligand, {[Ln(HOA)(μ 3 -OH)(H 2 O) 2 ]·H 2 O} n (Ln = Eu (1); Gd (2); Tb (3); Dy (4)), were synthesized under hydrothermal conditions. Single-crystal X-ray diffraction analyses demonstrate that complexes 1 – 4 have an one-dimensional (1D) chainlike structure consisting of rhomboid [Ln 4 (μ 3 -OH) 2 ] unit and HOA2- linker. Magnetic studies indicate that 2 displays a large magnetocaloric effect with magnetic entropy value of 37.11 J kg−1 K−1 at 2.0 K for Δ H = 7.0 T. This is a considerable value among the reported molecular magnetic coolants, and has a great application potential in the field of ultra-low temperature refrigeration. In addition, the solid-state photophysical properties of 1 and 3 exhibit obvious characteristic Eu(III) and Tb(III) photoluminescence emission in the visible region, suggesting that Eu- and Tb-based luminescence were sensitized effectively by the energy transfer from the ligand to the metal centers. [ABSTRACT FROM AUTHOR]