Synthesis, Crystal Structure and Hirshfeld Surface Evaluations of Lanthanide (III) Coumarin-3-Carboxylate Coordination Polymers

The reactions of 2-oxo-2 H -1-benzopyran-3-carboxylic acid (common name: coumarin-3-carboxylic acid, 3-CCAH), in an ethanol/acetone solution, with the lanthanide chloride salts of europium (III), gadolinium (III), terbium (III) and dysprosium (III), dissolved in ethanol/water, in a 1:1 molar ratio yielded the respective isostructural coordination compounds with generic formulae {[Ln(3-CCA)Cl₂(H₂O)₃]·H₂O}ₙ. The anionic coumarin-3-carboxylate ligands are almost planar and act as chelates, forming six-membered metallarings, and bridges the metal centers into coordination polymers along the a -axis. The coordination environments are fulfilled by two chloride and three water molecules acting as ligands, building highly distorted eight vertices coordination polyhedra, which was defined as a triangular dodecahedron geometry of TDD-8 type. A water molecule is observed as crystal-solvate in each structure, and the respective coordination compounds are connected by intermolecular hydrogen interactions of the O—H … O and O—H … Cl types into three-dimensional networks. The complexes crystallize in the space group P -1, with Z = 2, and the cell parameters for the Eu 3+ -compound, 1 , are: a = 6.4287(3) Å, b = 7.0855(3) Å, c = 17.5738(8) Å, α = 82.529(1)°, β = 85.415(1)°, γ = 64.087(1)° and V = 713.66(6)Å 3 ; for the Gd 3+ -compound, 2 , are: a = 6.4119(3) Å, b = 7.0230(4) Å, c = 17.4946(8) Å, α = 82.501(3)°, β = 85.193(3)°, γ = 63.541(2)° and V = 698.95(6) Å 3 ; for the Tb 3+ -compound, 3 , are: a = 6.4006(2) Å, b = 7.0120(3) Å, c = 17.4874(7) Å, α = 82.527(2)°, β = 85.121(2)°, γ = 63.654(2)° and V = 697.03(5) Å 3 , and for the Dy 3+ -compound, 4 , are: a = 6.3891(4) Å, b = 7.0133(4) Å, c = 17.4794(11) Å, α = 82.556(4)°, β = 85.231(3)°, γ = 63.590(4)° and V = 695.29(8) Å 3 . The Hirshfeld analysis (HS) was performed for all complexes and the surfaces mapped over the d norm , shape-index, and curvedness properties. The Hirshfeld surface finger plots (HSFP) suggest that the major contributions for the crystal packing are the H···H, H···C/C···H, H···Cl/Cl···H and H···O/O···H intermolecular contacts in all cases. Simplified graphical representation of the 1-D coordination polymers along the a-axis comprised of Ln3 + -metal centers bridged by coumarin-3-carboxilate ligands. The polymers are related by inversion centers through hydrogen bonds, being one of O—H … Cl type drawn as dashed lines.