Abstract New isostructural lanthanide cymantrenecarboxylates [Ln2(μ-О,η2-OOCCym)2(μ2-OOCCym)2(η2-ООССym)2(py)4]·2py, where Ln = Pr (1), Sm (2), Eu (3), Gd (4) and Cym = (η5-C5H4)Mn(CO)3, were synthesized and characterized by X-ray diffraction. The crystals of 1–4 are built of discrete binuclear molecules; the Ln atoms are nine-coordinate. The phases produced by thermal elimination of pyridine from complexes 3 and 4 are identical to the phases formed by elimination of THF from the THF-containing cymantrenecarboxylates prepared earlier. The magnetic properties of complex 4 indicate an enhancement of antiferromagnetic interactions between Gd3+ ions due to the substitution of THF for pyridine; in the product of ligand elimination from 4, ferromagnetic interactions were found. It was shown that the lanthanide cymantrenecarboxylates are virtually nonvolatile. The thermal decomposition of the complexes was studied by differential scanning calorimetry (DSC) and thermogravimetry (TGA). Thermolysis of 1–4 in air affords mixtures of LnMn2O5 and Mn2O3. For the earlier prepared complex [Nd2(μ2-OOCCym)4(OOCCym)2(THF)4] (5), standard thermodynamic functions were calculated from adiabatic calorimetry data. Cymantrenecarboxylate ligands appreciably suppress Eu3+ luminescence and determine the spectral and the fluorescent properties of the lanthanide cymantrenecarboxylates.