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Solvothermal reactions of lanthanide (III) salts with 1,2-phenylenediacetic acid in N,N′-dimethylformamide (DMF) solvent lead to the formation of the metal complexes of the general formula Ln2(1,2-pda)3(DMF)2, where Ln(III) = Pr(1), Sm(2), Eu(3), Tb(4), Dy(5), and Er(6), 1,2-pda=[C6H4(CH2COO)2]2−. The compounds were characterized by elemental analysis, powder and single-crystal X-ray diffraction methods, thermal analysis methods (TG-DSC and TG-FTIR), infrared and luminescence spectroscopy. They exhibit structural similarity in the two groups (Pr, Sm, and Eu, Tb, Dy, and Er), which was reflected in their thermal behaviours and spectroscopic properties. Single-crystal X-ray diffraction studies reveal that Sm(2) and Eu(3) complexes form 2D coordination polymers with four crystallographically independent metal centers. Every second lanthanide ion is additionally coordinated by two DMF molecules. The 1,2-phenylenediacetate linker shows different denticity being: penta- and hexadentate while carboxylate groups exhibit bidentate-bridging, bidentate-chelating, and three-dentate bridging-chelating modes. The infrared spectra reflect divergence between these two groups of complexes. The complexes of lighter lanthanides contain in the structure coordinated DMF molecules, while in the structures of heavier complexes, DMF molecules appear in the inner and outer coordination sphere. Both carboxylate groups are deprotonated and engaged in the coordination of metal centers but in different ways in such groups of complexes. In the groups, the thermal decomposition of the isostructural complexes occurs similarly. Pyrolysis of complexes takes place with the formation of such gaseous products as DMF, carbon oxides, ortho-xylene, ethers, water, carboxylic acids, and esters. The complexes of Eu and Tb exhibit characteristic luminescence in the VIS region, while the erbium complex emits NIR wavelength.

Four isostructural lanthanide coordination polymers of the formula [Ln2(1,3-pda)3(H2O)]·H2O where Ln = Gd(1), Dy(2), Er(3), Lu(4) and 1,3-pda = 1,3-phenylenediacetate were hydrothermally synthesized and characterized by vibrational spectroscopy, thermal analysis, powder and single-crystal X-ray diffraction methods. All 1,3-phenylenediacetates act as μ4-linkers and connect the eight-coordinate lanthanide ions into the 3-D coordination networks. Carboxylate groups in the ligands molecules exhibit diverse conformations: both trans or trans and cis. Changes of Ln–O bond lengths among the investigated compounds point out to the lanthanide contraction. Infrared and Raman spectra confirmed that both carboxylic groups of ligand were deprotonated. The presence of the band of non-hydrogen bonded hydroxyl group from water molecule in the infrared spectra was discussed. Thermal behaviour of the complexes was investigated by the TG-DSC and TG-FTIR methods. The investigated complexes are thermally stable in air and nitrogen atmosphere up to 106–135 °C. Further heating of the complexes leads to dehydration and decomposition. Water, carbon oxides, m-xylene and methane are main volatile products of complexes thermal decomposition in nitrogen.

The metal–organic frameworks of the formula Ln(bta)·nH2O where n = 3, 4, 5 or 6; bta = benzene-1,3,5-triacetate ion: [C9H9(COO)3]3−; Ln = La(III), Nd(III), Eu(III), Tb(III), Ho(III), Tm(III), Lu(III) were synthesized by the reaction of LnCl3·xH2O with ammonium salt of H3bta acid in water solution. Insoluble water compounds crystallize in the monoclinic or triclinic crystal system, and they are stable up to 30 °C. When heated, they decompose up to 160–200 °C in two stages to stable anhydrous compounds. The dehydrated compounds Ln(bta) are still crystalline and stable up to about 350 °C. When heated above 350 °C, they undergo decomposition where the intermediate products are Ln2O2CO3 or Tb4O6CO3 and the residues are: Ln2O3 or Tb4O7. The interpretation of IR spectra of title compounds was made taking into consideration the experimental and theoretical wavenumbers obtained for H3bta specie. The XPS spectra of H3bta and its complexes were recorded. The way of metal–carboxylate group of ligand coordination was discussed. This work presents the results of the XPS analyses, which allowed to determine the binding energies (E b) for the main lines of Ln3d, Ln4d, Ln5p, C1s, O1s spectra, spin–orbital splitting and full width at half maximum complexes.

(Benzylthio)acetic acid (Hbta) was synthesized with 78% yield from benzyl chloride and thiourea as substrates. Well-shaped crystals of Hbta were grown by slow solvent evaporation technique from pure methanol. The compound was investigated by single-crystal X-ray and powder diffraction techniques and was also characterized by other analytical methods, like ATR-FTIR, 1H and 13C NMR and TG/DSC. The acid molecule adopts bent conformation in the solid state. The crystal structure of Hbta is stabilized by numerous intermolecular interactions, including O–H···O, C–H···O, C–H···S and C–H···π contacts. Thermal decomposition of the obtained material takes place above 150 °C.

A novel 4,4′-disubstituted biphenyl derivative featuring two acetic acid side arms symmetrically attached to a biphenyl system, that is biphenyl-4,4′-diacetic acid (H2bpda), has been successfully synthesized by means of the three-stage organic strategy. The synthesis product was characterized by elemental analysis, various spectroscopic techniques including FT-IR, Raman, 1H and 13C NMR as well as thermogravimetric and TG–FT-IR coupled measurements. The phase purity of material was verified on the basis of the X-ray powder diffraction. The studied compound crystallizes in the monoclinic P21/c space group with half of the molecule in the asymmetric unit. Structural studies indicate intermolecular O H⋯O hydrogen bonding between the carboxylic groups of the adjacent molecules of H2bpda. The occurrence of intermolecularly associated carboxylic groups can also be clearly seen in the vibrational spectra of the acid. On thermal analysis both in air and nitrogen an anhydrous compound demonstrates considerable thermal stability.

The series of isostructural lanthanide coordination polymers with the empirical formula [Ln2(PDA)3(H2O)]·2H2O, where PDA = 1,4-phenylenediacetate anion = [C8H8(COO)2]2−; Ln = La-Lu(III), and Y(III) were produced in the reaction of LnCl3·nH2O with ammonium salt of 1,4-phenylenediacetic acid in water solution. The compounds were characterised structurally using powder X-ray diffraction, elemental and thermogravimetric analyses as well as FT-IR spectroscopy. Thermogravimetric analyses show that in the range 60–170 °C the dehydration process occurs. The thermal stability of dehydrated compounds, Ln2(PDA)3 increased from about 200–350 °C in the whole series of complexes. Single-crystal X-ray diffraction analysis for the Gd(III) complex revealed that the compound crystallizes in the monoclinic P21/c space group with a = 21.863(2) A, b = 10.035(1) A, c = 13.854(1) A, β = 91.53(1)° and V = 3,038.5(4) A3. The complex contains one-dimensional gadolinium-carboxylato chains, which are connected with the –CH2–C6H4–CH2– spacers of PDA ligand to the three-dimensional metal–organic framework.

The influence of synthesis conditions on the structural and thermal properties of solid lanthanide 1,2,3,4,5,6-benzenehexacarboxylates (mellitates) was investigated. The general formula of the complexes is Ln 2 (C 12 O 12 )· n H 2 O (where Ln = Nd(III) and Er(III), n = 10 for Nd, and n = 14 for Er – mild conditions; n = 6 for Nd and Er – hydrothermal synthesis). They were characterized by elemental analysis, X-ray diffraction methods, IR spectroscopy and thermal analysis methods (TG-DSC and TG-FTIR). The prepared complexes are crystalline but not isostructural. The IR spectra confirm deprotonation of all carboxylic groups in all investigated complexes. Their thermal stability as well as pathway of thermal decomposition differ significantly.

Rare earth complexes with 2,2 0 -biphenyldi- carboxylic acid (diphenic acid = H2dpa) were obtained as hydrated precipitates of the general formula Ln2(C14H8O4)3� nH2O, where n = 3 for the of Y(III) and Ce(III)-Er(III) and n = 6 for La(III), Tm(III), Yb(III) and Lu(III) complexes. On heating in air atmosphere complexes lose all water molecules in the temperature range 30-210 C in one step and form anhydrous compounds, which are stable up to 315- 370 C. During further heating they decompose to oxides. The trihydrated compounds are crystalline powders whereas the hexahydrated are amorphous solids. The trihydrated complexes crystallize in the monoclinic (Pr(III) and Ce(III) complexes) and triclinic (Y(III) and Nd(III)-Er(III) com- plexes) crystal systems.

The lanthanide biphenyl-4,4 0 -dicarboxylates (bpdc) series of the general formulae Ln2(bpdc)3� nH2O, where Ln = lanthanides from La(III) to Lu(III); bpdc = C12H5(COO)2- ; n = 4, 5 or 6 have been obtained by the conventional precipitation method. All prepared complexes were characterized by elemental analysis, simultaneous thermal analyses thermogravimetric-differential scanning calorimetry (TG-DSC) and TG-FT-IR, FT-IR, and FT- Raman spectroscopy as well as X-ray diffraction patterns measurements. In the whole series of analyzed complexes the bpdc 2- ligand is completely deprotonated. In view of that, four carboxylate oxygen atoms are engaged in the coordination of Ln(III) ions. The synthesized compounds are polycrystalline and insoluble in water. They crystallize in the low symmetry crystal systems, like monoclinic and triclinic. Heating in the air atmosphere resulted in the multi-steps decomposition process, namely endothermic dehydration and strong exothermic decomposition pro- cesses. The dehydration process leads to the formation of stable anhydrous Ln2bpdc3 compounds which subsequently decompose to the corresponding lanthanide oxides.

The reaction of sodium hydroxide with 2-aminoterephthalic acid leads to the formation of a complex of the general formula: [Na2(atpt)(H2O)5]·H2O, where atpt = [NH2C6H3(COO)2]2−. Sodium 2-aminoterephthalate was synthesized and characterized by single-crystal X-ray diffraction, FT-IR spectroscopy, thermal analysis and coupled TG–FT-IR technique. Crystallographic study of the sodium complex reveals that the compound crystallizes in the triclinic system, the space group P-1 with a = 7.983(3) A, b = 8.405(3) A, c = 11.311(5) A, α = 70.74(3)°, β = 76.57(3)°, γ = 83.12(3)° and V = 696.1(5) A3. On heating in air atmosphere the compound in question loses all water molecules in two steps in the temperature range 30–205 °C. The anhydrous form of the complex is stable up to 370 °C and then decomposes to sodium carbonate.