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Two neodymium(III) six-coordinate complexes NdCl3(3-Br-4-CH3OC7H7NO)3 (Nd1) and Nd(C7H9NO)5(C4H8O2)(ClO4)3 (Nd2) have been synthesized and characterized. The FT-IR and FT-Raman data were acquired, and a complete vibrational assignment of the fundamental modes of the compounds was carried out. The frequencies calculated for the both ligands and scaled using the B3LYP approach with the 6-311G(2d,2p) basis set correspond very well to the experimental values. The XRD results, IR and Raman spectra were discussed in terms of a possible structure and composition of the studied compounds. The optical absorption and emission spectra were investigated at room temperature. The emission decay is mono exponential indicating that the energy transfer from the ligand occurs straight to the 4F3/2 level. The lifetime of this level is about 2.5 μs? A possibility of the energy transfer between the ligands under study and neodymium ions was considered. The calculations of the spin Hamiltonian parameters and EPR data simulation were performed using the electron paramagnetic resonance and nuclear magnetic resonance (EPR-NMR) program.

The crystal structure of the all studied compounds was refined in the monoclinic C2/m ( C 2 h 3 ) space group. The IR and Raman spectra of polycrystalline AgRE(WO4)2 have been recorded and analysed using the factor group approach. In the theoretical considerations the C2/m, P2/c and C2/c unit cell structures were taken into account. The change of the unit cell parameters induced by the RE ions exchange has been analysed. The assignment of the observed bands to the internal and external modes has been proposed. The verification of the structure has been done on the basis of the vibrational behaviour of the studied tungstates. Absorption, emission and excitation spectra of the investigated AgRE(WO4)2 polycrystals have been measured and analysed. The luminescence decay times of 5D0 → 7F2 (Eu3+) and 5D4 → 7F5 (Tb3+) transitions have been calculated.

New europium and terbium [LnCl3L3(H2O)2] polycrystalline complexes were synthesized with the ligand L = 3-bromo-4-methylthio-2,6-lutidine N-oxide. IR, Raman, electron absorption UV-VIS and emission spectra measurements were carried out for these compounds. Re-crystallization of these materials led to formation of single crystals with another composition [LnL(H2O)7]Cl3∙L3, they were characterized by X-ray diffraction technique and spectroscopic measurements. Both types of the materials consist of eight coordinated LnCl3O3O’2 or LnOO’7 polyhedrons containing O - oxygen atoms of the N-oxide group, chlorine atoms or O’ - oxygen atoms of the water units. The crystal structure was solved for two complexes of the formula [Ln(L)(H2O)7]Cl3∙(L)3 where Ln = Eu and Tb. X-ray diffraction analysis reveals that these complexes are isostructural with P21/m space group. The optimization of the molecular system and frequency calculations were carried out using density functional theory (DFT). The DFT quantum chemical calculations of the vibrational wavenumbers were performed for the ligands used for the Eu3+ and Tb3+ ions complexation. The emission measurements were carried out with the femtosecond excitation. The effective ligand-to-metal energy transfer was discovered in the [LnCl3L3(H2O)2] complexes formed in the polycrystalline state.

Room temperature FT-IR spectra in the range 30–4000 cm −1 and FT-Raman spectra in the range 80–4000 cm −1 of indium and lutetium MPX-type phthalocyanines have been compared. The assignment of the observed bands has been accomplished on the basis of DFT chemical calculations using the B3LYP functional and its long range corrected version - CAM-B3LYP. The calculations were carried out for the indium derivative using the LANL2DZ, CC-PVDZ basis sets, i.e. the following approximations were used: B3LYP/CC-PVDZ, B3LYP/CC-PVTZ, B3LYP/LANL2DZ, CAM-B3LYP/CC-PVDZ and CAM-B3LYP/LANL2DZ. The molecular structures of these derivatives have been discussed in terms of group theory and geometry optimisation taking into account the shape and number of the bands corresponding to the stretching and bending vibrations of MN 4 coordination polyhedron as well as the whole studied complex. The calculated structural parameters have been related to those from XRD studies. The usefulness of the proposed theoretical approaches in the prediction of the structural and vibrational data were analysed.

Sodium-magnesium pentaphosphate with a formula Na 3 Mg 2 P 5 O 16 doped with europium(III) have been synthesized. The concentration of the rare earth ion activators was established to be 1 to 10 at.% in the doped samples. Spectroscopic and structural properties of the obtained samples were investigated by X-ray, Raman, infrared, absorption and luminescence studies. The structure of the studied material was confirmed as monoclinic P2/a = C 2h 4 (No. 13) similar to this described in the literature. The decay times were measured for all samples monitoring the maximum of emission at λ mon = 611 nm and exciting in the 5 L 6 band (λ exc = 396 nm). All decay curves were single exponential and lifetimes remain constant with value τ = 2 ms ± 0.2 ms for the all dopant concentration.

[Ln2(2-hydroxy-5-methyl-nicotinic acid)6(H2O)4] and Ln2(5-methyl-nicotinic acid)6(H2O)4] complexes (Ln = Gd, Tb) have been synthesized and characterized by means of powder X-ray diffraction, IR, Raman, electron UV–Vis and emission measurements. The luminescence and dynamics of the excited states depopulation have been studied using femtosecond laser excitation. The singlet and triplet states of nicotinic acid were localized using DFT quantum chemical calculations. The energy transfer mechanism between the electron levels of the ligands and Tb3+ ion have been proposed.

We report the structural, phonon and luminescence properties of Eu3+-doped Gd3-xEuxNbO7 niobates prepared by conventional solid state reaction. Although a few different crystal structures of pure Gd3NbO7 have been reported so far, their properties still remain controversial and the mechanism of their structural phase transition is not well understood. The temperature-dependent IR and Raman spectra show a structural phase transition occurring at 340 K. The detailed analysis of vibrational spectra and correlation diagrams as well as theoretical factor group considerations allowed us to propose the detailed assignment of the observed bands, define the symmetry of low and high-temperature phases and explain the mechanism of their structural transformation from the Pmcn to the Cmcm centrosymmetric orthorhombic space group. Powder X-Ray diffraction patterns confirm our analysis. The temperature-dependent emission, room-temperature excitation spectra and luminescence decay times are reported to achieve more information on structural and optical properties of the studied niobates.

Na 3 RE(PO 4 ) 2 orthophosphates, where RE = Y and Gd, doped with Yb 3+ ions were synthesised by hydrothermal method and characterised by X-ray diffraction, microscopic, IR and Raman techniques. The emission, excitation spectra were recorded at room temperature and fluorescence decay time was determined. As-synthesised samples crystallise in a trigonal modification and during calcination at 500 °C they transform to a monoclinic or orthorhombic symmetry (for yttrium and gadolinium compounds, respectively). Finally, the samples calcined at 700 °C do not reveal the trigonal symmetry. The morphology of particles for all samples is similar and resembles rice grains. All the obtained for the studied orthophosphates data were compared to those previously reported for the same compounds synthesised by Pechini method.

Na 3 RE (PO 4 ) 2 orthophosphates ( RE = Y, La, Gd) doped with Yb 3+ ions were synthesized by Pechini method and characterized by differential scanning calorimetry/thermogravimetric analysis, X-ray diffraction, IR and Raman spectroscopies as well as optical techniques (emission spectra and fluorescence decay time). All measurements, apart from DSC, were performed at room temperature. The spectroscopic properties were discussed in terms of the structure of the obtained materials. They show that lanthanum and gadolinium phosphates synthesized by Pechini method crystallize in the orthorhombic structure, similar to that of Na 3 Ce(PO 4 ) 2 . For the first time double sodium yttrium orthophosphate has been obtained in monoclinic modification, that could be compared to one of the Na 3 Gd(PO 4 ) 2 polymorph. Annealing of the obtained orthophosphates at 700 °C leads to grain of ∼200 nm. The microstructure of the powders annealed at 700 °C strongly depends on RE 3+ cations.

Micro-crystalline powders of Na 3 Ce(PO 4 ) 2 orthophosphate doped with Cr 3+ ions were synthesized and characterised by means of X-ray diffraction, IR and Raman, electron absorption, magnetic and EPR studies. The emission and excitation spectra and fluorescence decay time were recorded in the temperature range 70–293 K. The spectroscopic properties of Ce 3+ and Cr 3+ ions in the studied materials were discussed in terms of the structure and local symmetry of the optical ions. These data were compared to those obtained for NaCe(PO 3 ) 4 metaphosphate.

Fourier transform IR and Raman spectra, XRD studies and DFT quantum chemical calculations have been used to characterize the structural and vibrational properties of 2-hydroxy-5-methylpyridine-3-carboxylic acid. In the unit-cell of this compound two molecules related by the inversion center interact via O H⋯N hydrogen bonds. The double hydrogen bridge system is spaced parallel to the (1 0 2) crystallographic plane forming eight-membered arrangement characteristic for pyridine derivatives. The six-membered ring is the second characteristic unit formed via the intramolecular O H⋯O hydrogen bond. The geometry optimization of the monomer and dimer have been performed applying the Gaussian03 program package. All calculations were performed in the B3LYP/6-31G(d,p) basis set using the XRD data as input parameters. The relation between the molecular and crystal structures has been discussed in terms of the hydrogen bonds formed in the unit cell. The vibrations of the dimer have been discussed in terms of the resonance inside the system built of five rings coupled via hydrogen bonds.

The undoped and Cr3+-doped NaCe(PO3)4 metaphosphates were synthesized by the modified Pechini method and obtained as the crystalline powders. They were characterized by means of X-ray diffraction, vibrational and optical spectroscopy to clarify the structure and mechanism of Cr3+ emission in NaCe(PO3)4. This phosphor crystallizes in the monoclinic P121/n1 structure with an infinite (PO3)n chain. The Cr3+ ions can substitute the C1 symmetry site occupied by cerium ions. They can also occupy the tunnels formed in the anionic layer. Spectroscopic properties of the Cr3+ and Ce3+ ions were discussed in terms of structure of the studied crystalline powders. IR and Raman data confirm the predicted structure and indicate C1 site symmetry of the Cr3+ active ions. The Cr3+ ions appear in the distorted octahedral environment of the weak crystal field. Optical studies were confirmed by EPR results carried out in the temperature range of 4–293 K. In addition, the magnetic measurements were performed up to 305 K. The Cr3+ ions reveal negligible ferromagnetic interactions while the Ce3+ ions change their magnetic interactions from slightly antiferromagnetic to significantly ferromagnetic above 20 K.

Fourier transform IR and Raman spectra of the Cd1−3xGd2x□xMoO4 solid solutions have been studied and analysed using the factor group approach (□ denotes the cationic vacancies). The tetragonal I41/a (C4h6) space group with Z = 2 have been applied in the discussion. The assignment of the bands observed to the internal and external modes has been proposed and related to the formation of the solid solutions in which the gadolinium content has been changed in the range 0–1.0. The optical spectroscopic studies show visible dependence of the transition corresponds to the cationic vacancy on the Gd3+ content. The correlation between the crystallographic and spectroscopic data has been discussed in terms of the structural changes of the solid solutions induced by the defects in the CdMoO4 host lattice.

Cadmium-rare earth Cd 0.25 RE 0.5 □ 0.25 MoO 4 molybdates, where RE = Pr–Dy, have been prepared and characterised by powder XRD analysis and spectroscopic studies. IR and Raman spectra at room temperature have been measured in the MIR and FIR ranges. The correlation between the lattice parameters and spectroscopic data has been discussed in terms of factor group analysis. The dependences between the RE 3+ ionic radius, atomic mass and IR and Raman wavenumbers have been discussed.

Room temperature Fourier transform IR and Raman spectra in the range 30–4000 cm−1 and 80–4000 cm−1 of Dy, Ho, Er and Lu phthalocyanide PcLn(OAc)-type complexes have been measured, respectively. The assignment of the bands observed has been made on the literature data. The molecular structure of the PcLnX-type derivatives has been discussed on the basis of the group theory taking into account the shape and number of the bands corresponding to the stretching and bending vibrations of the LnN4O coordination polyhedron as well as whole PcLn(OAc) complex.

Er3+ and Yb3+ doped K3La(PO4)2 ortho- and KLa(PO3)4 metaphosphates were synthesised by the solid state reaction method. The obtained powders were characterised by XRD method, IR and Raman spectroscopy as well as optical absorption spectroscopy. The emission spectra were measured and fluorescence decay studies were carried out at room temperature. The energy transfer from Yb3+ to Er3+ and two-photon up-conversion processes were observed and discussed. The influence of the ortho- and metaphosphate host on efficiency of the luminescence was discussed.

New praseodymium complexes of 2,6-lutidine, 4-methoxy-2,6-lutidine and 3-halo-2,6-lutidine N -oxides (LuO) have been synthesised and chemically characterised. The Fourier transform IR and Raman spectra have been measured in the range 50–4000 and 80–4000 cm −1 , respectively, and discussed in terms of possible structure and composition of compounds studied. The frequencies of the stretching N–O, Pr–O and Pr–Cl vibrations have been assigned and related to the possible molecular structures of the Pr(LuO) 8 , Pr(LuO) 7 O′, Pr(LuO) 5 O′ 2 O″, Pr(LuO) 6 , PrCl 3 (LuO) 3 and PrCl 3 (LuO) 2 O′ complexes (O′ and O″ denotes the H 2 O and C 2 H 5 OH ligands).