New cyanido-bridged iron(II) spin crossover coordination polymers with an unusual ladder-like topology: an alternative to Hofmann clathrates

Two new cyanido-bridged {FeIIMII} double chains were obtained by reacting cyanido anions [M(CN)4]2- with complex cations [FeII(tptz)]2+ (preformed in situ by mixing a hydrated tetrafluoroborate salt of iron(II) and a tptz ligand, tptz = 2,4,6-tri(2-pyridyl)-1,3,5-triazine) having the general formula [FeII(tptz)MII(CN)4]·2H2O·CH3CN, where M = Pd (1) or Pt (2). Additionally, two molecular complexes formulated as [FeII(tptz)2][MII(CN)4]·4.25H2O, where M = Pd (3) or Pt (4), were subsequently obtained from the same reaction, as secondary products. Single crystal X-ray analysis revealed that 1 and 2 are isostructural and crystallize in the P-1 triclinic space group. Their structure consists of a double-chain with a ladder-like topology, in which cyanido-based [M(CN)4]2- metalloligands coordinate, through three CN- ligands and three [FeII(tptz)]2+ complex cations. Compounds 3 and 4 are also isostructural and crystallize in the P1̄ triclinic space group, and the X-ray structural data show the formation of [FeII(tptz)2]2+ and [MII(CN)4]2- ionic units interconnected through H-bonds and π⋯π stacking supramolecular interactions. The static DC magnetic measurements recorded in the temperature range of 2-300 K showed that 1 and 2 exhibit incomplete spin transition on cooling, which is also confirmed by single crystal XRD analysis and Mössbauer spectroscopy. Compounds 3 and 4 are diamagnetic, most likely due to the encapsulation of Fe(II) in a tight pocket formed by two tptz ligands that preserve the low-spin state in the temperature range of 2-400 K.

Pyrrolidine-Derived Phenanthroline Diamides: An Influence of Fluorine Atoms on the Coordination of Lu(III) and Some Other f-Elements and Their Solvent Extraction

Three pyrrolidine-derived phenanthroline diamides were studied as ligands for lutetium trinitrate. The structural features of the complexes have been studied using various spectral methods and X-ray. The presence of halogen atoms in the structure of phenanthroline ligands has a significant impact on both the coordination number of lutetium and the number of solvate water molecules in the internal coordination sphere. The stability constants of complexes with La(NO3)3, Nd(NO3)3, Eu(NO3)3, and Lu(NO3)3 were measured to demonstrate higher efficiency of fluorinated ligands. NMR titration was performed for this ligand, and it was found that complexation with lutetium leads to an approximately 13 ppm shift of the corresponding signal in the 19F NMR spectrum. The possibility of formation of a polymeric oxo-complex of this ligand with lutetium nitrate was demonstrated. Experiments on the liquid–liquid extraction of Am(III) and Ln(III) nitrates were carried out to demonstrate advantageous features of chlorinated and fluorinated pyrrolidine diamides.

Achieving colour tuneable and white-light luminescence in a large family of dual-emission lanthanide coordination polymers

Expanding the family of lanthanide terpyridine coordination polymers has yielded eighteen new complexes with two different phases, Ln(TPC)₂(HCOO)(H₂O) (Ln-1) and Ln(TPC)(HCOO)₂ (Ln-2) (Ln = Sm-Lu, except Tm). Both structures are composed of lanthanide cations interconnected by 2,2':6',2''-terpyridine-4'-carboxylate ligands to yield one-dimensional chain topologies. However, the incorporation of an additional crystallographically unique decorative TPC ligand into Ln-1 gives rises to a distinct phase. The encapsulation of both metal- and ligand-based phosphors within single coordination polymers leads to dual-emission of the afforded materials. Furthermore, judicious lanthanide doping in heterometallic Ln-1 and Ln-2 allows for fine-tuning the photoluminescent colours over a wide range of gamut. Such a combination showcases the capability to fine-tune the emission colours from deep green, to red, and to blue. In addition, direct white-light emission upon UV excitation can be achieved in the Sm_xGd_1-x-1 system.

Occurrence of polyoxouranium motifs in uranyl organic networks constructed by using silicon-centered carboxylate linkers: structures, spectroscopy and computation

Four polyoxouranium-based uranyl carboxylates have been synthesized based on silicon-centered carboxylate linkers. Oligomerization of the uranyl units from tetrameric unit, to octameric motif and ultimately infinite polyoxouranium chain was observed.