Bis(LeuOH) (1a), bis-(ValOH) (2a) and bis(PhgOH) (5a) (Phg denotes (R)-phenylglycine) oxalyl amides are efficient low molecular weight organic gelators of various organic solvents and their mixtures as well as water, water/DMSO, and water/DMF mixtures. The organisational motifs in aqueous gels are dominated primarily by lipophilic interactions while those in organic solvents are formed by intermolecular hydrogen bonding. Most of the gels are thermoreversible and stable for many months. However, 2a forms unstable gels with organic solvents which upon ageing transform into variety of crystalline shapes. For some 1a/alcohol gels, a linear correlation between alcohol dielectric constants (epsilon) and gel melting temperatures (Tg) was found. The 1H NMR and FTIR spectroscopic investigations of selected gels reveal the existence of temperature dependent network assembly/dissolution equilibrium. In the 1H NMR spectra of gels only the molecules dissolved in entrapped solvent could be observed. By using an internal standard, the concentration of dissolved gelator molecules could be determined. In FTIR spectra, the bands corresponding to network assembled and dissolved gelator molecules are simultaneously present. This enabled determination of the Kgel values by using both methods. From the plots of InKgel versus 1/T, the deltaHgel values of selected gels have been determined (-deltaHgel in 10-36 kJ mol(-1) range) and found to be strongly solvent dependent. The deltaHgel values determined by 1H NMR and FTIR spectroscopy are in excellent agreement. Crystal structures of 2a and rac-5a show the presence of organisational motifs and intermolecular interactions in agreement with those in gel fibres elucidated by spectroscopic methods.

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A non-covalent self-assembled chiral alanyl aminopyridine ligand exhibits supramolecular chirality in solution, independent of the organic solvent used. The supramolecular chirality of the assemblies is completely inverted by complexation to zinc ions. To date, such a supramolecular metal-ligand system has not been reported in the literature.

Metal complexes of iminodiacetamide (imda) ligands and metal ions Zn(II), Cu(II), Ni(II) and Co(II) were prepared, using eight imda ligands (L1-L8) substituted with groups of different steric and electronic properties on the central amine nitrogen atom (hydrogen atom, methyl, isopropyl, benzyl) and the para-position of phenyl rings (nitro, dimethylamino). The effect of these substituents on the stoichiometry (ML, ML2), geometry and stereochemistry (mer, transfac, cis-fac) of the complexes was studied in solid state, in solution and by DFT calculations. X-Ray single crystal and powder diffraction, thermogravimetry, and IR spectroscopy showed that in the solid state imda ligands preferentially form transfac ML2 complexes, with the exception of the cis-fac complex 7Zn. NMR spectroscopy of diamagnetic Zn(II) and paramagnetic Co(II) complexes revealed the formation of both ML and ML2 complexes in solution. Variable temperature NMR was used to study the effect of the substituent on the central amine nitrogen on the Zn─N bond strength and nitrogen inversion. Relative stabilities of isomers were rationalized by computations and the optimized structures used for the geometry analysis.

Solvatomorphism has been found between two series of complexes of the composition [M(bpy)3]2[NbO(C2O4)3]Cl.nH2O [M = Fe2+ (1, 2), Co2+ (3, 4), Ni2+ (5, 6), Cu2+ (7) and Zn2+ (8, 9); bpy = 2,2'-bipyridine)], crystallizing in the monoclinic space group P2 1/c [3, 5, 8 (n = 11)] or in the orthorhombic space group P21 21 21 [2, 4, 6, 7 (n = 12)]. All the structures contain two symmetry independent [M(bpy)3]2+ cations, one [NbO(C2O4)3]3- anion, one Cl(-) anion, and crystal water molecules. The cations possess a trigonally distorted octahedral geometry, with an additional tetragonal distortion in 7. Analysis of crystal packing reveals a specific type of supramolecular contact comprising four bipyridine ligands from two neighbouring [M(bpy)3]2+ cations--quadruple aryl embrace (QAE) contact. The contact is realized by the alignment of two molecular two-fold rotation axes, preserving the parallel orientation of the molecular three-fold rotation axes. The resulting two-dimensional honeycomb lattices of [M(bpy)3]2+ cations are placed between the hydrogen bonding layers made of [NbO(C2O4)3]3- and Cl(-) anions and the majority of the crystal water molecules. The temperature-dependent magnetic susceptibility measurements (1.8-300 K) show a significant orbital angular momentum contribution for 3 and 4 (high-spin Co2+), the influence of zero-field splitting for 5 and 6(Ni2+) and a substantially paramagnetic Curie behaviour for the Cu2+ compound (7).

Magnetic properties of single crystals of the heterometallic complex [Cu(bpy) 3 ] 2 [Cr(C 2 O 4 ) 3 ]NO 3 ·9H 2 O (bpy = 2,2'-bipyridine) have been investigated. From the recorded EPR spectra, the spin-Hamiltonian parameters have been determined. The magnetization measurements have shown magnetic anisotropy at low temperatures, which has been analysed as a result of the zero-field splitting of the Cr III ion. By fitting the exactly derived magnetization expression to the measured magnetization data, the axial zero-field splitting parameter, D, has been calculated. Comparing to the EPR measurements, it has been confirmed that D can be determined from the measurements of the macroscopic magnetization on the single crystals.

The compound Rb 3 [NbO(C 2 O 4 ) 3 ]·2H 2 O (1) has been synthesized by two different methods and its exact chemical composition established. The niobium atom is heptacoordinated by oxygen atoms forming a distorted pentagonal bipyramid. Inspite of some similarities, the structure of 1 is not isotypic with the structure of (NH 4 ) 3 [NbO(C 2 O 4 ) 3 ]·H 2 O.

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