New mononuclear Cu(II) complexes and 1D chains with 4-amino-4H-1,2,4-triazole.

The crystal structures of two mononuclear Cu(II) NH2trz complexes [Cu(NH2trz)4(H2O)](AsF6)2 (I) and [Cu(NH2trz)4(H2O)](PF6)2 (II) as well as two coordination polymers [Cu(µ2-NH2trz)2Cl]Cl∙H2O (III) and [Cu(µ2-NH2trz)2Cl] (SiF6)0.5∙1.5H2O (IV) are presented. Cationic 1D chains with bridging bis-monodentate µ2-coordinated NH2trz and bridging µ2-coordinated chloride ligands are present in III and IV. In these coordination polymers, the Cu(II) ions are strongly antiferromagnetically coupled with J=-128.4 cm(-1) for III and J=-143 cm(-1) for IV (H=-JΣSiSi+1), due to the nature of the bridges between spin centers. Inter-chain interactions present in the crystal structures were taken into consideration, as well as g factors, which were determined experimentally, for the quantitative modeling of their magnetic properties.

Dynamics and supramolecular organization of the 1D spin transition polymeric chain compound [Fe(NH2trz)3](NO3)2. Muon spin relaxation.

The thermal spin transition that occurs in the polymeric chain compound [Fe(NH(2)trz)3](NO3)2 above room temperature has been investigated by zero-field muon spin relaxation (microSR) over the temperature range approximately 8-402 K. The depolarization curves are best described by a Lorentzian and a Gaussian line that represent fast and slow components, respectively. The spin transition is associated with a hysteresis loop of width DeltaT = 34 K (T1/2 upward arrow = 346 K and T1/2 downward arrow = 312 K) that has been delineated by the temperature variation of the initial asymmetry parameter, in good agreement with previously published magnetic measurements. Zero-field and applied field (20-2000 Oe) microSR measurements show the presence of diamagnetic muon species and paramagnetic muonium radical species (A = 753 +/- 77 MHz) over the entire temperature range. Fast dynamics have been revealed in the high-spin state of [Fe(NH(2)trz)3](NO3)2 with the presence of a Gaussian relaxation mode that is mostly due to the dipolar interaction with static nuclear moments. This situation, where the muonium radicals are totally decoupled and not able to sense paramagnetic fluctuations, implies that the high-spin dynamics fall outside the muon time scale. Insights to the origin of the cooperative effects associated with the spin transition of [Fe(NH(2)trz)3](NO3)2 through muon implantation are presented.

Selective thin-layer chromatography of 4-R-1,2,4-triazoles.

A convenient and selective TLC of 4-R-1,2,4-triazoles (Rtrz) and nitrogen containing aromatic rings is presented (molecules 1-11). This simple revelation method implies a complexation of heterocycles to Co(II) ions on a TLC plate, followed by a subsequent modification of the reduction potential which enables oxidation of Co(II) by permanganate.