Nuno D. Martins

4-Amino-3,5-di-2-pyridyl-4H-1,2,4-triazole

In the crystal structure of the title compound, C12H10N6, the molecules deviate slightly from planarity. The plane of the central triazole ring makes angles of 6.13 (9) and 3.28 (10)° with the pyridyl ring planes. Intramolecular N—H⋯N interactions form six-membered closed rings. The crystal packing also shows weak C—H⋯π and C—H⋯N interactions.

Pyromellitic acid-sarcosine (1/2).

The title compound, C10H6O8·2C3H7NO2, crystallizes as an adduct with the acid and amino acid molecules in their neutral forms. The asymmetric unit contains one half of a centrosymmetric pyromellitic acid molecule and one sarcosine molecule. The sarcosine has the amine group protonated and the carboxyl group deprotonated, as is usual for amino acids (zwitterionic form). The pyromellitic acid molecules retain the four carboxyl H atoms with the carboxyl groups rotated out of the ring plane [O—C—C—C torsion angles = 24.1 (3) and 61.6 (2)°]. There is a three-dimensional hydrogen-bond network linking the molecules.

Bis[(2-quinol­yl)methane­diol-κ2N,O](sulfato-κO)copper(II) dihydrate

In the title compound, [Cu(SO4)(C10H9NO2)2]·2H2O, the CuII ion is chelated by two (2-quinolyl)methanediol ligands and coordinated by a monodentate sulfate ligand in a distorted trigonal–bipyramidal environment, with O atoms occupying the equatorial sites and N atoms in the axial sites. The dihedral angle between the two essentially planar quinoline ring systems is 45.02 (9)°. In the crystal structure, an extensive O—H⋯O hydrogen-bonding network forms layers parallel to the ab plane.

Bis(triphenyl­guanidinium) tetra­chlorido­cuprate(II)

The structure of the title compound, (C19H18N3)2[CuCl4], consists of square-planar [CuCl4]2− anions and triphenylguanidinium cations. The CuII ion occupies a crystallographic inversion centre. In the cation, the dihedral angles between the phenyl rings and the plane defined by the central guanidinium fragment are in the range 51.9 (4)–64.4 (3)°. N—H⋯Cl hydrogen bonds assemble the ions into infinite chains running along the b axis.

(Benzoato-κ2 O,O′)(quinoline-2-carboxyl­ato-κ2 N,O)(quinoline-2-carboxylic acid-κ2 N,O)copper(II)

The crystal structure of the title compound, [Mn(C7H5O2)(C10H6NO2)(C10H7NO2)], contains manganese(II) ions six-coordinated in a distorted octahedral environment. The equatorial plane is occupied by four O atoms, two from the carboxylate group of the benzoate ion, the other two from carboxylate/carboxyl groups of the quinaldate/quinaldic acid molecules. The axial positions are occupied by the N atoms of the quinoline ring systems. The metal ion lies on a twofold rotation axis that bisects the benzoate ligand; the quinaldate and quinaldic acid ligands are therefore equivalent by symmetry, and the carboxylate/carboxyl groups are disordered. The complexes are joined together by hydrogen bonds between the carboxylate/carboxyl groups of adjacent quinaldate/quinaldic acid molecules, forming zigzag chains that run along the c axis.

Magnetic and structural properties of some triazole metal complexes

Recently, multiferroic materials exhibiting ferromagnetic and ferroelectric properties have attract much attention because of the control of a magnetism by an electric field and/or the control of an electric polarization by a magnetic field. We are studying the syntheses and the correlation between crystal structures and solidstate properties of a series of linear chain rhodium(I)-semiquinonato complexes from the viewpoint of the development of multifunctional materials based on the frontier orbital control. Here we report the crystal structure, magnetic and dielectric properties of a linear chain rhodium(I)-semiquinonato complex, [Rh(3,6-DBSQ-4,5(MeO)2)(CO)2] (1) (3,6-DBSQ-4,5-(MeO)2 = 3,6-di-tert-butyl4,5-dimethoxy-1,2-benzosemiquinonato). Complex molecules of 1 are stacked by the Rh-Rh interactions to form a linear chain structure. This compound undergoes first-order phase-transition in the temperature range of 208-224 K. Magnetic property changes from an antiferromagnetic interaction (room temperature (RT) phase) to a ferromagnetic one (low temperature (LT) phase, θ = +64 K). This compound undergoes a magnetic phase-transition to the metamagnet in which the interchain interaction is a ferromagnetic whereas the intrachain interaction is antiferromagnetic (TN = 13.8 K). Furthermore, the real part, ε’, of dielectric constant along 1-D chain in the RT phase shows the large value of 1000-2500 depending on the measuring frequency. ε’ decreases rapidly with first-order phasetransition and takes a temperature-independent value of ca. 160 in the LT phase. P-E hysteresis measurement to reveal the ferroelectricity of this compound is now in progress. References 1. Y. Tokura, Science, 2006, 312, 1481. 2. M. Mitsumi et al., Angew. Chem. Int. Ed., 2005, 44, 4164.