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Three-Dimensional Self-Assembly Supramolecular Structure of Hydrogen Bonded Melaminium Citrate

Perpetuo G., Janczak J.

Polish Journal of Chemistry

2003

Vol. 77 / nr 10

1323-1337

The melaminium dihydrogencitrate, (C3H7N6)(HOOC-CH2-C(OH)(COOH)-CH2-COO), crystallizes from water solution at room temperature in the P21/c space group of the monoclinic system with the lattice parameters of a = 5.531(1), b = 20.869(4), c = 11.282(2) A and = 99.96(3)_ and Z = 4. The crystals are built up from singly protonated at the one N-ring atom melaminium cations that interact in a near linear fashion through a pair of N-HN hydrogen bonds to form the centrosymmetric dimeric structure. The dihydrogencitrate(-) anions interact in the head-to-tail fashion via the terminal dissociated (COO-) and non-dissociated (COOH) carboxyl groups to form O-H _ O hydrogen bonded zigzag infinite chains. The hydroxyl group of dihydrogencitrate(-) ions is involved into O-HOhydrogen bonds that linked together the dihydrogencitrate(-) chains into two-dimensional network. The centrosymmetric dimers of melaminium moieties interact with the sheets of dihydrogencitrate(-) to form the three-dimensional hydrogen bonded network. The conformation of the dihydrogencitrate(-) ion in the crystal is compared with the conformation in the gas-phase obtained by the ab-initio molecular orbital calculation.

Synthesis, X-ray Crystal Structure and Solution Studies of Cu(II) Complexes of a Pyridine Containing Self-Assembling System

Ranjbar M., Taghavipur M., Aghabozorg H., Moghimi A., Jalali F., Shamsipur M.

Polish Journal of Chemistry

2002

Vol. 76 / nr 6

785-794

The complexation of a novel pyridine containing self-assembling system LH2, ([pyda_H2] [pydc] (pyda = 2,6-pyridinediamine and pydc_H2 = 2,6-pyridinedicarboxylic acid), with copper(II) acetate leads to the formation of an anionic self-assemble coordination compound, [(pyda_H)]2[Cu(pydc)2]_H2O. The crystal system is monoclinic with a space group P21/n and contains four molecules per unit cell. The unit cell dimensions are: a = 8.2567(19) A, b = 13.097(31) A, c = 23.384(6) A and _ = 94.685(5)_. The four carboxylate groups of two dianions are oriented in a flattened tetrahedral arrangement and the two dianionic units are almost perpendicular to each other. The axial N-Cu-N angle shows 2.65_ deviation from linearity. The complexation reactions in aqueous solution were investigated by potentiometric pH titrations and the equilibrium constants for all major complexes formed are described. The results are presented in the form of distribution diagrams revealing the concentration of individual complex species as a function of pH. The results revealed that, at pH = 4-5, the major complex species in solution is [(pyda_H)]2[Cu(pydc)2].