Sodium hydrogen dipicolinate dipicolinic acid trihydrate: Synthesis,structure, and valence bond sums

The synthesis and crystal structure of sodium hydrogen dipicolinate dipicolinic acid trihydrate, NaHdipic · H₂dipic · 3H₂O,I, is reported. There is a hydrogen bonded H₃(dipic)₂ ^– unit in which an Hdipic^– ion functions as a tridentate chelate to the Na⁺ ion while the second H₂dipic functions as a monodentate ligand and bridging unit. The Na⁺ ion is in the center of a pentagonal bipyramid with two water molecules in the axial positions. The equatorial plane is composed of an Hdipic^– ion, a water molecule and an oxygen from the H₂dipic. An analysis of data in the Cambridge Structural Database for Na⁺ compounds using Valence Bond Sums has produced newr ₀ values of 1.743 for Na–O and 1.891 for Na–N.     

Synthesis and structure of a novel copper (II) nitrate complex of 2,4-dioxo-4-phenylbutanoic acid

2,4-Dioxo-4-phenylbutanoic acid, 1, was synthesized as a biproduct of the attempted synthesis of 1,6-bisphenyl-1,3,4,6-hexanetetrone. Crystals of [Cu(H2O)(bipy) (L)][Cu(bipy)(L)(NO3)] (H2O)(NO3) (L = 2,4-dioxolato-4-phenylbutanoic acid and bipy = 2,2′-bipyridine), 2, were grown by slow evaporation of a solution of Cu(NO₃)₂·3 H₂O, 2,2′-bipyridine, and 1 in a mixture of ethanol and water. The compound crystallized in the triclinic space group P-1 and is made up of two distinct molecular units each with approximately square pyramidal geometry: a = 10.663(2) ?, b = 13.275(3) ?, c = 15.071(3) ?, α = 80.26(3)°, β = 74.13(3)°, γ = 89.12(3)°. The copper ions are chelated by molecules of 1 and molecules of bipyridine. The molecular units are arrayed in rows held together by pi-stacking interactions and hydrogen bonding.     

The crystal structure of a bis(2,6-pyridinedicarboxylato)chromate(III) anion with an elaborate network of hydrogen bonding and π stacking

The synthesis, X-ray crystallography, spectroscopic, and electrochemical properties of the title compound, [Hdpa][Cr(dipic)₂]·3H₂O, 1, are reported. Compound 1 crystallized in the triclinic space group P-1 with a = 7.1057(11) ?, b = 12.965(2) ?, c = 14.269(2) ?, α = 80.306(3)°, β = 82.101(2)°, γ = 83.799(2)°, and V = 1278.6(4) ?³ with Z = 2. The distorted octahedral chromium anions are part of an elaborate network of hydrogen bonding formed by the waters of solvation, the anion, and cation as well as π-stacking interactions.     

Conformational variability exhibited by mellitic acid anions (MA?n) with organic amine cations: Structures with an abundance of NH ?s OC hydrogen bonds and a paucity of hydrogen bonds

Benzenehexacarboxylic acid (mellitic acid) is an ideal substrate for the study of radially arranged ionic interactions with organic bases. Earlier work has shown that the net charge in MA (−4, −3, or −2) influences its assembly, respectively, either as ribbons or sheets. In the former case the cations intersperse the ribbons forming a tight network. In the MA sheets from the latter, the cations are arranged in orthogonal stacks. In the MA-phenanthroline complex such stacks are arranged exactly parallel resulting in significant π–π interactions. The present work relates to the modification of the phenanthroline motif to flexible structures. The reported ability of 2,3-bis-(2′-pyridyl) pyrazine (P2), prepared from 2,2′-pyridyl by reaction with ethylenediamine (EDA) followed by dehydrogenation of the resulting 2,3-bis-(2′-pyridyl)-5,6-dihydropyrazine, to form helical structures made it an obvious choice for complexation studies with MA. These resulted not only in the formation of the desired 7 MAP2 complex but also, surprisingly, with the dihydroprecursor complex with EDA 3 (MAEDA), a compound that eluded direct preparation with MA and EDA. The crystal structure of MAEDA reports the first complex of MA where MA⁻⁵ ions are encountered. The 15 hydrogen bonds, three for each N, result in hard packing. The complex with P2 7 (MAP2) showed the common features of MA⁻² sheets. Unlike phenanthroline, the nonplanar disposition of the pyridine rings made it possible for both pyridine protons to be available for salt formation, resulting in the arrangement of the cations in layers interposed between the sheets of MA⁻² ions. The pyrazine ring does not participate in hydrogen bonding or stacking in the crystal.     

Hydrothermal synthesis and structure of a novel terbium coordination polymer with packing cavities, {[Tb(TCB)1/2(H2TCB)1/2(H2O)](H2O)2}n (H2TCB = 1, 2, 4, 5‐benzenetetracarboxylic acid)

A novel terbium coordination polymer {[Tb(TCB)_1/2(H₂TCB)_1/2(H₂O)](H₂O)₂}_n (H₂TCB = 1, 2, 4, 5‐benzenetetracarboxylic acid) ( 1 ) has been hydrothermally synthesized and determined by single crystal X‐ray diffraction method, which features a very interesting three‐dimensional framework with large packing cavities. It crystallizes in the monoclinic space group P2₁/n with a = 1.0723(4) nm, b = 0.7168(3) nm, c = 1.7155(6) nm, β = 97.079(4)°, V = 1.3086(8) nm³, Z = 4, and final R₁ = 0.0203, wR₂ = 0.0404. In 1, the protonated carboxylate groups are free, the other carboxylate groups are bonded to Tb³⁺ ion in three modes: the chelating bidentate, the bridging bidentate and bridging tridentate. Moreover each Tb³⁺ ion is coordinated by nine oxygen atoms from six carboxylate groups and one water molecule respectively to complete a deformed tricapped trigonal prismatic geometry. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)