l‐Prolinium tartrate

In the title salt, C₅H₁₀NO₂⁺·C₄H₅O₆^?, proline exists as a cation and the tartaric acid as a semi‐tartrate anion. The semi‐tartrate ions form hydrogen‐bonded strings along the c axis. These strings are interconnected through the proline mol­ecules, forming a layered network parallel to the bc plane. The proline mol­ecules, however, do not directly interact among themselves, except for a weak C—H?O hydrogen bond.     

Three‐dimensional hydrogen‐bonded structures in the 1:1 proton‐transfer compounds of l‐tartaric acid with the associative‐group monosubstituted pyridines 3‐aminopyridine, 3‐carboxypyridine (nicotinic acid) and 2‐carboxypyridine (picolinic acid)

The 1:1 proton‐transfer compounds of l ‐tartaric acid with 3‐aminopyridine [3‐aminopyridinium hydrogen (2R,3R)‐tartrate dihydrate, C₅H₇N₂⁺·C₄H₅O₆⁻·2H₂O, (I)], pyridine‐3‐carboxylic acid (nicotinic acid) [anhydrous 3‐carboxypyridinium hydrogen (2R,3R)‐tartrate, C₆H₆NO₂⁺·C₄H₅O₆⁻, (II)] and pyridine‐2‐carboxylic acid [2‐carboxypyridinium hydrogen (2R,3R)‐tartrate monohydrate, C₆H₆NO₂⁺·C₄H₅O₆⁻·H₂O, (III)] have been determined. In (I) and (II), there is a direct pyridinium–carboxyl N⁺—H...O hydrogen‐bonding interaction, four‐centred in (II), giving conjoint cyclic R₁²(5) associations. In contrast, the N—H...O association in (III) is with a water O‐atom acceptor, which provides links to separate tartrate anions through O_hydroxy acceptors. All three compounds have the head‐to‐tail C(7) hydrogen‐bonded chain substructures commonly associated with 1:1 proton‐transfer hydrogen tartrate salts. These chains are extended into two‐dimensional sheets which, in hydrates (I) and (III) additionally involve the solvent water molecules. Three‐dimensional hydrogen‐bonded structures are generated via crosslinking through the associative functional groups of the substituted pyridinium cations. In the sheet struture of (I), both water molecules act as donors and acceptors in interactions with separate carboxyl and hydroxy O‐atom acceptors of the primary tartrate chains, closing conjoint cyclic R₄⁴(8), R₃⁴(11) and R₃³(12) associations. Also, in (II) and (III) there are strong cation carboxyl–carboxyl O—H...O hydrogen bonds [O...O = 2.5387 (17) Å in (II) and 2.441 (3) Å in (III)], which in (II) form part of a cyclic R₂²(6) inter‐sheet association. This series of heteroaromatic Lewis base–hydrogen l ‐tartrate salts provides further examples of molecular assembly facilitated by the presence of the classical two‐dimensional hydrogen‐bonded hydrogen tartrate or hydrogen tartrate–water sheet substructures which are expanded into three‐dimensional frameworks via peripheral cation bifunctional substituent‐group crosslinking interactions.     

A pair of diastereomeric 1:2 salts of (R)‐ and (S)‐2‐methylpiperazine with (2S,3S)‐tartaric acid

The crystal structures of a pair of diastereomeric 1:2 salts of (R)‐ and (S)‐2‐methylpiperazine with (2S,3S)‐tartaric acid, namely (R)‐2‐methylpiperazinediium bis[hydrogen (2S,3S)‐tartrate] monohydrate, (I), and (S)‐2‐methylpiperazinediium bis[hydrogen (2S,3S)‐tartrate] monohydrate, (II), both C₅H₁₄N₂²⁺·2C₄H₅O₆⁻·H₂O, each reveal the formation of well‐defined head‐to‐tail‐connected hydrogen tartrate chains; these chains are linked into a two‐dimensional sheet via intermolecular hydrogen bonds involving hydroxy groups and water molecules, resulting in a layer structure. The (R)‐2‐methylpiperazinediium ions lie between the hydrogen tartrate layers in the most stable equatorial conformation in (I), whereas in (II), these ions are in an unstable axial position inside the more interconnected layers and form a larger number of intermolecular hydrogen bonds than are observed in (I).     

4‐Carboxyanilinium (2R,3R)‐tartrate and a redetermination of the α‐polymorph of 4‐aminobenzoic acid

In the title compounds, 4‐carboxyanilinium (2R,3R)‐tartrate, C₇H₈NO₂⁺·C₄H₅O₆⁻, (I), and 4‐aminobenzoic acid, C₇H₇NO₂, (II), the carboxyl planes of the 4‐carboxyanilinium cations/4‐aminobenzoic acid are twisted from the aromatic plane. In (I), the characteristic head‐to‐tail interactions are observed through the tartrate anions, forming two C₂²(7) chain motifs propagating parallel to the a and c axes of the unit cell. Also, the tartrate anions are connected through two primary C₁¹(6) and C₁¹(7) chain motifs, leading to a secondary R₄⁴(22) ring motif. In (II), head‐to‐tail interaction is seen through a discrete D₁¹(2) motif and carboxyl group dimerization is observed through centrosymmetrically related R₂²(8) motifs around the inversion centres of the unit cell. The crystal structures of both compounds are stabilized by intricate three‐dimensional hydrogen‐bonding networks. Alternate hydrophobic and hydrophilic layers are observed in (I) as a result of a column‐like arrangement of the anions and the aromatic rings of the cations.     

A pair of diastereomeric 1:1 salts of (S)‐ and (R)‐2‐methylpiperazine with (2S,3S)‐tartaric acid

The structures of diastereomeric pairs consisting of (S)‐ and (R)‐2‐methylpiperazine with (2S,3S)‐tartaric acid are both 1:1 salts, namely (S)‐2‐methylpiperazinium (2S,3S)‐tartrate dihydrate, C₅H₁₄N₂²⁺·C₄H₄O₆²⁻·2H₂O, (I), and (R)‐2‐methylpiperazinium (2S,3S)‐tartrate dihydrate, C₅H₁₄N₂²⁺·C₄H₄O₆²⁻·2H₂O, (II), which reveal the formation of well defined ammonium carboxylate salts linked via strong intermolecular hydrogen bonds. Unlike the situation in the more soluble salt (II), the alternating columns of tartrate and ammonium ions of the less soluble salt (I) are packed neatly in a grid around the a axis, which incorporates water molecules at regular intervals. The increased efficiency of packing for (I) is evident in its lower `packing coefficient', and the hydrogen‐bond contribution is stronger in the more soluble salt (II).     

Three salts from the reactions of cysteamine and cystamine with L‐(+)‐tartaric acid

Reaction between cysteamine (systematic name: 2‐aminoethanethiol, C₂H₇NS) and L‐(+)‐tartaric acid [systematic name: (2R,3R)‐2,3‐dihydroxybutanedioic acid, C₄H₆O₆] results in a mixture of cysteamine tartrate(1−) monohydrate, C₂H₈NS⁺·C₄H₅O₆⁻·H₂O, (I), and cystamine bis[tartrate(1−)] dihydrate, C₄H₁₄N₂S₂²⁺·2C₄H₅O₆⁻·2H₂O, (III). Cystamine [systematic name: 2,2′‐dithiobis(ethylamine), C₄H₁₂N₂S₂], reacts with L‐(+)‐tartaric acid to produce a mixture of cystamine tartrate(2−), C₄H₁₄N₂S₂²⁺·C₄H₄O₆²⁻, (II), and (III). In each crystal structure, the anions are linked by O—H...O hydrogen bonds that run parallel to the a axis. In addition, hydrogen bonding involving protonated amino groups in all three salts, and water molecules in (I) and (III), leads to extensive three‐dimensional hydrogen‐bonding networks. All three salts crystallize in the orthorhombic space group P2₁2₁2₁.     

Phenyl‐ring rotational disorder in the two‐dimensional hydrogen‐bonded structure of the 1:1 proton‐transfer salt of the diazo‐dye precursor 4‐(phenyldiazenyl)aniline (aniline yellow) with l‐tartaric acid

In the structure of the 1:1 proton‐transfer compound from the reaction of l ‐tartaric acid with the azo‐dye precursor aniline yellow [4‐(phenyldiazenyl)aniline], namely 4‐(phenyldiazenyl)anilinium (2R,3R)‐3‐carboxy‐2,3‐dihydroxypropanoate, C₁₂H₁₂N₃⁺·C₄H₅O₆⁻, the asymmetric unit contains two independent 4‐(phenyldiazenyl)anilinium cations and two hydrogen l ‐tartrate anions. The structure is unusual in that all four phenyl rings of the two cations have identical rotational disorder with equal occupancy of the conformations. The two hydrogen l ‐tartrate anions form independent but similar chains through head‐to‐tail carboxyl–carboxylate O—H...O hydrogen bonds [graph set C(7)], which are then extended into a two‐dimensional hydrogen‐bonded sheet structure through hydroxy O—H...O hydrogen‐bonded links. The anilinium groups of the 4‐(phenyldiazenyl)anilinium cations are incorporated into the sheets and also provide internal hydrogen‐bonded extensions, while their aromatic tails are layered in the structure without significant association except for weak π–π interactions [minimum ring centroid separation = 3.844 (3) Å]. The hydrogen l ‐tartrate residues of both anions exhibit the common short intramolecular hydroxy–carboxylate O—H...O hydogen bonds. This work provides a solution to the unusual disorder problem inherent in the structure of this salt, as well as giving another example of the utility of the hydrogen tartrate anion in the generation of sheet substructures in molecular assembly processes.     

Tolterodinium (+)‐(2R,3R)‐hydrogen tartrate

In the crystal structure of (R)‐N,N‐diisopropyl‐3‐(2‐hydroxy‐5‐methyl­phenyl)‐3‐phenyl­propyl­aminium (2R,3R)‐hydrogen tartrate, C₂₂H₃₂NO⁺·C₄H₅O₆⁻, the hydrogen tartrate anions are linked by O—H⋯O hydrogen bonds to form helical chains built from (9) rings. These chains are linked by the tolterodine molecules via N—H⋯O and O—H⋯O hydrogen bonds to form separate sheets parallel to the (101) plane.     

Brucine salts of l‐α‐hydr­oxy acids: brucinium hydrogen (S)‐malate penta­hydrate and anhydrous brucinium hydrogen (2R,3R)‐tartrate at 130 K

The structures of two brucinium (2,3‐dimeth­oxy‐10‐oxostrychnidinium) salts of the α‐hydr­oxy acids l ‐malic acid and l ‐tartaric acid, namely brucinium hydrogen (S)‐malate penta­hydrate, C₂₃H₂₇N₂O₄⁺·C₄H₅O₅⁻·5H₂O, (I), and anhydrous brucinium hydrogen (2R,3R)‐tartrate, C₂₃H₂₇N₂O₄⁺·C₄H₅O₆⁻,(II), have been determined at 130 K. Compound (I) has two brucinium cations, two hydrogen malate anions and ten water mol­ecules of solvation in the asymmetric unit, and forms an extensively hydrogen‐bonded three‐dimensional framework structure. In compound (II), the brucinium cations form the common undulating brucine sheet substructures, which accommodate parallel chains of head‐to‐tail hydrogen‐bonded tartrate anion species in the inter­stitial cavities.     

Magnetic studies of vanadyl(IV) tartrate dimers

Temperature-dependent magnetic susceptibility data have been collected for solid sodium salts of the binuclearvanadyl(IV) complexes [(VO)₂(d-tart)₂]^4?, [(VO)₂(dl-tart)₂]^4?, [(VO)₂(dl-mmt)₂]^4?,and [(VO)₂(dl-dmt)₂]^4?. (“tart” = tartrate(4?), “mmt” = monomethyl-tartrate(4?), “dmt” = dimethyltartrate(4?).) Ferromagnetic intradimer- and antiferromagnetic interdimer exchange is found; however, both interactions are small and similar in magnitude and reliable exchange constants cannot be extracted. The intradimer interaction probably occurs by a superexchange mechanism.     

Proton‐transfer and non‐transfer in compounds of quinoline and quinaldic acid with l‐tartaric acid

The structures of two compounds of l ‐tartaric acid with quinoline, viz. the proton‐transfer compound quinolinium hydrogen (2R,3R)‐tartrate monohydrate, C₉H₈N⁺·C₄H₅O₆⁻·H₂O, (I), and the anhydrous non‐proton‐transfer adduct with quinaldic acid, bis­(quinolinium‐2‐carboxyl­ate) (2R,3R)‐tar­taric acid, 2C₁₀H₇NO₂·C₄H₆O₆, (II), have been determined at 130 K. Compound (I) has a three‐dimensional honeycomb substructure formed from head‐to‐tail hydrogen‐bonded hydrogen tartrate anions and water mol­ecules. The stacks of π‐bonded quinolinium cations are accommodated within the channels and are hydrogen bonded to it peripherally. Compound (II) has a two‐dimensional network structure based on pseudo‐centrosymmetric head‐to‐tail hydrogen‐bonded cyclic dimers comprising zwitterionic quinaldic acid species which are inter­linked by tartaric acid mol­ecules.     

Was Bijvoet right? Sodium rubidium (+)‐tartrate tetrahydrate revisited

The first determination of the absolute configuration of an organic compound was published in 1951 on sodium rubidium (+)‐tartrate tetrahydrate, Na⁺·Rb⁺·C₄H₄O₆²⁻·4H₂O, but the atomic coordinates are not available in the public literature. This structure has therefore been redetermined using current equipment. The most up‐to‐date techniques for the determination of the absolute configuration have been applied and the question posed in the title can be answered with an unequivocal `yes'.     

Porphyrin Nanorods Modified Glassy Carbon Electrode for the Electrocatalysis of Dioxygen,Methanol and Hydrazine

Porphyrin nanorods (PNR) were prepared by ionic self‐assembly of two oppositely charged porphyrin molecules consisting of free base meso‐tetraphenylsulfonate porphyrin (H₄TPPS₄^2?) and meso‐tetra(N‐methyl‐4‐pyridyl) porphyrin (MTMePyP⁴⁺M=Sn, Mn, In, Co). These consist of H₄TPPS₄^2?? SnTMePyP⁴⁺, H₄TPPS₄^2?? CoTMePyP⁴⁺, H₄TPPS₄^2?? InTMePyP⁴⁺ and H₄TPPS₄^2?? MnTMePyP⁴⁺ porphyrin nanorods. The absorption spectra and transmission electron microscopic (TEM) images of these structures were obtained. These porphyrin nanostructures were used to modify a glassy carbon electrode for the electrocatalytic reduction of oxygen, and the oxidation of hydrazine and methanol at low pH. The cyclic voltammogram of PNR‐modified GCE in pH 2 buffer solution has five irreversible processes, two distinct reduction processes and three oxidation processes. The porphyrin nanorods modified GCE produce good responses especially towards oxygen reduction at ?0.50 V vs. Ag|AgCl (3 M KCl). The process of electrocatalytic oxidation of methanol using PNR‐modified GCE begins at 0.71 V vs. Ag|AgCl (3 M KCl). The electrochemical oxidation of hydrazine began at around 0.36 V on H₄TPPS₄^2?? SnTMePyP⁴⁺ modified GCE. The GCE modified with H₄TPPS₄^2?? CoTMePyP⁴⁺ H₄TPPS₄^2?? InTMePyP⁴⁺ and H₄TPPS₄^2?? MnTMePyP⁴⁺ porphyrin nanorods began oxidizing hydrazine at 0.54 V, 0.59 V and 0.56 V, respectively.     

Kinetic Spectrophotometric Determination of Metoprolol Tartrate in Commercial Dosage Forms

A kinetic spectrophotometric method has been described for the determination of metoprolol tartrate in commercial dosage forms. The procedure is based on the reaction of the drug with 1‐chloro‐2, 4‐dinitrobenzene (CDNB) in dimethylsulfoxide (DMSO) at 100 ± 1 °C. The reaction is investigated by measuring the change in absorbance with time at 420 nm. Fixed‐time (ΔA) and equilibrium methods are chosen for obtaining the calibration curves. Both calibration curves were found to be linear over the concentration range of 5‐60 μg mL^?1. The regression analysis of calibration data resulted in the linear regression equations of ΔA = ?1.608 × 10^?4 + 3.96 × 10^?3 C and A = 7.31 × 10^?4 + 1.90 × 10^?2 C for fixed time (ΔA) and equilibrium methods, respectively. The limit of detection (LOD) for fixed time and equilibrium methods are 1.16 and 0.415 μg mL^?1, respectively. The method has been successfully applied to the quantitation of metoprolol tartrate in commercial dosage forms. Statistical comparison of the results shows that there is no significant difference between the proposed methods and El‐Ries's spectrophotometric method.     

Design and Function of Pre‐organised Outer‐Sphere Amidopyridyl Extractants for Zinc(II) and Cobalt(II) Chlorometallates: The Role of C?H Hydrogen Bonds

Four new sterically hindered pyridines, L¹–L⁴‐containing amido substituents at the 2‐position act as efficient solvent extractants for [CoCl₄]^2? or [ZnCl₄]^2? from acidic chloride solutions through protonation of the pyridino N‐centre to form the neutral outer‐sphere complexes [(LH)₂MCl₄]. These ionophores show very high selectivity for chlorometallate anions over chloride ion and are readily stripped to liberate the free‐metal chlorides without the formation of inner‐sphere complexes [ML₂Cl₂]. Single‐crystal X‐ray structure determinations of [(L²H)₂CoCl₄] and [(L²H)₂ZnCl₄] (L²=2‐(4,6‐di‐tert‐butylpyridin‐2‐yl)‐N,N′‐dihexylmalonamide) coupled with ¹H NMR spectroscopy and DFT calculations on L²H⁺ and other complexes of [ZnCl₄]^2? confirm that the pyridinium NH group does not address the outer co‐ordination sphere of the metallanion, but rather forms a hydrogen bond to the pendant amide groups and thus pre‐organizes the ligand to present both C? H and amido N? H hydrogen‐bond donors to the [MCl₄]^2? ions. The selectivity for chlorometallates over chloride ions shown by this class of extractants arises from their ability to present several polarized C? H units towards the charge‐diffuse ions [MCl₄]^2?, whereas the smaller, “harder” chloride anion prefers to be associated with the amido N? H hydrogen‐bond donors.     

Host–Guest Chemistry: Oxoanion Recognition Based on Combined Charge‐Assisted C−H or Halogen‐Bonding Interactions and Anion⋅⋅⋅Anion Interactions Mediated by Hydrogen Bonds

Several bis‐triazolium‐based receptors have been synthesized and their anion‐recognition capabilities have been studied. The central chiral 1,1′‐bi‐2‐naphthol (BINOL) core features either two aryl or ferrocenyl end‐capped side arms with central halogen‐ or hydrogen‐bonding triazolium receptors. NMR spectroscopic data indicate the simultaneous occurrence of several charge‐assisted aliphatic and heteroaromatic C?H noncovalent interactions and combinations of C?H hydrogen and halogen bonding. The receptors are able to selectively interact with HP₂O₇^3?, H₂PO₄^?, and SO₄^2? anions, and the value of the association constant follows the sequence: HP₂O₇^3?>SO₄^2?>H₂PO₄^?. The ferrocenyl end‐capped 7²⁺?2 BF₄ ^? receptor allows recognition and differentiation of H₂PO₄^? and HP₂O₇^3? anions by using different channels: H₂PO₄^? is selectively detected through absorption and emission methods and HP₂O₇^3? by using electrochemical techniques. Significant structural results are the observation of an anion???anion interaction in the solid state (2:2 complex, 6²⁺? [ H₂P₂O₇ ] ^2? ), and a short C?I???O contact is observed in the structure of the complex [ 8 ²⁺][SO₄]_0.5[BF₄].     

Unusual Nitrile–Nitrile and Nitrile–Alkyne Coupling of FcCN and FcCCCN

The reactions of the Group 4 metallocene alkyne complexes, [Cp*₂M(η²‐Me₃SiC₂SiMe₃)] ( 1 a : M=Ti, 1 b : M=Zr, Cp*=η⁵‐pentamethylcyclopentadienyl), with the ferrocenyl nitriles, Fc?C?N and Fc?C?C?C?N (Fc=Fe(η⁵‐C₅H₅)(η⁵‐C₅H₄)), is described. In case of Fc?C?N an unusual nitrile–nitrile C?C homocoupling was observed and 1‐metalla‐2,5‐diaza‐cyclopenta‐2,4‐dienes ( 3 a , b ) were obtained. As the first step of the reaction with 1 b , the nitrile was coordinated to give [Cp*₂Zr(η²‐Me₃SiC₂SiMe₃)(N?C‐Fc)] ( 2 b ). The reactions with the 3‐ferrocenyl‐2‐propyne‐nitrile Fc?C?C?C?N lead to an alkyne–nitrile C?C coupling of two substrates and the formation of 1‐metalla‐2‐aza‐cyclopenta‐2,4‐dienes ( 4 a , b ). For M=Zr, the compound is stabilized by dimerization as evidenced by single‐crystal X‐ray structure analysis. The electrochemical behavior of 3 a , b and 4 a , b was investigated, showing decomposition after oxidation, leading to different redox‐active products.     

Adsorption affinity of anions on metal oxyhydroxides

The dependences of anion (phosphate, carbonate, sulfate, chromate, oxalate, tartrate, and citrate) adsorption affinity anions from geometric characteristics, acid-base properties, and complex forming ability are generalized. It is shown that adsorption depends on the nature of both the anions and the ionic medium and adsorbent. It is established that anions are generally grouped into the following series of adsorption affinity reduction: PO ₄ ^3? , CO ₃ ^2? > C₂O ₄ ^2? , C(OH)(CH₂)₂(COO) ₃ ^3? , (CHOH)₂(COO) ₂ ^2? > CrO ₄ ^2? ? SO ₄ ^2? .     

Polarographic study of mixed ligand complexes of Pb(II) with carboxylate ions and imidazole

Mixed complexes of Pb(II) with some carboxylate ions, viz. tartrate (tart^2?), malonate (mal^2?) and citrate (citr^3?); and imidazole (im) have been studied polarographically at 25°C and at constant ionic strength μ = 2.0 (NaNO₃) and at pH 6. The polarographic reduction of the complexes in each case is reversible and diffusion-controlled. Pb(II) forms a single mixed complex with tartrate and imidazole, viz [Pb(tart)(im)] with stability constant log β₁₁ = 4.19; with mal^2? and im, three mixed complexes, [Pb(mal)(im)], [Pb(mal)(im)₂] and [Pb(mal)₂(im)]^2? with stability constants log β₁₁ = 4.3, log β₁₂ = 7.3 and log β₂₁ = 5.5 respectively are formed. With citr^3? and im a single mixed species, [Pb(citr)(im)]^? with stability constant log β₁₁ = 8.0 is formed. Various equilibria involved in the mixed systems have been discussed.     

Two Heterometallic–Organic Frameworks Composed of Iron(III)‐Salen‐Based Ligands and d10 Metals: Gas Sorption and Visible‐Light Photocatalytic Degradation of 2‐Chlorophenol

Two examples of heterometallic–organic frameworks (HMOFs) composed of dicarboxyl‐functionalized Fe^III‐salen complexes and d¹⁰ metals (Zn, Cd), [Zn₂(Fe‐L)₂(μ₂‐O)(H₂O)₂] ? 4 DMF ? 4 H₂O ( 1 ) and [Cd₂(Fe‐L)₂(μ₂‐O)(H₂O)₂] ? 2 DMF ? H₂O ( 2 ) (H₄L=1,2‐cyclohexanediamino‐N,N′‐bis(3‐methyl‐5‐carboxysalicylidene), have been synthesized and structurally characterized. In 1 and 2 , each square‐pyramidal Fe^III atom is embedded in the [N₂O₂] pocket of an L^4? anion, and these units are further bridged by a μ₂‐O anion to give an (Fe‐L)₂(μ₂‐O) dimer. The two carboxylate groups of each L^4? anion bridge Zn^II or Cd^II atoms to afford a 3D porous HMOF. The gas sorption and magnetic properties of 1 and 2 have been studied. Remarkably, 1 and 2 show activity for the photocatalytic degradation of 2‐chlorophenol (2‐CP) under visible‐light irradiation, which, to the best of our knowledge, is the first time that this has been observed for Fe^III‐salen‐based HMOFs.