Molecular aggregation in selected crystalline 1:1 complexes of hydrophobic d‐ and l‐amino acids. IV. The l‐phenylalanine series

The amino acid l ‐phenylalanine has been cocrystallized with d ‐2‐aminobutyric acid, C₉H₁₁NO₂·C₄H₉NO₂, d ‐norvaline, C₉H₁₁NO₂·C₅H₁₁NO₂, and d ‐methionine, C₉H₁₁NO₂·C₅H₁₁NO₂S, with linear side chains, as well as with d ‐leucine, C₉H₁₁NO₂·C₆H₁₃NO₂, d ‐isoleucine, C₉H₁₁NO₂·C₆H₁₃NO₂, and d ‐allo‐isoleucine, C₉H₁₁NO₂·C₆H₁₃NO₂, with branched side chains. The structures of these 1:1 complexes fall into two classes based on the observed hydrogen‐bonding pattern. From a comparison with other l :d complexes involving hydrophobic amino acids and regular racemates, it is shown that the structure‐directing properties of phenylalanine closely parallel those of valine and isoleucine but not those of leucine, which shares side‐chain branching at C^γ with phenylalanine and is normally considered to be the most closely related non‐aromatic amino acid.     

Volume properties and refraction of aqueous solutions of bisadducts of light fullerene С60 and essential amino acids lysine,threonine, and oxyproline (С60(C6H13N2O2)2, С60(C4H8NO3)2, and С60(C5H9NO2)2) at 25°C

Concentration dependences of the density of aqueous solutions of bisadducts of light fullerene С₆₀ and essential amino acids are studied by pycnometry. Concentration dependences of the average molar volumes and partial volumes of components (Н₂О and corresponding bisadducts) are calculated for С₆₀(C₆H₁₃N₂O₂)₂–Н₂О, С₆₀(C₄H₈NO₃)₂–Н₂О, and С₆₀(C₅H₉NO₂)₂–Н₂О binary systems at 25°C. Concentration dependences of the indices of refraction of С₆₀(C₆H₁₃N₂O₂)₂–Н₂О, С₆₀(C₄H₈NO₃)₂–Н₂О, and С₆₀(C₅H₉NO₂)₂–Н₂О binary systems are determined at 25°C. The concentration dependences of specific refraction and molar refraction of bisadducts and aqueous solutions of them are calculated.

     

Mixed-ligand platinum(IV) complexes with amino acids and adenine

Complexing in platinum(IV)-adenine-amino acid (α-alanine (Ala), lysine (Lys), or histidine (His)) systems was studied by pH titration. The stability constants of 1: 1: 1 complexes were determined. The stability of these mixed-ligand complexes changes in the following order: Lys < Ala < His. Reactions between aqueous solutions of H₂PtCl₆ and amino acids produced the following coordination compounds: Pt(C₃H₆NO₂)(C₅H₅N₅)Cl₃ · 2H₂O, or Pt(Ala^?)(Ade)Cl₃ · 2H₂O (I); Pt(C₅H₅N₅)(C₆H₁₄N₂O₂)Cl₄ · 2H₂O, or Pt(Ade)(Lys)Cl₄ · 2H₂O (II); and Pt(C₅H₅N₅)(C₆H₉N₃O₂)Cl₄ · 3H₂O or Pt(Ade)(Hist)Cl₄ · 3H₂O (III). These complexes were characterized by ¹³C NMR, IR, and X-ray photoelectron spectroscopy. Alanine is complexed via both amino and carboxy groups; lysine, via α-amino group exclusively; and histidine, via the amino group and the N3 heterocyclic atom. Adenine in these complexes is monodentate due to the N7 heterocyclic atom. The adenine amino group is apparently H-bonded to a water oxygen atom.     

Environmentally friendly acylaminocarboxylates yttrium (III) complexes: Synthesis,solubility and aggregation behavior

In order to investigate the effect of differences in amino acid alkyl chains, In order to investigate the effect of difference amino acid alkyl chains on the Rare earth complexes, the lipoaminic acids rare earth surfactant complexes of yttrium hexanoyl alaninc acid (Y(hex-ala)₃), yttrium octanoyl alaninc (Y(oct-ala)₃) and yttrium dodecanoyl alaninc acid (Y(dod-ala)₃) are synthesized by the reaction of C₉H₁₇NO₃, C₁₁H₂₁NO₃, C1₅H₂₉NO₃ with YCl₃, respectively. These complexes have been compared to the yttrium octanoate soap (Y(octnt)₃). At the same time, the formation of molecular glasses of these complexes are compared with the aggregation behavior in solution, evaluate properties as glass. Furthermore, the aggregation behavior of the above surfactant complexes in the pure solvent are studied using nuclear magnetic resonance (NMR) spectrometry, vapor pressure osmometry (VPO), electrical conductivity and Fourier Transform-Infrared spectroscopy (FT-IR). As results, these Y(III) complexes aggregate in the organic solvents system and tend to form aggregates. After the organic solvents evaporated, organic rare earth vitreous bodies was obtained.     

New 1:1 and 2:1 salts in the `dl‐norvaline–maleic acid' system as an example of assembling various crystal structures from similar supramolecular building blocks

Molecular salts and cocrystals of amino acids have potential applications as molecular materials with nonlinear optical, ferroelectric, piezoelectric, and other various target physical properties. The wide choice of amino acids and coformers makes it possible to design various crystal structures. The amino acid–maleic acid system provides a perfect example of a rich variety of crystal structures with different stoichiometries, symmetries and packing motifs built from the molecular building blocks, which are either exactly the same, or differ merely by protonation or as optical isomers. The present paper reports the crystal structures of two new salts of the dl ‐norvaline–maleic acid system with 1:1 and 2:1 stoichiometries, namely dl ‐norvalinium hydrogen maleate, C₅H₁₂NO₂⁺·C₄H₃O₄⁻, (I), and dl ‐norvalinium hydrogen maleate–dl ‐norvaline, C₅H₁₂NO₂⁺·C₄H₃O₄⁻·C₅H₁₁NO₂, (II). These are the first examples of molecular salts of dl ‐norvaline with an organic anion. The crystal structure of (I) has the same C ₂²(12) structure‐forming motif which is common for hydrogen maleates of amino acids. The structure of (II) has dimeric cations. Of special interest is that the single crystals of (I) which are originally formed on crystallization from aqueous solution transform into single crystals of (II) if stored in the mother liquor for several hours.     

Lanthanon (III) Complexes of Bifunctional Tridentate and Tetradentate Schiff Bases

Reactions of isopropoxides of praseodymium, neodymium and samarium with bifunctional tridentate and tetradentate schiff bases (i.e. salicylidene-O-aminophenol and bis-salicylaldehyde ethylenediamine) have been carried out in benzene in different stoichiometric ratios resulting in the formation of products with the formula M(OPrⁱ)(C₁₁H₉NO₂), M(C₁₃H₉NO₂)(C₁₃H₁₀NO₂). M₂(C₁₃H₉NO₂) M(OPrⁱ)(C₁₅H₁₄N₂O₂), M(C₁₆H₁₄N₂O₂)(C₁₆H₁₅N₂O₂) and M₂(C₁₆H₁₄N₂O₂)₃ (where M stands for Pr, Nd and Sm). The products were found to be yellow to orange solids soluble in benzene and alcohol. The absorption spectra of these complexes were also recorded in methanol.     

Salt Effects on Reactivity of Some Fe(II)-Azo Complexes Catalyzing Disproportionation of Hydrogen Peroxide

Summary. Salt effects on kinetics of oxidation and decomposition of novel low-spin Fe(II) complexes of azo amino acids with hydrogen peroxide have been investigated in aqueous medium. The ligands are derived from amino acids (DL-phenylalanine, DL-tryptophane, histidine, and alanine) and p-nitroso aromatic substituted amines (N,N-dimethyl-4-nitrosoaniline and N,N-diethyl-4-nitrosoaniline). Hydrophobic salts of alkali metal and tetraalkylammonium halides, e.g., KBr, tetrabutylammonium bromide (TBAB), tetraethylammonium bromide (TEAB), and tetramethylammonium bromide (TMAB) have been used. Dilute salt solutions exhibit little effects on the reactivities of oxidation and decomposition of the title compounds. This behaviour would be ascribed to a decrease in the activity coefficients of the reacting species in these solutions. Moreover, these effects support the reported pathway in these reactions occurring via the association of dicationic complexes and undissociated H₂O₂. On the other hand, higher salt concentration shows considerable effects on the reactivities. This behaviour is explained in terms of hydrophilicity of the complexes, ion pair formation, salting out, and substituent effects. Hyrophilic nature of the recent complexes enhances reactivity with increasing [KBr] due to salting out effects in the aqueous medium. Increasing [TBAB] retards reactivity via ion pair formation with the reactants. In the presence of R₄N⁺ ions, the reactivity increases with changing R in the following order; R = C₄H₉ < C₂H₅ < CH₃. The bulky R groups in the added tetraalkylammonium salts, exert medium steric hindrance against the approach of reactants.     

Partitioning of Amino Acids in Surfactant Based Aqueous Two-Phase Systems Containing the Nonionic Surfactant (Triton X-100) and Salts

The partitioning of three amino acids, L-phenylalanine, L-tryptophan and L-tyrosine, has been studied in surfactant-based aqueous two-phase systems (ATPS) of Triton X-100 + salts + H₂O at 298.15 K. Sodium citrate as an organic salt and magnesium sulfate as an inorganic salt were used to prepare the ATP systems. The effects of tie-line length and salt type on the partitioning of amino acids have been discussed. The results show that the partitioning behavior of the amino acids in the systems containing MgSO₄ and Na₃C₆H₅O₇ are significantly different, because increasing the tie-line length in MgSO₄ solutions leads to a decrease of the partition coefficient, whereas the opposite trend is found in Na₃C₆H₅O₇ solutions.     

Salt Effects on Reactivity of Some Fe(II)-Azo Complexes Catalyzing Disproportionation of Hydrogen Peroxide

Salt effects on kinetics of oxidation and decomposition of novel low-spin Fe(II) complexes of azo amino acids with hydrogen peroxide have been investigated in aqueous medium. The ligands are derived from amino acids (DL-phenylalanine, DL-tryptophane, histidine, and alanine) and p-nitroso aromatic substituted amines (N,N-dimethyl-4-nitrosoaniline and N,N-diethyl-4-nitrosoaniline). Hydrophobic salts of alkali metal and tetraalkylammonium halides, e.g., KBr, tetrabutylammonium bromide (TBAB), tetraethylammonium bromide (TEAB), and tetramethylammonium bromide (TMAB) have been used. Dilute salt solutions exhibit little effects on the reactivities of oxidation and decomposition of the title compounds. This behaviour would be ascribed to a decrease in the activity coefficients of the reacting species in these solutions. Moreover, these effects support the reported pathway in these reactions occurring via the association of dicationic complexes and undissociated H₂O₂. On the other hand, higher salt concentration shows considerable effects on the reactivities. This behaviour is explained in terms of hydrophilicity of the complexes, ion pair formation, salting out, and substituent effects. Hyrophilic nature of the recent complexes enhances reactivity with increasing [KBr] due to salting out effects in the aqueous medium. Increasing [TBAB] retards reactivity via ion pair formation with the reactants. In the presence of R₄N⁺ ions, the reactivity increases with changing R in the following order; R = C₄H₉ < C₂H₅ < CH₃. The bulky R groups in the added tetraalkylammonium salts, exert medium steric hindrance against the approach of reactants.     

3-D Hydrogen-bonded networks of metal complexes with chelidamic acid and 1,10-phenanthroline: syntheses,structures, and optical properties

The title complexes, (C₁₂H₈N₂) ? [La(C₇H₃NO₅)(C₇H₄NO₅) ? 3H₂O] ? 1.75H₂O (1), (C₁₂H₈N₂) ? [Pr(C₇H₃NO₅)(C₇H₄NO₅) ? 3H₂O] ? 2H₂O (2), (C₁₂H₈N₂)[Nd(C₇H₃NO₅)(C₇H₄NO₅) ? 3H₂O] ? 2.25H₂O (3), and (C₁₂H₈N₂) ? [Fe(C₇H₃NO₅)(C₇H₄NO₅)] ? 2H₂O (4), were synthesized and characterized by single-crystal X-ray diffraction. The crystal structures of 1–3 reveal that they are isomorphous, among which the metal atoms are all nine-coordinate with distorted tricapped trigonal prismatic coordination geometries. The Fe is six-coordinate with a distorted octahedron by two chelidamic acid ligands in 4. Complexes 1–4 are formed into 3-D networks by H-bonds and π–π stacking interactions. The fluorescence spectra of 1–3 were investigated and all exhibit strong luminescence.     

New hydrophobic L‐amino acid salts: maleates of L‐leucine,L‐isoleucine and L‐norvaline

Crystals of maleates of three amino acids with hydrophobic side chains [L‐leucenium hydrogen maleate, C₆H₁₄NO₂⁺·C₄H₃O₄⁻, (I), L‐isoleucenium hydrogen maleate hemihydrate, C₆H₁₄NO₂⁺·C₄H₃O₄⁻·0.5H₂O, (II), and L‐norvalinium hydrogen maleate–L‐norvaline (1/1), C₅H₁₁NO₂⁺·C₄H₃O₄⁻·C₅H₁₂NO₂, (III)], were obtained. The new structures contain C₂²(12) chains, or variants thereof, that are a common feature in the crystal structures of amino acid maleates. The L‐leucenium salt is remarkable due to a large number of symmetrically non‐equivalent units (Z′ = 3). The L‐isoleucenium salt is a hydrate despite the fact that L‐isoleucine is a nonpolar hydrophobic amino acid (previously known amino acid maleates formed hydrates only with lysine and histidine, which are polar and hydrophilic). The L‐norvalinium salt provides the first example where the dimeric cation L‐Nva...L‐NvaH⁺ was observed. All three compounds have layered noncentrosymmetric structures. Preliminary tests have shown the presence of the second harmonic generation (SGH) effect for all three compounds.     

Pyridinium tetrakis(nitrato-κ2O,O′)(2,2′:6′,2′′-terpyridine-κ3N)cerate(III) pyridine solvate and bis(methanol-κO)tris(nitrato-κ2O,O′)(2,2′:6′,2′′-terpyridine-κ3N)cerium(III)

The title complexes, (C₅H₆N)[Ce(NO₃)₄(C₁₅H₁₁N₃)]·C₅H₅N or (Hpy)­[Ce(NO₃)₄(terpy)]·py, (I) (py is pyridine, C₅H₅N, and terpy is ter­pyridine, C₁₅H₁₁N₃), and [Ce(NO₃)₃­(C₁₅H₁₁N₃)(CH₄O)₂] or [Ce(NO₃)₃(terpy)(OHCH₃)₂], (II), are 11-coordinate. The coordination polyhedron of the Ce atom in (I) is irregular, while that in (II) can be described as an icosahedron with two vertices replaced by one.     

Synthesis and Self‐Assembly of Bolaamphiphiles Based on β‐Amino Acids or an Alcohol

The synthesis of bolaamphiphiles from unusual β‐amino acids or an alcohol and C₁₂ or C₂₀ spacers is described. Unusual β‐amino acids such as a sugar amino acid, an AZT‐derived amino acid, a norbornene amino acid, and an AZT‐derived amino alcohol were coupled with spacers under standard conditions to get the novel bolaamphiphiles 5 – 8 (Scheme 1), 12 and 13 (Scheme 2), and 17 and 20 (Scheme 3). Some of these compounds, on precipitation from MeOH/H₂O, self‐assembled into organized molecular structures.     

Precipitation of Bismuth(III) Tartrates from Nitrate Solutions

The precipitation of bismuth(III) from nitrate solutions on addition of aqueous solutions of tartaric acid and sodium tartrate was studied by X-ray phase analysis, thermogravimetry, IR spectroscopy, and chemical analysis. Conditions for the formation of [Bi(NO₃)(H₂O)₃]C₄H₄O₆ and [Bi(C₄H₄O₆)(C₄H₅O₆)] · 3H₂O were determined.     

Syntheses and structures of mononuclear and binuclear transition metal complexes (Cu,Zn, Ni) with (salicylideneglycine and imidazole)

Four transition metal (Cu(II), Zn(II) and Ni(II)) complexes with a Schiff-base ligand (salicylideneglycine) have been synthesized. All complexes have been characterized by elemental analysis, IR spectra and UV-vis spectroscopy. Single-crystal analyses were performed with (C₉H₇NO₃)Cu(C₃H₄N₂) (1), (C₉H₇NO₃)Zn(C₃H₄N₂)₂ (2), (C₉H₇NO₃)₂Ni₂(C₃H₄N₂)₄ (3) and (C₉H₇NO₃)Ni(C₃H₄N₂)₂(C₄H₅N₂O) · CH₃OH · 0.5H₂O (4) and fluorescence spectra and thermogravimetric analyses were also carried out. Structural analyses show that 1, 2 and 4 have similar coordinated modes with the tridentate amino-Schiff-base ligand, but differ from the binuclear nickel complex 3. The tridentate amino-Schiff-base ligand contains aliphatic nitrogen, phenoxy, and carboxylic oxygen as three donor atoms. In addition, inter- and intra-molecular hydrogen bonds are also discussed.     

A phase transition from monoclinic C2 with Z′ = 1 to triclinic P1 with Z′ = 4 for the quasiracemate l‐2‐aminobutyric acid–d‐methionine (1/1)

Racemates of hydrophobic amino acids with linear side chains are known to undergo a unique series of solid‐state phase transitions that involve sliding of molecular bilayers upon heating or cooling. Recently, this behaviour was shown to extend also to quasiracemates of two different amino acids with opposite handedness [Görbitz & Karen (2015). J. Phys. Chem. B, 119 , 4975–4984]. Previous investigations are here extended to an l ‐2‐aminobutyric acid–d ‐methionine (1/1) co‐crystal, C₄H₉NO₂·C₅H₁₁NO₂S. The significant difference in size between the –CH₂CH₃ and –CH₂CH₂SCH₃ side chains leads to extensive disorder at room temperature, which is essentially resolved after a phase transition at 229 K to an unprecedented triclinic form where all four d ‐methionine molecules in the asymmetric unit have different side‐chain conformations and all three side‐chain rotamers are used for the four partner l ‐2‐aminobutyric acid molecules.     

以稀土为连接单元基于Anderson型[Al(OH)6Mo6O18]3-的一维拓展结构的合成及性质研究

在常规条件下合成4个新型的稀土-Anderson型多金属氧酸盐拓展结构化合物(C5H9NO2)2[Ln(H2O)7AlMo6H6O24].11H2O(Ln=La(1),Ce(2),Pr(3),Gd(4);C5H9NO2=脯氨酸),并通过元素分析、红外光谱、紫外可见光谱、热重分析和X射线单晶衍射等方法对化合物晶体结构进行了表征。结构分析表明:以上4个化合物是同构的,均结晶在单斜C2/c空间群。在这些结构中,[Al(OH)6Mo6O18]3-首先通过稀土离子连接形成一维链,相邻的链再进一步通过脯氨酸和结晶水分子的氢键作用形成三维超分子结构化合物。我们以化合物1为代表研究了这类化合物的光催化性能,在紫外光照射下表现出很好的降解RhB(罗丹明B)的光催化性质。     

Pseudopolymorphs of chelidamic acid and its dimethyl ester

Different tautomeric and zwitterionic forms of chelidamic acid (4‐hydroxypyridine‐2,6‐dicarboxylic acid) are present in the crystal structures of chelidamic acid methanol monosolvate, C₇H₅NO₅·CH₄O, (Ia), dimethylammonium chelidamate (dimethylammonium 6‐carboxy‐4‐hydroxypyridine‐2‐carboxylate), C₂H₈N⁺·C₇H₄NO₅⁻, (Ib), and chelidamic acid dimethyl sulfoxide monosolvate, C₇H₅NO₅·C₂H₆OS, (Ic). While the zwitterionic pyridinium carboxylate in (Ia) can be explained from the pK_a values, a (partially) deprotonated hydroxy group in the presence of a neutral carboxy group, as observed in (Ib) and (Ic), is unexpected. In (Ib), there are two formula units in the asymmetric unit with the chelidamic acid entities connected by a symmetric O—H...O hydrogen bond. Also, crystals of chelidamic acid dimethyl ester (dimethyl 4‐hydroxypyridine‐2,6‐dicarboxylate) were obtained as a monohydrate, C₉H₉NO₅·H₂O, (IIa), and as a solvent‐free modification, in which both ester molecules adopt the hydroxypyridine form. In (IIa), the solvent water molecule stabilizes the synperiplanar conformation of both carbonyl O atoms with respect to the pyridine N atom by two O—H...O hydrogen bonds, whereas an antiperiplanar arrangement is observed in the water‐free structure. A database study and ab initio energy calculations help to compare the stabilities of the various ester conformations.     

Theoretical chemical ionization rate constants of the concurrent reactions of hydronium ions (H3O+) and oxygen ions (O ) with selected organic iodides

Short chain volatile iodinated organic compounds (VIOCs) are of great importance in many fields that include atmospheric chemistry, agriculture, and environmental chemistry related to nuclear power plant safety. Proton‐transfer‐reaction mass spectrometry (PTR‐MS) allows for fast, sensitive, and online quantification of VIOCs if the chemical ionization (CI) reaction rate coefficients are known. In this work, the theoretical CI rate coefficients for the reactions of hydronium ions (H₃O⁺) and oxygen ions (O ) with selected atmospherically important short chain VIOCs are determined. The neutral CH₃I, CH₂I₂, C₂H₅I, iso‐C₃H₇I, n‐C₃H₇I, n‐C₄H₉I, 2‐C₄H₉I, n‐C₅H₁₁I, 2‐C₅H₁₁I, and 3‐C₅H₁₁I have been chosen because these compounds are of atmospheric and environmental importance in the field of safety of nuclear plant reactors. Theoretical ion‐molecule collision rate coefficients were determined using the Su and Chesnavich theory based on parametrized trajectory calculations. The proton affinity, ionization energy, dipole moment, and polarizability values of the neutral molecules were determined from density functional theory and coupled‐cluster calculations. The newly calculated rate constants facilitate the use of the CI mass spectrometry in the atmospheric quantification of selected VIOCs.     

The formation of aryloxenium ion in the reaction of N-nitro-O-(4-nitrophenyl)hydroxylamine with strong acids

The reaction of N-nitro-O-(4-nitrophenyl)hydroxylamine (1) with conc. H₂SO₄ affords 4-nitropyrocatechol and that with conc. sulfonic acids (RSO₃H where R = Me, CF₃) affords 2-hydroxy-5-nitrophenyl-R-sulfonates in yields of 80?C85%. These reactions are assumed to proceed through an intermediate (phenoxy)oxodiazonium ion [NO₂C₆H₄O-N=N=O]⁺, which eliminates the N₂O molecule to form the aryloxenium ion [NO₂C₆H₄O]⁺. The latter reacts with acid anions at the ortho-carbon atom of the phenyl ring. The thermodynamical parameters of the elementary reactions resulting in the formation of the (phenoxy)oxodiazonium ion [NO₂C₆H₄O-N=N=O]⁺ and aryloxenium ion [NO₂C₆H₄O]⁺ were calculated in the B3LYP/6?311+G(d) study of the combined molecular system (nitrohydroxylamine 1 + [H₃SO₄]⁺). The reaction of nitrohydroxylamine 1 with aqueous solutions of strong acids (??70% H₂SO₄, CF₃SO₃H) affords mainly 4-nitrophenol. It appears that the mechanism of this reaction does not involve the formation of the aryloxenium ion.