First MnIII complexes with tetradentate (N2O2) Schiff bases and tricyanomethanide: synthesis,crystal structure,and magnetic properties

The first Mn^III complexes with Schiff bases and tricyanomethanide-anion were synthesized: [Mn(salen)C(CN)₃(H₂O)] (1), [Mn(5-Brsalen)C(CN)₃(H₂O)] (2), [Mn(salpn)C(CN)₃(H₂O)] (3), [Mn(3-MeOsalen)C(CN)₃(H₂O)] (4), [Mn(5-Brsalen)(MeOH)(H₂O)][C(CN)₃] (5), and [Mn(3-MeOsalpn)(H₂O)₂][C(CN)₃] (6), where SalenH₂ is N,N′-bis(salicylidene)ethylenediamine, 5-BrsalenH₂ is N,N′-bis(5-bromosalicylidene)ethylenediamine, SalpnH₂ is N,N′-bis-(salicylidene)-1,3-diaminopropane, 3-MeOsalenH₂ is N,N′-bis(3-methoxysalicylidene)-ethylenediamine, 3-MeOsalpnH₂ — N,N′-bis(3-methoxysalicylidene)-1,3-diaminopropane. The tricyanomethanide anion in complexes 1–4 acts as a the terminal ligand, whereas in complexes 5 and 6 tricyanomethanide is not coordinated by Mn^III and acts as an out-of-sphere counterion. The structures of complexes 1–4 are characterized by the formation of dimers due to hydrogen bonds between the water molecules and oxygen atoms of the Schiff bases. The Mn...Mn distances inside the dimers are 4.69–5.41 Å. Complex 6 has a zigzag chain structure consisting of the [Mn(3-MeOsalpn)(H₂O)₂]⁺ cations bound by double bridging aqua ligands. The study of the magnetic properties of complexes 1, 3, 4, and 6 showed the existence of antiferromagnetic interactions between the Mn^III ions through the system of hydrogen bonds.     

Spectroscopic characterization, crystal structure determination and interaction with DNA of novel cyano substituted benzimidazole derivative

Novel cyano-substituted benzimidazole derivatives 3 and 4 were synthesized from 4-N,N-dimethylamino-benzaldehyde and 2-cyanomethyl-benzimidazole. 2-(1H-benzimidazol-2-yl)-3-(4-N,N-dimethylamino-phenyl)-acrylonitrile hydrochloride monohydrate 4 has been studied by ¹H and ¹³C NMR, IR, MS, UV/Vis and fluorescence spectroscopy and confirmed by X-ray crystal structure analysis. The interaction of 4 with ct-DNA has also been investigated by fluorescence spectroscopy and melting temperature determination experiment. According to the emission spectra recorded in the absence and presence of ct-DNA at different ratios r ([compound]/[polynucleotide]), 4 showed marked decrease in the fluorescence intensity and very strong hypochromic effect. Melting temperature experiment showed weak stabilization of double helix. To determine binding mode of 4, other additional experiments are necessary. The molecules of 4 are almost planar with the dihedral angle between benzimidazole and phenyl rings of 6.99(6)°. The protonation of nitrogen atom of benzimidazole ring is followed by π-electrons delocalization in the region resulting in C–N bond distances equality [1.341(2) and 1.337(2) Å]. Both NH groups of benzimidazole ring form intermolecular hydrogen bonds, one with the oxygen atom of water molecule [N···O 2.689(2) Å] and the other with Cl^? ion (N···Cl^? 3.051(1) Å). Except proton acceptor, water molecule acts as double proton donor in the formation of intermolecular hydrogen bonds with Cl^? ion [O···Cl^? 3.126(2) and 3.169(2) Å]. In that way, infinite chains along [110] direction are formed.     

Effect of anions on supramolecular architecture of benzimidazole-based ionic salts

The reaction of N,N,N′,N′-tetrakis-(1H,benzimidazol-2ylmethyl) propane-1,3-diamine (L) with different inorganic acids affords salts viz., LH₄ ⁴⁺·4ClO₄ ^?·H₂O (1), LH₄ ⁴⁺·4Cl^?·2H₂O (2), LH₄ ⁴⁺·2H₂PO₄ ^?·H₇P₃O₁₂ ^2?·3H₃PO₄ (3), LH₄ ⁴⁺·4NO₃ ^? (4), and 2LH⁺·2CF₃COO^?·5H₂O (5). The X-ray crystallographic studies revealed that the proton transfer occurred from acid to the ligand. It also demonstrated that different type of hydrogen bond between protonated ligand and anions is responsible for the supramolecular framework. The colorimetric test showed color change upon the addition of acids in the solution of the ligand. The photo-physical experiments suggested the fluorescence properties of ligand in the presence of acids.     

Transformation of a ditopic Schiff base nickel(II) nitrate complex into an unsymmetrical Schiff base complex by partial hydrolytic degradation: structural and density functional theory studies

A new Schiff base complex [Ni(H₂L¹)(NO₃)](NO₃) (1) (H₂L¹ = 3-[N,N′-bis-2-(5-bromo-3-(morpholinomethyl) salicylideneamino) ethyl amine]) was synthesized from reaction of the ditopic ligand H₂L¹ with Ni(NO₃)₂ in anhydrous MeOH. Complex 1 is stable in the solid state, but prone to hydrolysis. Recrystallization of 1 from wet MeOH led to the isolation of a novel unsymmetrical complex [Ni(HL²)(NO₃)](NO₃) (2) (HL² = 2-[(2-(2-aminoethylamino) ethylimino) ethyl)-5-bromo-3-(morpholino methyl) salicylidene amine]). X-ray single-crystal analysis of complex 2 showed that complex 1 had undergone partial decomposition of one imine bond. In contrast, the Schiff base complex [Ni(HL³)](NO₃) (3) (H₂L³ = N,N′-bis(5-methyl-salicylidene) diethylenetriamine) was stable in wet methanol, and the single-crystal structure of 3 showed that the Ni(II) center was coordinated in an unsymmetrical square planar geometry. Density functional theory calculations were performed in order to obtain a geometry-optimized model of complex 1, in which the Ni(II) center was coordinated in a similar manner as that in complex 3. The thermodynamic parameters were calculated, in order to rationalize the difference in hydrolytic reactivity between complexes 1 and 3.     

Synthesis and structure of tris(4-N,N-dimethylaminophenyl)antimony(V) difluoride, dichloride, and dibenzoate

tris(4-N,N-Dimethylaminophenyl)antimony dichloride (I) was prepared by the reaction of tris(4-N,N-dimethylaminophenyl)antimony with copper dichloride. tris(4-N,N-Dimethylaminophenyl)antimony difluoride benzene disolvate II was synthesized from dichloride I and sodium fluoride in aqueous acetone with the subsequent crystallization from benzene. tris(4-N,N-Dimethylaminophenyl)antimony dibenzoate III was obtained from tris(4-N,N-dimethylaminophenyl)antimony and benzoic acid in the presence of hydrogen peroxide in ether or from silver benzoate and the corresponding dichloride in acetone. According to X-ray studies Sb atoms in two crystallographically independent molecules of dichloride, difluoride benzene solvate, and dibenzoate have the distorted trigonal bipyramide coordination [ClSbCl, FSbF, and OSbO trans angles are 178.12(2)°, 178.57(3)°, 177.30°, and 176.49° respectively). Sb-Cl, Sb-F, and Sb-O interatomic distances are 2.4719(7)-2.505(7); 2.106(4); 2.438(2); 2.1212(13) Å respectively. The oxygen atoms of carbonyl groups of the molecule III (C _2v molecular symmetry) are coordinated to the central atom [Sb-O distance 2.987(1) Å].     

Synthesis, characterization, and biological properties of N-phenolato-N′-(3-dimethylaminopropyl)oxamide and its binuclear copper(II) complexes

A new asymmetric N,N′-bis(substituent)oxamide ligand, N-phenolato-N′-(3-dimethylaminopropyl)oxamide (H₃pdmapo), and two of its binuclear Cu(II) complexes with different terminal ligands, namely [Cu₂(pdmapo)(phen)(H₂O)](ClO₄) (1) and [Cu₂(pdmapo)(bpy)(CH₃OH)](ClO₄) (2), where phen = 1,10-phenanthroline and bpy = 2,2′-bipyridine, have been synthesized and characterized. The crystal structures of both complexes have been determined by single-crystal X-ray diffraction. Both structures contain binuclear Cu(II) cationic complexes with pdmapo^3? ligands. The asymmetric pdmapo^3? ligands bridge two Cu(II) atoms in the cis conformation and the Cu···Cu separations through the oxamide bridge are 5.2046(18) and 5.207(2) Å for complexes 1 and 2, respectively. The coordination environments of the two Cu(II) atoms in each binuclear complex are different. The copper occupying the inner site of the pdmapo^3? ligand is four-coordinated in a CuN₃O distorted square-planar environment, while the other is five-coordinated in a square pyramid geometry. In complex 1, O–H···O and C–H···O hydrogen bonds link the complex into a one-dimensional chain. In complex 2, O–H···O hydrogen bonds link the molecules to form a dimer, together with two types of strong π–π interactions, giving a two-dimensional network structure. The cytotoxicities and DNA-binding properties of H₃pdmapo and the two complexes were studied. The experimental evidence suggests that the ligand binds to DNA via a groove binding mode, while the binuclear complexes bind intercalatively to DNA.     

Intra- and intermolecular interactions in crystals ofN′-furfurylideneisonicotinic hydrazide and related compounds. IR spectroscopic and X-ray diffraction studies

The reaction of isonicotinic hydrazide with furfural yieldedN′-furfurylideneisonicotinic hydrazide. IR spectroscopic studies demonstrated that crystallization from different solvents afforded products with an intermolecular NH...O=C hydrogen bond. Conditions of crystallization were chosen under which single crystals with the NH...N_Py intermolecular hydrogen bond (1) were grown. X-ray diffraction analysis demonstrated that the molecular and crystal structure of1 is identical to that ofN′-thienylideneisonicotinic hydrazide (2). The crystal structure consists of layers. The molecules in the layers are linked in zigzag chains through NH...N_Py intermolecular hydrogen bonds. The molecules of the adjacent chains (in the layer) are linked through C=O...H?C intermolecular hydrogen bonds between the O atom of the carbonyl group and the α-H atom of the furan ring. (In the structure of2, the chains are linked through specific intermolecular interactions of different nature but with approximately identical energy.) The replacement of the thiophene fragment (2) by the furan ring (1) is accompanied by a change in the intramolecular electronic effects, which is reflected both in the geometric and spectral characteristics of the molecules in the crystal.     

Octahedral CuII and NiII complexes manifesting with N′-[1-(pyridin-2-yl)ethylidene] acetohydrazide: Structural outlooks and spectral characteristics

A tridentate hydrazone precursor, N′-[1-(pyridin-2-yl)ethylidene]acetohydrazide (L) (1:1 refluxed product of acetichydrazide and 2-acetylpyridine), produced two octahedral Cu^II and Ni^II derivatives, [CuL₂]·NO₃ (1) and [NiL₂]·ClO₄·H₂O (2). Both are subjected to X-ray diffraction system, and structural investigation shows that the central metal atom (Cu^II or Ni^II) adopts a distorted octahedral geometry with N₄O₂ donor sets by coordination of a pair of independent hydrazone precursors. Besides X-ray study, IR and UV-vis spectra, thermal analysis and room temperature magnetic moments are utilized for establishing significant characteristics of both complexes. It is apparent that the M-N_pyridine bonds are slightly longer than the M-N_imino bonds, Cu1-N1 and Cu1-N4 [2.300(2) and 2.038(2) ?] for 1 and Ni1-N1 and Ni1-N4 [2.075(2) and 2.084(1) ?] for 2, Cu1-N2 and Cu1-N5 [2.062(1) and 1.932(1) ?] for 1 and Ni1-N2 and Ni1-N5 [2.008(2) and 1.975(2) ?] for 2, respectively. As per our observation, the effective magnetic moment value (μ_eff) is found to be 1.77 B.M. for 1 and 3.06 BM for 2, respectively.     

Solvent-free synthesis and crystal structures of s-cis and s-trans N,N′-bis(2-hydroxycyclohexyl)ethane-1,2-diamine

The symmetrical amino alcohol synthesis via ring opening of cyclohexene oxide with ethylendiamine is illustrated by synthesis and characterization of β-amino alcohols s-cis-(SSSS)-cy₂en (1) and s-trans-(SSRR)-cy₂en (2) (cy₂en = N,N′-bis(2-hydroxycyclohexyl)ethane-1,2-diamine) in one step and with high yield. The reaction was carried out in a microwave reactor under solvent-free conditions. These products were characterized by IR and Raman spectroscopy, elemental analysis, thermal methods (TGA, DTG and DTA), mass spectrometry and ¹H and ¹³C NMR spectroscopy. The crystal structures of 1 and 2 were determined by single crystal X-ray structural analysis, followed by DFT calculations. Intramolecular hydrogen bond was observed in 1 with C ₂ symmetry, but not in 2 with C _i symmetry. The nature of intramolecular hydrogen bond in 1 has been investigated by AIM and NBO analyses. The molecules in 1 are linked into an infinite chain along the [001] direction, giving rise to R ₄ ⁴ (8) graph-set motif, while the molecules in 2 are linked into a 2D network in the bc plane, giving rise to R ₂ ² (10) and R ₃ ³ (12) motifs. The protonation equilibria of 1 and 2 have been studied by pH-potentiometry, with pK ₁ 9.01 and pK ₂ 5.50 determined for 1 and pK ₁ 8.58 and pK ₂ 5.26 determined for 2.     

Hypervalent pyrrolidinium radicals by neutralization-reionization mass spectrometry: Metastability and radical leaving group abilities

Neutralization-reionization mass spectrometry was used to generate hypervalent radicals pyrrolidinium (1H ^·), N-methylpyrrolidinium (2H ^·), N-ethylpyrrolidinium (3H ^·), N-phenylpyrrolidinium (4H ^·), N,N-dimethylpyrrolidinium (5^·), N-methyl-N-ethylpyrrolidinium (6 ^·), and their deuterium-labeled derivatives and to study their dissociations in the gas phase. Isotopomers of pyrrolidinium and N-phenylpyrrolidinium showed small fractions of stable radicals of microsecond lifetimes that were detected following collisional reionization. The leaving group abilities in radical dissociations were established as H^· » C₂H₅ ^· ≈ C₆H₅ ^·> CH₃ ^·. The hydrogen atom was the best leaving group in secondary and tertiary pyrrolidinium radicals 1H ^·–4H^·, whereas losses of ethyl, phenyl, and ring openings by N-C bond cleavages were less facile. Methyl was the worst leaving group among those studied. Ring cleavages dominated the dissociations of quaternary pyrrolidinium radicals 5^· and 6^·, whereas losses of alkyl substituents were less efficient. The electronic properties of hypervalent ammonium radicals are discussed to rationalize the experimental leaving group abilities of hydrogen atom, alkyl, and phenyl radicals.     

Anion-directed organized assemblies of protonated pyrazole-based ionic salts

The reactions of 3(5)-(4-methoxyphenyl)-5(3)-phenyl-1H-pyrazole (L ¹ ) with nitric acid and 5-(4-benzyloxyphenyl)-3-(furan-2-yl)-1H-pyrazole(L ² ) with hydrochloric acid produced [HL ¹ · NO₃] (Salt-1) and [HL ² · Cl] (Salt-2). The structures of Salt-1 and Salt-2 were determined by single crystal X-diffraction. In Salt-1, HL ¹ showed [2 + 2] binding of NO₃ ^? ions in the solid state to form dimer architecture with R ₁ ² (4) and R ₄ ⁴ (14) graph sets. An anion directed one-dimensional anion-assisted helical chain with active participation of the chloride ion and protonated pyrazole via N–H···Cl hydrogen bonding in Salt-2. In addition, the protonated HL ² molecules interacted with each other through weak C–H···π interactions resulting in the formation of another one-dimensional helical chain.     

Synthesis, crystal structures and electrochemical properties of CoIII complexes with hexadentate ligand containing thioether-amidopyridyl donor set

Two new cobalt(III) complexes of the hexadentate ligand [1,4-bis[o-(pyridine-2-carboxamidophenyl)]-1,4-dithiobutane] (H₂bpctb) with N₄S₂ donor set atoms have been synthesized. A reaction of Co(CH₃COO)₂·4H₂O with (H₂bpctb) leads to the formation of [Co^III(bpctb)]PF₆ (1) having a CoN₂(pyridine)N′₂(amide)S₂(thioether) coordination by symmetric bpctb^2? ligand. A similar reaction under slightly different conditions, however, gives [Co^III(L ^a )(L ^b )] (2), resulting from a C–S bond cleavage reaction triggered by an acetate ion as a base, having CoN₂(pyridine)N′₂(amide)S(thioether)S′(thiolate) coordination. These two Co(III) complexes have been characterized by elemental analyses and spectroscopic methods, and the crystal and molecular structures of [Co^III(bpctb)]PF₆ (1) in the form of the solvate (1·MeOH·H₂O) and of [Co^III(L ^a )(L ^b )] (2) have been determined by X-ray crystallography. The Co atoms of both complexes exhibit distorted octahedral geometry. The electrochemical investigation of [Co(bpctb)]PF₆·MeOH·H₂O (1·MeOH·H₂O) and [Co^III(L ^a )(L ^b )] (2) by cyclic voltammetry reveals a reversible Co^III–Co^II redox process at E _1/2 = ?0.32 V (ΔE _p = 80 mV); for 1, and E _1/2 = ?0. 87 V (ΔE _p = 70 mV) for 2.     

A multidentate ligand based on two triazole groups from “click chemistry” and its copper(II) and iron(II) complexes: synthesis,structure, and electrochemistry

A multidentate ligand, namely N,N-bis[[1-(phenylmethyl)-1H-1,2,3-triazol-4-yl]methyl]-2-pyridinemethaneamine (L), was synthesized through a click reaction of N,N-di-2-propyn-1-yl-2-pyridinemethanamine with benzyl azide in the presence of CuI catalyst. Treatment of L with CuCl₂ or Fe(NCS)₂ gave the complexes [CuLCl₂]·EtOH (1) and [FeL(NCS)₂]·MeCN (2). Single-crystal X-ray studies show that in 1, the Cu(II) center has slightly distorted square pyramidal geometry resulting from the coordination of one pyridinyl nitrogen atom, one tertiary amine nitrogen atom, one triazole nitrogen atom, and two chloride atoms; in 2, the Fe(II) center has distorted octahedral geometry, coordinated by six nitrogen atoms; two each from NCS^? groups and triazole rings, one from a pyridinyl ring, and one from tertiary amine nitrogen. In addition, complexes 1 and 2 were characterized by spectroscopic and electrochemical methods.     

Guest inclusion in cyclic imides containing flexible tethers

Guest inclusion properties of two cyclic imides which have carboxylic acids connected through flexible tether, namely, 4-(1,3-dioxo-1,3-dihydro-isoindol-2-ylmethyl)-cyclohexanecarboxylic acid (1) and 4-(1,3-dioxo-1H,3H-benzo[de]isoquinolin-2-ylmethyl)-cyclohexanecarboxylic acid (2) are studied. The crystals of host 1 containing one molecule of 1, the crystals of 4,4′-bipyridine (bpy) cocrystal of 1 containing one molecule of 1 and half molecule of bpy (1a), the crystals of 1,4-dioxane solvate of 1 containing two molecule of 1 and one and half molecule of 1,4-dioxane (1b) and the crystals of quinoline solvate of 1 containing one molecule of 1 and one molecule of quinoline (1c) in their crystallographic asymmetric units are investigated. Intermolecular hydrogen bonded two dimensional (2D) sheet structure of 1 and 3D channel network of 1b are comprised of cyclic R ₂ ² (8) hydrogen bond motifs; whereas cleavage of dimeric carboxylic acid R ₂ ² (8) motifs occurs in the structures of 1a and 1c in which 3D host–guest networks are comprised of discrete O–H···N and cyclic R ₂ ² (7) interactions, respectively. Various types of weak interactions between the two symmetry nonequivalent host molecule are found to be responsible for the formation of channels (14 × 11 Å) filled by guest 1,4-dioxane molecules in the crystal lattice of 1b. Two different solvates of 2 containing one molecule of 2 with a water molecule (2a) and one molecule of 2 with a quinoline molecule (2b) in their crystallographic asymmetric units, respectively, are also crystallized in different space groups. The quinoline molecules are held with host molecules by discrete O–H···N and C–H···O interactions and reside inside the voids formed by 3D repeated hexameric assemblies of host molecules in the crystal lattice of 2b.     

Comparative investigation of the copper(II) complexes of (R)-, (S)- and (R,S)-1-phenyl-N,N-bis(pyridine-3-ylmethyl)ethanamine along with the related complex of (R,S)-1-cyclohexyl-N,N-bis(pyridine-3-ylmethyl)ethanamine. Synthetic, magnetic, and structural studies

The interaction of the enantiopure (R)- and (S)-1-phenyl-N,N-bis(pyridine-3- ylmethyl)ethanamine ligands, R-L ¹ and S-L ¹ , with copper(II) chloride followed by addition of hexafluorophosphate resulted in the isolation of the corresponding enantiomeric complexes [Cu(R-L ¹ )Cl](PF₆) (1), [Cu(S-L ¹ )Cl](PF₆) (2) and [Cu(S-L ¹ )Cl](PF₆)??0.5Et₂O (3), in which dimerization occurs through two long Cu??????Cl interactions, the ??-chloro bridges being thus strongly asymmetric. The organic ligand is bound to the metal centre via its N₃-donor dipyridylmethylamine fragment in a planar fashion, such that each copper centre is in a square planar environment (or distorted square pyramidal with a long axial bond length if the additional interaction is considered). When R,S-L ¹ was employed in a parallel synthesis, the similar racemic complex [Cu(R,S-L ¹ )Cl](PF₆)??0.5MeOH (4) was obtained, in which the L ¹ ligands in each dimeric unit have opposite hands. In contrast to the complexes of L ¹ , the reaction of Cu(II) chloride with the related ligand, (R)-1-cyclohexyl-N,N-bis(pyridine-3-ylmethyl)ethanamine (R-L ² ), yielded the mononuclear complex [Cu(R,S-L ² )Cl₂] (5), displaying a distorted square pyramidal coordination geometry. The structure of this product along with its corresponding circular dichroism spectrum revealed that racemisation of the starting R-L ² ligand has occurred under the relatively mild (basic) conditions employed for the synthesis. A temperature-dependent magnetic studies of the complexes 1, 2 and 5 indicate that a week ferromagnetic interaction is operative in each dicopper core in 1 and 2 with 2J?=?1.2?cm^?1. On the other hand, a week antiferromagnetic intermolecular interaction is operative for 5.     

Structure and inclusion property of supramolecular host framework [H2 L1][XCl4], L1 = N,N,N′,N′-tetra-p-methoxybenzyl-ethylenediamine; X = Fe, Co, Pd

In this paper, we have used the hydrogen-bonding interactions, combining the designed diamine ligands and anionic metal chlorides, into the construction of a series of new pillar-layered supramolecular complexes. The flexible molecule N,N,N′,N′-tetra-p-methoxybenzyl-ethylenediamine (L1) bearing doubly protonated H-bond donors, has been synthesized and reacted with the metal chlorides (such as [PdCl₄]^2?, [FeCl₄]^? and [CoCl₄]^2?) via weak C–H···Cl interactions, yielding crystal products [H₂ L1]²⁺·Cl^?·[FeCl₄]^? (1), 0.5H₂O ? [H₂ L1]²⁺·Cl^?·0.5[PdCl₄]^2? (2) and [2-hydroxy naphthyl]_1.5 ? 2[H₂ L1]²⁺·2Cl^?·[CoCl₄]^2? (3). The 3-D networks are organic double layers formed by the self-assembly of the ligands through extensive hydrogen-bonding interactions (C–H···O or C–H···π interactions) and further interconnected by [PdCl₄]^2?/[FeCl₄]^?/[CoCl₄]^2? in a pillar fashion, constructing into pillar-layered networks with channels accessible to various guest molecules. The inclusion property of [H₂ L1][CoCl₄] was studied, varieties of guest molecules, such as 2-hydroxy naphthyl, phenanthrene and hydroquinone, can be included in the framework.     

fac-Cobalt(III)-azido complexes derived from substituted pyridyl-based tridentate amines

Four new mononuclear triazido-cobalt(III) complexes [Co(L ^1/2/4 )(N₃)₃] and [Co(L ³ )(N₃)₃]·CH₃CN where L ¹  = [(2-pyridyl)-2-ethyl]-(2-pyridylmethyl)-N-methylamine, L ²  = [(2-pyridyl)-2-ethyl]-[6-methyl-(2-pyridylmethyl)]-N-methylamine, L ³  = [(2-pyridyl)-2-ethyl]-[3,5-dimethyl-4-methoxy-(2-pyridylmethyl)]-N-methylamine, and L ⁴  = [(2-pyridyl)-2-ethyl]-[3,4-dimethoxy-(2-pyridylmethyl)]-N-methylamine, respectively, were synthesized and structurally characterized. The four complexes were characterized by elemental microanalyses, IR and UV–VIS spectroscopy and X-ray single crystal crystallography. The complexes display two strong IR bands over the frequency region 2,020–2,050 cm^?1 assigned for the asymmetric stretching frequency, ν_a(N₃) of the coordinated azides indicating facial geometry. The molecular structure determinations of the complexes were in complete agreement with fac-[Co(L)(N₃)₃] conformation in distorted octahedral Co(III) environment.     

Simplified bicyclic cage-type molecule as a C 3 -symmetric host: X-ray and FTIR characterization of encapsulation of a nitrile molecule

We synthesized a new amine-type host molecule 2 by 2 steps, using 1,3,5-tris(aminomethyl)-2,4,6-trimethylbenzene and 2,6-pyridinedicarboxaldehyde as starting materials. Recrystallization of 2·6H₂O from hot acetonitrile, hot propionitrile and hexane/benzonitrile solutions gave colorless crystals of MeCN@2·MeCN·2H₂O, EtCN@2·EtCN, and 8H₂O@2·PhCN. In the former two crystals, the nitrile compounds were captured inside of the cavity of 2. On the other hand, in the latter one, the benzonitrile was laid outside 2. Infrared spectral measurements of MeCN@2·MeCN·2H₂O, EtCN@2·EtCN, and 8H₂O@2·PhCN showed that absorption bands assignable to the C ≡ N stretching vibrations of nitrile compounds were observed at 2240, 2241, and 2226 cm^?1 for MeCN@2·MeCN·2H₂O, EtCN@2·EtCN, and 8H₂O@2·PhCN, respectively. The former two peaks shifted to a lower energy region by 6–13 and 21–26 cm^?1 than those of liquid and gas phases of MeCN and EtCN, respectively. That for 8H₂O@2·PhCN shifted to a slightly lower region by 2 and 12 cm^?1 those of liquid and gas states of PhCN, respectively, indicating that the outer benzonitrile molecule dose not so much interact with 2 in the crystal.     

Über die Reaktionen von monosubstituierten Guanidinen mit 1-Phenyl-1,3-butandion

Methyl-, benzyl- and phenylguanidine (2 b–d) react with 1-phenyl-1,3-butanedione to yield exclusively N²-substituted 4-methyl-6-phenyl-2-pyrimidinamines10 b–d. The formation of isomeric N¹-substituted 2(1H)-pyrimidinimines11 or12 cannot be observed. The structural formulae of10 b and c were proved by spectroscopical methods. The structure of the phenylguanidine-phenylbutanedione-condensate was determined by comparison and establishment of the identity of its picrate with an authentical sample of10 d-picrate, which had been synthetized from pyrimidinthione13 (via methylthiopyrimidine16 · HI). Boiling13 with aniline in butanol yields thiodipyrimidine15 (and not10 d).     

Heat stable and organosoluble benzoxazole or benzothiazole-containing poly(imide-ester)s and poly(etherimide-ester)s: synthesis and characterization

Two series of poly(imide-ester)s (PIEs) and poly(ether-imide-ester)s (PEIEs), having benzoxazole or benzothiazole pendent groups, were conveniently prepared by the diphenylchlorophosphate-activated direct polyesterification of two bis(imide-carboxylic acid)s (1), such as 2-[3,5-bis(N-trimellitimidoyl)phenyl]benzoxazole (1 _O ) and 2-[3,5-bis(Ntrimellitimidoyl) phenyl]benzothiazole (1 _S ) and two bis(imide-ether-carboxylic acid)s (2), such as 2-[3,5-bis(4-trimellitimidophenoxy)-phenyl]benzoxazole (2 _O ), and 2-[3,5-bis(4-trimellitimidophenoxy)-phenyl]benzothiazole (2 _S ) with various aromatic dihydroxy compounds in the presence of pyridine and lithium chloride. The structures, solubilities and thermal properties of obtained polymers were investigated in detail. All of the resulting polymers were characterized by FTIR and ¹H-NMR spectroscopy and elemental analysis. All of the resulting polymers exhibited excellent solubility in common organic solvents, such as pyridine, tetrahydrofuran and m-cresol, as well as in polar organic solvents, such as N-methyl-2-pyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide and dimethyl sulfoxide. The modified polymers were obtained in quantitative yields with inherent viscosities between 0.47 and 0.67 dl·g^?1. Experimental results indicated that all the polymers had glass transition temperature between 198 °C and 262 °C, the decomposition temperature at 10% weight loss between 398 °C and 531 °C under nitrogen.