X-ray structures of cobalt(III) complexes with bio-relevant pyrazolyl thiosemicarbazone: Indication of structural changes on the increasing bulkiness of the alkyl substituents on thiosemicarbazone moiety

X-ray crystallographic studies of cobalt(III) complexes of 5-methyl-3-formylpyrazole-N(4)-diethylthiosemicarbazone (HMP_zNEt₂), [Co(MP _z NEt ₂ ) ₂ ]Br·2H ₂ O, 5-methyl-3-formylpyrazole-N(4)-dipropylthiosemicarbazone (HMP_zNPr ₂ ), [Co(MP _z NPr ₂ ) ₂ ]Br·2H ₂ O and 5-methyl-3formylpyrazole-N(4)-dibutylthiosemicarbazone (HMP_zNBu ₂ ), [Co(MP _z NBu ₂ ) ₂ ]Br·H ₂ O, have been reported. In all the three complex species, X-ray crystallography has authenticated a CoN₄S₂ octahedral coordination with the pair of orthogonally coordinated NNS tridentate ligands in the monodeprotonated form of the ligand. The two azomethine nitrogen atoms are trans to each other, while the pyrazolyl ring nitrogens and the thiolato sulfurs are in cis positions. A gradual decrease in the dihedral angle between the coordinating ligands has been observed with increase in the bulkiness of the aliphatic side chains of the substituent on the thiosemicarbazone moieties. In all the three complexes, intraligand C–H···S contacts appear to arrest the free rotation of the side chains about the C(6)–N(5) single bond. ^†Deceased     

Copper coordination complexes of bis(4-(pyridin-2-yl)pyrimidin-2-ylthio)methane with in situ metal redox reactions

Five copper coordination complexes 1–5 with 2-bppm (2-bppm?=?bis(4-(pyridin-2-yl)pyrimidin-2-ylthio)methane) have been prepared and structurally elucidated. Complexes 1 and 2 are both discrete dinuclear [2?+?2] macrocyclic structures, simultaneously formed in one-pot reaction with Cu(NO₃)₂ with in situ reduction of Cu²⁺. Similarly, dinuclear [2?+?2] macrocyclic motifs are found with 3 and 4, which are also obtained by one-pot reaction but with CuCl accompanied by in situ air oxidation of Cu⁺. Compound 5 exhibits a 1-D chain structure with 2-bppm and Cu₂I₂ connected one by one. Luminescence is measured for 2, 4, and 5, all based on d¹⁰-closed shell Cu(I).     

In quest of reversibility of Friedel-Crafts acyl rearrangements in the pyrene series

Friedel-Crafts acyl rearrangements in PPA of diacetylpyrenes (80–120 °C), dibenzoylpyrenes (80–200 °C), and bis(4-flurobenzoyl)pyrenes (80–120 °C) and Scholl reactions in AlCl₃/NaCl of dibenzoylpyrenes (140–200 °C) have been studied. The substrates were 1-AcPY, 2-AcPY, 1,3-Ac₂PY, 1,6-Ac₂PY, 1,8-Ac₂PY, 2,7-Ac₂PY, 1-BzPY, 1,6-Bz₂PY, 1,8-Bz₂PY, 1-4FBzPY, 1,6-4FBz₂PY, 1,8-4FBz₂PY. The mixtures of pyrene, 1-AcPY, 2-AcPY, 1,3-Ac₂PY, 1,6-Ac₂PY, 1,8-Ac₂PY, and 2,7-Ac₂PY were separated by HPLC. The following reversible intermolecular isomerizations were established: 1,6-Ac₂PY ? 1,8-Ac₂PY, 1,6-Bz₂PY ? 1,8-Bz₂PY, and 1,6-4'FBz₂PY ? 1,8-4'FBz₂PY, albeit not in high yields. The results substantiate Gore’s 1955 proposition that “The Friedel–Crafts acylation reaction of reactive aromatic hydrocarbons is a reversible process.” The isomerizations reported here differ from the few previously reported completely reversible intramolecular Friedel-Crafts acyl rearrangements. At ≥ 140 °C, in PPA and in AlCl₃/NaCl, 1,6-Bz₂PY and 1,8-Bz₂PY underwent a highly regioselective double Scholl reaction to give pyranthrone (3) and deacylations to 1-BzPy (and pyrene), followed by mono-Scholl reactions to give 8H-dibenzo[def,qr]chrysen-8-one (1), and 11H-indeno[2,1-a]pyren-11-one (2). The formation of 3 and not the expected tribenzo[a,ghi,o]perylene-7,16-dione (4) from 1,8-Bz₂PY indicates that 1,8-Bz₂PY has first undergone isomerization to 1,6-Bz₂PY. The present study confirms the linkage between Friedel-Crafts acyl rearrangements and the Scholl reaction.

     

Synthesis,crystal structure,redox behavior and DNA-binding properties of a series of copper(II) complexes with two new carboxamide derivatives

Four mononuclear copper(II) complexes of two new carboxamide derivatives formulated as [Cu(L¹)₂](ClO₄)₂ (1a), [Cu(L¹)₂](NO₃)₂ (1b), [Cu(L²)₂(H₂O)₂](ClO₄)₂ (2a), and [Cu(L²)₂(H₂O)](NO₃)₂ (2b) have been isolated in pure form from the reaction of L¹ and L² [where L¹ = N-(furan-2-ylmethyl)-2-pyridinecarboxamide and L² = N-(thiophen-2-ylmethyl)-2-pyridinecarboxamide] with copper(II) salts of perchlorate and nitrate. All the complexes were characterized by physicochemical and spectroscopic tools along with single-crystal X-ray diffraction studies. The structural analyses showed that 1 is monomeric of square planar geometry with copper(II) chelated by two L¹ ligands. Complex 2 differs in coordination geometry, being octahedral and distorted square pyramidal. Two L² ligands occupy the equatorial positions of the octahedral 2a and the basal sites of the pyramidal 2b, with water molecules that complete the coordination sphere in each case. Electrochemical studies using cyclic voltammetry showed a reversible redox behavior of the copper(II) in 1 and 2. The electronic spectroscopic behavior and the trend of one electron equivalent redox potential corresponding to a Cu^II/Cu^I couple have also been confirmed by density functional theory calculations. The spectroscopic and viscosity measurement study in tris–HCl buffer suggested an intercalative interaction of 1a and 2 with calf thymus DNA likely due to the stacking between the non-coordinated furan and thiophene chromophore with the base pairs of DNA.     

Thermodynamics of Dissociation of <Emphasis Type="Italic">ortho</Emphasis>-Hydroxyphenylhydrazo-<Emphasis Type="Italic">β</Emphasis>-diketones and of Their Complexation with Copper(II) in Aqueous–Ethanol Solutions

The thermodynamics of dissociation of 3-(2-hydroxyphenylhydrazo)pentane-2,4-dione (H ₂ L ¹ ), 5,5-dimethyl-2-(2-hydroxyphenylhydrazo)cyclohexane-1,3-dione (H ₂ L ² ), 5,5-dimethyl-2-(2-hydroxy-4-nitrophenylhydrazo)cyclohexane-1,3-dione (H ₂ L ³ ), 1-ethoxy-2-(2-hydroxyphenylhydrazo)butane-1,3-dione (H ₂ L ⁴ ) and 1-ethoxy-2-(2-hydroxy-4-nitrophenylhydrazo)butane-1,3-dione (H ₂ L ⁵ ) and of their complexation with copper(II) was studied in aqueous–ethanol solutions by potentiometry and UV–vis spectrophotometry. It was found that the thermodynamic parameters of the proton dissociation in H₂L^1–5 and of their complexation with copper(II) depend on the substituents in the aromatic and β-diketone fragments of the molecules. Thus, the acidic properties of H₂L increase from H₂L¹ to H₂L⁵, reflecting the electron-acceptor character of the substituents, whereas all of the thermodynamic functions tend to decrease with increasing electron-withdrawing capacity of the substituents. The complexation of Cu(II) with H₂L^1–5 is exothermic, which is connected with the formation of two stable chelating cycles.     

Synthesis and molecular and crystal structures of mono-and bis-chelate hypercoordinate silicon compounds containing the C,O-chelating 2,2-dimethyl-4-oxo-2,3-dihydro-1,3-oxazin-3-ylmethyl ligand

New mono-and bis-chelate hypercoordinate silicon complexes containing the monoanionic C,O-chelating 2,2-dimethyl-2,3-dihydrobenzo-1,3-oxazin-3-ylmethyl (BonCH₂) ligand were synthesized starting from 2,2-dimethyl-2,3-dihydrobenzo-1,3-oxazin-4-one (1) through its TMS derivative 2. The reactions of compound 2 with the chlorosilylmethylating agents ClCH₂SiMe₂Cl, ClCH₂SiMeCl₂, and (ClCH₂)₂SiCl₂ followed by the transformations of the initially formed chlorosilanes BonCH₂SiMe₂Cl (3), BonCH₂SiMeCl₂ (6), and [(BonCH₂)₂Si(Cl)]⁺Cl⁻ (8), respectively, into the target products afforded neutral monochelates, viz., monofluoride BonCH₂SiMe₂F (5) and difluoride BonCH₂SiMeF₂ (7), and the bis-chelate disiloxane cation-anion complexes {[(BonCH₂)₂Si]₂O}²⁺·Cl⁻·ClHCl⁻ (9) and {[(BonCH₂)₂Si]₂O}²⁺·2TfO⁻ (10). The reaction of ditriflate 10 with boron trifluoride etherate produced fluoride triflate (BonCH₂)₂Si(F)OTf (11). The X-ray diffraction study of compounds 5, 7, 9, 10, and 11, as well as of NH-heterocycle 1 and disiloxane (BonCH₂SiMe₂)₂O (4) studied earlier, demonstrated that the Si atoms in complexes 5, 7, 9, and 10 are pentacoordinate through the formation of an intramolecular O→Si bond. The coordination of silicon in fluoride triflate 11 can be described as 5+1. In disiloxane 4, one of two Si atoms is pentacoordinate. Dinuclear cation-anion complexes 9 and 10 contain the diastereomeric bis-silylium ions {[(BonCH₂)₂Si]₂O}²⁺, which differ in the configuration of the chiral bis-chelate fragments (BonCH₂)₂Si. In complex 9, these fragments have opposite configurations (ΛΔ); in ditriflate 10, the same configurations (ΛΛ). Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 446–458, March, 2007.     

Copper(I) bromide complexes of two 15-memberd O2S2-macrocycles with different sulfur-to-sulfur separations: dimer and one-dimensional coordination polymer

Abstract

A comparative study on the exo-coordination-based networking of 15-membered O₂S₂-macrocycle isomers (L¹ and L²) induced by interdonor distances is reported. In copper(I) bromide complexation, the isomer L¹ incorporating a shorter sulfur-to-sulfur separation yielded a discrete dimer complex [(μ-Cu₂Br₂)(L¹)₂] (1) in which two macrocycles are bridged by a Cu₂Br₂ square cluster. While, the reaction of copper(I) bromide with the isomer L² incorporating a longer sulfur-to-sulfur separation afforded a double-stranded one-dimensional (1D) coordination polymer {[(μ₄-Cu₂Br₂)(L²)₂]·CH₂Cl₂}_n (2) as a kinetic product which converted to [(μ₄-Cu₂Br₂)(L²)₂]_n (3) with different 1D connectivity pattern as a thermodynamic product. The results indicate as examples of programmed self-assembly that the proposed interdonor distances and the ligand isomerism play decisive roles cooperatively in the topologies of the supramolecular products via different coordination modes.     

Some diazinon analogues containing the 4-trifluoromethyl group

Summary Diazinon analogues were prepared containing trifluoromethyl in place of the 4-methyl group and methylthio (2 a), amino (2 b), dimethylamino (2 c), methylphenylamino (2 d), or isopropyl (2 e) in position 2 of the pyrimidine ring. The most active analogue (2 b) was less than half as insecticidal as Diazinon.

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Einige Diazinon-Analoga mit einer 4-Trifluormethylgruppe

Zusammenfassung Es wurden Diazinon-Analoga hergestellt, die anstelle der 4-Methylgruppe die Trifluormethylgruppe und in 2-Position des Pyrimidin-Rings verschiedene Substituenten enthielten.2 a: 2-Methylthio-;2 b: 2-Amino;2 c: 2-Dimethylamino-;2 d: 2-Methylphenylamino-;2 e: 2-Isopropyl-. Das aktivste Analogon war2 b, das allerdings auch weniger als die Hälfte der insektiziden Wirkung des Diazinon aufwies.

     

A facile synthesis of 4-aryl-2H-1-benzopyran-2-ones

Reaction of 2-hydroxybenzophenones (1,3,7,8) with ethoxycarbonyl-methylenetriphenylphosphorane affords 4-aryl-2H-1-benzopyran-2-ones (2,4–6) in excellent yields.

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Eine einfache Synthese für 4-Aryl-2H-1-benzopyran-2-one

Zusammenfassung Die Reaktion der 2-Hydroxybenzophenone1,3,7 und8 mit Ethoxycarbonyl-methylentriphenylphosphoran ergab die 4-Aryl-2H-1-benzopyran-2-one2 und4–6 in ausgezeichneten Ausbeuten.

     

金属卡宾模板导向的多咪唑鎓盐大环合成

本文报道了一种共价有机大环化合物的高效合成方法。利用双咪唑鎓盐H₂-L1(BF₄)₂(L1=A1,B1)和氧化银反应,生成双核银卡宾大环化合物[Ag₂(L1)₂](BF₄)₂(L1=A1,B1),其中连接在2个卡宾配体上的端烯取代基分别排列在环的两侧。随后,通过金属卡宾模板导向的烯烃复分解反应进行关环,制备得到闭环的双核银卡宾大环化合物[Ag₂(L2)](BF₄)₂(L2=A2,B2)。最后,移除模板银离子即可得到拥有空腔结构的共价有机大环化合物H₄-L2(BF₄)₄(L2=A2,B2)。此类多咪唑鎓盐大环的尺寸和形状可以通过改变氮杂环卡宾前驱体连接单元的长度或者宽度进行精细调节。初步研究表明,该大环受体在碘离子的传感、检测和识别方面具有潜在的应用前景。     

Reaction of Quinoline-5,8-Diones with Selected Charged Phosphorus Nucleophiles

Abstract

The redox reactivity of the two quinoline-5,8-dione derivatives—2-methyl-5,8-dioxo-5,8-dihydroquinoline-7-amine (2a) and N-(2-methyl-5,8-dioxo-5,8-dihydroquinolin-7-yl)acet-amide (2b)—has been demonstrated by their reaction with negatively charged three-coordinated phosphorus nucleophiles, such as R₂P-YM (1a–d, Y = O or lone pair; R = Ph, tBu, OCH₂CMe₂CH₂O, or EtO; M = Li or Na). 1a–d participated in single-electron transfer (SET) to 2a and 2b, generating the radical anions 3 and 4, respectively, together with short-lived phosphorus-centered radical intermediates of type R₂P(= Y)· (5). The radicals 5 dimerize to give R₂P(Y)–(Y)PR₂ (6). Both 3 and 4 are remarkably persistent with half-lives of more than 1 month in THF (tetrahydrofuran) at 300 K.     

Multidentate bis(pyrazolylmethyl)pyridine ligands: coordination chemistry and binding properties with zinc(II) and cadmium(II) cations

The coordination chemistry and cationic binding properties of 2,6-bis(pyrazol-1-ylmethyl)pyridine (L1), 2,6-bis(3,5-dimethylpyrazol-1-ylmethyl)pyridine (L2), and 2,6-bis(3,5-ditertbutylpyrazol-1-ylmethyl)pyridine (L3) with zinc(II) and cadmium(II) have been investigated. Reactions of L2 with zinc(II) and cadmium(II) nitrate or chloride salts produced monometallic complexes [Zn(NO₃)₂(L2)] (1), [ZnCl₂(L2)] (2), [Cd(NO₃)₂(L2)] (3), and [CdCl₂(L2)] (4). Solid state structures of 1 and 3 confirmed that L2 binds in a tridentate mode. While the nitrates in the zinc complex (1) adopt monodentate binding fashion, in cadmium complex (3), they exhibit bidentate mode. L1–L3 show binding efficiencies of 99% for zinc(II), 60% for lead(II), and 30% for cadmium(II) cations from aqueous solutions of the metal ions. Theoretical studies using Density Functional Theory were consistent with the observed extraction results.     

Some Reactions of 2-Cyanomethyl-1,3-benzothiazole with Expected Biological Activity

New pyrido[2,1-b]benzothiazoles 2a,b, 3, 2-aminoquinoline 4, coumarin 5, cyclohexane 6a,b, and 2-(1,3-benzothiazol-2-yl) methylidene 7 derivatives have been prepared via the reaction of 2-cyanomethyl-1,3-benzothiazole 1 with α,β-unsaturated nitriles, α-chloro ethyl acetoacetate, 2-amino benzaldehyde, 5-chlorosalicylaldehyde, α,β-unsaturated ketone, and 2-aminobenzothiol hydrochloride. 2-Thiazole derivatives 9a,b were prepared from compound 1, which was converted to thioamide derivative 8 by reaction with HCl and thioacetamide, and cyclization of this thioamide with α-halogenated ketone gave 9a,b. Reaction of compound 1 and ethylacetate to afford ketonitrile 10. Treatment of 10 with hydrazine hydrate afforded aminopyrazole derivative 11. Substituted 4-aminothiophene 13 has been synthesized by reaction of compound 1 with p-chlorophenyl isothiocyanate. The resulting product 12 was then alkylated with phenacylbromide. Phenyl-2-yl-carbonylhydroximoyl-chloride 15 was prepared by treatment of the corresponding sulfonium bromide with sodium nitrite and hydrochloric acid in dioxane. Compound 15 reacted with α-(1,3-benzothiazol-2-yl) cinnamonitrile 14 afforded the isoxazole derivatives 16. Reaction of coumarin derivative 5 with anthranilamide, pyrimidine diamine, thiosemicarbazide, acetylacetone, and hydrazine hydrate yielded quinazoline-2-one 17, purine 18, triazole 19, 2-acetyl naphthalene-2-one 20, and N-aminoquinoline-2-one 21 derivatives.     

Complexes of unsymmetric bis-hydrazide ligands: crystal structures and properties

Two unsymmetric bis-aroyl-hydrazines, N′-(2-hydroxybenzoyl)isonicotinohydrazide (L1) and N′-(2-hydroxybenzoyl)nicotinohydrazide (L2), were synthesized through reactions of salicyl hydrazide with isonicotinoyl chloride and nicotinoyl chloride, respectively. Reactions of metal salts with L1 or L2 gave three new complexes, [Cd(L1)₂(SCN)₂] _n (1), [Zn(L1)₂Cl₂]?·?H₂O (2), and [Zn(L2)₂Cl₂] (3). Complex 1 features a 1-D double-chain structure built by SCN^– bridging six-coordinate Cd^II centers while 2 and 3 are mononuclear Zn^II complexes. In 1–3, isomeric ligands L1 and L2 coordinate with metal ions in a terminal coordination mode. Ligands L1 and L2 through O–H···N and N–H···O hydrogen-bonding interactions in 1–3 are crucial for the structure extension into 3-D supramolecular structures of 1 and 2, or 2-D sheet of 3. Complexes 1–3 emit interesting blue-green luminescence. Thermal behaviors of 1–3 as well as the specific rotation of 2 were also investigated.     

Three copper complexes containing the sulfur-bridged bis-pyridine ligands, 2,2′-dithiodipyridine and di-2-pyridyl sulfide

Three copper complexes constructed with sulfur-bridged bis-pyridine ligands 2,2′-dithiodipyridine (dtdp) and di-2-pyridyl sulfide (dps), [Cu₂(dps)₂(H₂O)₂(μ-SO₄)₂]·(H₂O)₂ (1), [Cu₂I₂(dps)₂] (2), and [Cu₄I₄(dtdp)₂] (3), have been synthesized by reaction of copper(I) iodide with dtdp under solvothermal and solution-diffusion conditions, and characterized by single crystal X-ray diffraction. The dps ligands were generated via in situ cleavage of S–S and S–C(py) bonds of dtdp. Cu ions are divalent in 1, implying involvement of the starting Cu⁺ cations in a redox process, while the Cu ions remained univalent in 2 and 3. In 1 and 2, the dps adopted N,N-chelate coordination, in contrast to the N,S-chelation of the dtdp ligand in 3. Complex 1 displays a 2-D framework linked by hydrogen bonds and was further connected into a 3-D supramolecular structure by π–π stacking interactions between adjacent layers. Complexes 2 and 3 exhibited 2-D layer structures through π–π stacking interactions. The luminescent properties of 2 and 3 were also studied in the solid state at room temperature.     

大环金属铜(II)、镍(II)配合物的模板合成与晶体结构

用模板法合成了1个大环金属铜(II)配合物[CuLCl₂]·3H₂O (1)和3个大环金属镍(II)配合物[NiLCl₂] (2)，[NiL](ClO₄)₂ (3)和[NiLH₂](ClO₄)₄ (4)(L=3,10-二乙基-1，3，5，8，10，12-六氮杂十四烷)，通过X-射线衍射单晶结构分析测定了它们的晶体结构。晶体结构显示：配合物1和2的金属离子与大环配体的4个氮原子及大环平面轴向的2个氯离子以八面体配位方式配位；配合物3和4的金属离子与大环配体的4个氮原子以平面正方形配位方式配位，配合物4的侧链氮原子的质子化导致侧链结构翻转，使得其侧链与大环平面共面。     

X-ray crystallographic,spectroscopic, and electrochemical properties of Group 12 metal-chlorides of di-2-pyridyl ketone acetic acid hydrazone (dpkaah)

Abstract

Di-2-pyridyl ketone acetic acid hydrazone hydrate, dpkaah.0.5H₂O (1), prepared from the acid catalyzed condensation of di-2-pyridyl ketone (dpk) with acetic acid hydrazide in refluxing ethanol, undergoes facile coordination to Group 12 metal-chlorides in CH₃CN to form [MCl₂(κ³-N,N,O-dpkaah)] {M=Zn (3), Cd (4) or Hg(5)}. X-ray structural analysis on single crystals of dpkaah (2) and 3–5 confirmed their identities and revealed pseudo-coordination of the carbonyl group (C=O). Infrared measurements confirmed the pseudo-coordination of the carbonyl group to MCl₂. The geometries of 3–5 vary, while 5 adopts a square pyramidal geometry, 4 has a structure halfway between square pyramidal and trigonal bipyramidal and 3 is less distorted from square pyramidal than 3. The extended structures of 3–5 exposed extensive networks of non-covalent interactions, and in the case of 4 chloride bridges of the type Cd(μ-Cl)₂Cd were observed. Spectroscopic measurements in different solvents and variable temperature studies confirmed the stability of the keto form of 1 and 3–5. Spectrophotometric titrations of protophilic solutions (dmf or dmso) of 1 with MCl₂ revealed facile coordination of MCl₂ to 1 and disclosed low concentrations of MCl₂ can be detected and determined using protophilic solutions of 1. Electrochemical measurements on dmf solutions divulged electrochemical decomposition of uncoordinated 1, the facile coordination of 1 to MCl₂, and the stability of 3–5 decreases as the size of the metal ion increases.     

Nouvelle Synthese Des 2-Thioxoethylphosphonates, 2- mercaptovinylphosphonates, 2-Phosphoryl-3-thioxopropanoates, 2-Thiomethylvinylphosphonates, 2-Thioethoxycarbonylmethylvinylphosphonates

The cyanomethylphosphonates 1 and the ethyl phosphoacetates 2 were reacted with some fluorophenylisothiocyanates to give the 2-thioxoethylphosphonates 3 in tautomeric equilibrium with the corresponding 2-mercaptovinylphosphonates 3 ′ and the 2-phosphoryl-3-thioxopropanoates 4 , respectively. Reaction of the cyanomethylphosphonates 1 with fluorophenylisothiocyanates in presence of methyliodide furnished the 2- thiometylvinylphosphonates 5 . The 2-mercaptovinylphosphonates 3 ′ reacted with ethyl chloroacetate in refluxing ethanol in the presence of triethylamine to give S-substitued derivatives 6 .     

Syntheses and structures of three zinc coordination polymers with 1-D zigzag chain,double chain,and triple chain

Three new coordination polymers [Zn(btp)(NCS)₂] _n (1), {[Zn(btp)₂(dca)₂] _n (2), and {[Zn(btp)₃](BF₄)₂} _n (3) (btp = 1,3-bis(1,2,4-triazol-1-yl)propane, dca = dicyanamide) were synthesized and characterized. In 1, 2, and 3, one-, double-, triple-btp ligands link two Zn(II) atoms and extend to form a 1-D zigzag chain for 1, 1-D double chain for 2, and 1-D triple chain for 3. The conformations of the btp ligands in 1, 2, and 3 are analyzed. 1, 2, and 3 have emission maxima at approximately 405, 407, and 409 nm, respectively, in the solid state at room temperature.     

Solution structure and equilibrium of new calix[4]resorcinarene complexes—prototype of molecular machines. NMR data

Association properties and molecular machine application of water soluble calix[4]resorcinarene (1) with two aromatic guests (2-naphthol (2) and 1,5-naphthalenediamine (3)) have been investigated by various NMR methods (chemical shift, nOe and diffusion measurements) in aqueous solution at different concentrations and pH range. In neutral solution 1 strongly associates with 2, while only moderately associating with 3. Increase in concentration causes an increase in the stability of 1 + 3 and 1 + 2 + 3 complexes and produces high order complexes. The decrease of pH does not have an influence on 1 + 2 association, but disrupts 1 + 3 assembly. 1 can be used for the separation of 2 + 3 mixture in aqueous solution at moderate concentrations. The pH dependency of the association properties of the 1 + 3 system makes these compounds prime candidates for pH-responsive molecular machines applications.