Ethylammonium Perchlorate Research Articles

Structural characterization of the crystalline diastereomeric complexes of enantiopure dimethylacridino-18-crown-6 ether and the enantiomers of 1-(1-naphthyl)ethylamine hydrogen perchlorate

This paper describes the X-ray crystal structure of the diastereomeric complexes formed by enantiopure dimethyl-substituted acridino-18-crown-6 ether (R,R)-1 and the enantiomers of 1-(1-naphthyl)ethylammonium perchlorate. We found that the heterochiral complex (R,R)-1–(S)-1-NEA is more stable than the homochiral one (R,R)-1–(R)-1-NEA. In the case of the heterochiral complex, the X-ray studies revealed a strong intermolecular π–π interaction between the naphthyl unit and the acridine moiety. However, in the case of the homochiral complex, π–π interaction was not found. We suggest that the existence or absence of the π–π interaction and the difference in steric repulsions in the diastereomers is responsible for the enantiomeric discrimination.

ChemInform Abstract: Synthesis of Rigid and C2‐Symmetric Pyridino‐15‐crown‐5‐Type Macrocycles Bearing Diamide—Diester Functions: Enantiomeric Recognition for Chiral Primary Organoammonium Perchlorate Salts.

Abstract Four novel C 2 -symmetric macrocyclic compounds with a pyridine function and possessing amide and ester lingeages were prepared. The enantiomeric discrimination abilities of these macrocycles against α-phenylethylammonium and α-(1-naphthyl)ethylammonium perchlorate salts were measured by standard 1 H NMR titration techniques in DMSO- d 6 . A binding constant ratio of 31 (Kbind(S)/Kbind(R)) for two enantiomers of α-(1-naphthyl)ethylammonium salt with the macrocyclic host ( S , S )- 4 bearing phenyl arms was observed, which corresponds to an enantiomeric discrimination of approximately 94%. Molecular dynamic calculations were performed for some of the supramolecular complexes to in order to gain insight into the mode of molecular recognition between the macrocyclic compounds and ammonium salts; these results were consistent with experimental observations, which may be relevant to those in biochemical processes occurring in organisms.

Synthesis of rigid and C2-symmetric pyridino-15-crown-5 type macrocycles bearing diamide–diester functions: enantiomeric recognition for chiral primary organoammonium perchlorate salts

Four novel C2-symmetric macrocyclic compounds with a pyridine function and possessing amide and ester lingeages were prepared. The enantiomeric discrimination abilities of these macrocycles against α-phenylethylammonium and α-(1-naphthyl)ethylammonium perchlorate salts were measured by standard 1H NMR titration techniques in DMSO-d6. A binding constant ratio of 31 (Kbind(S)/Kbind(R)) for two enantiomers of α-(1-naphthyl)ethylammonium salt with the macrocyclic host (S,S)-4 bearing phenyl arms was observed, which corresponds to an enantiomeric discrimination of approximately 94%. Molecular dynamic calculations were performed for some of the supramolecular complexes to in order to gain insight into the mode of molecular recognition between the macrocyclic compounds and ammonium salts; these results were consistent with experimental observations, which may be relevant to those in biochemical processes occurring in organisms.

Synthesis and Preliminary Structural and Binding Characterization of New Enantiopure Crown Ethers Containing an Alkyl Diarylphosphinate or a Proton‐Ionizable Diarylphosphinic Acid Unit

AbstractNew enantiopure crown ethers containing either an ethyl diarylphosphinate moiety [(S,S)‐4 to (S,S)‐7] or a proton‐ionizable diarylphosphinic acid unit [(S,S)‐8 to (S,S)‐11] have been synthesized. Electronic circular dichroism (ECD) studies on the complexation of these new enantiopure crown ethers with the enantiomers of α‐(1‐naphthyl)ethylammonium perchlorate (1‐NEA) and with α‐(2‐naphthyl)ethylammonium perchlorate (2‐NEA) were also carried out. These studies showed appreciable enantiomeric recognition with heterochiral [(S,S)‐crown ether plus either (R)‐1‐ or (R)‐2‐NEA] preference. Theoretical calculations found three significant intermolecular hydrogen bonds in the complexes of (S,S)‐9. Furthermore, preference for heterochiral complexes was also observed, in good agreement with ECD results. Complex formation constants were determined by NMR titration for four selected crown ether/NEA pairs.

Spectrophotometric study of complexation between a series of salophens and some transition metal ions in DMF solvent

The complexation behaviour of some salophen,s derivatives with few transition and heavy metal cations in N , N '-dimethyl formamid as nonaqueous solvent at 25 o C and 0.05 M tetra ethylammonium perchlorate to investigate the effect of structure were studied by spectrophotometric method. The formation of complexes between ligands and metal ions of the types ML, ML 2 or M 2 L was observed. The overall stability constants of such complexes were evaluated by computer refinement of absorption-mole ratio data using the KINFIT program.

Synthesis of rigid and C2-symmetric 18-crown-6 type macrocycles bearing diamide–diester groups: enantiomeric recognition for α-(1-naphthyl)ethylammonium perchlorate salts

A series of rigid and chiral C 2-symmetric 18-crown-6 type macrocycles ( S, S)- 4, ( S, S)- 5, ( S, S)- 6 and ( R, R)- 2 bearing diamide–ester groups were synthesized. The binding properties of these macrocycles were examined for α-(1-naphthyl)ethylammonium perchlorates salts by an 1H NMR titration method. Taking into account the host employed, important differences were observed in the K a values of ( R)- and ( S)-enantiomers of guests for macrocycles ( S, S)- 4 and ( S, S)- 6, K S/ K R = 3.6, and K S/ K R = 0.1 ( K R/ K S = 10.3) ΔΔ G = 3.19 and ΔΔ G = −5.77 kJ mol −1, respectively. The results indicated excellent enantioselectivity of macrocyclic ( S, S)- 6 towards the enantiomers of α-(1-naphthyl)ethylammonium perchlorate salts.

Enantiomeric discrimination of chiral crown ether ionophores containing phenazine subcyclic unit by ion-selective potentiometry

In this paper the enatiomeric selectivity of two chiral phenazino-18-crown-6 ether hosts ((R,R)-\textbf1 and (R,R)-\textbf2) is quantified. These hosts were incorporated into plasticized PVC membranes and used as recognition elements of ion-selective electrodes. The potentiometric response towards the two enantiomers of 1-phenylethylammonium ions (PEA+) was measured. Potentiometric selectivity coefficients were calculated which reflect the ratio of the stability constants of the diastereomeric complexes. Ligand (R,R)-\textbf1 does not show enantiomeric recognition, while ligand (R,R)-\textbf2 has a slight preference for the (S)-(-) enantiomer over the (R)-(+) enantiomer manifested by a selectivity coefficient of 0.77. The results were compared to enantioselectivity patterns of the ligands towards α -(1-naphthyl)ethyl ammonium perchlorate (NEA+ClO4-) enantiomers measured by circular dichroism and by 1H NMR titrations.

Synthesis and optical characterization of novel azacrown ethers containing an acridinone or an N-methylacridinone unit as potential fluorescent chemosensors

Four new achiral and four new chiral monoazacrown ethers containing an acridinone or an N-methylacridinone fluorescent signalling unit were prepared by reacting chloromethyl-substituted acridinone derivatives with achiral monoazacrown ethers with different cavity sizes and enantiopure monoaza-18-crown-6 ethers having two methyl and two isobutyl groups on their chiral centres, respectively. The operation of these chemosensors is based on the photoinduced electron transfer (PET) process, thus they show fluorescence enhancement in the presence of cationic guests. Their fluorescent behaviour as well as their complexation properties towards selected metal ions and the enantiomers of α-(1-naphthyl)ethylammonium perchlorate and potassium mandelate were examined.

Synthesis and preliminary studies on novel enantiopure crown ethers containing an alkyl diarylphosphinate or a proton-ionizable diarylphosphinic acid unit

This paper reports the synthesis, characterization and electronic circular dichroism (ECD) spectroscopic studies of a new type of crown ethers and their achiral analogues containing a tetrahedral phosphorous centre. The synthetic routes to the two chiral phosphinate derivatives [( R, R)- 10 and ( R, R)- 11] were similar, starting from the earlier reported ethyl bis(2-hydroxyphenyl)phosphinate and the unreported methyl bis(2-hydroxyphenyl)phosphinate, respectively. The enantiopure crown ether containing phosphinic acid unit ( R, R)- 14 was obtained by hydrolysis of the phosphinates ( R, R)- 10 and ( R, R)- 11, respectively. ECD spectroscopy was used for investigation of the chiroptical properties as well as complex formation ability of the novel enantiopure ligands. Owing to the presence of the aryl substituents the ECD spectra are rich in bands in the 1B b, 1L a and 1L b regions (190–250 nm and 260–330 nm, respectively). In the case of ( R, R)- 14, a solvent dependent conformational behaviour was observed due to the strong dimer or aggregate forming ability of the POOH groups. This finding was supported by theoretical calculation of the monomer and the dimer forms. Phosphinates ( R, R)- 10 and ( R, R)- 11 form complexes with α-phenylethylammonium perchlorate (PEA) and α-(1-naphthyl)ethyl ammonium perchlorate (NEA) but do not discriminate between their enantiomers. All three chiral crown ethers bind strongly cations of ionic radii <∼1 Å.

Synthesis of chiral crown ethers and complexation with chiral protonated amine compounds: X-ray crystal and nuclear magnetic resonance studies of perchlorate salt of chiral benzo-monoaza-15-crown-5 and chiral monoaza-15-crown-5

The X-ray crystal structure of IX, perchlorate salt of R-(−-2-ethyl-N-benzyl-4,7,19,13-tetraoxa-8,9-benzo-1-azacyclopentadec-8-ene has been determined. In the molecule, the protonated nitrogen atom participates in two N-H⋯O hydrogen bonds. The unusually high proton affinity of aza crown ether leads to the formation of diastreomer instead of complex formation with chiral R-(+)-1-phenyl ethyl ammonium perchlorate and S-(−)-1-phenyl ethyl ammonium perchlorate. The complex ability of host ethers was evaluated in terms of structural modification.

All solid-state redox supercapacitors based on supramolecular 1,5-diaminoanthraquinone oligomeric electrode and polymeric electrolytes

Supramolecular conducting oligomeric 1,5-diaminoanthraquinone (DAAQ)-based all solid-state redox supercapacitors have been fabricated with the solid polymer electrolyte, poly vinyl alcohol (PVA)–H 3 PO 4 blend and polymeric gel electrolyte poly methyl methacrylate (PMMA)–ethylene carbonate (EC)–propylene carbonate (PC)–tetra ethyl ammonium perchlorate (TEAClO 4 ) system. The films of gel electrolyte of the optimized composition PMMA (35 wt.%)–EC:PC (1:1 v/v)–1 M TEAClO 4 and polymer electrolyte PVA–H 3 PO 4 (50:50 w/w) blend exhibited high ionic conductivity (10 −4 to 10 −3 S cm −1 at room temperature) with good mechanical strength, suitable for application in electrochemical supercapacitors. The capacitors have been characterized using a.c. impedance spectroscopy, linear sweep voltammetry and prolonged cyclic test. The maximum capacitance value of 3.7–5.4 mF cm −2 (equivalent to single electrode capacitance 125–184 F g −1 of DAAQ electrode) has been observed for the PMMA–gel electrolyte based capacitor. This corresponds to the energy density 92–135 Wh kg −1 . System based on the proton-conducting PVA–H 3 PO 4 polymer blend, however has relatively lower capacitance of 1.1–4.0 mF cm −2 (equivalent to single electrode capacitance of 36–136 F g −1 ).

18-crown-6 ether complexes with aralkylammonium perchlorates

Thermochemical properties of crown ether complexes have been studied by simultaneous TG-DTA (thermogravimetric analysis-differential thermal analysis) coupled with a mass spectrometer, DSC (differential scanning calorimetry) and hot stage microscopy (HSM). The examined complexes contain benzylammonium- [BA], (R)-(+)-a-phenylethylammonium- [(R)-PEA], (R)-(+)- and (S)-(-)-a-(1-naphthyl)ethylammonium perchlorate [(R)-NEA and (S)-NEA] salts as guests. In the cases of BA and (R)-PEA an achiral pyridono-18-crown-6 ligand [P18C6], and in the case of (R)-NEA and (S)-NEA a chiral (R,R)-dimethylphenazino-18-crown-6 ligand [(R,R)-DMPh18C6] was used as host molecule to obtain four different crown ether complexes. In all cases, the melting points of the complexes were higher than those of both the host and the guest compounds. The decomposition of the complexes begins immediately after their melting is completed, while the BA and (R)-PEA salts and the crown ether ligands are thermally stable by 50 to 100 K above their melting points. During the decomposition of the salts and the four complexes strongly exothermic processes can be observed which are due to oxidative reactions of the perchlorate anion. Ammonium perchlorate crystals were identified among the decomposition residues of the salts. P18C6 was observed to crystallize with two molecules of water. The studied complexes of P18C6 did not contain any solvate. BA was observed to exhibit a reversible solid-solid phase transition upon heating. The heterochiral complex consisting of (S)-NEA and (R,R)-DMPh18C6 shows a solid-solid phase transition followed by two melting points. HSM observations identified three crystal modifications, two of them simultaneously co-existing.

Theoretical CD spectrum calculations of the crown-ether aralkyl-ammonium salt complex.

Rotatory strengths of the alpha-(1-naphtyl)-ethylammonium perchlorate (NEA)-phenazino-18-crown-6 ether molecular complex is determined theoretically by the coupled oscillator model and using ab initio random phase approximation (RPA) to describe local excitations on the chromophores. The computational results are compared to the experimental circular dichroism (CD) spectrum published previously. The good qualitative agreement between calculated and measured optical rotatory strengths allows one to assign the CD bands of the complex in a unique manner.

Preparation of a New Chiral Pyridino-Crown Ether-Based Stationary Phase for Enantioseparation of Racemic Primary Organic Ammonium Salts

Three novel enantiomerically pure chiral pyridino-18-crown-6 ligands [(S,S)-7, (S,S)-8 and (R,R)-9] containing a linker with a terminal carboxyl function were prepared. One of them [(R,R)-9] containing two tert-butyl groups at the stereogenic centers was covalently attached to silica gel by an amide bond using 3-aminopropyltrimethoxysilane. The resulting chiral stationary phase [(R,R)-11] separated the enantiomers of racemic α-(1-naphthyl)ethylammonium perchlorate and 1-phenylethylammonium perchlorate by high-performance liquid chromatography.

Chromatographic enantioseparation of racemic α-(1-naphthyl)ethylammonium perchlorate by a Merrifield resin-bound enantiomerically pure chiral dimethylpyridino-18-crown-6 ligand

Three novel chiral pyridino-18-crown-6 ligands ( S,S)- 1, ( S,S)- 2 and ( S,S)- 3 were prepared and ( S,S)- 1 was attached to a Merrifield resin. The resulting adsorbent ( S,S)- 5 was used as a chiral stationary phase in the chromatographic enantioseparation of racemic α-(1-naphthyl)ethylammonium perchlorate. Also, a new chiral pyridono-18-crown-6 ligand ( S,S)- 6, used for the synthesis of ( S,S)- 1 and ( S,S)- 2, was prepared in two different ways.

Enantiomerically pure chiral pyridino-crown ethers: synthesis and enantioselectivity toward the enantiomers of α-(1-naphthyl)ethylammonium perchlorate

Seven new enantiomerically pure chiral pyridino-crown ethers ( S,S)- 4–( R,R)- 10 were prepared. Three of them [( S,S)- 4, ( S,S)- 7 and ( R,R)- 10] contain one, and two of them [( S,S)- 5 and ( S,S)- 8] contain two linker chains with a terminal double bond. These linker chains were connected to the carbon atom at position 9 (opposite the pyridine moiety) of the macrocycle. The terminal double bond of the linker makes it possible to attach these ligands to silica gel to obtain chiral stationary phases (CSPs). The enantioselectivity of the new ligands toward the enantiomers of α-(1-naphthyl)ethylammonium perchlorate (NEA) was also determined by a titration 1H NMR method.

Enantiomerically pure chiral phenazino-crown ethers: synthesis, preliminary circular dichroism spectroscopic studies and complexes with the enantiomers of 1-arethyl ammonium salts

Enantiomerically pure chiral crown ethers containing the phenazine unit [( R,R)- 2–( S,S)- 8] were prepared by two types of cyclization reactions. Ligands ( R,R)- 2, ( R,R)- 3, ( S,S)- 4, ( R,R)- 5, ( R,R)- 6 and ( R,R)- 7 were prepared from phenazine-1,9-diol 9 and the appropriate ditosylates ( S,S)- 10–( S,S)- 15 in weak basic conditions with complete inversion of configuration. Ligands ( S,S)- 2, ( S,S)- 7 and ( S,S)- 8, however, were prepared from 1,9-dichlorophenazine 19 and the appropriate diols ( S,S)- 16–( S,S)- 18 in strong basic conditions with retention of configuration. Enantiomeric recognition of most of the chiral ligands with α-(1-naphthyl)ethylammonium perchlorate (NEA) and α-phenylethylammonium perchlorate (PEA) has been studied by CD spectroscopy.

Enantiomeric recognition of α-(1-naphthyl)ethylammonium perchlorate by enantiomerically pure dimethylphenazino-18-crown-6 ligand in solid and gas phases

X-Ray crystallographic studies of enantiomerically pure dimethylphenazino-18-crown-6 ligand ( R, R)- 1 and its complexes with the enantiomers of α-(1-naphthyl)ethylammonium perchlorate NapEt were carried out. These studies clearly show that the heterochiral complex ( R, R)- 1–( S)-NapEt is more stable than the homochiral one ( R, R)- 1–( R)-NapEt. It was pointed out that besides the hydrogen bonding, mainly the π–π interaction between the aromatic systems of the host and guest, and the difference in steric repulsions were responsible for enantioselectivity. Molecular mechanical calculations using the LMOD/MINTA method also predicted the heterochiral complex to be more stable than the homochiral one in the gas phase.

Synthesis and Complexation Properties of Pyrimidine‐Derived Crown Ether Ligands

AbstractFive new proton‐ionizable macrocyclic ligands containing a pyrimidone‐subcyclic unit, 6–10, were prepared from the previously prepared pyrimidinocrown ethers 1–5 (see Figure 1 and Scheme 1). One of the new proton‐ionizable crown ethers is chiral. The proton‐ionizable pyrimidonocrown ethers were prepared in high yields by treating the appropriate methoxy‐substituted pyrimidinocrown with 5 M sodium hydroxide in a 50% alcohol‐water mixture. Complexation properties of four of the pyrimidine‐derived macrocycles were studied by various nmr techniques. Pyrimidono‐18‐crown‐6 (9) forms a strong complex with benzylammonium perchlorate and also forms a complex with benzylamine. (S, S)‐Dimethyl‐substituted pyrimidino‐ and pyrimidono‐18‐crown‐6 ligands 4 and 9 form stronger complexes with the (R)‐form of α‐(1‐naphthyl)ethylammonium perchlorate than with the (S)‐form. (S, S)‐Dimethyl‐substituted pyrimidono‐18‐crown‐6 (9) also forms a stronger complex with (R)‐α‐(1‐naphthyl)ethylamine than with the (S)‐form. The crystal structure for compound 7 is reported.

Pyrimidino- and Proton-ionizable Pyrimidono-crown Ether Ligands: Synthesis and Preliminary Complexation Studies

Pyrimidino-crown ethers were prepared in 30-50% yields by reactingthe ditosylate derivative of the appropriate oligoethylene glycol with4-methoxy-5-methyl-2,6-pyrimidinedimethanol under basic conditions. A newmacrocyclic ligand containing a proton-ionizable pyrimidone subcyclic unitwas prepared in 88% yield by treating the appropriatepyrimidino-crown ether with 5 M NaOH in 50% (v/v) aqueous methanol.Preliminary complexation properties of some of these new compounds werestudied using various NMR spectral techniques. Good enantiomeric recognitionwas exhibited by a chiral pyrimidino-crown ether for the enantiomers of1-(α-naphthyl)ethylammonium perchlorate.