Oxaalkyl Chains Research Articles

Potentiometric and AM1d studies of a new class of Tr-podands–silver(I) complexes

Formation of complexes of structurally comparable six silicon, boron and phosphorous Triton X podands (Tr-podands) and silver(I) cations in propylene carbonate has been studied by the potentiometric and AM1d semi-empirical methods. Three types of these podands (2–7) form stable complexes with Ag+ cations. The stability constants of the complexes including different number of silver(I) cations are determined. It has been shown that the number of Ag+ cations complexed by the podands depends strongly on the number of oxaalkyl chains and on the type of central podand's atom (Si, B or P). The (7) podand (with six polyoxaalkyl chains) can complex as many as six silver(I) cations. The structures of these complexes are visualised by the AM1d semi-empirical method.

Hydrogen bonds in phenylboronic acids with polyoxaalkyl substituents at ortho-position

Phenylboronic acids with polyoxaalkyl substituents at ortho position were synthesized from the corresponding bromides. Structures in solid state, determined by single crystal X-ray diffraction, reveal the presence of inter- and intramolecular hydrogen bonds. Presence of several oxygen atoms in oxaalkyl chains enables the formation of intramolecular hydrogen bonds by B(OH) 2 group with different oxygen centers which lead to the formation of bifurcated hydrogen bonds. Investigated compounds were characterized by 1H, 13C, 11B and 17O NMR spectroscopy in solution. Assignment of 1H and 13C signals was made on the basis of HSQC and HMBC spectra. 17O NMR spectra show that in acetonitrile solution hydrogen bonds with solvent molecules are predominant.

The synthesis and structural studies of a new Kemp’s triacid oxaalkyl ester and its complexes with Li +, Na + and K + cations

A new derivative of Kemp’s triacid (KTA) with 2-bromoethyl methyl ether (triester, KTEG1) and its complexes with monovalent cations (Li +, Na + and K +) have been synthesized and studied by EI MS, multinuclear NMR, FT-IR as well as by the PM5 semiempirical methods. It has been demonstrated that KTEG1 forms stable complexes of 1:1 stoichiometry with the metal cations studied. The mass fragmentation pathways for triester and its complexes are proposed. The FT-IR spectra of the complexes show that in the coordination process no oxygen atoms of the carbonyl groups are involved. The FT-IR and NMR data taken together indicated that the coordination process is realized by the oxygen atoms from the oxaalkyl chains. The structures of the KTEG1 and its complexes with Li +, Na + and K + cations are visualized and discussed in detail.

B-podand complexes with sodium ions: the reaction heats and PM5 semiempirical calculation

The complexation reactions of two types of tris(oxaalkyl) borates (B-podands with CH 3 or C 16H 33 terminal groups) with Na + cations have been studied by calorimetric and PM5 theoretical methods. Both methods provide evidence for formation of the respective complexes with Na + cations of different stoichiometry. For compounds with short oxaalkyl chains the formation of 1:1 complexes and for compounds with longer oxaalkyl chains the formation of 1: x ( x > 1) complexes has been found. The stoichiometry of the complexes estimated from the HOF values of the complexes is in well agreement with the calorimetric results. The structures of the complexes are visualised using semiempirical PM5 method.

Polyoxaalkyl esters of phenylboronic acids as new podands

Three oxaalkyl esters of phenylboronic acid and one oxaalkyl ester of phenyldiboronic acid have been synthesized and their ability to form complexes with Li + and Na + cations has been studied using multinuclear NMR, ESI mass spectrometric and PM5 semiempirical methods. It has been demonstrated that the esters of phenylboronic acid form 1:1 complexes with Li + and Na + cations whereas the ester of phenyldiboronic acid can additionally form complexes of 1:2 stoichiometry. The stability constants of these complexes have been determined to show that with increasing number of oxygen atoms in the oxaalkyl chains the complexes of increasing stability are formed. The exemplary 1:1 and 1:2 structures of the complexes of esters with Li + and Na + cations, respectively, are given. They show that the cations are coordinated within a pseudo-crown structures formed by oxaalkyl chains.

Potentiometric and AM1d studies of silicon and boron podands—silver (I) complexes

The two new types of podands: silicon ones with the C C bonds and boron podands, have been synthesised and the formation of their complexes with silver (I) cations has been studied by potentiometric and AM1d semiempirical methods. The stability constants for the complexes including different numbers of silver (I) cations are determined. It has been shown that the silver (I) cation is preferentially coordinated by the π electrons of the C C bonds of the vinyl or allyl groups. It has been also shown that the number of Ag + cations complexed by the boron podands depends strongly on the number of oxygen atoms in the oxaalkyl chains. The energetically favourable structures of the selected complexes are visualised by the AM1d semiempirical method.

Spectroscopic and PM5 semiempirical studies of new hydrazone of gossypol with 3,6-dioxaheptylhydrazine

A new hydrazone of gossypol with 3,6-dioxaheptylhydrazine (GHDO) has been synthesised and its structure has been studied by FT-IR, 1H NMR, 13C NMR as well as PM5 semiempirical methods. All the studies have provided clear evidence of the existence of GHDO in the solution in the N-imine– N-imine tautomeric form. The structure and the spectroscopic behaviour of this tautomer are discussed in details. It is shown the structure of GHDO is strongly stabilised by different types of intramolecular hydrogen bonds. In two of them the oxygen atoms of the oxaalkyl chains are also engaged. The strongest intramolecular hydrogen bond is formed between the O 7H proton and N 16 atom from the hydrazone group.

Potentiometric and AM1d studies of silicon and phosphorous podands-silver (I) complexes

Formation of complexes of structurally comparable silicon and phosphorous podands and silver (I) cations in propylene carbonate has been studied by the potentiometric and AM1d semi-empirical methods. Both types of podands form stable complexes with Ag + cations. The stability constants of complexes including different number of silver (I) cations are determined. It has been shown that the number of Ag + cations complexed by the podands depends strongly on the number of oxygen atoms in the oxaalkyl chains. The influence of the hydrophobic chains on the stability constants of the complexes has been found. The structures of these complexes are visualised by the AM1d semi-empirical method.

The reaction heats and PM5 semiempirical studies of complexes formed between silicon podand and Li + cations

The complexation reaction of Li + cations by silicon podands (1–12) was studied by calorimetric and PM5 semiempirical methods. Both methods provide evidence for formation of the respective complexes with Li + cations of different stoichiometry. For compounds 1, 2, 4, 6 and 10 only formation of 1:1 complexes were observed whereas for compounds with longer oxaalkyl chains the formation of 1: x ( x>1) complexes have been found. The structures of the complexes are visualised and discussed.

Potentiometric and AM1d studies of silicon podands—silver(I) complexes

Formation of complexes of various silicon podands and silver(I) cations in propylene carbonate has been studied by the potentiometric and AM1d semiempirical methods. Silicon podands form stable complexes with Ag + cations. The stability constants of various complexes are determined. It has been shown that the number of Ag + cations complexed by the Si-podands depends strongly on the number of oxygen atoms in the oxaalkyl chains. The PhSi15.3 podand can complex as many as 6 silver(I) cations. The structures of these complexes are visualised by the AM1d semiempirical method.

The reaction heats and PM5 semiempirical studies of complexes formed between silicon podand and monovalent cations

Silicon podands (1–10) were synthesised and their complexation reaction of Na + cations were studied by calorimetric and PM5 theoretical methods. Both methods provide evidence for formation of the respective complexes with Na + cations of different stoichiometry. In most cases, only formation of the complexes of 1:1 stoichiometry has been observed. For compounds with longer oxaalkyl chains (9 and 10) the formation of 1:4 and 1:6 complexes has been found. The structures of the complexes are visualised and discussed.

Complexes of Schiff base of gossypol with 5-hydroxy-3-oxapentylamine and Ca 2+, Ba 2+ or Pb 2+ cations studied by NMR, FT-IR, ESI MS as well as PM5 semiempirical methods

A new Schiff base of gossypol with 5-hydroxy-3-oxapentylamine (GSBH) has been found to complex bivalent metal cations, in particular Ca 2+, Ba 2+ and Pb 2+. This process of complex formation has been studied by ESI mass spectrometry, 1H, 13C NMR and FT-IR spectroscopy as well as by PM5 semiempirical method. It has been established that GSBH forms stable 1:1 complexes with all these cations. In all complexes the Schiff base of gossypol exists as the enamine–enamine tautomer. The Ca 2+, Ba 2+ cations are coordinated through oxygen atoms from the four hydroxyl groups, and Pb 2+ cation additionally also by two oxygen atoms from oxaalkyl chains. The structures of these complexes have been calculated by PM5 semiempirical method and discussed.

Studies of lithium and sodium complexation by silicon podand solvents

The complex formation of lithium and sodium ions with silicon podand solvents: phenyl-tris(1,4-dioxapentyl) silane (PhSi23) and ethyl-tris(1,4-dioxapentyl) silane (EtSi23) has been studied by FTIR, 1H-, 13C-, 7Li- and 23Na NMR. The far FTIR spectra show that the Li + cations fluctuate very fast whereas Na + cations are still localised between the oxygen atoms of the oxaalkyl chains. The 7Li NMR spectra prove that one Li + cation can be coordinated not only by one but also two silicon podand molecules. The concentration dependence of the molar conductivity of LiClO 4 in the podand solvents indicates charge transfer between ion clusters.

FTIR and NMR studies of bis(oxaalkyl) sulphates(IV) and their complexes with proton and some metal cations

The complexation of Li + and Na + cations by three bis(oxaalkyl) sulphates(IV) was studied by FTIR and NMR on 1H, 13C, 7Li and 23Na nuclei. The NMR results have proved the formation of complexes and the fluctuation of Li + and Na + cations in respective circular arrangements. In the FTIR spectra of protonated sulphates intense continuous absorptions were observed indicating fast fluctuation of the protons in the respective multiminima potentials. The continuous absorptions in the far infrared region of the FTIR spectra of Li + or Na + complexes with three bis(oxaalkyl) sulphates(IV) indicate fast fluctuations of Li + or Na + cations between O-atoms of the oxaalkyl chains. The independence of the shape of the continua on the length of the oxaalkyl chains, i. e. the number of minima in the multiminima potential, demonstrates that the fluctuation of cations occurs in the respective circular arrangements.

NMR study of the complexes of tris(oxaalkyl) borates with SbCl5

The complex formation between three tris(oxaalkyl) borates (B2, B3, B4) and SbCl5 as well as the structure of these complexes were studied by calorimetric and NMR methods. Results of the calorimetric titration indicate a dependence of ΔH of the reaction heats on the length of the oxaalkyl chains, and a formation of stable complexes. The 1H and 13C NMR data confirmed the formation of the respective stable complexes. The structure of the complexes is discussed.

FTIR and multinuclear magnetic resonance studies of tris(oxaalkyl) borates and their complexes with Li+ and Na+ cations

FTIR and NMR of 1H, 13C, 11B, 7Li and 23Na nuclei were used for the study of the complexation of Li+ and Na+ cations by three tris(oxaalkyl) borates. The NMR techniques proved the formation of complexes and the fluctuation of Li+ and Na+ cations in the respective channels formed by three oxaalkyl chains. In the FTIR spectra of Li+ complexes with three tris(oxaalkyl) borates, continuous absorption in the far-infrared region indicates the fast fluctuations of Li+ ion between O atoms of the channels. The dependence of the continua shape on the length of the channels, i.e., the number of minima in the multiminima potentials, demonstrates that the fluctuation of Li+ ion occurs along the channel. Owing to the larger mass and diameter of the Na+ cation in the Na+–tris(oxaalkyl) borate complexes, only systems with longer channels show a large Na+ polarizability due to the fast fluctuation of Na+ cations in a multiminima potential.

Synthesis and characterization of oligo- and crown ether-substituted polythiophenes-a comparative study

The synthesis of two series of thiophenes substituted with crown and oligoether groups either via isolating oxaalkyl chains (2, 7-11) or in direct π-conjugation (4, 12-15) is described. Electrooxidative polymerization leads to the corresponding crown and oligoether-functionalized polythiophenes P2, P7-P11, and P4, P12, respectively. Their electrochemical and spectroscopic properties depend on the length of the spacer and the type of the ether unit. The polymers reveal a high mean conjugation. A specific and strong influence of alkali ions on the electrochemical behavior is found for several polymers. The selectivities correspond to the match of the cation size without solvent shell and the inner diameter of the crown ether units. Spectroelectrochemical experiments corroborate that the changes in redox properties are due to a hindered diffusion of the counter anions into the film when the polymer is oxidized. Due to the structural variation novel materials sensitive to different cations are obtained. Importantly, in these conjugated polymers chemical information which corresponds to a selective host-guest interaction of the alkali metal cations and the ether units is transduced into the change of an electrical signal.