Search

In the crystal of the 2:2 complex of 1,5,7-triazabicyclo[4.4.0]dec-5-ene with 5,5′-dibromo-2,2′-biphenol a cooperative inter-intra-molecular hydrogen-bonded system is formed. The intermolecular hydrogen bonds are relatively long [2.708(6) and 2.895(7)] and do not show large proton polarizability. The intramolecular OHO−hydrogen bond is relatively short [2.489(6)]. The structure of the complex is very well reflected in its FT-IR spectrum in the solid. On the basis of the FT-IR and 1H NMR studies of the complex in chloroform and in acetonitrile a structure different than in the solid is proposed. DFT structures of both isolated ions in their ground electronic states at the B3LYP/6-31++G(d,p) level are employed to follow the effects of the hydrogen bonding on the intrinsic ionic structures.

In the crystal of the 1:1 complex of 4-nitrophenyl[bis(diethylsulfonyl)]methane with 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) the proton is transferred from the C–H acid to TBD to yield an ion pair. In the ionic structure the N–H protons of protonated TBD molecule are hydrogen-bonded with sulfonyl oxygens. The lengths of these N–H⋯O hydrogen bonds are of 2.851(2) and 2.911(2)Å. The structure of the complex in solid is very well reflected in its FT-IR spectrum. On the basis of the FT-IR and 1H NMR studies of the complex, in chloroform, its structure similar to that in the solid state is postulated. In acetonitrile a dissociation of the complex and a formation of a new structure is proposed.

The complex formation for two different types of proton sponges (2-methylsparteine, 13-hydroxylupanine and three 1,2-bis(dialkylaminomethyl) benzenes, (alkyl=methyl, ethyl or pyperidil)) with Cu(II) cation in ethanol was studied by kinetic, potentiometric and MS methods. The studied proton sponges with Cu(II) cation formed 1:1 and 1:2 complexes. The kinetic parameters and the equilibrium constants of their formation were determined. Both kinetic and thermodynamic parameters depend strongly on the structure of the proton sponge.

5,5′-dibromo-3-diethylaminomethyl-2,2′-biphenol N-oxide was studied by IR and NMR spectroscopy in chloroform and acetonitrile solutions. Two intramolecular hydrogen bonds are present in these molecules. The NO⋯H+⋯O−bond formed between the OH and the N-oxide groups is very strong. The proton potential is flat and broad and has probably no barrier. This hydrogen bond shows only slight proton polarizability. The other hydrogen bond formed between two hydroxyl groups OH⋯O−⇌−O⋯HO is weaker and show large proton polarizability. The proton motions in both hydrogen bonds are not coupled and therefore these hydrogen bonds are not cooperative.

In the reaction between 3,5-dinitrosalicylic acid and urotropine, the proton of the phenolic group is transferred to a nitrogen atom of urotropine to form a hydrogen-bonded ion-paired [N⋯Ophenolate=2.777(4)Å]compound. An analogous reaction between the acid and dicyclohexylamine yields a centrosymmetric ion-paired dimer [N⋯Ophenolate=2.864(4), N⋯Ocarbonyl=2.940(5)Å].The structures of the two compounds are discussed in relation to their infrared spectral features. The structure of the anion is also investigated theoretically by geometry-optimization calculations.

A complex of 5,5′-dibromo-2,2′-biphenol with 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (MTBD) hydrochloride has been studied using X-ray diffraction, FT-IR, and 1H NMR spectroscopy. The compound crystallises in the space group P21/cwith a=9.738(2), b=12.100(2), c=18.347(4)Å,β=92.62(3)° (at 100K), and Z=4. In the crystal structure, the MTBDH+cation, a chloride anion, and one molecule of 5,5′-dibromo-2,2′-biphenol are present. In the solid state the Cl−anion is an acceptor in N+–H⋯Cl−, O–H⋯Cl−and C–H⋯Cl−intermolecular hydrogen bonds.

The product of the reaction between urotropine and p-nitrophenol, reported as a 1:1 adduct that belongs to the triclinic P1 space group, is, in fact, a 1:2 [C6H12N4]·[p-HOC6H4NO2]2·[H2O] hydrate that crystallizes in the monoclinic C2 space group. In the crystal structure, one nitrogen atom of the urotropine moiety is linked by a hydrogen bond to the hydroxyl group of a p-nitrophenol molecule [N⋯O=2.655(7)Å];the [C6H12N4]·[p-HOC6H4NO2] entities are linked into a linear one-dimensional chain through the lattice water molecule [O⋯N=2.871(8),O⋯O=2.878(7)Å].The other p-nitrophenol moiety is disordered over two positions across the two-fold axis; its interaction with adjacent water molecules [O⋯O=2.53(1),2.57(2)Å] holds neighboring chains together. The FTIR spectrum of the complex in the solid indicate the formation of OH⋯N intermolecular hydrogen bond described by an asymmetric double minimum potential and weak Zundel's polarizability. The spectroscopic measurements in solution demonstrate the dissociation of the complex observed in the solid and prove the presence of the 1:1 complexes urotropine–p-nitrophenol. In these complexes no proton transfer from p-nitrophenol to urotropine is observed.

Hydrated complexes of gramicidin A (gA) with K+, Rb+and Cs+cations were studied by FT-IR spectroscopy. The water bands observed in the FT-IR spectrum are identical as those obtained for the hydrated gA–Li+and gA–Na+complexes studied previously. In the far infrared spectrum of the gA–K+and gA–Rb+complexes an intense continuum and a strongly broadened band were found indicating large K+and Rb+polarizability in the gA channels. These K+and Rb+polarizabilities appear, similarly as in the case of the Li+and Na+complexes, as a result of the fast fluctuation of the K+and Rb+ions between two water molecules and four CO groups of the gA backbone. The much smaller barriers in the six minima Na+potential explain the much larger mobility of Na+when compared with the Li+and other cations.

5,5′-dibromo-3-diethylaminomethyl-2,2′-biphenol was synthesized and the collective proton motion in two intramolecular hydrogen bonds was studied by 1H and 13C NMR as well as by FTIR spectroscopy in chloroform, acetonitrile and chloroform containing traces of water solutions. In dry chloroform, always, two separated proton signals for the two OH groups were observed. If traces of water were present at room temperature in the chloroform solution only one signal for the two OH protons was found. With decreasing temperature the collective proton motion, indicated by continuous absorption in the FTIR spectrum, was interrupted and two separate signals appeared in the 1H NMR spectrum. In acetonitrile the collective proton motion in the two intramolecular hydrogen-bonded system observed at room temperature vanished with decreasing temperature and finally only a cooperative hydrogen-bonded system, like in the solid state, was observed.

2,2′-Biphenol mixtures with 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (MTBD) were studied by FTIR spectroscopy. In chloroform, a proton transfer from 2,2′-biphenol to MTBD occurs. In this solution the protonated MTBD molecules are hydrogen-bonded to the 2,2′-biphenol–2,2′-biphenolate chains. In acetonitrile, after the proton transfer, the complexes dissociate and hence protonated MTBD molecules and hydrogen-bonded 2,2′-biphenol–2,2′-biphenolate chains are present. The hydrogen bonds and the hydrogen-bonded chains show large proton polarizability. In the systems intra- as well as inter-molecular hydrogen bonds are formed.

The heats of reactions between the acyclic and cyclic macro-compounds are determined. The values can be used as a measure of the donor abilities of the macro ligands. Formation of two types of complexes between the macro compounds and SbCl5is established. The acyclic macro-compounds form 1:1 complexes, whereas the macrocyclic compounds only 1:2 complexes.

The results of X-ray diffraction and IR spectroscopic studies for 2:1 pentachlorophenol-7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene [(PCP)2·MTBD] adduct are reported. The geometry of MTBD cations reflects the equal distribution of the positive charge among three nitrogen atoms. Short asymmetric [OHO]−hydrogen bonds with O⋯O distance of 2.508(2)Å and NH+⋯O−hydrogen bonds with N⋯O distance of 2.802(2)Å are formed showing broad IR absorption with two maxima located at ∼1200 and ∼2400cm−1. The second maximum is interpreted as due to the 0→2 transition between split levels in an asymmetric double minimum potential. One of the oxygen atoms forms an additional O⋯H–N+hydrogen bonding with an MTBD cation. The situation is somewhat different in acetonitrile solution whose IR spectrum shows continuous absorption extended over whole the IR region. In acetonitrile, dissociation to free OHO−and +NH ions takes place and the OHO−bridges become dynamically symmetric. The broadening is interpreted in terms of a stochastic distribution of the geometry and the Zundel polarizability theory.

Twenty-two 2,4-dinitroanilines were synthesised and their pKavalues were determined. The 2,4-dinitroanilines and their protonated forms were studied by 15N NMR spectroscopy. The relations between the 15N NMR chemical shifts and the pKavalues of the 2,4-dinitroanilines and their salts were found to be linear. The deprotonation reaction of N-methyl-2,4-dinitroanilines and N-methyl-2,4,6-trinitroaniline by MTBD was successful only for the latter and yielded protonated MTBD molecule and the anion in which the electrons are strongly delocalised. The kinetic parameters of the 2,4-dinitroanilines in reactions with hydroxide ions in mixed solvent DMSO:water (95:5, v/v) were determinated and discussed.

Lasalocid forms 1:1 or 2:2 complexes with sodium ions. The process of complexation was studied in different solvents at various temperatures by 23Na NMR. The formation constants and ΔGvalues were determined. The nature of the complex between lasalocid and Na+ions was also studied by FT-IR spectroscopy. In chloroform, a 2:2 complex of lasalocid and Na+ions is formed. A continuous absorption is observed in the far FT-IR spectrum of this complex. It indicates the large Na+polarizability due to fast fluctuations of the Na+ions in multiminima potentials, in the dimeric structure.

The complexes formed by tetrazole with MTBD, an N-base of guanidin-like character, were studied by FTIR spectroscopy. In the chloroform solution of 1:1 ratio, a −N⋯H+MTBD asymmetrical complex is formed and no dissociation of this complex is visible. With increasing tetrazole–MTBD ratio, the formation of chains of tetrazole molecules is observed. In acetonitrile solution of tetrazole with MTBD, the amount of protonated and dissociated H+MTBD species increases with increasing concentration of tetrazole. In these mixtures, negatively charged chains are observed to be formed with tetrazole molecules only; however, some amount of free tetrazole molecules is also detected in this case. All these chains show large proton polarizability

The complexation of some cations (Zn2+, Fe2+, Fe3+, Ni2+, Cu2+, Co2+, Pb2+, Na+, Li+, Mn2+, Cd2+, K+, Mg2+, Cr3+) by tris(3,6-dioxaheptyl)amine in various solvents was studied by the thin layer chromatography, liquid secondary ion mass spectra, FT-IR and 13C NMR spectroscopies as well as kinetic methods. In this article, the structure of the complexes is discussed.

The mono- as well as the di-Mannich bases of 5,5′-dimethoxy-2,2′-biphenol are studied by FT-IR spectroscopy. It is shown that in these bases the protons remain localized at the phenol O atom. This result is in contrast to those obtained earlier for more acidic biphenols in which the protons are not localized but fluctuate and the relevant hydrogen bonds show large polarizability. An intense infrared continuum in the FT-IR spectrum of the mono-protonated di-Mannich base of 5,5′-dimethoxy-2,2′-biphenol demonstrates that the intramolecular hydrogen bond in this compound shows large proton polarizability.