Grzegorz Wojciechowski

Spectroscopic study and PM5 semiempirical calculations of tautomeric forms of gossypol Schiff base with n-butylamine in the solid state and in the solution

Abstract The Schiff base of gossypol with n -butylamine was synthesised and its structure was studied by FT-IR and 1 H NMR, 13 C NMR and 15 N NMR as well as PM5 semiempirical methods. It is shown that the Schiff base exists in solution and in solid state as the enamine–enamine tautomer. The structure of this tautomer is discussed in detail.

Structural and spectroscopic studies on 3,5-dinitrosalicylic acid complexes of urotropine and dicyclohexylamine. A theoretical analysis of the structure of the complex anion

Abstract 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 ⋯ O phenolate =2.777(4) A ] compound. An analogous reaction between the acid and dicyclohexylamine yields a centrosymmetric ion-paired dimer [N⋯O phenolate =2.864(4), N ⋯ O carbonyl =2.940(5) A ]. 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.

Spectroscopic studies of Schiff bases of 2,2'-dihydroxybiphenyl-3-carbaldehyde and para substituted anilines

Abstract Five Schiff bases derivatives of 2,2′-dihydroxybiphenyl-3-carboxaldehyde and various para substituted anilines have been synthesised and studied by FT-IR, 1 H, 13 C, 15 N NMR and CPMAS spectroscopy. The structure of the Schiff base includes two intramolecular OH⋯O and OH⋯N hydrogen bonds forming a hydrogen-bonded chain. All Schiff bases studied exist in imine form in chloroform and acetonitrile solution. On the basis of the CPMAS and FT-IR spectra in solid state the SCH5 base has been proved to exist in the enamine form.

Crystal structure of Schiff base derivative of gossypol with 3,6,9-trioxa-decylamine

Abstract Crystals of the Schiff base derivative of gossypol with 3,6,9-trioxa-decylamine were examined using X-ray diffraction, FT-IR and CPMAS spectroscopy. The Schiff base crystallizes as a racemate in the space group C2/c with a =24.390(5), b =12.026(2), c =14.810(3) A, β =102.78(3)°, and Z =4. The results of the FT-IR, and CPMAS study of the crystals are in agreement with the X-ray data. The FT-IR spectrum of the crystals shows that the OH groups at position 1,1′ and 6,6′ as well as the N 16 –H proton are involved in weak intermolecular and intramolecular hydrogen bonds, respectively. The FTIR and CP-MAS spectral behaviour is in agreement with the crystallographic results demonstrating the existence of the enamine-enamine tautomeric form of the Schiff base studied.

Spectroscopic and semiempirical studies of gossypol complexes with Fe2+ and Fe3+ cations

Abstract The complexes of gossypol with Fe2+ and Fe3+ cations were studied in acetonitrile by UV–Vis and FT-IR spectroscopy. Very complex equilibria and structural changes were observed for various ratios of gossypol–iron cation mixtures. With the formation of complexes, the ketol–ketol tautomer form of gossypol was favored. With increasing concentration of iron cation in the mixture, the deprotonation of hydroxyl groups was indicated. The semiempirical studies show that the most stable complexes of gossypol with iron cations are 1:4, 1:1 and 2:1. The structures of these complexes are discussed.

STUDIES OF COMPLEXATION OF METAL CATIONS BY TRIS(3,6-DIOXAHEPTYL)AMINE IN SOLUTION

Abstract The complexation of some cations (Zn 2+ , Fe 2+ , Fe 3+ , Ni 2+ , Cu 2+ , Co 2+ , Pb 2+ , Na + , Li + , Mn 2+ , Cd 2+ , K + , Mg 2+ , Cr 3+ ) by tris(3,6-dioxaheptyl)amine in various solvents was studied by the thin layer chromatography, liquid secondary ion mass spectra, FT-IR and 13 C NMR spectroscopies as well as kinetic methods. In this article, the structure of the complexes is discussed.

Cooperative intramolecularly hydrogen-bonded motif in the structure of 2:2 complex of TBD with 4-nitrocatechol

Abstract In the crystal of the 2:2 complex of 1,5,7-triazabicyclo[4.4.0]dec-5-ene with 4-nitrocatechol the proton from 1-hydroxyl group of 4-nitrocatechol moiety is transferred to TBD to form ion-pair; two adjacent ion-pairs are linked across a center of inversion. The structure exhibits a cooperative, intramolecularly hydrogen-bonded motif. The hydrogen bonds are relatively long and, and they display only minor proton polarizability. The structure of the complex is retained in chloroform solution, as shown by FT-IR and 1H NMR measurement; in acetonitrile, the compound partially dissociates. The partial dissociation is implied by the presence of free cations, and also by that of the (O⋯H⋯O)− hydrogen bonds formed between two mono-deprotonated 4-nitrocatechol molecules.

Structural, spectroscopic and theoretical studies of the 2:2 complex of 5,5′-dibromo-2,2′-biphenol with 1,5,7-triazabicyclo[4.4.0]dec-5-ene

Abstract 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.

Formation of hydrogen-bonded chains through inter- and intra-molecular hydrogen bonds by a strong base of guanidine-like character and 5,5′-dibromo-2,2′-biphenols

Abstract 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.

FT-IR study of the proton polarizability of hydrogen bonds and of the hydrogen-bonded systems in a di-Mannich base of 5,5′-dimethoxy-2,2′-biphenol

Abstract 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.