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Abstract: A complex of 5,5′-dibromo-2,2′-biphenol with 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene hydroiodide has been studied by X-ray diffraction, FT-IR, and 1HNMR spectroscopy. In the crystal structure, the iodide anion is hydrogen-bonded to the MTBDH+ cation and to two hydroxyl groups of two 5,5′-dibromo-2,2′-biphenol molecules. In chloroform and acetonitrile the structure of the complex assumes a new structure due to almost complete dissociation of the protonated MTBD molecule. In chloroform the MTBDH+ cation is hydrogen bonded to 5,5′-dibromo-2,2′-biphenol whereas in acetonitrile it is free and solvated by the solvent. In both cases the 5,5′-dibromo-2,2′-biphenol molecule is hydrogen bonded to the iodide anion. In chloroform the iodide ion interacts strongly with the solvent. [Copyright &y& Elsevier]

Crystals of the Schiff base derivative of 2,2′-dihydroxybiphenyl-3-carbaldehyde with n-butylamine were examined using X-ray diffraction, FT-IR and CPMAS spectroscopy. Their space group is P-1 with a=8.377(2), b=12.214(2), c=14.774(3) A˚, α=76.62(3)°, β=81.34(3)°, γ=86.62(3)° and Z=4. The unit cell contains two symmetry-independent zwitterions. The hydrogen atom of the protonated N atom of the Schiff base is linked to the oxygen atom of the carbonyl group at position 2, which in turn is linked to the hydroxyl group by a short hydrogen bond [molecule A: N⋯O=2.614(3), O⋯O=2.520(3) A˚; molecule B: N⋯O=2.594(4), O⋯O=2.526(3) A˚]. The OH⋯O−⋯H+N bifurcated intramolecular hydrogen bonds are crystallographically asymmetric. The results of the FT-IR, 1H, 13C, 15N NMR and CPMAS study of the crystals are in agreement with the X-ray data. Instead of a continuous absorption, only a broad band is found indicating relatively low proton polarizability in the two types of the cooperative relatively short intramolecular hydrogen bonds. The 15N NMR chemical shift indicates the protonation of the Schiff base. [Copyright &y& Elsevier]

Five Schiff bases derivatives of 2,2′-dihydroxybiphenyl-3-carboxaldehyde and various para substituted anilines have been synthesised and studied by FT-IR, 1H, 13C, 15N 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. [Copyright &y& Elsevier]

The Schiff base of gossypol with n-butylamine was synthesised and its structure was studied by FT-IR and 1H NMR, 13C NMR and 15N 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. [Copyright &y& Elsevier]

A complex of 5,5′-dibromo-2,2′-biphenol (DBBPh) with 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (MTBD) hydrofluoride has been studied using X-ray diffraction, FT-IR, and 1H NMR spectroscopy. The formula unit of the crystal structure consists of a MTBDH+ cation, a fluoride anion, and one neutral molecule of 5,5′-dibromo-2,2′-biphenol. In the solid state the F− anion is an acceptor in two very short O–H⋯F− intermolecular hydrogen bonds of 2.487 and 2.390 Å involving the hydroxyl groups. One oxygen atom of these groups forms also an N+–H⋯O intermolecular hydrogen bond of 2.775 Å with the MTBDH+ cation. In chloroform and acetonitrile, the structures of the complexes are comparable with those studied previously for 5,5′-dibromo-2,2′-biphenol with MTBD, because the hydrogen fluoride goes into the gas phase during the solution process. [Copyright &y& Elsevier]

A complex of 5,5′-dibromo-2,2′-biphenol with 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene hydrobromide has been studied using X-ray diffraction, FT-IR, and 1H NMR spectroscopy. In the crystal structure, a bromide anion is hydrogen-bonded with MTBDH+ cation and two hydroxyl groups of two 5,5′-dibromo-2,2′-biphenol molecules. In the solid state, the Br− anion is an acceptor in N+–H⋯Br−, and two O–H⋯Br− intermolecular hydrogen bonds. In chloroform and acetonitrile, the structure of the complex assumes a new structure due to almost complete dissociation of protonated MTBD molecule. In chloroform, the MTBDH+ cation is hydrogen-bonded with 5,5′-dibromo-2,2′-biphenol whereas in acetonitrile it is free and solvated by the solvent. In both cases, the 5,5′-dibromo-2,2′-biphenol molecule is hydrogen-bonded to the bromide anion. [Copyright &y& Elsevier]

The crystals of 5,5′-dibromo-3-diethylaminomethyl-2,2′-biphenol N-oxide were studied by X-ray and FT-IR spectroscopy. Within this molecule two short OHO intramolecular hydrogen bonds are formed. The NO⋯H+⋯O− bond between the OH and the N-oxide groups is very strong, of 2.419(7) A˚ between the oxygen atoms. The proton potential of this hydrogen bond is flat, broad and has probably no barrier—consequently it could not be located from X-ray diffraction data. The other hydrogen bond formed between two hydroxyl groups appears asymmetrical from FT-IR spectra, and shows also relatively limited proton polarizability. The molecular conformation is non-planar, due to strong overcrowding effect between the oxygen atoms involved in the hydrogen bonds. [Copyright &y& Elsevier]

We studied 1:1 and 1:2 complexes of triethylamine (TEA) with 5,5′-dibromo-2,2′-biphenol (DBBPh) in chloroform and acetonitrile solution using FT-IR and 1H NMR spectroscopy, and for comparison, the tetrabutylammonium 5,5′-dibromo-2,2′-biphenolate salt. In chloroform the 1:1 and 1:2 complexes are very stable and exist as hydrogen-bonded chains. In acetonitrile the 1:1 complexes are also stable, whereas the 1:2 complexes dissociate yielding protonated TEA and cyclic dimers of 5,5′-dibromo-2,2′-biphenol. The formation of cyclic dimers is favored in the case of the complex formed between tetrabutylammonium 5,5′-dibromo-2,2′-biphenolate and 5,5′-dibromo-2,2′-biphenol. All hydrogen bonds and hydrogen-bonded systems in the complexes studied show great proton polarizabity, since the protons may undergo fast fluctuations within these bonds. [Copyright &y& Elsevier]

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 N16–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. [Copyright &y& Elsevier]