Cooperative intramolecular hydrogen bonds in the structure of 5,5 '-dibromo-3-diethylaminomethyl-2,2 '-biphenol

Crystals of 5,5'-dibromo-3-diethylaminomethyl-1-2,2'-biphenol were examined using X-ray diffraction and FT-IR spectrascopy. The space group is P2(l)/n with a = 8.617(2), b = 16.356(3), c = 12.854(3) Angstrom, beta = 108.03(3) degrees and Z = 4. The molecule exists in the crystal in zwitterionic state as a result of proton transfer from a hydroxyl group to the adjacent amino group. These two groups, together with the hydroxyl group of the second ph enol moiety are involved in a system of cooperative intramolecular hydrogen bonds, O(2)H .. O(1)-H+N(1). The O ... O and O ... N distances are 2.476(5 ) and 2.584(5) Angstrom, the O-H and H-N distances 0.89 and 1.04 Angstrom. and the O-H ... O and O ... N-N+ angles 163 and 141 degrees, respectively. The IR spectra of the crystals are consistent with the results of the X-ray analysis, instead of a continuous absorption, only broad bands are found i ndicating very low proton polarizability in the two types of intramolecular hydrogen bonds. (C) 2000 Elsevier Science B.V. All rights reserved.