Vibrational spectra and crystal structure of the di-amino acid peptide cyclo(L-Met-L-Met): comparison of experimental data and DFT calculations

TY - JOUR

T1 - Vibrational spectra and crystal structure of the di-amino acid peptide cyclo(L-Met-L-Met)

T2 - comparison of experimental data and DFT calculations

AU - Mendham, Andrew P.

AU - Potter, Brian S.

AU - Palmer, Rex A.

AU - Dines, Trevor J.

AU - Mitchell, John C.

AU - Withnall, Robert

AU - Chowdhry, Babur Z.

PY - 2010/2

Y1 - 2010/2

N2 - Experimental Raman and FT-IR spectra of solid-state non-deuterated and N-deuterated samples of cyclo(L-Met-L-Met) are reported and discussed. The Raman and FT-IR results show characteristic amide I vibrations (Raman: 1649 cm(-1), infrared: 1675 cm(-1)) for molecules exhibiting a cis amide conformation. A Raman band, assigned to the cis amide 11 vibrational mode, is observed at similar to 1493 cm(-1) but no IR band is observed in this region. Cyclo(L-Met-L-Met) crystallises in the triclinic space group P1 with one molecule per unit cell. The overall shape of the diketopiperazine (DKP) ring displays a (slightly distorted) boat conformation. The crystal packing employs two strong hydrogen bonds, which traverse the entire crystal via translational repeats. B3-LYP/cc-pVDZ calculations of the structure of the molecule predict a boat conformation for the DKP ring, in agreement with the experimentally determined X-ray structure. Copyright (C) 2009 John Wiley & Sons, Ltd.

AB - Experimental Raman and FT-IR spectra of solid-state non-deuterated and N-deuterated samples of cyclo(L-Met-L-Met) are reported and discussed. The Raman and FT-IR results show characteristic amide I vibrations (Raman: 1649 cm(-1), infrared: 1675 cm(-1)) for molecules exhibiting a cis amide conformation. A Raman band, assigned to the cis amide 11 vibrational mode, is observed at similar to 1493 cm(-1) but no IR band is observed in this region. Cyclo(L-Met-L-Met) crystallises in the triclinic space group P1 with one molecule per unit cell. The overall shape of the diketopiperazine (DKP) ring displays a (slightly distorted) boat conformation. The crystal packing employs two strong hydrogen bonds, which traverse the entire crystal via translational repeats. B3-LYP/cc-pVDZ calculations of the structure of the molecule predict a boat conformation for the DKP ring, in agreement with the experimentally determined X-ray structure. Copyright (C) 2009 John Wiley & Sons, Ltd.

KW - cyclic di-amino acid peptides

KW - X-ray structure

KW - X-ray crystallography

KW - ab initio calculations

KW - vibrational spectra

KW - X-RAY-DIFFRACTION

KW - ALANYL-L-ALANYL

KW - CYCLIC DIPEPTIDES

KW - DIKETOPIPERAZINES

KW - IDENTIFICATION

KW - HYDROGEN

KW - DENSITY

KW - BRAIN

U2 - 10.1002/jrs.2426

DO - 10.1002/jrs.2426

M3 - Article

SN - 0377-0486

VL - 41

SP - 148

EP - 159

JO - Journal of Raman Spectroscopy

JF - Journal of Raman Spectroscopy

IS - 2

ER -