Reduction in crystal symmetry of a solid solution: A neutron diffraction study at 15 K of the host/guest system asparagine/aspartic acid

Journal Article · Wed Feb 01 00:00:00 EST 1989 · Journal of the American Chemical Society; (USA)

DOI:https://doi.org/10.1021/ja00185a037· OSTI ID:7071690

Weisinger-Lewin, Y; Frolow, F; Lahav, M; Leiserowitz, L ^[1]; McMullan, R K; Koetzle, T F ^[2]

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1. Weizmann Institute of Science, Rehovot (Israel)
2. Brookhaven National Lab., Upton, NY (USA)

It has been demonstrated, for the first time by diffraction methods, that a solid solution composed of host and guest molecules can exhibit a crystal symmetry lower than that of the host. The study proves that the symmetry of a solid solution is dependent not only upon the host crystal structure and the guest molecular structure but also upon the surface structure and symmetry of the host crystal. The crystal structures of (S)-asparagine monohydrate (D{sub 2}NCOCH{sub 2}CH(ND{sub 3})CO{sub 2} {times} D{sub 2}O) and of the solid solution (0.848:0.152) (S)-asparagine/(S)-aspartic acid (DO{sub 2}CCD{sub 2}CD(ND{sub 3})CO{sub 2}) monohydrate were refined by using neutron diffraction data obtained at 15 K. The space group of the pure host crystal is P2{sub 1}2{sub 1}2{sub 1} (Z = 4), whereas that of the host/guest crystal is monoclinic P12{sub 1}1 with two molecular sites per asymmetric unit. The ratios of guest/host occupancies of the two independent sites are 0.173:0.827 and 0.132:0.868. The reduction in symmetry is in accordance with the preferred adsorption of guest aspartic acid on the (010) crystal face at half of the orthorhombic, symmetry-related surface sites. Aspartic acid mimics, at the preferred (010) surface sites, molecular asparagine, participating in all hydrogen bonds. At the less-favored (010) surface sites a normal N-H{hor ellipsis}O(host) hydrogen bond is replaced by O(hydroxyl){hor ellipsis}O(host) repulsion between lone-pair electrons. 21 refs., 5 figs., 6 tabs.

• DOE Contract Number: AC02-76CH00016
• OSTI ID: 7071690
• Journal Information: Journal of the American Chemical Society; (USA), Vol. 111:3; ISSN 0002-7863
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
ASPARAGINE
CRYSTAL STRUCTURE
ASPARTIC ACID
DEUTERIUM
LABELLED COMPOUNDS
EXPERIMENTAL DATA
NEUTRON DIFFRACTION
TRACER TECHNIQUES
VERY LOW TEMPERATURE
AMIDES
AMINO ACIDS
CARBOXYLIC ACIDS
COHERENT SCATTERING
DATA
DIFFRACTION
HYDROGEN ISOTOPES
INFORMATION
ISOTOPE APPLICATIONS
ISOTOPES
LIGHT NUCLEI
NUCLEI
NUMERICAL DATA
ODD-ODD NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
SCATTERING
STABLE ISOTOPES
400201* - Chemical & Physicochemical Properties
400202 - Isotope Effects
Isotope Exchange
& Isotope Separation