Spectroscopic studies of the phase transition in ammonia borane: Raman spectroscopy of single crystal NH3BH3 as a function of temperature from 88to330K

2008 ◽  
Vol 128 (3) ◽  
pp. 034508 ◽  
Author(s):  
Nancy J. Hess ◽  
Mark E. Bowden ◽  
Vencislav M. Parvanov ◽  
Chris Mundy ◽  
Shawn M. Kathmann ◽  
...  
Keyword(s):  
Phase Transition ◽  
Raman Spectroscopy ◽  
Single Crystal ◽  
Ammonia Borane ◽  
Spectroscopic Studies

scholarly journals The Only N-H...O Hydrogen Bond - Two Ways to Build a Structure of Dimethylglycine

2014 ◽  
Vol 70 (a1) ◽  
pp. C550-C550
Author(s):  
Eugene Kapustin ◽  
Vasily Minkov ◽  
Elena Boldyreva
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
Amino Acids ◽  
Raman Spectroscopy ◽  
Single Crystal ◽  
Van Der Waals Interactions ◽  
X Ray Diffraction ◽  
Space Symmetry ◽  
Polarized Raman ◽  
Crystalline Amino Acids

Crystalline amino acids are considered to mimic important interactions in peptides, therefore the studies of the structure-forming factors in these systems attract much attention. N,N-dimethylglycine is an interesting model compound that was used to test the role of the N-H...O H-bonds in forming the head-to-tail chains – the main structural unit in the crystals of amino acids. It was hypothesized previously that additional side N-H...O H-bonds play an important role in forming the head-to-tail chains of amino acid zwitterions linked via N-H...O H-bonds between the charged -NH3 and -COO terminal groups. Twice methylated amino group of N,N-dimethylglycine is able to form only one N-H...O H-bond in the crystal structure, so that this hypothesis could be tested. There are two polymorphs of N,N-dimethylglycine, in which the zwitterions are packed in two different ways. In one polymorph (orthorhombic, Pbca) they form finite four member ring motifs not linked to each other via any H-bonds, but only by weak van der Waals interactions. However, in the second polymorph (monoclinic, P21/n) the zwitterions do form infinite head-to-tail chains though the N-H...O H-bond is the only one and is not assisted via any additional H-bonds. The effect of cooling on the two crystal structures was followed by single-crystal X-ray diffraction combined with polarized Raman spectroscopy of oriented single crystals, in order to compare the response of the N-H...O H-bonds to temperature variations. The crystal structure of the monoclinic polymorph compresses anisotropically on cooling, whereas that of the orthorhombic polymorph undergoes a reversible single-crystal to single-crystal phase transition at ~200 K accompanied by non-merohedral twinning, reducing the space symmetry to monoclinic (P21/b), and doubling the asymmetric unit from 2 to 4 molecules. This phase transition could not be detected by Raman spectroscopy and DSC because of the subtle related changes in intermolecular energies.

Low-temperature phase transition in glycine–glutaric acid co-crystals studied by single-crystal X-ray diffraction, Raman spectroscopy and differential scanning calorimetry

2012 ◽  
Vol 68 (3) ◽  
pp. 287-296 ◽  
Author(s):  
Boris A. Zakharov ◽  
Evgeniy A. Losev ◽  
Boris A. Kolesov ◽  
Valeri A. Drebushchak ◽  
Elena V. Boldyreva
Keyword(s):  
Phase Transition ◽  
Differential Scanning Calorimetry ◽  
Raman Spectroscopy ◽  
Single Crystal ◽  
Glutaric Acid ◽  
Group Symmetry ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray

The occurrence of a first-order reversible phase transition in glycine–glutaric acid co-crystals at 220–230 K has been confirmed by three different techniques – single-crystal X-ray diffraction, polarized Raman spectroscopy and differential scanning calorimetry. The most interesting feature of this phase transition is that every second glutaric acid molecule changes its conformation, and this fact results in the space-group symmetry change from P21/c to P\bar 1. The topology of the hydrogen-bonded motifs remains almost the same and hydrogen bonds do not switch to other atoms, although the hydrogen bond lengths do change and some of the bonds become inequivalent.

High-pressure single-crystal X-ray diffraction and infrared spectroscopic studies of the C2/m-P21/m phase transition in cummingtonite

1998 ◽  
Vol 83 (3-4) ◽  
pp. 288-299 ◽  
Author(s):  
Hexiong Yang ◽  
Robert M. Hazen ◽  
Charles T. Prewitt ◽  
Larry W. Finger ◽  
Lu Ren ◽  
...  
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Single Crystal ◽  
Spectroscopic Studies ◽  
X Ray Diffraction ◽  
X Ray ◽  
Infrared Spectroscopic ◽  
M Phase

Phase transitions in adamantane derivatives: 1-fluoroadamantane

1991 ◽  
Vol 69 (11) ◽  
pp. 1758-1765 ◽  
Author(s):  
Nancy T. Kawai ◽  
Denis F. R. Gilson ◽  
Ian S. Butler
Keyword(s):  
Phase Transition ◽  
Raman Spectroscopy ◽  
High Pressures ◽  
Spectroscopic Studies ◽  
Phase Behaviour ◽  
Slow Heating ◽  
Adamantane Derivatives ◽  
Scanning Calorimetry ◽  
Line Narrowing ◽  
Infrared And Raman Spectroscopy

The solid-state phase behaviour of 1-fluoroadamantane (1-C10H15F) has been investigated by differential scanning calorimetry, and by infrared and Raman spectroscopy. The phase transition occurs at 227 K on cooling and at 231 K upon heating, with average ΔHt and ΔSt of 1.65 kJ mol−1 and 7.3 J K−1 mol−1. The transition was also apparent in the low-temperature IR and Raman spectra by a sudden line narrowing, and characteristic spectral features of each phase were identified. Both phases I and II were disordered, and further cooling of phase II resulted in the formation of a glass. Attempts to induce a glass transition (predicted to occur at ~90 K) by slow heating were unsuccessful. Vibrational spectroscopic studies at high pressures showed a phase transition at 3.3 ± 1.0 kbar, upon compression. The phases formed under pressure were the same as those induced by lowering temperature. Key words: high-pressure infrared and Raman spectroscopy, phase transition, plastic crystal, orientational disorder.

Single Crystal Raman Spectra of the Phase Transition in KTCNQ

1982 ◽  
Vol 85 (1) ◽  
pp. 297-303 ◽  
Author(s):  
A. D. Bandrauk ◽  
K. D. Truong ◽  
S. Jandl
Keyword(s):  
Phase Transition ◽  
Single Crystal ◽  
Raman Spectra
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