Colorful 4,4-Bipyridine–Squaric Acid Multicomponent Complexes with Varying Degrees of Proton Transfer: Exploring the Nature of New Form IV in the Salt Co-Crystal Continuum

2021 ◽  
Author(s):  
Joanna S. Stevens
Keyword(s):  
Proton Transfer ◽  
Squaric Acid ◽  
New Form

Antiferroelectric Phase Transition in a Proton-Transfer Salt of Squaric Acid and 2,3-Dimethylpyrazine

2019 ◽  
Vol 141 (41) ◽  
pp. 16279-16287 ◽  
Author(s):  
Jeff Lengyel ◽  
Xiaoping Wang ◽  
Eun Sang Choi ◽  
Tiglet Besara ◽  
Rico Schönemann ◽  
...  
Keyword(s):  
Phase Transition ◽  
Proton Transfer ◽  
Squaric Acid ◽  
Antiferroelectric Phase

scholarly journals High Pressure Spectroscopic Investigation on Proton Transfer in Squaric Acid and 4,4′-Bipyridine Co-crystal

2017 ◽  
Vol 7 (1) ◽  
Author(s):  
Zhiwei Ma ◽  
Juntao Li ◽  
Chunyu Liu ◽  
Chenglin Sun ◽  
Mi Zhou
Keyword(s):  
High Pressure ◽  
Proton Transfer ◽  
Spectroscopic Investigation ◽  
Squaric Acid

Proton-Transfer-Dependent Reversible Phase Changes in the 4,4′-Bipyridinium Salt of Squaric Acid

1994 ◽  
Vol 33 (2) ◽  
pp. 181-183 ◽  
Author(s):  
Manfred T. Reetz ◽  
Sigurd Höger ◽  
Klaus Harms
Keyword(s):  
Proton Transfer ◽  
Phase Changes ◽  
Squaric Acid ◽  
Reversible Phase

scholarly journals Temperature- and Pressure-Induced Proton Transfer in the 1:1 Adduct Formed between Squaric Acid and 4,4′-Bipyridine

2009 ◽  
Vol 131 (11) ◽  
pp. 3884-3893 ◽  
Author(s):  
David M. S. Martins ◽  
Derek S. Middlemiss ◽  
Colin R. Pulham ◽  
Chick C. Wilson ◽  
Mark T. Weller ◽  
...  
Keyword(s):  
Proton Transfer ◽  
Squaric Acid ◽  
Temperature And Pressure

scholarly journals Core level crystallography: Probing H-bonding through nitrogen XPS and NEXAFS

2014 ◽  
Vol 70 (a1) ◽  
pp. C560-C560
Author(s):  
Joanna Stevens ◽  
Stephan Byard ◽  
Lauren Newton ◽  
Cherno Jaye ◽  
Colin Seaton ◽  
...  
Keyword(s):  
Proton Transfer ◽  
Photoelectron Spectroscopy ◽  
Disordered Systems ◽  
Structural Information ◽  
Chemical Shifts ◽  
Colour Change ◽  
Squaric Acid ◽  
X Ray ◽  
Bond Lengths ◽  
Donor And Acceptor

Determining the location of hydrogen is not always straightforward, despite its potential for wide-reaching effects, such as altering physicochemical properties and biological/chemical processes. Proton transfer can be considered a simple chemical reaction, with a continuum from neutral to protonated states, and short, strong H-bonds (SSHB) and disordered systems between the two extremes. X-ray Photoelectron Spectroscopy (XPS) and Near Edge X-ray Absorption Fine Structure (NEXAFS) intrinsically probe the local environment, with sensitivity to the chemical state of the atom and, importantly, nature of the local chemical and bonding environment. Organic molecular crystals have been studied by nitrogen XPS and NEXAFS, offering an alternative to X-ray and neutron diffraction. Strong chemical shifts occur with proton transfer to nitrogen (+N-H---O vs. N---H-O), unambiguously characterizing protonated and H-bonded systems,[1] leading to direct observation of an unusual solid-state colour change for 4,4'-bipyridine/squaric acid with heating[2] involving proton transfer to nitrogen with temperature-dependent measurements. Correlation between H-bond lengths and chemical shifts indicates potential for predicting H-bond lengths. SSHBs provide an interesting case, as hydrogen can reside midway between donor and acceptor, having a 3-centre, 4-electron bond with quasi-covalent character and atypical properties. Intermediate chemical shifts are found with hydrogen midway between donor and acceptor in 3,5-pyridinedicarboxylic acid, with increased peak width representative of hydrogen's broadened single minimum potential well.[3] This contrasts with conventional 2-site hydrogen disorder, in which signals from both donor and acceptor environments result in 2 peaks reflecting the % occupancy. Valuable electronic and structural information is obtained from the variety of organic systems investigated, with XPS clearly distinguishing different types of crystallographic materials (Fig 1).

Fine Structure of Platelet Interaction with a New Microcrystalline Collagen Preparation

1974 ◽  
Vol 32 ◽  
pp. 58-59
Author(s):  
W. H. Zucker ◽  
R. G. Mason
Keyword(s):  
Fine Structure ◽  
Platelet Aggregation ◽  
Hydrochloric Acid ◽  
Whole Blood ◽  
Platelet Adhesion ◽  
Hemostatic Agent ◽  
Native Collagen ◽  
Fibrillar Morphology ◽  
Clinical Interest ◽  
New Form

Platelet adhesion initiates platelet aggregation and is an important component of the hemostatic process. Since the development of a new form of collagen as a topical hemostatic agent is of both basic and clinical interest, an ultrastructural and hematologic study of the interaction of platelets with the microcrystalline collagen preparation was undertaken.In this study, whole blood anticoagulated with EDTA was used in order to inhibit aggregation and permit study of platelet adhesion to collagen as an isolated event. The microcrystalline collagen was prepared from bovine dermal corium; milling was with sharp blades. The preparation consists of partial hydrochloric acid amine collagen salts and retains much of the fibrillar morphology of native collagen.

The staining pattern of the tropomyosin sequence is displayed in a new paracrystal

1986 ◽  
Vol 44 ◽  
pp. 150-151
Author(s):  
M.K. Lamvik ◽  
L.L. Klatt
Keyword(s):  
Amino Acid ◽  
Amino Acid Sequence ◽  
Staining Pattern ◽  
Banding Patterns ◽  
Mass Thickness ◽  
New Form

Tropomyosin paracrystals have been used extensively as test specimens and magnification standards due to their clear periodic banding patterns. The paracrystal type discovered by Ohtsuki1 has been of particular interest as a test of unstained specimens because of alternating bands that differ by 50% in mass thickness. While producing specimens of this type, we came across a new paracrystal form. Since this new form displays aligned tropomyosin molecules without the overlaps that are characteristic of the Ohtsuki-type paracrystal, it presents a staining pattern that corresponds to the amino acid sequence of the molecule.

A New Form and Function for Personality

2013 ◽  
Author(s):  
Joshua Wilt ◽  
William Revelle
Keyword(s):  
Form And Function ◽  
New Form ◽  
And Function

Material physics: A new form of carbon

Nature China ◽  
2011 ◽  
Author(s):  
Felix Cheung
Keyword(s):  
Material Physics ◽  
New Form
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