Squaric acids hydrogen bonding complexes

Hydrogen-bonding interactions in complexes of squaric acid have recently been reviewed 71) therefore, only such interactions in the complexes of monosubstituted squarates and aspects of hydrogen bonding not covered in that review will be discussed. 

Most of the complexes of squaric acid and its derivatives contain hydrogen bonds that appear to have a significant influence on the tertiary structure 19, 21, 22, 28, 30, 41, 56, 62, 65, 69, 76, 82, 90, 111, 112, 121, 123, 129, 131-137). The prevalence of hydrogen bonding in these complexes is not surprising, since the metals in most instances have... 

Complexes of Heavier Transition Metals Electrochemical Studies Luminescence Studies IV. Hydrogen Bonding and Other Weak Interactions in Complexes of Squaric Acid and Its Monosubstituted Derivatives References... 

The first illustration is provided by ferroelectrics belonging to the family of pyridinium salts. Complex interplay between the contributions of van der Waals, Coulomb, dipolar and hydrogen-bonding interactions are expected because of the hybrid nature of the compound. The majority of reported NMR experiments are proton second-moment and relaxation studies on polycrystalline samples. The most sophisticated NMR methods with regard to resolution, symmetry and time-scale interpretations applied to the historical problem of assigning a pure order disorder or displacive mechanism to a ferroelectric phase transition will provide the second example with the study of squaric acids and perovskites compounds like BaTi03. 

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