Crystal structures and spectroscopic properties of ester amide and diamide of squaric acid with prolinamide

Tsonko Kolev, Rüdiger W. Seidel, Heike Mayer-Figge, Michael Spiteller, William S. Sheldrick, Bojidarka B. Koleva, Tsonko Kolev, Rüdiger W. Seidel, Heike Mayer-Figge, Michael Spiteller, William S. Sheldrick, Bojidarka B. Koleva

Index: Spectrochim. Acta. A. Mol. Biomol. Spectrosc. 72(3) , 502-9, (2009)

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Abstract

We report the synthesis, spectroscopic and structural elucidation of two prolinamide derivatives of squaric acid, i.e. prolinamide ester amide of squaric acid ethyl ester ( 1) and prolinamide diamide of squaric acid dihydrate ( 2). Both compounds crystallize in non-centrosymmetric space groups, monoclinic P2 1 ( 1) and orthorhombic P2 12 12 1 ( 2), respectively. For first time in the literature the crystal structure of homodiamide of amino acid amide of squaric acid is reported. The data for heterodiamides is also absent. Supramolecular zig-zag chains by hydrogen bonds of H 2N–C O⋯HNH (3.020 Å) and HNH⋯O C (Sq) (2.972 Å) types with the participation of amide and squaric acid (Sq) fragments, –C O–NH 2 and O C (Sq) are refined in ( 1). A helix supramolecular structure is formed in ( 2) by moderate intermolecular HNH⋯O C(NH 2) hydrogen bond with length of 2.947 Å. The two crystallographical non-equivalent water molecules stabilized the helix by interactions of types HOH⋯O C (Sq) (2.917 Å), HOH⋯O C(NH 2) (2.899 Å), H 2O⋯NH 2(C O) (2.972 Å), respectively. Optical and magnetic properties are investigated with a view to explain the correlation structure-properties of the newly synthesized molecules.