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A NiII-directed template synthesis using 2-acetyl-1,3-indandione and ethylenediamine results in formation of octahedral NiII complex, whose crystal structure has been resolved using single crystal X-ray diffraction. The structure indicates that only exocyclic enolic oxygen atom of the triketone takes part in the condensation with ethylenediamine. Quantum chemical calculations reveal insights into the observed reactivity of an initial NiII complex of 2-acetyl-1,3-indandione with ethylenediamine and point out steric effects as the main restriction for a complete cyclization into a tetraaza macrocycle. [ABSTRACT FROM AUTHOR]

A new crystalline complex of dl -serine and squaric acid (H 2 Sq) in stoichiometric ratio 1:1 ( dl -Ser·HSq) was synthesized, isolated and structurally characterized by single crystal X-ray diffraction. The compound crystallizes in the monoclinic space group P2 1 /n and its structure consists of a 3D supramolecular network of hydrogensquarate anions and serinium cations directed by intermolecular hydrogen bonding interactions. The 3D network is formed by hydrogen bonds with participation of C O–OH, hydrogensquarate ion and NH 3 + group, (Sq) C O…O C (OH) (2.525 Å), – NH 3 + …O C (Sq) (2.915, 2.985 and 3.016 Å), hydroxyl group CH 2 –OH…O C (Sq) (2.739 Å), O…H–N + (3.016 Å) and (C–OH A …O C (Sq) (3.242), respectively. The structural information shows a new structural motif, a non-classic α-chain of the hydrogensquarate anions with dihedral angle between neighbouring HSq − anions 43.66°. The Raman and infrared spectra of the new crystal were measured in the 4000–50 cm −1 and 4000–400 cm −1 region frequency range respectively. The assignment of bands in infrared and Raman spectra of the crystal was performed on the basis of DFT (B3LYP) calculations, X-ray structural results and by the comparison with literature data. [ABSTRACT FROM AUTHOR]