engleski

The Modelling of Noncovalent Interactions in the Crystal Structures of bis(L-valinato)copper (II)

In this work the experimental and theoretical crystal structures of trans and cis isomers of bis(L-valinato)copper(II), Cu(L-Val)2, are presented. The crystal and molecular structures of trans bis(L-valinato)copper(II) and cis aquabis(L-valinato)copper(II) have been determined by using X-ray diffraction. The crystal structure of trans-Cu(L-Val)2 contains polymeric chains made up of complex dimers that are formed by interlinkage of adjacent molecules via axial copper(II)-to-carbonyl oxygen contacts, and are further stabilised by N– H&middot ; &middot ; &middot ; O hydrogen bonds. Molecular chains are self-assembled into molecular sheets by further N– H&middot ; &middot ; &middot ; O and C– H&middot ; &middot ; &middot ; O hydrogen bonding. In the aqua cis-isomer, the copper(II) has a distorted pyramidal coordination geometry with a water oxygen atom at the pyramid apex. The cis-Cu(L-Val)2&middot ; H2O molecules are packed in the crystal lattice so as to allow the forming of intermolecular N– H&middot ; &middot ; &middot ; &middot ; Ocarbonyl, N– H&middot ; &middot ; &middot ; &middot ; Ocarboxyl, and Owater-H&middot ; &middot ; &middot ; &middot ; Ocarbonyl hydrogen bonds. In both crystals intermolecular aliphatic-aliphatic van der Waals interactions between the valine residue chains are present. The molecular mechanics force field FFW [1], developed for modelling of trans and cis anhydrous and aqua copper(II) amino acid complexes, was used to calculate the minimum molecular and crystal structures of cis- and trans-Cu(L-Val)2 in simulated crystalline environment via energy minimisation. The ability of FFW to model the intermolecular noncovalent interactions in the two different crystals was examined by comparing the experimental and theoretical crystal structures.

crystal structure; crystal simulation; hydrogen bonding; copper; animo acid

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