Naslov
Why does aquabis(L-valinato)copper(II) crystallise as a cis-isomer? Molecular mechanics calculations in simulated crystal lattice

Autori
Marković, Marijana ; Sabolović, Jasmina

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
From Solid State To Biophysics IV / Forró, László ; Pavuna, Davor - Lausanne : Vlastita naklada, 2008, Nije označena-nije označena

Skup
From Solid State To BioPhysics IV

Mjesto i datum
Cavtat, Hrvatska, 06.06.2008. - 13.06.2008

Vrsta sudjelovanja
Poster

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
bakar; aminokiseline; kristalna struktura; MM simulacija u kristalu
(copper; amino acids; crystal structure; MM crystal simulation)

Sažetak
Bis(amino acidato)copper(II) complexes are biologically important compounds. They take part in transporting copper to copper enzymes (such as superoxide dismutase, cytochrome c oxidase and nitrous-oxide reductase) and electron-transfer copper proteins (e.g., plastocyanin, azurin). The X-ray crystal structures are the most common source of experimental information on the structural properties of this class of compounds. Bis(L-valinato)copper(II), Cu(L-Val)2, crystallised from aqueous solution as a cis-isomer with one water molecule in the asymmetric unit (space group I2), as determined by the X-ray diffraction measurements [1]. The coordination geometry of the copper(II) is a distorted pyramid, with a water oxygen atom at the pyramid apex. The molecules are bonded together via intermolecular N– H• • • Ocarbonyl, N– H• • • Ocarboxyl and Owater– H• • • Ocarbonyl hydrogen bonds. Molecular mechanics force field FFW [2], developed for studying the properties of anhydrous and aqua bis(amino acidato)copper(II) complexes with either cis- or trans-N2O2 copper(II) coordination geometry in the solid state and in vacuo, was used for conformational analysis of the title compound. Each chelate ring of Cu(L-Val)2 can have 6 conformations, with C in 3 axial and 3 equatorial positions, and therefore the molecule can have 21 trans and 21 cis conformations. Conformational analysis in vacuo, without the influence of the intermolecular interactions, showed that the trans conformers were more stable than the cis ones (by ≈ 17.5 kcal mol-1). To account the crystal lattice effects, the experimental molecule orientation, unit cell lengths and angles, as well as the I2 space group symmetry operations were taken as the starting input data for the geometry optimisation of all possible conformers. During the energy minimisation of a crystal all degrees of freedom were allowed to vary, except the  and γ unit cell angles were kept fixed to 90o. The calculations of the unit cell packings and intermolecular interactions for the series of conformers suggest the reasons why experimentally obtained conformer occurs in the real crystal structure. [1] Marković, M. ; Judaš, N. ; Sabolović, J. Humboldt Conference on Noncovalent Interactions, Vršac, Serbia 2007 ; Book of abstracts, p. 58 [2] Sabolović, J. ; Tautermann, C. S. ; Loerting, T. ; Liedl, K. R. Inorg. Chem. 47 (2003) 2268-2279.

Izvorni jezik
Engleski

Znanstvena područja
Fizika, Kemija

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