Theoretical insight into the coordination of cyclic β-D-glucose to [Al(OH)(aq)](2+) and [Al(OH)2(aq)](1+) ions.

The coordination of cyclic β-D-glucose (CDG) to both [Al(OH)(aq)](2+) and [Al(OH)2(aq)](1+) ions has been theoretically investigated, using quantum chemical calculations at the PBE0/6-311++G(d,p), aug-cc-pvtz level under polarizable continuum model IEF-PCM, and molecular dynamics simulations. [Al(OH)(aq)](2+) ion prefers to form both six- and five-coordination complexes, and [Al(OH)2(aq)](+) ion to form four-coordination complex. The two kinds of oxygen atoms (on hydroxyl and ring) of CDG can coordinate to both [Al(OH)(aq)](2+) and [Al(OH)2(aq)](+) ions through single-O-ligand and double-O-ligand coordination, wherein there exists some negative charge transfer from the lone pair electron on 2p orbital of the coordinated oxygen atom to the empty 3s orbital of aluminum atom. The charge transfer from both the polarization and H-bond effects stabilizes the coordinated complex. When the CDG coordinates to both [Al(OH)(H2O)4](2+) and [Al(OH)2(H2O)2](1+) ions, the exchange of water with CDG would take place. The six-coordination complex [(ηO4,O6(2)-CDG)Al(OH)(H2O)3](2+) and the five-coordination complex [(ηO4,O6(2)-CDG)Al(OH)2(H2O)](1+) are predicted to be the thermodynamically most preferable, in which the polarization effect plays a crucial role. The molecular dynamics simulations testify the exchange of water with CDG, and then support a five-coordination complex [(ηO4,O6(2)-CDG)Al(OH)2(H2O)](1+) as the predominant form of the CDG coordination to [Al(OH)2(aq)](1+) ion.