Abstract:

The influence of solvent polarity on the molecular geometries and electronic structures of organic π-conjugated ligand, N,N'-bis-(3-pyridyl)ethylene-bis-urea(BPEBU), was theoretically investigated within the framework of the polarized continuum model(PCM) via the density functional theory (DFT) calculations. The solute-solvent intermolecular interactions of BPEBU in acetone and ethanol solutions were studied by adopting the discrete solvent model through molecular dynamics (MD) simulations. It is demonstrated that CO and N-H bonds in urea moiety group and C-N bonds in pyridine rings of BPEBU are polarized and leng-thened with increasing the solvent polarity through DFT calculations. Correspondingly, the magnitudes of ne-gative charges of oxygen atoms and positive charges of hydrogen atoms in urea group are increased significantly. The MD simulations show the specific O…H-O, N…H-O and N-H…O hydrogen bonding interactions between BPEBU and ethanol solvents. Only N…H-O hydrogen bonds are formed in acetone solutions. And the N…H-O intermolecular interaction in acetone solution is weaker than that in ethanol solution. Furthermore, the solute-solvent hydrogen-bonded trimers are optimized by adopting the combined discrete/continuum solvation model through DFT method. The structures of trimers are qualitatively agreement with supramolecular clusters in the first solvation shell from molecular dynamics simulations.

Key words: Density functional theory, Electronic structure, Molecular dynamics simulation, Intermolecular interaction, Solvent effect