THEORETICAL RESEARCH ON EFFECTS OF SUBSTITUENTS AND THE SOLVENT ON QUADRUPLE HYDROGEN BONDED COMPLEXES

Semiempirical AM1 and INDO/CIS methods were used to study the structures and spectroscopy of hydrogen bonded complexes formed by the oligophenyleneethynylene (monomer A) with isophthalic acid (monomer B). The binding energies of the complexes are lowered by increasing electron-donating abilities of the substituents near the hydrogen bonds on monomer A. The first absorptions in the electronic spectra and the vibration frequencies of the N-H bonds in the IR spectra for the complexes are both red-shifted compared with those of the monomers. The presence of dimethylsulfoxide (DMSO) can reduce the binding energy of the complex through hydrogen bonding. This results in a blue-shift for the first absorption in the electronic spectrum and red-shift for the vibration frequencies of the N-H bonds in the IR spectrum of the complex. KEY WORDS: Oligophenyleneethynylene, Hydrogen bonding, Solvent effect, Semiempirical methods Bull. Chem. Soc. Ethiop. 2007, 21(3), 419-426.