Effect of Frontier Orbital on Aggregation Behavior of Barbituric Acid Derivatives

Two amphiphilic barbituric acid derivatives with a D-π-A structure, 5-(4-dodecyloxybenzylidene)-(1H,3H)-2,4,6-pyrimidinetrione(PB12) and 5-(4-N,N-didodecylaminobenzylidene)-(1H,3H)-2,4,6-pyrimidintrione(AB12) were found to show different aggregation behavior in chloroform. PB12, a derivative with weak electron donating and strong electron drawing substituents, tends to aggregate in a head-to-tail manner, whereas AB12, a derivative with both strong electron donating and drawing substituents, tends to aggregate in a face-to-face manner at a higher concentration. The cyclic voltammograms of AB12 and PB12 show that their energy levels of LUMO approach each other, however, the energy level of HOMO of AB12 is much higher than that of PB12.