Interfacial Supramolecular Assembly Of Achiral Phthalocyanine And Porphyrin Derivatives

Optically active supramolecular assemblies consisted of achiral building blocks are attracting considerable interest in current supramolecular chemistry and chiral science because it is related to the origin of chirality or even the life. Previously, we have found that achiral molecules could be assembled into optically active molecular assemblies through the air/water interfacial organization, owing to the symmetry breaking at the air/water interface. As one of the extend subjects, In this thesis chiral supramolecular assemblies were fabricated by using an achiral Phthalocyanine derivative and two achiral porphyrin derivatives through the Langmuir and Langmuir-Blodgett(LB) strategies followed by the subsequent annealing under high vaccum. It was found that the LB films of these optically inactive compounds showed weak chiral signals, which could be amplified significantly after their LB films were heated in vaccum for a designed period of time. The followings are main results I have obtained:1. It was shown that an achiral dihydroxy(phthalocyanine)silicon, silicon 2,3,9,10,16,17,23,24-octakis(octyloxy)-29H,31H-phthalocyanine(short for Pcs), could be interfacially assembled to form macroscopically optically active thin solid films by the Langmuir-Blodgett method, where the achiral building blocks were arranged in a type of H-type aggregates with a helical sense conformation. Such helical sense supramolecular assemblies exhibited faint Cotton effect. Upon subsequent polymerization at 167-340 degree under high vaccum for 10hours, the helical stacking was fixed through the conversion of noncovalent interactions(π-πinteraction) to covalent bond(Si-O-Si), resulting in the remarkable increasing of the Cotton effect of convalent polymer phthalocyaninto-polysiloxane. These results have been confirmed by various investigations such as UV, CD, FT-IR spectroscopy ,AFM, SEM.2. Two achiral porphyrin derivatives, 5,10,15,20-tetrakis(4-methoxyphenyl)- 21H,23H-porphine (TPPOMe), and 5,10,15,20-tetrakis(4-hydroxyphenyl)-21H,23H- porphine (TPPOH), were spread onto the air/water interface. The spreading films were transferred onto solid substrates by Langmuir-Blodgett (LB) method. It wasfound that although both of the porphyrin derivatives were achiral, the transferred multilayer films showed macroscopic supramolecular chirality, which was suggested to be due to the spontaneous symmetry breaking. Strong CD signal was observed from the as-deposited TPPOH film, while relative weak CD signal was detected from that of TPPOMe. It is interesting to find that when TPPOMe LB film was annealed in high vacuum,120-180℃and 10 hours, a significantly amplification of the supramolecular chirality was observed. AFM observation has confirmed that TPPOMe formed more ordered aggregates upon annealing. It was suggested that the small amount of chiral assemblies formed in the as-deposited LB film grew into the larger ones followed the"Sergeants and Soldiers"principle during the annealing process. For TPPOH, the appearance of typical of hyperporphyrin spectra indicated that most of the TPPOH molecules are in a protonated state, which could induce the formation of zwitterionic species. Apparently, Electrostatic interaction plays an important role in fabricating of supramolecular chirality assemblies. Subsequent annealing resulted in the normal molecular structure of TPPOH in the LB films, but the helical structure was reserved.