title: The optical characterization of metal-mediated aggregation behaviour of amphiphilic Zn(ii) phthalocyanines.
abstract: Ag(+) mediated aggregation behaviour of two different amphiphilic zinc phthalocyanines (Zn-Pcs) (symmetric and asymmetric) has been investigated in solution, at the air-water interface and in Langmuir-Blodgett (LB) films transferred onto glass substrates. A 4 : 1 ([Ag(+)]/[Pc]) complexation was observed for both symmetric and asymmetric Zn-Pcs at high [Ag(+)] concentrations which led to the formation of H-aggregates in solution. At the air-water interface, both symmetric and asymmetric Zn-Pcs showed a tilted, edge-on orientation in columnar stacks. Addition of Ag(+) to the subphase enhanced the order in the monolayers. LB films on glass substrates showed a split Q-band indicating the presence of "herring-bone" type aggregation consisting of both H- and J-aggregates. For LB films deposited from a Ag(+) containing subphase, a shoulder appeared in the absorption spectra at longer wavelengths which indicates that the fraction of J-aggregates was enhanced by Ag(+) in LB films. The molecular orientation in LB films was investigated by polarized absorption spectroscopy and a tilt angle was calculated to be 49° with the substrate normal for symmetric and 74.6° for the asymmetric Zn-Pc. The presence of Ag(+) cations in the subphase decreased the tilt angles slightly by 4-5°. These results indicate that Ag(+) induced the aggregation of Zn-Pcs and acted as a linker between Pc molecules in the ultrathin films of both symmetric and asymmetric Zn-Pcs. These results are important in inducing J-aggregates for the fabrication of molecular devices based on phthalocyanine thin films.
authors.affiliation: Chemistry Department, Koç University, Sarıyer, I[combining dot above]stanbul, 34450, Turkey. pinarbatat@hotmail.com.
authors.forename: P
authors.initials: P
authors.lastname: Batat
authors.forename: M
authors.initials: M
authors.lastname: Bayar
authors.forename: B
authors.initials: B
authors.lastname: Pur
authors.forename: E
authors.initials: E
authors.lastname: Çoker
authors.forename: V
authors.initials: V
authors.lastname: Ahsen
authors.forename: F
authors.initials: F
authors.lastname: Yuksel
authors.forename: A L
authors.initials: AL
authors.lastname: Demirel