title: Ethane-bridged zinc porphyrin dimers in Langmuir-Shäfer thin films: structural and spectroscopic properties.
abstract: This work reports on the structural and spectroscopic properties of ethane-bridged Zn porphyrin dimers (1) in Langmuir-Schäfer (LS) thin films by combining scanning force microscopy (SFM) with film balance, UV-vis absorption, fluorescence, and nanosecond laser flash photolysis measurements. Results show that depending on the surface pressure the Langmuir films of pure 1 can be arranged in two different condensed phases, whereas SFM of the LS films shows characteristic fractal networks constituted by nanoscopic aggregates. The spectral findings agree with a picture in which 1 is apparently present in the anti conformation but aggregated in a sort of H-type structure whose optical features resemble those of the syn conformer. This type of structure is not responsive to light stimuli. By diluting 1 in arachidic acid the porphyrin aggregation is significantly minimized with 1 exhibiting almost exclusively the anti conformation. As a result the LS films become photoresponsive, showing fluorescence emission and triplet-triplet transient absorption.
authors.affiliation: Dipartimento di Ingegneria dell'Innovazione, Universià di Lecce, I-73100 Lecce, Italy. ludovico.valli@unile.it
authors.forename: Ludovico
authors.initials: L
authors.lastname: Valli
authors.forename: Serena
authors.initials: S
authors.lastname: Casilli
authors.forename: Livia
authors.initials: L
authors.lastname: Giotta
authors.forename: Bruno
authors.initials: B
authors.lastname: Pignataro
authors.forename: Sabrina
authors.initials: S
authors.lastname: Conoci
authors.forename: Victor V
authors.initials: VV
authors.lastname: Borovkov
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Inoue
authors.forename: Salvatore
authors.initials: S
authors.lastname: Sortino