title: Observation and photophysical characterization of silicon phthalocyanine J-aggregate dimers in aqueous solutions.
abstract: The use of macrocyclic molecules for both imaging and photodynamic therapy (PDT) has proven to be a powerful method for assessing and treating diseases, respectively. However, many potential candidates for these applications rely on rigid organic structures which are hydrophobic and thus lead to possible aggregation in aqueous solutions such as blood. Here, we describe the discovery of noncovalent J-aggregate dimers of the asymmetrically, axially modified silicon phthalocyanine 4 (Pc 4) in aqueous solutions through steady-state and time-resolved spectroscopy. Remarkably, the monomer-dimer equilibrium is dictated by water content and pH, with free monomers resulting in favorable solvation conditions even after formation of the dimer complex. This work sheds light on previous observations of Pc 4 behavior in cells during PDT, and can further elucidate the structure-activity relationship of these important molecules.
authors.affiliation: Center for Chemical Dynamics, Department of Chemistry, Case Western Reserve University, 10900 Euclid Avenue, Cleveland (USA), Fax: (+1) 216-368-3006.
authors.forename: Tennyson
authors.initials: T
authors.lastname: Doane
authors.forename: Andrew
authors.initials: A
authors.lastname: Chomas
authors.forename: Shriya
authors.initials: S
authors.lastname: Srinivasan
authors.forename: Clemens
authors.initials: C
authors.lastname: Burda
mesh_terms: D057927:Hydrophobic and Hydrophilic Interactions; D007211:Indoles / Q000737:chemistry*; D017646:Organosilicon Compounds / Q000737:chemistry*; D010778:Photochemotherapy / Q000379:methods*; D013329:Structure-Activity Relationship
chemical_list: D007211:Indoles; D017646:Organosilicon Compounds; C082854:silicon phthalocyanine
keywords: aggregation; hydrophobicity; photophysics; phthalocyanines; water content