We investigate a rapid energy transfer (ET) process and its temperature dependence in a star-shaped stilbenoid phthalocyanine (SSS1Pc) dendrimer having π -conjugated light-harvesting (LH) antennas. In SSS1Pc, intense core-photoluminescence is observed under selective excitation on the LH-antenna as a result of the highly efficient ET from the LH-antenna. Pump-probe experiments show that ET occurs rapidly with a rising time constant (∼ 250 fs).
To understand such rapid ET, we employ a simplified ET model through a π -conjugated network between the Lhantenna and the core that takes into account the steric hindrance between the LH-antenna subunits. Our model reveals that the highly efficient ET at room temperature in SSS1Pc takes place through the π -conjugated network mediated by a thermally activated torsional vibration of the aromatic ring subgroup in the LH-antenna. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)