Light Harvesting Unsymmetrical Conjugated Dendrimders as Photosynthetic Mimics

Abstract

We review the synthesis and photophysical properties of light harvesting phenylacetylene dendrimers with unsymmetrical branching. We describe the steady state and time dependent experiments that are used to characterize energy transfer properties in the conjugated dendrimers. Finally, we describe investigations of the unsymmetrical phenylacetylene dendrimers as potential materials for applications in fluorescence-based sensors, and for non-linear optics.

Exciton Scattering on Symmetric Branching Centers in Conjugated Molecules

“…Carbon-rich molecular structures may exhibit remarkable electronic and optical properties [1][2][3][4][5][6][7][8][9][10][11] due to the high degree of π-conjugation, strong electron-electron correlations, and electronphonon coupling. Such conjugated molecules can be used in a variety of optical and photovoltaic applications.…”

Optical absorption and energy transport in compact dendrimers with unsymmetrical branching

“…In addition we have assumed g 0 ¼ 0:001 eV and g 1 ¼ 0:0001 eV. We find a red shift of the lowest absorption peak with growing dendrimer size, but this shift is much smaller than the one found in experimental results [3]. Also the position of the absorption peak with the highest energy is shifted to even higher energies with growing dendrimer size, whereas in experimental results the corresponding peak shifts to the red with growing dendrimer size.…”

“…In the case of symmetrical branching the global position and width of the absorption curve remain unchanged with growing dendrimer size. In contrast, the spectra of compact dendrimers with unsymmetrical branching show a large shift and broadening of the whole absorption spectrum with growing dendrimer size [3], similar to the spectral behavior of extended dendrimers. It is argued, that this effect is due to the fact, that at meta-and ortho-substituted branching points the ground state p-conjugation is disrupted, whereas this is not the case for para-substituted branching points.…”

“…In recent years there have been reports about a large variety of compact phenylacetylene dendrimers with asymmetric branching [3]. In contrast to compact dendrimers with symmetric branching, where all branching points (phenyl rings) are connected via meta-substituted bonds, in compact dendrimers with unsymmetrical branching the branching points are connected through the ortho-and para-positions of the phenyl rings.…”

Adjacency matrix formulation of energy flow in dendrimeric polymers

“…dendrimer-based molecular sensors and nonlinear optical materials. [15][16][17][18] To elicit details of the principles and mechanisms that govern the flow of excitation energy between chromophores, following the capture of optical energy in a dendrimeric system, the methods of quantum electrodynamics have been successfully applied in a number of recent studies, addressing both the optically linear and nonlinear regimes. 19,20 The main focus of these studies has been the fundamental nature of excitation transfer between one chromophore and another, and identification of the constraints imposed by molecular symmetry and energetics.…”