Photophysical properties of directly linked linear porphyrin arrays

A variety of porphyrin arrays connected by diverse linkers have been envisaged and prepared for the applications in molecular photonics and electronics. From a viewpoint of operational requirements, the porphyrin arrays should have the very regular pigment arrangements which allow a facile light energy or charge flow along the arrays but do not result in the alteration of individual properties of the constituent pigments leading to formation of so-called energy or charge sink. In these respects, the directly coupled (orthogonal and fused) porphyrin arrays without any linkers are ideal, because the conformational heterogeneity mainly arising from a dihedral angle distribution between the neighboring porphyrin moieties should be minimized. In addition, the electronic effect of the linker can be disregarded in design strategy of molecular photonic devices, because the linker can also be considered as a transmission element in electronic communication. Considering these features, these types (orthogonal vs fused) of porphyrin arrays would be one of the most suitable synthetic molecular modules for the realization of molecular photonic and electronic devices. To unveil the functionalities of various porphyrin arrays, starting from the dihedral angle dependence on the photophysical properties of the porphyrin dimers, we have extended our knowledge to longer orthogonal and fused porphyrin arrays. Overall, the regularly arranged porphyrin arrays with ample electronic interactions will be promising in the applications such as molecular wires, sensors, optical nonlinear materials, and so on.