Molecular-shape-dependent photophysical properties of meso-β doubly Linked Zn(II) porphyrin arrays and their indene-fused analogues

meso-β doubly linked Zn(II) porphyrin arrays and their indene-fused analogues were prepared by Suzuki - Miyaura coupling and subsequent oxidation with DDQ-Sc(OTf)₃. The excited state properties of these conjugated porphyrin arrays have been investigated by steady-state and time-resolved spectroscopy along with quantum mechanical calculations to reveal their molecular shape dependencies with respect to syn- versus anti-connectivity as well as nonfused versus fused structures. Nonfused syn-trimer exhibits nearly the same S₁-state lifetime and two-photon absorption (TPA) value as the nonfused dimer, while the nonfused anti-trimer exhibits different values. The TD-DFT calculations also demonstrate that the nonfused anti-trimer has a different electronic structure from the corresponding iyn-trimer. Indene-fused dimers and trimers exhibit the enhanced TPA values and shortened S ₁-state lifetime because of the elongated π-conjugation and the perturbation of electronic structures. Our research provides further insight into the molecular-shape-dependent electronic properties of meso-β doubly linked Zn(II) porphyrin arrays.