A comparative study of two-photon properties of zinc(II)-porphyrin, meso–meso singly-linked zinc(II)-diporphyrin and zinc(II) meso,meso-coupled porphyrin dimer via hydrogen bonding interactions

Abstract: Electronic structures, one- and two-photon absorption (TPA) properties of zinc(II)-porphyrin compound (Z H ), meso–meso singly-linked zinc(II)-diporphyrin compound (Z2 H ) and zinc(II) meso,meso-coupled porphyrin dimer (Z2 H -G) via intermolecular hydrogen bonding interactions have been comparatively studied by using ZINDO–SOS method. The results show that formation of hydrogen bondings between carboxyl groups and cyclic urea reduces the dihedral angle between the adjacent porphyrin planes in Z2 H -G, leading to increased electronic interactions between the two porphyrin planes and increased couplings between electronic states. Electronic spectrum of Z H can be described with the four-orbital model, while the descriptions of the electronic spectra of Z2 H and Z2 H -G need eight frontier orbitals. Theoretical calculations reveal that TPA cross sections increase on going from Z H to Z2 H to Z2 H -G due to increase of the couplings between electronic states through transition dipole moments. [Copyright &y& Elsevier]