Large Third-Order Optical Nonlinearity of Self-Assembled Porphyrin Oligomers

Abstract

Third-order nonlinear optical properties of two series of self-assembled porphyrin wires, one being terminated by zinc porphyrin and the other by free base porphyrin, were measured by femtosecond time-resolved optical Kerr effect. The hyperpolarizability values of the latter series were extremely large ranging from 10-30 to 10-29 esu, 10 times larger than the former. The behavior is accounted for by the contribution of terminal free base porphyrin to enhance the molecular polarization by acceptor nature toward central metalloporphyrin array.

An Insight into a Novel Class of Self‐Assembled Porphyrins: Geometric Structure, Electronic Structure, One‐ and Two‐Photon Absorption Properties

“…In the case of molecules 4, 5, and 6, with the replacement of zinc porphyrin with free-base porphyrin, the splitting slightly increases from 83.3 nm for 4 to 90.7 nm for 5 and to 93.2 nm for 6. The large splitting of the Soret bands that appeared in the calculated OPA spectra of molecules around 300-500 nm was also observed experimentally by Ogawa et al [38] The results in Table 1 demonstrate that the expansion of the p conjugation between porphyrin units by introducing a butadiyne linkage and the increase of molecular dimensionality from monomers to dimers play different roles in the enhancement of OPA intensities of the studied compounds. For the Q-band absorption of molecules, the introduction of a butadiyne linkage is the most important parameter for de-termining the OPA intensities.…”

Nonlinear Absorption by Porphyrin Supramolecules

“…Thus, the reorganization can serve an efficient method for introducing appropriate donor and/or acceptor groups at the molecular terminals of the array as a substituent R 2 . For example, when freebase porphyrin was used as an acceptor, large enhancements of the real part of the molecular second hyperpolarizability were observed (Ogawa et al, 2002). However, almost no nonlinear absorption was observed in femtosecond optical Kerr effect (OKE) measurements at the off-resonant wavelength of 800 nm.…”

Challenges and breakthroughs in recent research on self-assembly

“…Kobuke and coworkers developed a non-covalent supramolecular approach for construction of porphyrin arrays from rather simple units [384], principally using coordination between central metal and imidazole groups attached at the meso-position (figure 44A) [385,386]. The lengths of the supramolecular arrays can be controlled simply by fixing the ratio between a porphyrin dimer with two zinc centers and a porphyrin dimer with a single zinc center.…”